U.S. patent application number 10/794794 was filed with the patent office on 2005-04-07 for precision measuring collision avoidance system.
This patent application is currently assigned to Altra Technologies Incorporated. Invention is credited to Gorman, Richard P., Gunderson, Richard A., Melin, Kurtis W., Parisi, Michael A.
Application Number | 20050073433 10/794794 |
Document ID | / |
Family ID | 22443934 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050073433 |
Kind Code |
A1 |
Gunderson, Richard A. ; et
al. |
April 7, 2005 |
Precision measuring collision avoidance system
Abstract
A collision avoidance system including a control module, a first
transmitting device connected to the control module, wherein the
first transmitting device transmits a signal, a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device, a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal, and a second
receiving device connected to the control module device, wherein
the second receiving device receives a return of the signal
transmitted from the second transmitting device and transmits a
second return signal representative of the return to the control
device, wherein the control module includes measurement circuitry
used to measure the first and second return signals and display
means for displaying a transverse location of an object as a
function of said first and second return signals.
Inventors: |
Gunderson, Richard A.; (Eden
Prairie, MN) ; Parisi, Michael A; (Jamison, PA)
; Gorman, Richard P.; (Jamison, PA) ; Melin,
Kurtis W.; (Forest Lake, MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Altra Technologies
Incorporated
|
Family ID: |
22443934 |
Appl. No.: |
10/794794 |
Filed: |
March 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10794794 |
Mar 4, 2004 |
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09587244 |
Jun 2, 2000 |
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09587244 |
Jun 2, 2000 |
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09130279 |
Aug 6, 1998 |
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6268803 |
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Current U.S.
Class: |
340/903 ;
701/301 |
Current CPC
Class: |
B60Q 9/006 20130101;
G01S 7/003 20130101; G01S 2013/93273 20200101; G01S 2013/93272
20200101; G08G 1/166 20130101; G08G 1/165 20130101; G01S 13/878
20130101; B60Q 9/007 20130101; G01S 2013/9324 20200101; G01S 13/726
20130101; B60Q 9/008 20130101; G08G 1/161 20130101; G01S 2013/93275
20200101; G01S 13/931 20130101 |
Class at
Publication: |
340/903 ;
701/301 |
International
Class: |
G01S 001/00; G08G
001/16 |
Claims
What is claimed is:
1. A collision avoidance system, comprising: a control module; a
plurality of transmitting devices connected to the control module,
wherein the plurality of transmitting devices includes a first and
a second transmitting device, wherein the first and second
transmitting devices transmit a first signal and a second signal,
respectively; a plurality of receiving devices connected to the
control module, wherein the plurality of receiving devices includes
a first and a second receiving device, wherein the first receiving
device receives a return representative of the signal transmitted
from the first transmitting device and transmits to the control
device a first return signal representative of the first return and
wherein the second receiving device receives a return of the signal
transmitted from the second transmitting device and transmits to
the control device a second return signal representative of the
return; and wherein the control module includes measurement
circuitry used to measure the first and second return signals and
display means for displaying a transverse location of an object as
a function of said first and second return signals.
2. The collision avoidance system of claim 1, wherein the first
transmitting device and the first receiving device are
cooperatively integrated into a single transceiver.
3. The collision avoidance system of claim 1, wherein the second
transmitting device and the second receiving device are
cooperatively integrated into a single transceiver.
4. The collision avoidance system of claim 1, wherein the control
module logs the transverse location of the object.
5. In a collision avoidance system having a plurality of sensors,
including a first and a second sensor, a method of displaying a
transverse location, comprising the steps of: placing the system
proximate an object; transmitting a signal from the first sensor to
said object; sensing a return from the object of the signal
transmitted from the first sensor and generating a first return
signal as a function of the sensed return of the signal transmitted
from the first sensor; transmitting a signal from the second sensor
to said object; sensing the a return from the object of the signal
transmitted from the second sensor and generating a second return
signal as a function of the sensed return of the signal transmitted
from the second sensor; calculating a transverse location as a
function of the first and second return signals; and displaying an
indication of the calculated transverse location.
6. The system according to claim 5, wherein the step of displaying
an indication includes the steps of creating a display showing an
area behind the vehicle and showing the object at a location within
the display corresponding to the transverse location.
7. The system according to claim 5, wherein the step of displaying
an indication includes the steps of: dividing a line into a
plurality of zones; and selecting a zone from the plurality of
zones; and placing an indication within the selected zone.
8. The method according to claim 7, wherein the step of placing an
indication includes the step of lighting a light-emitting diode
representative of the selected zone.
9. For a vehicle having a collision avoidance system with a
plurality of sensors, including a first and a second sensor, a
method of calculating the distance from a rear-most portion of the
vehicle to an object, comprising the steps of: transmitting a
signal from the first sensor to the object; sensing a return from
the object of the signal transmitted from the first sensor and
generating a first return signal as a function of the sensed return
of the signal transmitted by the first sensor; transmitting a
signal from the second sensor to said object; sensing a return from
the object of the signal transmitted from the second sensor and
generating a second return signal as a function of the sensed
return of the signal transmitted by the second sensor; determining
spacing between the first and second sensors; determining a
perpendicular distance from the sensors to the rear-most portion of
the vehicle; and calculating the distance from the rear-most
portion of the vehicle to the object as a function of the spacing,
the perpendicular distance, and the first and second return
signals.
10. For a vehicle having a collision avoidance system with a
plurality of sensors, including a first and a second sensor, a
method of calculating a distance from a rear-most portion of the
vehicle to a loading dock impact plank, wherein the loading dock
impact plane lies within a plane, the method comprising the steps
of: transmitting a signal from the first sensor to the loading dock
impact plank; sensing a return from the plank of the signal
transmitted from the first sensor and generating a first return
signal as a function of the sensed return of the signal transmitted
by the first sensor; transmitting a signal from the second sensor
to said plank; sensing a return from the plank of the signal
transmitted from the second sensor and generating a second return
signal as a function of the sensed return of the signal transmitted
by the second sensor; determining a distance between the plane and
the first and second sensors; and compensating the distance
measurement when the first and second sensors are mounted in excess
of a minimum distance below an impact point of the vehicle and the
plane of the loading dock impact plank.
11. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module, wherein
the first transmitting device transmits a signal; a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device; a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal; and a second
receiving device connected to the control module, wherein the
second receiving device receives a return of the signal transmitted
from the second transmitting device and transmits a second return
signal representative of the return to the control device; wherein
the control module includes measurement circuitry used to measure
the first and second return signals and temperature compensation
means for adjusting calculated distance readings for variations in
the speed of ultrasonic sound through air due to differences in the
temperature of the air.
12. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module, wherein
the first transmitting device transmits a signal; a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device; a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal; and a second
receiving device connected to the control module and the second
transmitting device, wherein the second receiving device receives a
return of the signal transmitted from the second transmitting
device and transmits a second return signal representative of the
return to the control device, wherein the control module includes
measurement circuitry used to measure the first and second return
signals and automatic sensitivity control used to adjust the energy
of the transmitted signal or a sensitivity of the first and second
receiving device.
13. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module, wherein
the first transmitting device transmits a signal; a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device; a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal; and a second
receiving device connected to the control module, wherein the
second receiving device receives a return of the signal transmitted
from the second transmitting device and transmits a second return
signal representative of the return to the control device, wherein
the control module includes measurement circuitry used to measure
the first and second return signals and automatic scan rate control
used to increase a rate of updating a distance measurement when a
distance to the nearest object drops below 10 feet.
14. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module, wherein
the first transmitting device transmits a signal; a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device; a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal; and a second
receiving device connected to the control module, wherein the
second receiving device receives a return of the signal transmitted
from the second transmitting device and transmits a second return
signal representative of the return to the control device, wherein
the control module includes measurement circuitry used to measure
the first and second return signals and a backup warning system
which distinguishes between emergency, hazardous, and alert
conditions as a function of the measurement of the first and second
return signals.
15. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module, wherein
the first transmitting device transmits a signal; a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device; a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal; and a second
receiving device connected to the control module, wherein the
second receiving device receives a return of the signal transmitted
from the second transmitting device and transmits a second return
signal representative of the return to the control device, wherein
the control module includes measurement circuitry used to measure
the first and second return signals and programmable memory which
can be programmed with an external programmer to define system
configuration parameters which are used to control system
operation.
16. The collision avoidance system of claim 15, wherein the control
module is programmed to log the measurement of the first and second
return signals.
17. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module and
mounted toward the top of the back of a vehicle, wherein the first
transmitting device transmits a signal; a first receiving device
connected to the control module and the first transmitting device,
wherein the first receiving device receives a return of the signal
transmitted from the first transmitting device and transmits a
first return signal representative of the return to the control
device; a second transmitting device connected to the control
module and mounted toward the bottom of the back of a vehicle,
wherein the second transmitting device transmits a signal; and a
second receiving device connected to the control module and the
second transmitting device, wherein the second receiving device
receives a return of the signal transmitted from the second
transmitting device and transmits a second return signal
representative of the return to the control device; wherein the
control module includes measurement circuitry used to measure the
first and second return signals, a distance measurement display and
a high and a low indicator, wherein when an object is near a top of
the vehicle, the high indicator illuminates and the distance
measurement displays a perpendicular distance from the top of the
vehicle to the object, and further wherein when an object is near a
bottom of the vehicle, the low indicator illuminates and the
distance measurement displays a perpendicular distance from the
bottom of the vehicle to the object.
18. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module and
mounted toward the top of the back of a vehicle, wherein the first
transmitting device transmits a signal; a first receiving device
connected to the control module, wherein the first receiving device
receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device; a second
transmitting device connected to the control module and mounted
toward the bottom of the back of a vehicle, wherein the second
transmitting device transmits a signal; and a second receiving
device connected to the control module, wherein the second
receiving device receives a return of the signal transmitted from
the second transmitting device and transmits a second return signal
representative of the return to the control device, wherein the
control module includes measurement circuitry used to measure the
first and second return signals, a distance measurement display and
a vertical clearance indicator.
19. A collision avoidance system for a vehicle, comprising: a
control module; a first transmitting device connected to the
control module, wherein the first transmitting device transmits a
signal; a first receiving device connected to the control module,
wherein the first receiving device receives a return of the signal
transmitted from the first transmitting device and transmits a
first return signal representative of the return to the control
device; a second transmitting device connected to the control
module, wherein the second transmitting device transmits a signal;
and a second receiving device connected to the control module,
wherein the second receiving device receives a return of the signal
transmitted from the second transmitting device and transmits a
second return signal representative of the return to the control
device, wherein the control module activates a guidance system when
the vehicle is operated in reverse.
20. The collision avoidance system of claim 19, wherein the
guidance system includes a bar graph display and the audible
feedback.
21. The collision avoidance system of claim 19, wherein the
guidance system includes a first indicator that is energized when
the vehicle is right of a target, a second indicator that is
energized when the vehicle is left of the target and a third
indicator that is energized when the vehicle is centered on the
target.
22. The collision avoidance system of claim 21, wherein the control
module logs a location of the vehicle relative to the target.
23. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module, wherein
the first transmitting device transmits a signal; a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device; a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal; a second receiving
device connected to the control module, wherein the second
receiving device receives a return of the signal transmitted from
the second transmitting device and transmits a second return signal
representative of the return to the control device; and a security
monitor/alarm system coupled to the control module for detecting an
intruder in the cab, wherein the security monitor/alarm system
includes a key switch, a transmit transducer, a receive transducer
and an alarm.
24. A collision avoidance system, comprising: a control module; a
first transmitting device connected to the control module, wherein
the first transmitting device transmits a signal; a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device; a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal; and a second
receiving device connected to the control module, wherein the
second receiving device receives a return of the signal transmitted
from the second transmitting device and transmits a second return
signal representative of the return to the control device, wherein
the control module includes measurement circuitry used to measure
the first and second return signals and an interface between the
control module and an on-board computer information system.
25. A method of testing a collision avoidance system, comprising
the steps of: flashing indicators for each of a plurality of
transducers; transmitting signals looking for object in each
transducer's field of view; walking around the vehicle on a path in
which each transducer will be activated; and turning off each
indicator as its corresponding transducer reports detection of an
object.
26. A wireless portable transducer system, comprising: a control
module; first and second transmitting devices removably connected
to the control module and to the back of the vehicle, wherein each
transmitting devices transmit a corresponding signal; and a
wireless communicator connected to one of the transmitting devices
and in wireless communication with the control module.
27. A collision avoidance system for a vehicle comprising: a
control module; a sensing device connected to the control module; a
shield mounted to the vehicle proximate to the sensing device; and
an activation mechanism coupled between the control module and the
shield for moving the shield between a first position and a second
position.
28. The collision avoidance system of claim 27, wherein the control
module commands the activation mechanism to move the shield from
the first position to the second position when the vehicle is
engaged for movement, thereby exposing the sensing device.
29. The collision avoidance system of claim 27, wherein the control
module commands the activation mechanism to move the shield from
the second position to the first position when the vehicle is
moving, thereby covering the sensing device.
30. A collision avoidance system for a vehicle comprising: a
control module; a first transceiver connected to the control
module; and a second transceiver connected to the control module,
wherein the control module senses an object in front of the vehicle
as a function of an angular relationship of the first and second
transceivers.
31. The system according to claim 30, wherein the control module
reduces false alarms as a function of the angular relationship of
the first and second transceivers.
32. The system according to claim 30, wherein the control module
fuses data from the first and second transceivers.
33. A collision avoidance system for a vehicle comprising: a
control module; and a plurality of sensors connected to the control
module, wherein the control module, uses N out of M tracking to
detect objects proximate to the vehicle.
34. The system of claim 33, wherein the control module fuses data
received from the plurality of sensors to detect objects within a
360.degree. view surrounding the vehicle.
35. A collision avoidance system for a vehicle comprising: a
control module; a first transceiver connected to the control
module; and a second transceiver connected to the control module,
wherein the control module uses successive range rates and signal
strength data from the first transceiver to calculate an actual
range to the object.
36. A collision avoidance system for a vehicle comprising: a
control module; a plurality of transmitting devices coupled to the
control module; a plurality of receiving devices coupled to the
control module, wherein two or more of the transmitting devices are
sequentially commanded to transmit a signal, and further wherein a
plurality of returns from the transmitted signals are received by
the receiving devices and sequentially sent to the control
module.
37. The collision avoidance system of claim 36, wherein the control
module includes a display module, and further wherein the display
module indicates a status as a function of the returns received the
plurality of receiving devices.
38. The collision avoidance system of claim 37, wherein the returns
are received from objects within a vicinity of the vehicle.
39. The collision avoidance system of claim 38, wherein the returns
are received from reflections from a road surface.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to sensor-based
systems, and more particularly to a multi-sensor collision
avoidance system which combines data from two or more sensors to
provide range, range rate, or location information.
[0003] 2. Background Information
[0004] The roads are becoming more and more congested with
vehicular traffic. As traffic congestion has increased, the number
of accidents has also increased. Some of these accidents can be
traced to driver inattentiveness or to the failure of the driver to
see another vehicle. What is needed is a system and method for
warning drivers of possible problems before the problems result in
an accident.
[0005] Systems for making drivers aware of objects external to
their vehicle have been around for a long time. Mirrors, and
sometimes combinations of mirrors, are being used to reveal
locations hidden to the driver's view (i.e. "blind spots").
Mirrors, however, have a deficiency in that the driver can only
look in one spot at any one time. If they look behind the vehicle,
see that the way is clear, start looking elsewhere and then a
vehicle pulls behind them, they won't see it and may back into the
vehicle. There is a similar problem with changing lanes. Mirrors
don't work well in changing lanes, particularly in tractor-trailer
rigs, since, as soon as the rig begins to turn, the mirror that
looked down along the side of the vehicle is directed into the side
of the trailer and the driver is blinded to activity on that side
of his truck.
[0006] More recently, trucking and bussing companies have used
backup alarms to warn bystanders that the truck is backing. The
problem with backup alarms is that if you have somebody with a
hearing problem, or if you had an immovable object such as a car or
a trash container, the alarm isn't going to move that object out of
the way.
[0007] Companies have also experimented with the use of video
systems to view blind spots. For example, garbage pickup trucks for
Browning-Ferris are using video systems which have a video camera
installed on the back of the truck and a monitor up in the cab.
Some recreational vehicle (RV) owners are doing the same thing. The
problem with the video system approach is that such systems are
expensive (even if you use an inexpensive approach, it would likely
cost into the $1,000-$1,500 price range) and video monitors mounted
in the cab can distract the driver from what is happening outside
his vehicle. Finally, video lenses do not give depth perception.
So, when drivers are backing a vehicle, they don't know how close
they are to an object they are trying to avoid.
[0008] A final approach taken by a number of companies is the use
of sensors to locate objects external to the vehicle. Electronic
Controls Company of Boise, Id. sells an ultrasonic sensor system
that assists drivers in determining all is clear before the driver
changes lanes, backs up or docks. The system includes ultrasonic
sensors mounted on the back and sides of the vehicle and an alert
module mounted in the cab of the vehicle. Each ultrasonic sensor
continuously monitors a defined detection zone for objects moving
within the zone. When a vehicle enters the detection zone, the
sensor measures the time between sending the sound wave and
receiving its reflection and sends that measurement to the cab.
[0009] Sonar Safety Systems of Santa Fe Springs, Calif. has a
rear-mounted sensor system which detects objects in three distance
zones from the rear of the vehicle. That is, it doesn't display
distance to the object. Instead, the system provides alarms and
audible feedback that inform the driver whether the obstacle is
real close (Zone III), out a little farther (Zone II), or even
farther out yet (Zone I). And it only looks up to 8 feet behind the
vehicle. They also have a single sensory unit where they only put
one sensor in the back.
[0010] A common problem with rear-mounted sensors to date is that
sensors mounted on the rear of the vehicle detect the distance from
the sensor to the object, not the perpendicular distance from the
vehicle to the object. In addition, these systems do not
communicate to the driver the transverse location of the object
(i.e., is the object directly behind the vehicle, off to the side,
or far enough to the left or right that the driver will not hit
it). Furthermore, range measurement often does not exist, or is
inaccurate.
[0011] The collision avoidance systems used to date are deficient
in other ways as well. For instance, the systems provide only
partial coverage around the periphery of the vehicle. That is, they
either lack a forward-looking detection capability, lack range and
range rate measurement capability or they lack sufficient detection
capability around the periphery of the vehicle to eliminate blind
spots. Furthermore, even if present, range measurement often is
inaccurate. Finally, those systems which do have forward-looking
detection are prone to a high rate of false alarms from the
environment or to distracting off-the-road clutter.
[0012] Systems to date do not provide an adequate solution for the
combination tractor-trailer rig. Armatron International of Melrose,
Mass. has a side and rear obstacle detection system which includes
wireless communications between the tractor and trailer, however,
the sensors are all hard-wired to the trailer. This does not
address the need in which tractors often are required to pull a
multitude of trailers, some of which are owned by different
companies, which are not likely to be equipped with any
sensors.
[0013] Finally, systems to date lack the programmability to address
the configuration and installation variables that influence the
integrity of the sensor data. In addition, current systems are
designed such that changes in the transmitted sensor frequency
require a redesign of the software algorithms.
[0014] What is needed is a collision avoidance system and method
which avoids these deficiencies.
SUMMARY OF THE INVENTION
[0015] The present invention is a collision avoidance system. The
collision avoidance system includes a control module, a first
transmitting device connected to the control module, wherein the
first transmitting device transmits a signal, a first receiving
device connected to the control module, wherein the first receiving
device receives a return of the signal transmitted from the first
transmitting device and transmits a first return signal
representative of the return to the control device, a second
transmitting device connected to the control module, wherein the
second transmitting device transmits a signal, and a second
receiving device connected to the control module device, wherein
the second receiving device receives a return of the signal
transmitted from the second transmitting device and transmits a
second return signal representative of the return to the control
device, wherein the control module includes measurement circuitry
used to measure the first and second return signals and display
means for displaying a transverse location of an object as a
function of said first and second return signals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a collision avoidance system;
[0017] FIG. 2 shows a more complex embodiment of the collision
avoidance system shown in FIG. 1;
[0018] FIG. 3 is a system block diagram of the collision avoidance
system according to FIG. 2;
[0019] FIGS. 4a-c show operator interface units which can be used
with the Control modules of FIGS. 1 and 3;
[0020] FIGS. 5a-c show the operation of two rear-mounted sensors
according to the present invention;
[0021] FIGS. 6a-c show an alternate embodiment of the operator
interface units of FIGS. 4a-c;
[0022] FIG. 7 illustrates a backup warning system;
[0023] FIGS. 8a and 8b show wireless portable transducer
systems;
[0024] FIGS. 9a-d show a forward looking proximity sensor;
[0025] FIG. 10 shows a high/low detection system;
[0026] FIG. 11 shows an operator interface unit which can be used
with the Control modules of FIGS. 1 and 3;
[0027] FIG. 12 shows the guided operation of two rear-mounted
sensors according to the present invention; and
[0028] FIG. 13 illustrates a side display module.
[0029] FIG. 14 shows one embodiment of a forward looking detector
radar module system.
[0030] FIG. 15 illustrates one embodiment of a proximity detector
radar module system.
[0031] FIG. 16 illustrates one embodiment of rear guard detector
radar module system.
[0032] FIG. 17 is an illustration of one embodiment of a type C
radar module interface board.
[0033] FIG. 18 is a block diagram of one embodiment of the power
distribution plan.
[0034] FIG. 19 is a block diagram of one embodiment of the data
communications between radar modules.
[0035] FIGS. 20a-c show one embodiment of the pin configurations
for the connectors.
[0036] FIG. 21 is a block diagram of one embodiment of a forward
looking detector.
[0037] FIG. 22 is an illustration of the radar module alignment for
a forward looking detector.
[0038] FIG. 23 illustrates one embodiment of a functional design
for a proximity detector.
[0039] FIG. 24 is a proximity detector interface and operation
timing diagram.
[0040] FIG. 25a is a side view of one embodiment of a type A radar
module layout.
[0041] FIG. 25b is a top view of one embodiment of a type A radar
module layout.
[0042] FIG. 26 is a proximity detector system timing diagram.
[0043] FIG. 27 illustrates one embodiment of a functional design
for a rear guard detector.
[0044] FIG. 28 illustrates one embodiment of a functional design
for a control module.
[0045] FIG. 29 illustrates the signal/data processing functions of
one embodiment of a control module.
[0046] FIG. 30 illustrates one embodiment of forward looking
detector object data processing.
[0047] FIG. 31 illustrates one embodiment of track report generator
functions.
[0048] FIG. 32 illustrates one embodiment of proximity detector and
rear guard detector detection processing.
[0049] FIG. 33 illustrates one embodiment of data fusion and range
estimation.
[0050] FIG. 34 shows an example of multiple hypotheses through
amplitude versus time data for automatic ranging.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] In the following detailed description of the preferred
embodiments, reference is made to the accompanying drawings which
form a part hereof, and in which is shown by way of illustration
specific embodiments in which the invention may be practiced. It is
to be understood that other embodiments may be utilized and
structural changes may be made without departing from the scope of
the present invention.
[0052] FIG. 1 shows a collision avoidance system 10 according to
the present invention. System 10 includes a Control module 12 and
two sensors 14. Each sensor 14 includes a transmitter 16 and a
receiver 18. In one embodiment, transmitter 16 and receiver 18 are
mounted together in a single sensor housing. In another embodiment,
transmitter 16 and receiver 18 are mounted in separate
housings.
[0053] In one embodiment, sensors 14 include separate acoustic
transducers for each of transmitter 16 and receiver 18. In another
embodiment, a single acoustic transducer is used for both
transmitting a signal and receiving its echo. Some transducers
which would operate in such a system 10 are the 9000 Series Piezo
Transducers available from Polaroid OEM Components Group and the
KSN 6530 45 KHz transducer available from Motorola. In addition,
the KSN 6529 45 KHz transducer available from Motorola could be
used for receiver 18.
[0054] In another embodiment, sensors 14 are micropower impulse
radar (MIR) devices. In one embodiment, MIR devices such as those
described in the white paper entitled "Microwave Impulse Radar
(MIR) Technology Overview", available from Lawrence Livermore
National Laboratory, are used. The advantage of such devices are
that they are low power and fairly inexpensive. In addition, a
single device can be used as both transmitter 16 and receiver
18.
[0055] In yet another embodiment, sensors 14 are microwave
transceiver devices. In one such embodiment, each transceiver
includes a small integrated antenna and electronic interface board.
In another embodiment, sensors 14 include both proximity detectors
14.1 and longer range detectors 14.2. The longer range detectors
incorporate a larger antenna to operate as a Doppler Radar Forward
Looking Detector. An example of one such transducer is the model
DRO3000 Microwave Transceiver Module available from Advanced
Frequency Products of Andover, Mass.
[0056] In one embodiment, such as is shown in FIG. 2, a collision
avoidance system 30 includes up to seventeen sensors 14 mounted
around the periphery of a vehicle.
[0057] In one embodiment, sensors 14 of system 30 are grouped in
detection subsystems 34. The output from each proximity detector
subsystem 34 is fed into Control module 12, as is, shown in FIG. 3.
As shown in FIG. 3, system 30 includes a Control module 12, an
operator interface 32, and two sensors 14. Each sensor includes a
transmitter 16 and receiver 18.
[0058] In one such embodiment, sensors 14 of system 30 are grouped
in detection subsystems: namely, forward-looking detector subsystem
(with 2 sensors), proximity detector subsystem (with up to 15
sensors), and a rear-guard subsystem (with up to 7 sensors). The
output of each sensor in each detection subsystem is fed into
control module 12, as shown in FIG. 3. As shown in FIG. 3, system
30 includes a control module 12, an operator interface 32, and
other optional system features. In one embodiment, optional system
features include rear warning lights 98 and side warning lights 99.
Each sensor includes a transmitter 16 and receiver 18.
[0059] Collision avoidance systems to date typically put
transducers on the rear of the vehicle and measure the distance
from the sensor to the object. This is not optimal since those
sensors are transmitting in an arc. They are looking at the
distance from the sensor to the object and back again. That may
not, however, be the perpendicular distance from the vehicle to the
object. A deficiency, therefore, of systems to date is that they do
not communicate to the driver the transverse location of this
object.
[0060] In one embodiment of the system shown in FIGS. 1 and 2, a
plurality of sensors 14 are mounted on the back of the vehicle.
Control module 12 takes the readings from the rear-mounted sensors
14, determines whether it can triangulate and calculates an actual
perpendicular distance from the truck to the object. This is
important because the truck driver really wants to know, not that
the object is off at this angle over here five feet away, is how
far he can back up before he hits the object. Examples of these
measurements are shown in FIG. 4a-c and 5a-c. In contrast to other
approaches, this triangulation procedure makes system 10 a
precision distance measuring system. Alternate approaches to the
operator interfaces shown in FIGS. 4a-c are shown in FIGS.
6a-c.
[0061] FIG. 5a represents the top view of a tractor trailer rig 50
with a post 52 located behind the trailer 54. The post 50
represents a hazard unless the driver knows the precise distance
from the vehicle. Sensor 14 on the right rear of the trailer senses
the post 52 at a distance of six (6) feet. Sensor 14 on the left
rear of the trailer senses the post at a distance of just over six
and one half (6.5) feet. Control System 12 calculates that the
actual distance to the post as 5.2 feet and determines it is
located just to the right of the center of the trailer. The
distance is then displayed digitally on the control module 12. The
transverse location is displayed, for instance, on the bar graph
located just to the right of the digital display and it indicates
the location of the post.
[0062] Perpendicular distance between the rear of a vehicle and
external objects is increasingly important the closer the vehicle
gets to an external object. In the same example as above, when
sensor 14 on the right rear of the trailer senses the post at a
distance of four (4) feet and the sensor 14 on the left rear senses
the post at a distance of 4.8 feet, the actual perpendicular
distance is 2.6 feet. The Precision Measurement System correctly
uses the sensor 14 distance readings as well as the known distance
between the left and right sensors 14 to calculate the exact
perpendicular distance to the post. This is very important as an
aid to the driver in the prevention of an accident.
[0063] In one embodiment, a third sensor 14 is mounted between the
right and left sensors 14. With the aid of third sensor 14, the
system can determine that the object is a point source (such as a
post) as opposed to a wall or large vehicle. The sensor 14 on the
right rear of the trailer senses the post at a distance of six (6)
feet. The sensor 14 on the left rear of the trailer senses the post
at a distance of just over six and one half (6.6) feet. The Control
module 12, knowing that the object is a point source, calculates
that the actual distance to the post is 5.2 feet and is located
just to the right of the center of the trailer. The distance is
displayed digitally on the Operator Interface and Side Display
Modules. The transverse location is displayed in graphic form (e.g.
bar graph) on the Operator Interface.
[0064] FIG. 5b represents the top view of a tractor trailer rig
with a post located far behind the trailer. The post represents a
hazard unless the driver has sufficient information to aid in
maneuvering around the obstacle. The sensor 14 on the right rear of
the trailer senses the post at a distance of 21.0 feet. The sensor
14 on the left rear of the trailer senses the post at a distance of
22.1 feet. The control module 12 calculates that the actual
distance to the post is 21.0 feet, and that it is located near the
right side of the trailer. The distance is displayed digitally on
the operator interface. The transverse location is displayed on the
bar graph located just to the right of the digital display and it
indicates the location. Precision distance measurement is less of a
concern when obstacles are a long distance from the rear of the
vehicle. However, productivity is a concern. With the aid of the
transverse location information and the ability of the control
module 12 to detect objects up to 25 feet behind the vehicle, the
driver of the tractor trailer shown in FIG. 5b can readily maneuver
the vehicle to avoid the obstacle without having to stop, drive
forward, and then proceed in backing the vehicle.
[0065] In order to triangulate, the distance between sensors 14
must be known. Therefore, the distance between sensors 14 must be
controlled. In one embodiment, the distance between sensors 14 is a
system parameter that can be programmed. In one such programmable
embodiment, a programming device is provided to a dealer or a fleet
owner such that once sensors 14 are installed, they can measure the
actual distance between the sensors and the distance from the
sensors to the sides of the vehicle and program that into control
module 12. Control module 12 can then accurately calculate
distance.
[0066] For example, if a collision avoidance system 10 or 20
provides a measurement, is that object directly behind the vehicle,
or is it off to the left or right? Is it actually far enough off to
the left or far enough off to the right that he won't hit it but
needs to be aware of it? To provide more accurate information, in
one embodiment, control module 12 calculates transverse location
and communicates that information via a graphical indicator such as
bar graph 22 of FIG. 4a (also shown as 22' in FIG. 6a).
[0067] In the embodiment shown in FIGS. 4a-c and 6a-c, the purpose
of the bar graph display is to break the transverse set of
distances or locations, up into anywhere from 7 to 11 or more
segments on the bar graph display. Control module 12 lights the
segments that indicate where that object is from extreme left to
extreme right. In another embodiment, transverse location is
communicated through another graphic display, (e.g., a Liquid
Crystal or other Display). In addition, in one embodiment
transverse location is displayed through a little video monitor. In
one such embodiment, operator interface unit 32 also shown as 32'
in FIG. 6a displays an area behind the vehicle and places a dot
within that area showing the closest object. A representation such
as is shown in FIG. 5a would be sufficient. The operator interface
unit 32 includes a display 129, speakers 125, push-button switches
47, system status indicator 127 and switch legends 128.
[0068] Another issue is the vertical position of the rear-mounted
transducers, relative to the ground, and relative to the impact
point with a loading dock, is an important issue. For example,
loading docks have an impact plank that protrudes out from the
wall. If sensors 14 are mounted too low, you may actually look
underneath the impact plank. If so, the truck could hit the plank
under power with the driver thinking he or she had another 4-6
inches to go. In one embodiment, system 10 includes vertical
compensation as discussed below.
[0069] In one embodiment, vertical compensation is activated
automatically when the front panel switch in FIG. 4c or the soft
key in FIG. 6c is in the Loading Dock (LD) position. The purpose of
this feature is to compensate for the protrusion of loading dock
impact bars in cases where the Transducer Assembly is located below
the point of impact of the trailer with the loading dock impact
bar.
[0070] FIG. 5c represents the side view of a tractor-trailer
pulling up to a loading dock. The impact bar is the point of
contact with the trailer. The depth (i.e., front-to-back) of the
impact bar is typically 4.5 inches. The top of the impact bar is
typically 48 inches above the ground. When the Transducer Assembly
is located below the point of impact of the trailer with the impact
bar, the Precision Measurement System will adjust the distance
measurement by 4.5 inches if the Transducer Assembly is mounted so
low that it cannot detect the impact bar when the trailer is within
12 inches of the impact bar. For example, if the perpendicular
distance from the rear of the trailer to the loading dock is 1 foot
and the Transducer is 2 feet below the impact bar, the measured
distance of 1.0 feet will be corrected to 0.6 feet.
[0071] In one radar embodiment, software running in systems 10 and
30 uses Multi-Hypothesis Ranging to provide an accurate estimate of
range to an object. A range estimate will be calculated from the
signal strength versus time and closing rate of each tracked
object. As an object changes its relative position to the host
vehicle, the signal strength will vary, due to the properties of
radar, by range to the fourth power and by a scattering property
called scintillation. Combining this property with the distance
traveled by the object will yield the starting range and thus the
current range to the object. The distance traveled by the object is
computed in the system by combining time since the data collection
and tracking started, with the individual measured closing rates
versus time. Using multiple hypotheses, the signal strengths versus
time will be inserted into an algorithm which matches the
hypothetical signal strength curve to a "range and distance
traveled one over range to the fourth curve". One hypothesis, a set
of points drawn through the returned signal levels over time, will
correspond to the correct starting range for the object given the
measured distance traveled. This hypothesis will provide the best
statistical match to a one over range to the fourth curve and will
be the range estimate provided.
[0072] One sonar embodiment of system 10 incorporates temperature
compensation. Temperature compensation is needed because of the
fact that sonar travels at different speeds through air depending
on temperature. And so systems 10 and 30 measure the temperature of
the air, and compensate in the distance calculation for the effects
of temperature. In such an embodiment, transverse location
detection, triangulation, perpendicular position compensation and
temperature compensation cooperate to form a precision measurement
system.
[0073] In another sonar embodiment of systems 10 and 30, the
systems include automatic sensitivity control. When systems 10 and
30 are trying to sense an object at a far location, it is
advantageous to pulse your maximum energy, to transmit a high burst
of energy. When systems 10 and 30 transmit such a high burst of
energy, if there is an object at a far distance, systems 10 and 30
are more likely to get an echo they can sense. And the sensitivity
should be set to be very sensitive for that application. But once
you sense that far off object and you start backing toward it,
systems 10 and 30 should back off the transmitted energy. In
addition, it is advantageous to adjust receiver sensitivity. In one
embodiment, the output of transmitter 16 can be reduced and the
sensitivity of receiver 18 increased automatically by systems 10
and 30.
[0074] In yet another embodiment of systems 10 and 30, a backup
warning system is provided as shown in FIG. 7.
[0075] The intent is to provide immediate feedback to the driver
shortly after the vehicle transmission is shifted into reverse.
This information includes information on objects in the vicinity of
the rear of the vehicle as well as information on objects in the
path of the rear of the vehicle. In the case where objects are in
close proximity to the rear of the vehicle, but not in the path of
the vehicle, an auditory prompt representing an "alert" is sounded
for the driver. If an object is detected in the path of the
vehicle, in the range of 5 to 10 feet, the system will categorize
that as a hazard situation and an auditory prompt representing a
"warning" is sounded for the driver. If an object is detected in
the path of the vehicle, within a range of 5 feet, the system will
categorize that as an emergency situation and an auditory prompt
representing an "emergency" is sounded for the driver. After the
vehicle has been backing up for two or more seconds, the alert,
warning, and emergency will have cleared and the system will begin
providing range feedback to the driver in the form of distance
information, as displayed on the Operator Interface and Side
Display Modules, and auditory feedback in the form of pulsed tones.
The closer the vehicle gets to an object, the faster the repetition
rate of the pulses until the rear of the vehicle is within one foot
at which time the pulses have turned into a continuous tone. In the
process of backing up, if a person or vehicle suddenly appeared
behind the vehicle, the system will automatically detect a sudden
change in range to the object and the "emergency" auditory prompt
will be issued to the driver so he/she can take action.
[0076] In one such embodiment, when the driver is going to back up,
if there is an object within range, one of three scenarios will
happen. First, if the system senses a truck or other object real
close to it on either side, systems 10 and 30 will give him an
alert. The system knows that there is no collision potential here,
but just alerts him that there is something there. In one
embodiment systems 10 and 30 provide one set of tones to the driver
for an alert. Second, if there is an object in the range of 5-10
feet as soon as the driver throws it into reverse, systems 10 and
30 sense the object and provide the driver with a different alarm
(e.g., a different set of tones or a different flashing light).
This alarm is called a hazard alarm. And again, that's to alert the
driver so he can take action on the hazard alarm. Third, if there
is an object within 5 feet, the driver receives an emergency alarm
(i.e., a third set of tones, or a third flashing light). Systems 10
and 30 therefore provide feedback indicative of the distance to an
object behind the driver. In one such embodiment, audible or visual
feedback tells the driver he's getting closer; the pulses go faster
and faster to the point where, when he's within a foot, the pulses
are continuous. But, if in the process of backing up, the system
automatically detects that the distance suddenly became shorter, it
will provide the emergency alarm right away so the driver can take
action. For example, if somebody drove in behind the driver, or
some kid ran in back of the vehicle, systems 10 and 30 sense that
and automatically provide the emergency alarm so the driver can
take action. As noted above, some of the systems that are out there
actually detect zones of distance and provide feedback for that.
Systems 10 and 30 go beyond that in that they detect and
differentiate objects outside the area of potential collision from
those inside and secondly, they can detect sudden changes in
distance for an emergency alarm.
[0077] In one embodiment, control module 12 is highly programmable
and dealers and fleet owners are given an ability to program key
parameters that the system can use to more adequately address the
needs of that application and that customer. In one such
embodiment, an external programmer is plugged into a connector in
the back of control module 12; the dealer can then respond to
basically the number of fields and change a number (e.g., the
distance between the rear-mounted transducers as discussed above),
and key that in. When all the information is in, the programmer
downloads the data, and feeds it back to the control module 12.
Control module 12 then is configured for that vehicle.
[0078] In yet another embodiment, system 10 includes a security
monitor/alarm system coupled to control module 12. In one such
embodiment, an ultrasonic transmitter and an ultrasonic receiver is
placed in the cab of the vehicle. When the driver leaves the
vehicle, he turns the alarm system on with a key switch and it
automatically scans the cab to see what the distances are to the
closest object up in the cab. If somebody climbs up into the seat,
one of the distances changes and an alarm is set off. In one such
embodiment, the driver has approximately 15 seconds to get in and
disable the alarm with his key switch. But if it was somebody other
than the driver, the alarm will go off. In one embodiment, the
alarm also activates an auto alarm underneath the hood of his
vehicle to draw attention to and possibly scare off the
intruder.
[0079] In yet another embodiment, an on-board computer interface is
provided. The reason for this is some of the larger tractor-trailer
rigs, in particular, have on-board information systems that monitor
factors relating to use of the vehicle. They may monitor, for
instance, the location of the vehicle, the delivery route, the
delivery schedule, things that the driver does along the way,
engine performance or things that might be an indication to the
fleet owner that there's some service needed. In one embodiment of
systems 10 and 30, information relating to driver performance that
is detected with systems 10 and 30 is captured and downloaded into
the on-board computer so that when the fleet owner gets a download
from the on-board computer, it contains additional information
provided by systems 10 and 30. So, with an interface through a
single cable, systems 10 and 30 can tie into the on-board computer
and provide real time information.
[0080] In another embodiment, if there is no on-board computer
there, data storage is provided in control module 12 so that it can
store the data internally. Data can then be downloaded to a fleet
computer at a future date. In one such embodiment, systems 10 and
30 include an accident reconstruction memory installed in the
control module. This memory maintains a record, in nonvolatile
memory, of data pertinent to system operation, vehicle operation,
and obstacle detection. Some of these parameters are stored over
longer periods of time and some relate to the last 2 or more
minutes leading up to an accident. A G-force switch detects the
presence of a crash and discontinues the data recording process
thus saving data stored prior to the crash.
[0081] In one embodiment a self test capability is provided. Self
test addresses several issues. One is when systems 10 and 30 are
first turned on (i.e., the driver throws the power switch into an
"on" position) the systems will turn all the indicators on so that
the driver right away can see that all the indicators are lit. In
addition, control module 12 tests its internal circuitry to ensure
that the system comes up running. The second thing the system does
is while it's running, if the micro controller or microprocessor in
control module 12 were to fail, systems 10 and 30 then provide a
"watch-dog timer" that will detect the failure. Thirdly, the driver
can activate self test mode. On doing so, control module 12 flashes
all of the indicators of front panel 20. In one such embodiment,
control panel 20 includes an indicator 24 for each transducer
mounted around the vehicle and, on entering self test, transducer
indicators 24 begin to flash. The driver then walks around the
vehicle and gets back in the cab. Every one of those transducers
should detect him; each time they detect him, the transducer
indicator 24 associated with the transducer goes off (i.e., quits
flashing). If the driver gets back to the cab and there's a
transducer still flashing, he knows that something didn't work and
he can investigate the problem.
[0082] In another embodiment, systems 10 and 30 automatically and
sequentially activate a Built-In Test (BIT) function for each
sensor. The Built-In-Test (BIT) function is conducted in two ways:
initial power-up and an integrated BIT performed during vehicle
motion.
[0083] During initial power-up, when power is first turned ON,
control module 12 performs a BIT of control module 12 functions.
The BIT function verifies that sensor transmitter 16, receiver 18,
and the electronics of control module 12 and the rest of systems 10
and 30 are working properly. In one embodiment, indicators
associated with every element tested will turn off for all sensors
that pass the Built-In Test. If a sensor 14 repeatedly fails the
BIT, it will automatically be taken out of the service and the
driver will be alerted of the failure and the need to service that
particular sensor 14.
[0084] When the vehicle is in motion, the system will perform BIT
on all detector modules and integrate the results into the data
acquisition process to insure the integrity of the data being
processed. This is accomplished by looking for road clutter
signatures from each of the radar modules (i.e. forward-looking,
side-looking, and rear-looking detectors). When the vehicle is in
motion, the system will integrate the BIT of all sensor modules
into the data acquisition process to insure the integrity of the
data being processed. This is accomplished by looking for road
clutter signatures from each of the radar modules (i.e.
forward-looking, side-looking, and rear-looking detectors). If the
radar modules are working properly, they will always detect low
level return signals from the road surface while the vehicle is
moving and will transmit information pertaining to these signals
back to the control module. If the sensor is defective, the system
will continue to function, bypassing the defective sensor. If the
BIT detects a catastrophic failure, an error message will be
displayed on the operator interface and the system will halt. The
date, time, and results of the most recent BIT will be stored in
Accident Reconstruction System memory if that option is installed.
This integrated approach to BIT does not slow up the data
acquisition process and it insures the integrity of all sampled
data and the data communications from all sensors.
Wireless Portable Transducer System
[0085] In one embodiment sensors 14 are provided within a wireless
portable transducer system 40. The problem with that is if you look
at the number of trailers out there, they far exceed the number of
truck-tractors out there. And so truck-tractors are basically
moving from trailer to trailer. It could easily reach the point
where establishing a complete collision avoidance system 10 or 30
on each combination of tractors and trail would be prohibitively
expensive. To better address the needs of fleet owners, a system 10
is constructed having a wireless portable system 40. FIGS. 8a and
8b show two embodiments of such portable systems.
[0086] In FIG. 8a, two boxes 70 provide the portable transducer
function. Each box 70 includes an antenna sticking out the side.
Each box 70 mounts under the trailer and clamps to the frame of the
trailer. Inside each box 70 is an ultrasonic transmitter and
receiver, electronic circuitry, and a radio transmitter and
receiver. A two wire cable connects battery from the trailer to the
electronic circuitry to provide power. A cable between each box
provides common control signals from the radio transmitter/receiver
such that signals from either rear mounted antenna control both
Transducer Assemblies.
[0087] In FIG. 8b, there is one long extrusion 72 with an antenna
sticking out each side. The extrusion clamps to the frame on the
rear of the trailer. The extrusion may be made of one piece, or two
pieces (one within another) with a mechanism to adjust the width of
the extrusion 72 to the width of the trailer. A Transducer Assembly
(transmitter and receiver) is mounted on each end of the extrusion.
The electronic circuitry, including radio transmitter and receiver
are mounted inside the extrusion. In one embodiment, a two wire
cable connects battery from the trailer to provide power to the
electronic circuitry.
[0088] Signals to and from the boxes 70 and 72 are communicated to
the control module of the collision avoidance system via the
Wireless Communicator to detect, measure, and display distance to
objects behind the trailer.
[0089] System 40 is designed so that it can quickly be disconnected
from one trailer and moved to another trailer.
[0090] In one such embodiment, a Wireless Portable Transducer
System provides for wireless communication between the electronics
mounted in the cab of the vehicle and the Portable Transducer Array
mounted on the rear of the trailer. Power to operate the Portable
Transducer Array is provided by connecting in to existing power
wiring provided to the trailer from the truck's electrical
system.
[0091] Dependent on the transducer technology used, the Portable
Transducer Array could be made to be totally battery operated. For
example, if the Portable Transducer Array were designed using
Micropower Impulse Radar, Doppler Radar or other alternative
low-power technologies, the transmitting and receiving functions to
measure distance to objects behind the vehicle would be low power
and could operate on batteries built into the Portable Transducer
Array. The communications between the electronics in the cab of the
vehicle and the Portable Transducer Array could also use Micropower
Impulse Radar, Doppler Radar, or other alternative low-power
technologies, thus enabling portability with built-in battery
power. This solution will eliminate the need to tap into the
truck's electrical system to power the Portable Transducer
Array.
[0092] The bulk of the electronics stays with the tractor. In
addition, the rear transducer array stays with the tractor (i.e.,
as the driver goes from trailer to trailer he simply pulls off
system 40 and clamps it on the next trailer. In one such
embodiment, a connector arrangement is provided so the driver can
connect system 40 to the power that's already on the trailer and
quickly get the system up and running.
[0093] In another embodiment, multiple sensors are designed into
the wireless subsystem 40 to detect obstacles to the rear of the
vehicle and on either side of the vehicle. Communication with
control module 12 is via wireless digital signals. Control module
12 is designed to sense when the wireless portable sensor subsystem
is not installed or is not functioning properly.
[0094] Different quick-connect mounting arrangements might be
needed for different style trucks. In one embodiment, as is shown
in FIG. 8b, portable wireless sensor subsystem 40 is a tubular
structure with integral electronics, battery pack, and sensors
mounted internal or external to the structure. The unit would clamp
on the trailer chassis or the underride bumper provided on the rear
of many trailers. Antennas would be mounted on one or both sides of
the wireless portable sensor subsystem protruding just outside the
left and right edges of the trailer. In another embodiment, as is
shown in FIG. 8a, portable wireless sensor subsystem 40 is enclosed
in two separate housings mounted at the left rear or right rear of
the trailer. Again, quick connect mounting arrangements will be
made to secure each unit to the trailer. A cable will interconnect
each unit to allow the sharing of one battery pack, one controller,
and one wireless transceiver.
[0095] In another embodiment of system 40, the sensors on the
trailer are hardwired together, however, communication between the
sensors and the control module 12 is wireless. In this case, a
Transceiver Module will be mounted on the tractor and a second unit
on the trailer. The Transceiver Module on the trailer will receive
its power from the tractor-trailer umbilical electrical cable.
Electrical signals will be passed between tractor and trailer just
like any non-wireless system with the exception that the signals
will be converted to wireless communication and then reconverted
back to their electrical form at the other end. This approach
provides additional flexibility for the customer's needs.
[0096] Adding Additional Sensors
[0097] In certain situations, drivers need to be able to detect
objects directly in front of, or to the side of, the front of the
vehicle. For example, in the case of a school bus, one of the
problems that busses have is the number of small children in front
of and on the sides of the bus. There are deaths in school bus
accidents in the United States every year; they are generally
related to accidents at the front of the bus. To date, the only
options provided to these drivers are mirrors angled to see the
front of the bus. Even the use of angled mirrors, however, has only
limited effectiveness.
[0098] To address this need, in one embodiment, forward-looking
proximity detectors are provided in order to detect objects
immediately in front of the vehicle (an area that is a blind spot
for the driver).
[0099] Buses also have a problem with children that crawl under the
bus to retrieve a dropped toy or ball. Bus drivers cannot always
see these areas. To help prevent problems, in one embodiment,
side-looking proximity detectors are positioned on the bus to
monitor these areas.
[0100] Sensor Protection
[0101] Some forward-looking proximity detectors, however, have a
problem with clogging due to debris, dirt, ice, etc. accumulated
while the vehicle travels down the road. As noted above,
forward-looking transducers are typically needed only when the
vehicle is stationary and about to move forward. It would,
therefore, be advantageous to expose the forward-looking transducer
to the elements in only those situations where they are needed.
[0102] A forward-looking Transducer with an Environmental Shield
solves this problem in situations where the Transducer need not be
active while the vehicle is in motion. While the vehicle is in
motion, the shield covers the front of the Transducer Assembly,
protecting it from contamination. When the vehicle stops, the
system using this device will open the front door, thus enabling
the Transducer Assembly to detect and measure the distance to all
objects in front of the vehicle. Shortly after the vehicle starts
to move, the system closes the Environmental Shield to protect the
Transducers.
[0103] FIGS. 9a-d demonstrate one way of solving this problem. The
solution is independent of the type of Transducer technology being
used. However, the intended use is with ultrasonic Transducer
Assemblies.
[0104] FIGS. 9a and 9b represent a side view and a front view of a
mounting bracket with the Transducer Assembly 88 mounted via a
Transducer Mounting Bracket 90 to Mounting Bracket Top Plate 92.
Mounting Side Brackets are shown in place. Note the mounting holes
in the flanges that protrude beyond the width of the mounting
Bracket Side Plates 94. These mounting holes are used to mount the
completed assembly to the underside of the vehicle front bumper or
chassis just behind the front bumper. In one embodiment, spacers
are used to adjust the actual height of the overall assembly so as
to provide an unobstructed opening for the Transducers to work
properly.
[0105] FIG. 9c represents a side view of the Face Plate 91 used to
protect the front of the Transducer Assembly. The Face Plate 91 is
positioned at an angle to deflect air and contaminates down under
the overall assembly. A pivot arm 93 is an integral part of the
Face Plate 91. Attached to a slot in the pivot arm 93 is an
electrically activated solenoid 95 and a return spring 97. The
return spring holds the Face Plate 91 closed over the front of the
overall assembly when no power is applied to the solenoid 95. This
pivot arm 93 has a hole around which the Face Plate 91 will pivot
when the solenoid 95 is activated.
[0106] FIG. 9d represents a front view of the overall assembly.
Note that the face plate 91 fits just under the Mounting Bracket
Top Plate 92 and over the front of the Mounting Bracket Side Plates
94. This is to minimize moisture from seeping in behind the Face
Plate 91. However, there is a gap between the lower edge of the
Face Plate 91 and the front edge of the Bottom Plate 96 to allow
any moisture that might enter the assembly to drain out. The
assembly includes a nut, bolt and bushing 87.
[0107] Features not shown in the drawing include:
[0108] A bracket mounting the solenoid 95 to the inside of the
Mounting Bracket Side Plate 94;
[0109] An access hole provided in the Back Plate 98 for the
Transducer Cable Assembly which connects with the Transducer
Assembly 88; and
[0110] The other end of the return spring 97, that mounts to the
Mounting Bracket Side Plate 94 with a screw and washer.
[0111] One embodiment of such a forward-facing transducer is shown
in FIGS. 9a-d. Forward-looking systems only need to be activated
when the bus comes to a stop and it first goes into gear to move
forward.
[0112] In one embodiment, such as is shown in FIGS. 9a-d, a
forward-looking transducer includes an environmental shield. When
the vehicle comes to a stop and is in neutral, or in park, that
shield drops out of the way. When the driver goes into gear, the
forward-looking proximity detectors begin looking and alert the
driver with an alarm if there is an object in front of the vehicle.
Shortly thereafter, the shield goes back into place and protects
the detector from the environment.
[0113] In one embodiment shield 60 replaces the solenoid with a
motor. The motor is to rotate the shield cover out of position when
the transducer is operating.
[0114] As noted above, it can be advantageous to provide truckers
and other long-range drivers with early warning of slow or stopped
vehicles in their line of path. Collisions with such objects may
result from poor visibility, driver inattention, or driver
distraction. To counter this problem, in one embodiment one or more
forward-looking transducers 14.2 are attached to the front of the
vehicle as long range detectors that can see objects well ahead of
the vehicle. As noted above, forward-looking devices 14.2 have been
used in the past to detect slow or stopped objects in the path of
the vehicle. Such attempts have largely failed due to the inability
to control the false alarm and off-the-road clutter problems.
Therefore, it is important to control and monitor a broad range of
objects and clutter. Such objects and clutter must be properly
analyzed to detect potential accidents with minimal false
alarms.
[0115] In the software embodied in systems 10 and 30, there are
several advanced features built-into the software to minimize false
alarms, including (a) the combination of multiple sensors comparing
signals for same objects and using sensor antenna patterns to
derive angular position, (b) the use of a N out of M tracking
algorithm, and c) the fusion of data from multiple sensors.
[0116] In one embodiment of the Forward-Looking Detector (FLD), the
returns of both sensors at the same frequencies can be used to do
False Alarm Rate (FAR) Reduction. Depending on the angle to an
object, the frequency and amplitude will change. Stationary objects
on the side of the road at close ranges will appear stronger in one
sensor and at frequencies lower than the speed of the vehicle. Road
clutter from a specific object such as a sign or bridge will appear
at one frequency. As the vehicle approaches, if the object is on
the side of the road the frequency will decrease and the signal
strength in one sensor will decrease while the signal in the other
sensor will increase faster than expected. This will denote that
the object being detected is not in front of the host vehicle.
[0117] The difference in signal strength can be used to remove the
majority of the False Alarms resulting from side of the road
clutter. However, objects moving virtually in front of the host
vehicle may present themselves in a manner consistent with objects
directly in front of the host vehicle. An N out of M tracking
scheme is used to track these objects, such a tracking scheme uses
the statistical properties of scintillation and the FLD antenna
patterns to average the signal return and differentiate between the
lane in front and off to the side of the host vehicle.
[0118] The Proximity Detectors and Rear Guard Detectors, being wide
beam sensors, require both N out of M tracking and Data Fusion to
remove False Alarms. The Data Fusion system receives tracks from
each sensor surrounding the host vehicle. This data is fused into
one track for each object surrounding the truck with all data from
all contributing sensors used to differentiate between an alarming
condition and a False Alarm.
[0119] Another factor in FAR reduction is object identification.
With a range estimate from the Multiple Hypothesis Ranging
software, the signal strength versus time (scintillation
characteristics) and average signal strength at an estimated range,
an identification (ID) can be computed for a tracked object. The
signal strength at an estimated range provides an estimate of radar
cross section. From this radar cross section an initial
categorization as a truck/large vehicle, a car or other can be
determined. From scintillation combined with a small radar cross
section the categorization as a human/large animal or a sign can be
determined.
[0120] Another extremely important software feature for reliable
system performance is Data Fusion. The Data Fusion algorithm will
be designed to take inputs from a N out of M tracker. This Data
Fusion algorithm is specifically designed to not require any
specific set of sensors and adapts as sensors are added using a
lookup table of the new sensor parameters and an indication of the
number of and type of sensors added. The Data Fusion Algorithm can
also take into account any data from the host vehicle supplied by
various sensors. The absence of data will not cause a problem with
the algorithm, however, the more data the better the performance.
The purpose of the Data Fusion Algorithm is to reduce all of the
tracks and detections down to a small set of object tracks
representing the objects surrounding the host vehicle. Each radar
module and sensor set may detect the same object. It is the task of
the Data Fusion Algorithm to sort this out. The algorithm uses a
technique called Deepest Hole to combine the data from multiple
sensor and Kinematics Combination to fuse this data together.
[0121] The Deepest Hole function "associates" tracks from the
sensor sets with existing Fused Tracks. It is assumed that multiple
sensor sets may find the same object and that multiple radar
modules within a sensor set will often see and report on the same
object. The Deepest Hole function resolves these redundant tracks
into a set of fused tracks, one per object. The output of this
function is a list of track links linking the tracks from multiple
radar modules together for one object.
[0122] The track data from the tracks which are linked are merged
in this function. The speeds of each track are averaged together.
The Signal to Noise Ratios will be averaged using a weighted
average considering radar module antenna gain. The range estimate
for the new merged track is created using the time and sensor
averaged signal strength. The track ID is merged using the
Probability of Correct ID and the ID Confidence.
[0123] In one embodiment, sensors 14 include transducers placed on
the rear of the vehicle. Those transducers are activated when the
driver shifts his transmission into reverse. As soon as the driver
shifts into reverse, the transducers on the back begin to send out
sound energy from the transducers, which bounces off an object,
comes back to a receive transducer. Distance is then calculated as
a function of time of return (e.g., acoustic applications) or
intensity of the return signal (e.g., radar applications). In one
embodiment, a Multiple Hypothesis Ranging algorithm is used to
calculate distance. In addition, sensors 14 detect that there's
something back there. And if there is something back there, systems
10 and 30 can alert the driver immediately, so that he can take
action and not back into whatever that object happens to be.
[0124] In another embodiment, additional sensors 14 are mounted on
the side of the vehicle. Sensors on the right side of the vehicle
are activated when the right turn signal is active. Sensors on the
left side of the vehicle are activated when the left turn signal is
active. When the transmission is shifted into Reverse, the sensors
on both sides of the vehicle are activated to monitor for potential
accidents at the sides of the vehicle when backing up. When a
sensor is activated, it begins to send out signals which bounce of
any nearby object and come back to a receive transducer. Distance
is then calculated as a function of time of return (e.g. acoustic
sensors) or intensity of the return signal (e.g. radar
applications). In the case of radar, a Multiple Hypothesis Ranging
algorithm is then used to calculate distance. Based on the distance
to the object, the Control module software can determine whether a
valid alarm condition exists and the driver needs to be
notified.
[0125] In another embodiment of system 30, systems may be equipped
with a Side Display Module, such as is shown in FIG. 13. Side
Display Module 36 is mounted internal or adjacent to each Side View
Mirror. If one or more sensors 14 on the side of the cab detect an
object, Side Display Module 36 will flash a forward-directed arrow
on that side of the vehicle. In one embodiment, if one or more
sensors on the side of the trailer detect an object, Side Display
Module 36 flashes a rear-directed arrow on that side of the
vehicle. If objects are detected on both the side of the cab and
the side of the trailer, Side Display Module 36 flashes an arrow
pointed both forward and to the rear. In one such embodiment, Side
Display Module 36 also displays the distance between the rear of
the vehicle and any object behind the vehicle when the transmission
is in reverse.
[0126] In one such embodiment, Control module 12 includes a driver
performance log. This is similar to the system used for the
on-board computer interface, where Control module 13 actually
collects and stores data that pertains to driver performance. For
example, if a driver turned on his right turn signal and there was
something over on his right hand side, Control module 13 extracts
information from the scenario. If the driver turns off the signal,
the result is stored. On the other hand, if there is an accident
those results are also stored in the computer. The fleet owner can
go in and retrieve the stored information and find out really what
happened.
[0127] In yet another embodiment, as is shown in FIG. 10, sensors
14 are mounted toward the top and bottom of the back end of the
vehicle. Vehicles such as RVs can have a problem when pulling into
low overhang areas, low clearance areas, like with trees, large
tree branches, etc. This embodiment places additional sensors up
top, and can actually detect high up that there's a problem.
[0128] A system such as is shown in FIG. 10 may be used on a
variety of vehicles. Sensors 14 at the top of the vehicle alert the
driver of obstacles that may cause damage near the top of the
vehicle. These obstacles may be trees, storage shed doors, or other
similar objects. Sensors 14 at the bottom of the vehicle are
re-oriented to provide a wider dispersion angle from high to low as
opposed to their normal wide dispersion from left to right. With
this change in orientation, this system is also able to triangulate
on objects above the vehicle such that the system can calculate
available clearance and compare it with required clearance (which,
in one embodiment, is programmed into memory) for the vehicle.
[0129] Additional indicators on the operator interface 32
communicate to the driver whether an obstacle to the rear of the
vehicle was detected by the High Transducer Assemblies or the Low
Transducer Assemblies.
[0130] If the available clearance is less than the required
clearance, in one embodiment, an Emergency Alarm is sounded to
alert the driver to take action before damaging the vehicle. In
this special case, an additional indicator on the operator
interface 32 flashes to inform the driver that the alarm was caused
due to lack of clearance.
[0131] In the example shown in FIG. 10, the motor home is backing
under an overhanging building roof 62. Based on the known position
of the Low Transducer above the ground and the position of the High
Transducer above the ground, the MicroController in the control
module 12 can calculate the distance of the roof overhang above the
ground. Based on the required clearance, which is programmed into
the Memory of control module 12, the system can detect whether
there is sufficient clearance for the vehicle. If there is not
sufficient clearance, the Emergency Alarm will sound.
[0132] In another embodiment, systems 10 or 30 can be mounted on
farm trucks. Farm trucks are often pulling up into close spaces
with loading and unloading equipment, grain augers and whatever,
and in some cases even have to straddle a grain auger in order to
dump a load so that the grain auger can take the load away. And
that's a tough maneuvering situation. In one embodiment, software
is provided which not only prevents accidents but also helps guide
them into some of those tight maneuvering situations. In the
software, systems 10 and 30 sense the equipment the vehicle is
trying to mate with and guides the driver such that they stay
centered on that equipment. Such a system is shown in FIGS. 11 and
12.
[0133] A grain auger example is given in FIG. 12. The example shown
is that of a farm truck preparing to dump grain into a grain auger
55. To assist in guiding the truck up to the grain auger 55, the
driver will activate a TruTrack switch on operator interface 32. As
the vehicle approaches the grain auger 55, the system will
automatically measure the distance to the auger 55, will calculate
the transverse location of the auger 55, will display this location
on the bar graph, and will display the distance on the digital
readout on the operator interface 23.
[0134] In this example, the right rear Transducer has detected the
auger 55 at a distance of 6.0 feet. The left rear Transducer has
detected the auger 55 at a distance of 6.6 feet. The system will
automatically calculate a perpendicular distance of 5.2 feet. The
system will also calculate the transverse location and display it
on the bar graph as slightly right of center. With this
information, the driver can make minor maneuvering corrections to
keep the auger 55 centered.
[0135] In one embodiment, as is shown in FIG. 13, Side Display
Module 36 provides visual feedback to the driver when looking in
the direction of either side view mirror. These modules may be
mounted on the edge of the side view mirrors, or they may be
mounted inside the cab in the approximate line-of-sight as the side
view mirrors.
[0136] The Side Display Modules 36 (FIG. 13) consist of a plastic
housing, a small PCB Assembly with five LED indicators, two
half-inch high seven segment displays, a cable which runs into the
cab and connects to the rear of the Control module, and a clear
plastic cover on the front of the module. The Display Module 36
mounted on the left side of the cab is identical to the module
mounted on the right side of the cab.
[0137] The seven-segment display drivers and LED driver will be
located in the Control module. The above diagrams show a distance
reading of twelve feet (12'). Distance readings associated with the
Forward-Looking Detector Subsystem will not be displayed on the
Side Display Modules. Only Backup Mode rear distance readings will
be displayed. If an alarm condition exists anywhere around the
vehicle, all five LED's will flash. The LEDs are not meant to
provide any detector-specific information. Similarly, in one
embodiment, the graphics displays shown in FIGS. 6a-c will flash a
visual warning on detection of an alarm condition.
[0138] One embodiment of a system 30 for use on vehicles such as
commercial trucks is discussed below. Such an embodiment addresses
many of the safety and operation issues raised above.
[0139] System Description
[0140] The loss of life, personal injury, and property damage are
prime motivators when it comes to driver/vehicle safety
improvements. This is particularly true in the trucking industry
where continuing efforts are under way to improve driving safety
through implementation of new technology. Factors which contribute
to vehicle accidents are:
1 Speed Visibility: night, fog, rain, and snow Driver Fatigue
Highway congestion
[0141] Recent technology advances are available which could provide
a positive influence on these factors by providing warnings to the
operator and reduce the probability of and/or the intensity of a
collision. Collision avoidance is the primary goal in the
application of advanced technology. Collision Avoidance as applied
to truck vehicles can be defined in three categories:
[0142] Head-on and Rear-End collision warning
[0143] Backing collision warning
[0144] Lateral collision warning.
[0145] The purpose of the Collision Warning System is to monitor
the area around a large vehicle and provide warning to the operator
of the presence or approach of an object in the roadway, such as, a
vehicle or pedestrian, and the potential for a collision with that
object if action is not taken. The Collision Warning System must
also provide the operator with the distance to the object, its
speed of approach and classification. The Collision Warning Systems
consist of a display, a control module (CM) and a combination of a
Forward Looking Detector (FLD), a Proximity Detector (PD) and/or a
Rear Guard Detector (RGD). FIG. 1 presents the system concept for
the Collision Warning System.
[0146] Forward Looking Detector
[0147] The purpose of the forward looking detector is to monitor
the area in front of the vehicle, to detect objects in the path of
the vehicle that represent potential accidents, and to provide
distance and speed information to the CM.
[0148] Two radar modules 14.2 are mounted on the cab roof or lower
(bumper being the lowest mounting position), and aimed in the
direction of the truck's forward motion to detect objects in the
path of the vehicle. FIG. 14 shows the location of the detectors
14.2 on the cab and the area of coverage. Detector data is provided
to the control module where it is processed and the pertinent
information is displayed to the operator for his action.
Computations are performed on detected objects to determine their
position, size, speed and direction of travel. Time to impact will
be determined for those objects that are determined to be on a
collision course with the vehicle.
[0149] The FLD 14.2 must operate reliably in a complex environment
consisting of:
[0150] Varying rates of speed
[0151] Rural, urban, and freeway conditions
[0152] Straight stretches of road as well as curves in the road
[0153] 2 lane, 4 lane, 6 lane and off-road conditions
[0154] Divided highways with a median or barricade
[0155] Level roads, uphill roads, and downhill roads
[0156] Extreme variations in environmental conditions.
[0157] There are two modes of operation required. The Primary Mode
which is concerned with the potential for accidents directly in the
path of the vehicle, described above, and the Secondary Mode which
includes the Primary Mode plus detection of objects to the right of
a snow plow that could impact a wing plow.
[0158] Proximity Detector
[0159] The PD is designed to detect objects in the immediate
perimeter of a tractor-trailer. Radar modules are mounted in an
array around the periphery of the cab and trailer. FIG. 15 shows
the location of each radar module and the area of coverage. The
proximity detector modules detect objects in the perimeter field
and provide the data to the control module for processing. After
pertinent data is derived, it is sent to a display where the driver
is alerted to take appropriate action to avoid a collision. The
front modules will look for small children or objects immediately
in front of the vehicle. The right and left side mounted modules
will detect vehicles, pedestrians, and objects that may not be
clearly visible to the driver. The rear mounted modules will
monitor the area directly behind the vehicle.
[0160] A special case on snow plows requires that the center rear
mounted RM be used to measure time-to-impact for vehicles
approaching from the rear. The CM will activate a pulsed high
intensity light to warn the driver of the on-coming vehicle of the
presence of the snowplow.
[0161] The PD Modules are selectively activated by control signals
sent by the CM. The conditions under which they are activated
include:
[0162] Activate front PD Module group when speed is under five
mph.
[0163] Activate rear, left and right PD Module groups when the
transmission is in reverse.
[0164] Activate left or right PD Module group when left or right
turn signal is turned on.
[0165] Activate right, left, and front PD Module groups when the
three way mode is selected.
[0166] BIT initiation.
[0167] Master Clear: initializes all electronics in the proximity
detector.
[0168] Rear Guard Detector
[0169] The Rear Guard Detector 160 is functionally the same as the
Proximity Detector. The main difference is that the RGD 160 covers
the peripheral area around the trailer only. It is a portable
system which can be moved from trailer to trailer and works in
conjunction with the CM in the cab. Being portable, the RGD is self
powered and a RF link has been added to communicated with the CM in
the cab. Configuration, location, and area of coverage are shown in
FIG. 16.
[0170] The functional interface for the RGD is identical to the PD
except that the interface uses a RF link to transmit data to the CM
rather than a hard-wired connection. The CM sends activation
signals as follows:
[0171] Activate rear, left and right RGD Module groups when the
transmission is in reverse.
[0172] Activate left or right RGD Module group when left or right
turn signal is turned on.
[0173] Activate right, left, and front RGD Module when the three
way mode is selected.
[0174] BIT initiation.
[0175] Master Clear: initializes all electronics in the RGD.
[0176] Detailed functional descriptions for each of detector
subsystems are provided below.
[0177] Radar Module
[0178] The Radar Modules are a combination of motion sensors
available off-the-shelf, an amplifier and a signal processing chip.
They come in three configurations: Type A with a motion sensor, an
amplifier and a microcontroller; Type B with a motion sensor and an
amplifier; Type C with a motion sensor with a big antenna, an
amplifier and a microcontroller. A notional diagram of the Type C
RM Interface Board 170 is shown in FIG. 17. The motion sensors are
microwave motion sensors that operate in X-Band frequency range.
These modules utilize a dielectric resonator oscillator and a
microstrip patch antenna to achieve low current consumption, high
temperature stability, high reliability, and flat profile.
[0179] The radar modules for the PD and RGD systems will come in
two generic types. Type A will include the radar, an op-amp
circuit, and the RM interface board. Type B will include the radar
and an op-amp. Up to two type B RMs can be connected to a Type A.
The connection between a Type A and Type B will be a 4-wire cable.
The 4-wire cable will be for +12 volts, two for signal, and
ground.
[0180] The housing for the Type A and Type B RMs should be similar
or the same. The Type A will have two connectors for the Type B
inputs and one connector for connection to a serial port and for
power. The Type B will have one connector for output and power.
[0181] A Type A RM will distribute power to a maximum of three
radar motion sensors, the onboard motion sensor and two Type B RMs.
The Type A will use up to 10 A/D ports on a microcontroller and
sequentially sample data from each attached motion sensor. The Type
A will also perform a 64 point FFT on each set of 5 kHz sampled
motion sensor data. The first 20 samples from the FFT results will
be output via a serial channel. The location of all sensors is
important to the operation of the data fusion system. A typical
installation will only use five Type A's but there is really no
reason why all the sensors could not be Type A's. They can be put
in any PD or RGD position.
[0182] At installation the installer will set the CM into
installation mode and select on the menu, through the programmer,
the position of the first RM, Type A or B. The installer will then
approach the selected sensor location and wave his/her hand within
one inch in front of the antenna housing, until a tone is heard
from the CM and stop for five seconds and repeat the waving. A tone
will sound and the installer will repeat this step. The installer
will repeat the intermittent waving until the system gives a three
beep OK response. This will typically take only waving at the
sensor twice. The installer will then proceed to the next RM. All
RM's will be programmed in this fashion. This will allow the CM and
Type A modules to coordinate the location of each sensor.
[0183] At installation, the software in the CM will send an
initialization serial message to all Type A modules. The software
on the microcontroller will look for this message if it has not
been assigned an address. Upon receiving this message the software
will perform a 64 point FFT every 300 milliseconds. The first 20
samples out of the FFT will be sent back to the control module if
one of these samples crosses a threshold. The CM will use this data
to identify the RM which responded to the installer. Once the
installer has gotten the three beep OK, the CM will send out an
address number (1 to 15) to identify the RM's position (see FIG.
15). The CM will also send out the Type A's position along the
truck, height, transverse distance from the left front corner of
the truck, and distance from the front of the truck. The Type A,
will accept this data and store it in EPROM. The Type A which is
being positioned will then store the port number (connector) on
which the signal was being received. This will allow the Type A to
respond to this port number's address when polled by the CM.
[0184] The position of the sensors with respect to the tractor will
be communicated to the CM, by the Type A's, upon startup. When the
CM initializes the system the RM's will be polled (1 through 15).
Each Type A module will respond when its number or the number of an
attached Type B, is polled. The Type A module will send out
location and other information about the RM.
[0185] The Type C RM is similar to a Type A. It contains the radar
motion sensor, with a 16.times.2 pad antenna. The software samples
256 points of data from the onboard sensor. The data is fed to a
256 Point FFT. The first 128 samples from the FFT results will be
output via a serial channel. To distinguish between left and right
Type C, the last pin on the left connector will be shorted to
ground. This pin will not be used for anything else (power or
signal). The wiring in the FLD enclosure will be fixed such that it
cannot be confused and reversed. The FLD uses two Type C RMs.
[0186] One rear guard RM (#14-14) (the center one) will be
configured to search a shorter range to assist in increasing
back-up range accuracy. This RM must be a Type A RM. The CM will
command this RM to sample either a unity gain op-amp channel or to
sample the normal gain op-amp channel (every Type A will be able to
do this). This will allow the RM to be used for long-range
detection when the vehicle is not in reverse and short-range
measurements when the vehicle is in reverse. This same command from
the CM will change the sampling rate on the A/D unity gain channel
to 2 kHz when in reverse (provides a 2.5 times finer measurement of
vehicle speed).
[0187] Power Distribution
[0188] The power distribution plan 180 is shown in FIG. 18. The
vehicle battery powers the CM. The +12 volts is filtered and fused
in the CM. The +12 volts is then supplied to the FLD and any Type A
RM on the cab or truck without a trailer. Trucks with a trailer
will have power to all cab Type A RMs and to a transceiver. The
trailer will use either a set of PD's or an RGD. The PD's will use
the trailer's +12 power to supply the Transceiver/power convert
module. This module will filter and fuse the +12 volts and convert
the power to +3 volts for the transceiver and send the +12 volts
out. The +12 volt power will then be sent to all trailer Type A
modules. The Type A and B modules will DC to DC regulate the +12
down to +5 volts. The RGD is powered by its own battery and will
distribute power from this 12 volt battery the same as the PD.
[0189] Cabling
[0190] The communications signals between the modules are shown in
FIG. 19. Type B's send audio frequency signals to the Type A's.
Type A's send RS-485 at 19,200 Baud to either a transceiver or the
CM directly. The RS-485 cabling is T'ed between the Type A modules.
Type C's send data over a 400 Kbaud RS-485 interface. All RS-485
interfaces are two way.
[0191] The cabling between the Type A and Type B consists of four
wires: +12 volts, ground, and two for Signal. The cabling between a
Type A and the CM or a transceiver is four wires: two for RS-485,
+12 volts, and ground. The cabling between a Type C and the CM is
four wires: two for RS-485, +12 volts, and ground. The cabling
between a transceiver and the CM is four wires: two for RS-485, +12
volts, and ground. The pin configuration for the connectors is
shown in FIG. 20.
[0192] Calibration
[0193] At the time of manufacturing testing the Radar Modules may
need to be calibrated. A calibration fixture consisting of a fan
permanently mounted to one end of a rectangular tube assembly will
be used to program a gain characteristic number into the sensor
microcontroller memory. This will be done for Type A and C modules.
The coding in the microcontroller will be put in manufacturing mode
and will expect a specific return from the test assembly. A number
denoting the difference between the expected and the measured
value, to the nearest dB, will be stored. This will be sent via the
header message to the CM for use in signal processing.
[0194] Microcontroller Firmware
[0195] The microcontroller will perform the following functions in
firmware:
[0196] 1. Manufacturing test Calibration data storage
[0197] 2. Installation Initialization
[0198] 3. 2-way Serial Communications
[0199] 4. Multi-channel A/D
[0200] 5. 256 or 64 point FFT
[0201] 6. Command Logic Processing.
[0202] Forward Looking Detector Functional Description
[0203] The FLD consists of two Type C Radar Modules. The Block
diagram of the FLD 190 is shown in FIG. 21.
[0204] These two sensors are narrow beam motion sensors. The
beamwidth is 8.5 degrees at the 3 dB point of the antenna pattern.
The two sensors are pointed across each other as shown in FIG. 10.
This results in a 0 to 10 dB antenna pattern change for both of the
sensors focused in a 10 foot column 300 feet in front of the track.
The difference in antenna pattern gain will be used to
differentiate between objects directly in front of the truck and
objects not directly in front of the truck.
[0205] The RM alignment for the FLD 190 is shown in FIG. 22. This
alignment is such that the antenna gain is 10 dB lower than the
peak at the edge of a 10-foot by 300-foot rectangle.
[0206] Interface Board
[0207] The Interface Board is built into the FLD Type C RM and is
the primary interface between the RM and the CM. The Interface
Board uses chips from MicroChip Development Systems. These
MicroChip chips will be used to perform the A/D, FFT/signal
processing, and communications formatting for the messages. The
messages will either be parallel or serial depending on the most
cost-effective method that meets the FLD to CM data rate
requirements. These chips are powered by a +5 volt DC source and
are programmable in C and assembly language. The Interface Board
performs four primary functions:
[0208] Timing: generate on/off power pulses to the radar modules
for either minimization of power consumption or to meet FCC
regulations. Timing between the two MicroChip A/D chips is handled
by handshaking with the CM. This timing controls the sampling, FFT,
and data transfer to the control module. Sample time for each FLD
sensor is 25.6 ms for 256 samples of data at 10 kHz. Using two FLD
sensors collecting data simultaneously and combining the data in
the control module, the overall sensor report data rate would be
approximately 50 milliseconds.
[0209] A/D: Digitizes the FLD radar data. The A/D function performs
a ten-bit quantization of the incoming analog data. Individual
MicroChip A/D processors are used for each FLD sensor. This allows
minimal latency and a faster overall sampling rate. Two channels
will be used on the A/D. The first channel will sample a high gain
op-amp output. The second channel will sample a low gain op-amp
output, with the third channel sampling the lowest gain op-amp. The
fourth and fifth channels will be used to set the reference voltage
on the A/D. This will provide for 90 dB dynamic range when using a
10-bit A/D.
[0210] FFT: Performs a standard 256 point FFT using the 256 samples
collected. Only lower 128 points are returned to the control module
(this corresponds to a 1.25 mph per Doppler bin closing rate
resolution). (This is subject to change based on the speed of the
MicroChip processing. If processing is too slow in the MicroChip,
the FFT will be preformed in the CM and 256 samples of data will be
transferred).
[0211] Communications with the Control module: Provides a serial
data interface.
[0212] The MicroChip PIC17C756 series chip will be used for the
Type C radar Module. This chip requires one oscillator at 33
MHZ.
[0213] Data Communications
[0214] The first 128 samples from the FFT results, from each Type C
in the FLD, will be output via a serial channel. This channel will
be a two way communications link with the CM. When the data is
ready, finished the FFT, the chip will wait for the command to send
the data. The data (256 bytes) will be transferred in less than 10
milliseconds. This equates to a data rate of 257,000 Baud of
unpacked data. Each pair of bytes will contain one 16-bit point of
the FFT output. A header message will accompany the data,
identifying the RM being sampled. The Interface Design
Specification will define this message.
[0215] Circuit Design
[0216] The Type C RM consists of two major parts, the off-the-shelf
motion sensor and the interface board. The interface board will be
manufactured by ATI (Altra Technologies, Inc., 18220 South Shore
Lane W., Eden Prairie, Minn.). It is a 4-layer board approximately
4" by 3". It contains one MicroChip PIC17C756 chip, an op-amp and
various discrete components. It is wired to a five-pin connector on
the RM housing.
[0217] Proximity Detector Functional Description
[0218] The purpose of the PD is to monitor the area around the
periphery of the vehicle by detecting objects that could
potentially be struck by the vehicle if it moved left, right or
back and to provide distance information to the CM. FIG. 23
presents the Block diagram for the PD 230.
[0219] The PD uses Type A and B Radar Modules. This array of radars
will be interconnected in groups of up to three radars to a RM
Interface Board which is used to sample all three RMs
simultaneously and send the processed data to the CM upon request.
The multi-port interface card in the CM will cycle through each
device sampling the information. As in the FLD, the object signal
data from the RMs is digitized and sent by wire link to the CM for
processing. The CM will control the sampling. FIG. 24 is a diagram
of the timing for a single RM interface board and the associated
RM's. The only unknown time is the time for performing the FFT and
associated formatting of the data. It is not believed that this
time approaches the idle time for the interface board.
[0220] The individual sensors are switched on for 12.8 milliseconds
every 333 milliseconds (more than one sensor group will collect
data at the same time). They are sampled at 5 kHz, giving 64
samples of data. The CM multi-port Interface Card sequences through
the PD RM interface boards until all fifteen RMs have been sampled.
This function is repeated every 333 milliseconds.
[0221] An installation of the PD on a Cab and Trailer rig will
require an RF link between the trailer and the cab. The transceiver
at the trailer will contain a power supply to derive +3 volts from
the trailer power of +12 volts.
[0222] Hardwired installations will use a 4-wire cable between the
CM and the Type A RMs. The 4-wire cable will carry: +12 volts;
power ground; two wires for the two-way serial communication.
[0223] Type A Radar Module
[0224] Interface Boards are built into the Type A Radar Module and
they are the primary interface between groups of RMs and the CM.
The Interface Board uses a MicroChip chip in the same family as
described in Section 3.2 and performs similar functions. The
physical layout of the Type A module is shown in FIGS. 25A and 25B.
FIG. 25A is a side view of the Type A module layout and FIG. 25B is
a top View of the Type A module layout. The Interface Board
performs the following functions:
[0225] MicroChip
[0226] The MicroChip PIC17C756 series microcontroller chip will be
used for the Type A radar Module. This chip requires one oscillator
at 4 MHZ. Using a serial EEPROM, the microcontroller will have
identification encoded in it to provide RM ID back to the CM and
know when to respond to CM commands.
[0227] A/D
[0228] The A/D function of the MicroChip will use up to 10
channels, sampling at a rate of 5 kHz for 64 samples. The A/D will
be switched on and off via the software in the MicroChip. The
collection will be synchronized with the other Type B RMs connected
to the Type A (see 24). The 10 channels used on the A/D, are three
for each Type B motion sensor and four for the on-board Type A
motion sensor. The first channel of the three for a motion sensor
will sample a high gain op-amp output. The second channel will
sample a low gain op-amp output, with the third channel sampling
the lowest gain op-amp. This will provide at least 90 dB of dynamic
range necessary for close approach of objects. The channels will be
examined and when the high gain channel is at its maximum value,
the second channel will be used in the signal processing.
[0229] When in the reverse gear, the center rear facing RM will be
set to use the unity gain op-amp only. This sensor will be sampled
at a 2 kHz rate to get more precise measurement of vehicle
speed.
[0230] FFT
[0231] The software samples 64 points of data. This data is fed to
a 64 Point FFT. At this time it is believed that the PIC17C756
series of chip is capable of performing a 64 point FFT in the
required time.
[0232] Data Communications
[0233] The first 20 samples from the FFT results, for each attached
RM, will be output via a serial channel. This channel will be a
two-way communications link with the CM. When the data is ready,
finished the FFT, the chip will wait for the command to send the
data. The data (60 bytes) will be transferred in about 30
milliseconds. This equates to a data rate of 19,200 Baud. A header
message will accompany the data, identifying the RM being sampled.
The Interface Design Specification will define this message.
[0234] System Operation
[0235] Multiple Radar Modules
[0236] The PD consists of multiple Type A and Type B radar modules.
Possible PD RM combinations include at least one Type A and up to
two Type B modules. Upon initialization in the CM, the CM will poll
for each Type A RM. The Type A RM when first powered up will check
the two ports for Type B RMs and detect the existence of a RM. This
data will be reported back during the CM's initial poll. The CM
will build a table in RAM of each RM and its position, for use when
performing other detection and tracking functions.
[0237] The Type A RM's will have a code that will indicate to the
CM the location of each RM in its suite. The Type A RM will respond
to the CM commands when it receives a message with its address in
the header. These messages will be defined in the Interface Design
Document.
[0238] The Radar Modules will be positioned around the truck
according to the diagram in the System Specification. The RMs on
the side of the truck should not be more than 25 feet apart and not
closer than 10 feet. The RMs on the rear should be spaced such that
one is at the center and the others are as far on the edge as
possible.
[0239] System Timing
[0240] The System Timing is shown in FIG. 26 (for 2-Type A's
connected to 2-Type B's each). The data collection takes 12.8
milliseconds for each RM. The signal processing takes X
milliseconds per RM. The total data collection time and processing
time for 15 RMs is X milliseconds. The data transmission time is
160 milliseconds. To conserve time the transmission of data will be
going on from one set of RM's while another is collecting and
processing data.
[0241] The timing of the PD RM's will be integrated into the timing
of the FLD when the FLD is in operation. The CM will poll the FLD
and receive an 8-millisecond burst of serial data. The CM will then
poll one Type A PD RM and get up to 30 milliseconds of data. The CM
then does signal and data processing for 12 or more milliseconds,
processing the downloaded data. 50 milliseconds after the system
polled the FLD, it repeats this sequence.
[0242] System Interface
[0243] PD to Control Module
[0244] The following data will be transferred at 19,200-Baud or
faster.
[0245] Digital Object Data--Provides digitized object data from
each detector for signal processing analysis in the control module.
64 samples are collected over 12.8 milliseconds per RM. 20 samples
per RM are sent to the CM every 333 milliseconds. The 333
milliseconds will also be used for control transfer and other data.
When used with a trailer, the signals will be transferred via an RF
link for the trailer RM interface boards. The three RM interface
boards on the trailer will be wired to a transceiver and a
transceiver will be installed on the cab that is connected to the
CM. The cab RM interface boards will be hardwired to the CM.
[0246] BIT--Sends PD operational status data to the Control
Module.
[0247] RF Link
[0248] The RF Link to the trailer installation will use an RF
transceiver modem. The design of the PD will be set for a 19,200
Baud link (5 kHz sampling and 20 samples transferred). 20 samples
at 5 kHz represent 40-mph coverage with a 2-mph resolution.
[0249] The RF Link consists of a modem and a transceiver function.
The system currently under consideration contains an internal
battery which will last for years (advertised time with system
mostly in receive). It is anticipated that in the PD application
this battery will be replaced by a DC to DC 3 volt regulator
deriving power for the transceiver from the truck battery.
[0250] The modem provides two way serial communications. RS-485 is
the electrical interface for the serial link. The RF Link will
require a 6-inch antenna at both the tractor and the trailer. The
typical range for the link is 150 feet. If two antennas are mounted
on either side of the trailer at the rear or one antenna on the
front of the trailer and the top of the cab, the link will be able
to handle any size truck.
[0251] The manufacturer of the Transceiver is Axonn. Their address
is:
[0252] Axonn
[0253] Suite 202
[0254] 101 W. Robert E. Lee Blvd.
[0255] New Orleans, La. 70124
[0256] Phone (504) 282-8119
[0257] They have a product, the AX-550, which exceeds the
requirements for range. A new product is due out soon, which will
be less power. Two units per system are needed for either the PD or
the RGD.
[0258] The trailer mounted transceiver module in the PD application
will also provide the power filtering, fusing and regulation for
the trailer mounted PD radar modules.
[0259] Rear Guard Detector Functional Description
[0260] The Rear Guard Detector (RGD) is the functional equivalent
of the PD system for the trailer only. It's designed to be portable
and can be moved from trailer to trailer. Communications with the
CM in the cab will be made over a wireless RF data link. The RGD
purpose is to monitor the area around the periphery of the trailer
and to detect objects that could potentially be struck by the
vehicle as it moves left, right or backward and to provide object
distance information to the CM. The functional design for the RGD
270 is shown in FIG. 27.
[0261] The RGD has Type A RM located in the center of the three
rear facing sensors, and one for the pair of radar modules on the
right and one for the pair of radar modules on the left. The Type A
RMs output data into a RGD interface/transceiver, which sends the
signal to the front cab. In the tractor a transceiver picks up the
signal and converts it to a digital serial input to the CM.
[0262] A battery will be provided to power the RGD. This battery
will be rechargeable and have a 5 Amp Hour capacity for a 25-day
interval between recharging.
[0263] The RGD subsystem will be configured with three, five, or
seven sensors. All of the RMs are mounted on one multi-detector
array and will be mounted at the rear of the trailer. No electrical
connection to the trailer will be required since it has a
self-contained battery pack.
[0264] Interface Board
[0265] MicroChip
[0266] The MicroChip PIC17C756 series chip will be used for the
Type A Radar Module. This chip requires one oscillator at 4 MHZ.
The MicroChip will have identification encoded in it to provide RM
ID back to the CM and know when to respond to CM commands.
[0267] A/D
[0268] The A/D function of the MicroChip will use up to 10
channels, sampling at a rate of 5 kHz for 64 samples. The A/D will
be switched on and off via the software in the MicroChip. The
collection will be synchronized with the other Type B RMs connected
to the Type A (see FIG. 27). The 10 channels used on the A/D, are
three for each Type B motion sensor and four for the on-board Type
A motion sensor. The first channel of the three for a motion sensor
will sample a high gain op-amp output. The second channel will
sample a low gain op-amp output, with the third channel sampling
the lowest gain op-amp. This will provide at least 90 dB of dynamic
range necessary for close approach of objects. The channels will be
examined and when the high gain channel is at its maximum value the
second channel will be used in the signal processing.
[0269] When in the reverse gear, the center rear facing RM will be
set to use the unity gain op-amp only. This sensor will be sampled
at a 2 kHz rate to get more precise measurement of vehicle
speed.
[0270] FFT
[0271] The software samples 64 points of data. This data is fed to
a 64 Point FFT. At this time it is believed that the PIC17C756
series of chip is capable of performing a 64 point FFT in the
required time.
[0272] Data Communications
[0273] The first 20 samples from the FFT results, for each attached
RM, will be output via a serial channel. This channel will be a
two-way communications link with the CM. When the data is ready,
finished the FFT, the chip will wait for the command to send the
data. The data (60 bytes) will be transferred in about 30
milliseconds. This equates to a data rate of 19,200 Baud. This chip
performs a 10-bit A/D and 16-bit FFT. A header message will
accompany the data, identifying the RM being sampled. The Interface
Design Specification will define this message.
[0274] System Operation
[0275] Multiple Radar Modules
[0276] The radar modules used in the Rear Guard will be the same as
the PD. The RGD has a special condition where one Type A module can
be installed in the middle of the rear facing mounting bracket and
the signal processing in the CM will be set to give longer range
performance for a snow plow application.
[0277] System Timing
[0278] The functional interface for the RGD is identical to the PD,
including the use of the MicroChip chip set.
[0279] System Interface
[0280] RGD to Control Module
[0281] Digital Object Data--Provides digitized object data from
each detector for signal processing analysis in the control module.
64 samples are collected over 12.8 milliseconds per RM. 20 samples
per RM are sent to the CM every 333 milliseconds. The 333
milliseconds will also be used for control transfer and other data.
The RGD will use the same RF link as the PD.
[0282] BIT--Sends RGD operational status data to the CM.
[0283] RF Link
[0284] The RGD is equipped with the same RF link as is available on
the PD. A rechargeable 12-volt battery powers the RGD RF Link. The
power distribution from the trailer transceiver is the same as the
PD's. The RGD has a sleep mode to conserve battery power. If an
activation signal is not received by the RGD for 20 seconds the
system will go into standby or sleep mode. The CM will send out an
activation command every five seconds when the RGD should be
operational. The RF transceiver module on the trailer and the
microcontroller in each Type A RM controls the sleep mode. The RF
transceiver and microcontroller will have a sleep mode watch dog
timer set to two seconds. When in sleep mode the transceiver will
activate and search for a receive signal. The CM will command a
repeated transmit signal until the sleep mode stop data word is
received. This signal will be used if it has been over 20 seconds
since the RGD sent data to the CM. The receiver in the trailer
transceiver will come on for two milliseconds and search for the
transmit signal. If one is received the transceiver will activate a
serial message (controlled by the CM) to wake up the
microcontrollers. When all microcontrollers have reported back the
RGD operation will start. The entire wake up procedure will not
take more than four seconds and will usually take less than two
seconds. The duty cycle is 1% while in sleep mode for power
conservation.
[0285] Control Module Functional Description
[0286] The CM is a customized PC. Processor speed, memory, and
interface drivers will determine the CM configuration based on a
nominal set of performance requirements and hardware/cost
tradeoffs. A functional diagram of the CM 280 is shown in FIG. 28.
The CM 280 consists of two primary elements: an Interface Card 282
and the Processor Board 284.
[0287] CM Multi-Port Interface
[0288] The CM multi-port Interface 282 buffers the incoming data
from the FLD 281, PD 283 and RGD 285, routes it to the Processor
Board 284, and routes control signals from the Processor Board 284
to the FLD 281, PD 283 and RGD 285. The CM Multi-port Interface 282
routes the FLD Doppler spectrum to the Object Data Processing
module 288 on the Processor Board 284. It also routes the PD and
RGD Doppler spectrums to the Detection Processing module 286 on the
Processor Board 284.
[0289] Signal/Data Processing Functions
[0290] The CM performs the following signal/data processing
functions: Object Data Processing (FLD only), Track Report
Generator (FLD only), Detection Processing (PD and RGD only), Data
Fusion, Situation Report Generator, Display Driver, and System
Control. The Display Driver and the System Control function are the
responsibility of ATI and will not be discussed in this document
except where an interface exists with one of the other functions.
The remaining functions are shown in FIG. 29 and discussed
below.
[0291] Object Data Processing
[0292] The Object Data Processing module receives the 128 samples
of FFT'd data (frequency domain signal) from each radar module. It
processes these samples (256 per cycle) and determines the
existence of objects for reporting (see FIG. 30). A cycle for the
FLD is 50 milliseconds. The two forward looking radar modules are
treated separately for clutter removal. They are combined in the
Multi-Object Detector. The Object Data Processing module will
output detections/velocities, associated signal strengths, pulse
timing data, clutter estimates and clutter distribution.
[0293] Clutter Reduction
[0294] The frequency domain signal will be analyzed and the clutter
removed individually for each sensor. The clutter is removed in
four steps. These four steps are discussed in detail below. It
should be noted that to perform accurate calculations in this
process the height of each RM antenna is required along with the
dimensions of the truck and the location of each sensor. This
information will be programmed in the CM at the time of the system
installation.
[0295] Threshold Computation
[0296] The first step is to compute a threshold versus frequency
(speed) for the received spectrum. This set of numbers (128, one
for each sample) is computed from the speed of the truck and the
height of the sensor above the road. The road will reflect a
certain amount of energy back to the sensor. Each road surface type
will reflect a different amount but an average amount of reflection
will be used since height above the road is dominant. The frequency
spectrum of the clutter is related to the speed of the truck and
the distance to the road. The height of the sensor will be the
strongest return and it will be at 0 Hz in the spectrum. The 38.75
Hz return (1.25 mph) will be from a distance where the velocity
component of the road is 1.25 mph. The bin spacing is 38.75 Hz,
thus the first 1.25 mph will appear in the first bin. The next
spectral bin will be from 1.25 mph to 2.5 mph and so on. The
distance to the road for each frequency will be pre-computed and an
equation for clutter will use the resulting values. The values in
this equation are sensor height and truck speed.
[0297] The Average Spectral Power is given by: 1 P i = j = i - N /
2 i + N / 2 S j N ( 1 )
[0298] Where
[0299] P.sub.i is the i.sup.th Doppler bin's average power
[0300] S.sub.j is the j.sup.th Doppler bin's power
[0301] N is the size of the sliding window (Note: at either end of
the spectrum, i=0 to N/2 or 255-N/2 to 255, N/2 points will be
used).
[0302] The threshold for each bin (sample) is
T.sub.i=T.sub.m*P.sub.i (2)
[0303] Where T.sub.m is the threshold multiplier.
[0304] This value (T.sub.m) will start as 3 dB but it will be
determined through lab and initial field-testing. The result of
this multiplication is then multiplied by the truck speed based
road surface clutter.
[0305] This is given by: 2 M i = ( cos ( sin - 1 [ ( i * 38.75 ) /
( v t * 31 ) } h ) 4 ( 3 )
[0306] Where
[0307] M.sub.i is the i.sup.th Doppler Bin's road clutter
multiplier
[0308] V.sub.t is the truck speed
[0309] h is the mounting height of the RM
[0310] Thus the threshold is modified to:
Ti=Ti*M
[0311] Rain Clutter Removal
[0312] Removal of weather related clutter will be done in steps two
and three. Rain clutter produces a distinct pattern in the
frequency spectrum. The 128-sample frequency spectrum will be
examined for this pattern. If found, the threshold values at the
frequencies where rain is present will be adjusted for the presence
of rain.
[0313] The pattern is recognizable over time. Distinct lines at a
constant velocity and no real discernable change in signal strength
over several seconds will denote rain. This condition will be
flagged and the most prevalent frequencies will be marked.
[0314] Snow Clutter Removal
[0315] Snow will appear as colored noise. Several frequencies may
have more noise than others, but in general the average noise will
go up throughout the spectrum. The thresholds will be adjusted
accordingly.
[0316] Object Clutter Removal
[0317] Step four is the search for specific clutter from stationary
objects. This will be done by comparing the returns of both sensors
at the same frequencies.
[0318] Course Clutter Removal
[0319] for all frequency bins 3 { if S 1 i > S 2 i + 30 dB then
Fr i = TRUE ( 4 )
[0320] Where:
[0321] Fr.sub.i is the i.sup.th flag for probable road clutter
[0322] S.sub.1 is the left sensor's i.sup.th Doppler bin's
power
[0323] S.sub.2 is the right sensor's i.sup.th Doppler bin's
power
[0324] Depending on the angle to an object the frequency and
amplitude will change. Stationary objects on the side of the road
at close ranges will appear stronger in one sensor and at
frequencies lower than the speed of the truck. These objects and
their frequencies will be noted for processing later in the data
fusion function.
[0325] Road clutter from a specific object such as a sign or bridge
will appear at one frequency. As the truck approaches if the object
is on the side of the road the frequency will decrease and the
signal strength in one sensor will decrease (with respect to the
R.sup.4 curve) while the signal in the other sensor will increase
faster than expected.
[0326] Multi-Object Detection
[0327] After clutter reduction, the frequency spectrum, object
clutter candidates, and clutter thresholds will be fed into a
Multi-Object Detection algorithm. This algorithm will be used to
differentiate between multiple returns in the spectrum from objects
that are and are not clutter. This algorithm will be designed to
offer up candidate detections, which when combined with other
sensor and truck data can be used to determine the actual presence
of an object. The pair of FLD radar modules will be used in this
algorithm to differentiate between clutter and objects not in front
of the truck. Three steps are performed to find the candidate
detections.
[0328] Threshold Application
[0329] The first step is the application of the clutter thresholds
(equation 2) to the entire spectrum and the elimination of the
colored clutter.
[0330] For all Frequency Bins
C.sub.i=1 if S.sub.i>T.sub.i (5)
[0331] Where C.sub.i is one if a threshold crossing was detected at
the i.sup.th Doppler bin.
[0332] If a particular frequency bin exceeds the threshold it will
be stored for later processing as a detection candidate (C.sub.i).
If a certain segment of frequency bins produces an excessive number
of detections the thresholds will be raised (see equation 1) in
that region and the strongest detections will be reported.
[0333] Detection
[0334] The second step is to detect the threshold crossings. These
crossings will be compared to each other and to the estimated
road/object clutter data. The two sensors will be combined in this
step. After the initial clutter removal the frequency spectrums of
the two sensors will be compared for all threshold crossings. For a
candidate detection to be declared, a threshold crossing must have
occurred for each radar module at a frequency not more than .+-.1
FFT bin apart, with no more than 30 dB SNR difference (Fr
flag).
[0335] For all Frequency Bins
2 IF <NOT> Fr.sub.i IF (C.sub.Li <AND> C.sub.Ri-1)
<OR> (C.sub.Li <AND> C.sub.Ri) <OR> (C.sub.Li
<AND> C.sub.Ri+1) D.sub.i = 1
[0336] Where D.sub.i is the i.sup.th Frequency bin detection
flag.
[0337] If either condition is violated a detection will not be
declared for that threshold crossing. This step will output no more
than 15 candidate detections. The 15 candidates with the highest
frequency (fastest closing rate) will be given priority.
[0338] In the future the CM will tell the FLD when a turn is
underway and the direction of the turn. When a turn is detected the
sensor pointing in the direction of the turn will be allowed to
have stronger detections. If the sensor in the opposite direction
of the turn has a signal over 20 dB stronger that crossing will not
be accepted for detection.
[0339] If the Secondary Mode is in use this second step will allow
the radar module on the left side of the truck to have a miss match
in SNR with the radar module on the right. By allowing the left
radar module to have stronger returns it will effectively widen the
detection pattern to the right. The values for this imbalance will
be determined when the antenna patterns for the two radar modules
are provided by the manufacturer.
[0340] Pre-Tracker
[0341] The final step in the Multi-Object Detector is to eliminate
all but the five best detections. This algorithm is the first stage
of a tracker. The detections will be sorted by closing velocity and
SNR. The objects that will most likely reach the truck first will
be given highest priority. If over five detections exist the
pre-tracker will then sort the detections further. The pre-tracker
will compare the detection to objects already being tracked from
previous sensor cycles. Those detections closest to existing tracks
will receive priority within the original sort.
[0342] These detections will be "associated" with the existing
tracks. If more than one detection associates with a track the
closest detection, in speed and SNR, will be marked as the best
association with the track. More than one detection may associate
with one track. Up to five detections will be passed on. These
detections will be the objects that will reach the truck first and
have been around the longest. In all cases the shortest time to
impact will be given priority. Longevity will only be used to sort
on detections that have closing speeds within 10 mph and SNR's
within 20 dB of each other. That is if there are more than five
detections, all at about the same speed, the associated detections
with the longest track existence time will be output.
[0343] Association
[0344] for all detections--j
[0345] for all tracks--L
[0346] if
Rdot.sub.j--G.sub.s<Rdot.sub.l<Rdot.sub.j+G.sub.s
[0347] if (SNR.sub.j--SNR.sub.l)<20 dB
[0348] then Associate
[0349] Where Rdot is the closing rate
[0350] j is the detection counter
[0351] L is the current track
[0352] G.sub.s is the speed gate.
[0353] Objects extending over the track and across the road, such
as bridges and signs will require special processing. This
processing will use the combined SNR and examine stationary objects
over time. The characteristics of the SNR over time from flat or
non-complex objects such as a bridge or sign will be used to
identify these objects.
[0354] NOTE: The data collection and detection rate of the FLD is
50 milliseconds. The Data Processing, Tracking and Data Fusion
functions will use several cycles of detections to produce the best
answers. Several points need to be made clear here. First, within
the first 100 milliseconds the system can produce an alarm
condition when the appropriate time to impact is measured. Second,
the calculations for a tracking system of this type become stable
over 10 to 15 cycles, this corresponds to 0.5 to 0.75 seconds.
Third, the higher accuracy of a stable system is only required in
computing the larger time to impact numbers. Fourth, in most
conditions the stable track will allow the system to "track" an
object into the alarm area or region. The same approach is used in
the PD and RGD systems and is discussed later. These same four
points apply to the PD and RGD, except the cycle time is 6 time
longer. These systems are not measuring events that are as time
critical, since velocities in the directions being monitored are
not nearly as high.
[0355] Object ID
[0356] With a range estimate, the signal strength versus time
(scintillation characteristics) and average signal strength at an
estimated range, an ID can be computed for a tracked object. The
signal strength at an estimated range provides an estimate of radar
cross section. From this radar cross section an initial
categorization as a truck/large vehicle, a car or other can be
determined. From scintillation combined with a small radar cross
section the categorization as a human/large animal or a sign can be
determined.
[0357] First the algorithm will compare the two forward looking
radar module signals. This comparison will be a time-based
comparison of a track's speed and SNR, with the current associated
detection. Tracks, which are traveling slower then 20 mph, will be
designated human. All new tracks will be given a truck designator
until more than one cycle of data has been gathered. The SNR will
be averaged over time for each track.
RCS.sub.j={(Savg.sub.j)/R.sub.j.sup.4}.sup.1/2 (6)
[0358] Where RCS.sub.j is the j.sup.th track's radar cross
section
[0359] Savg.sub.j is the time averaged signal strength
[0360] R.sub.j is the estimated range (initialized to 300 feet for
the FLD and 25 feet for the PD/RGD
3 IF RCS.sub.j > XdB Then ID.sub.j = TRUCK ELSE IF RCS.sub.j
> YdB Then ID.sub.j = CAR ELSE ID.sub.j = HUMAN
[0361] Where XdB is the expected RCS for a truck in dB meters
[0362] YdB is the expected RCS for a car
[0363] ID.sub.j is the j.sup.th track's ID
[0364] The Object ID Algorithm will attempt to differentiate
between small objects and large objects. This algorithm will help
to eliminate false alarms from the side of the road and in front of
the truck when approaching and during a turn by identifying the
track as not a truck or a car.
[0365] A probability of correct ID and an associated confidence
level will be computed for each ID. These parameters will be set
from an equation empirically derived during testing of the
system.
4 IF ID.sub.j = TRUCK PCID.sub.j = 1 - (ZdB - Savg.sub.j)/ZdB ELSE
IF ID.sub.j = CAR PCID.sub.j = 1 - (VdB - Savg.sub.j)/VdB ELSE IF
ID.sub.j = HUMAN PCID.sub.j = 1 - (UdB - Savg.sub.j)/UdB
[0366] Where ZdB is the expected radar cross section of a truck
[0367] VdB is the expected radar cross section of a car
[0368] UdB is the expected radar cross section of a human
[0369] PCID.sub.j is the j.sup.th probability of correct ID for the
j.sup.th track.
[0370] The ID confidence is given by: 4 CF j = i = 1 N PCID ji
N
[0371] Where CF.sub.j is the confidence factor for the j.sup.th
track's ID
[0372] N is the current number of cycles tracked.
[0373] Track Report Generator
[0374] The candidate detections will be combined with the object ID
data and analyzed for the presence of an object for which a report
should be generated. Stable object reports or tracks will be
required to achieve the range estimate accuracy desired. The object
reports will be of the closest object determined to not be a false
object. There will be up to five reports every 50 milliseconds. The
object reports will be sent to the Data Fusion algorithm for
further processing.
[0375] Condition Checking
[0376] The trackfiles generated by the Multi-Object Detector
contain kinematics from previous tracks and, for each track, an
associated detection (if one was available). The track and the
detection need to be merged. The first step in merging the track
and detections is the reduction of detections associated with
track. The Condition Checking function will eliminate all but the
best detection. If more than one detection associates with a track,
this function will compare the SNR of the track to the SNR of the
Detection and compare the closing rate of the track with the
closing rate of the detection. The closest match in closing rate
with a reasonable match in SNR will be correlated with the track
and the other detections will be made available to create a new
track or correlate with another track.
[0377] For All Tracks j
[0378] For all Associations k
5 IF NA> 1 IF (Rdot.sub.j - Rdot .sub.k) < (Rdot.sub.j - Rdot
.sub.b) IF (SNR.sub.j - SNR.sub.k) < (SNR.sub.j - SNR.sub.b) b =
CRID.sub.j =k
[0379] Where b is the association number for the best correlated
detection
[0380] CRID.sub.j is the j.sup.th track best correlating
association.
[0381] The Condition Checking function will output a set of
"correlated" tracks and detections, one detection per track. There
will be up to five existing tracks and five new tracks (if all five
detections did not associate with any tracks) output from this
function. Normally there will be five correlated tracks. NOTE:
Track speed will be used to convert the detection and track closing
rate into object speed. This will prevent large changes in truck
speed from eliminating the track correlation.
[0382] Track Maintenance
[0383] The correlated track/detection data will be used to maintain
the tracks. A new track will be created from detections not
associated with tracks. New tracks will be kept for up to five
radar module cycles (50 milliseconds per cycle). If a second
detection is associated with a new track before five cycles without
an association, the new track is made a hold track. Hold tracks
must experience 10 cycles in a row of no detection associations
before they are eliminated. The Track Maintenance function will
apply these rules and output a set of trackfiles containing new and
hold tracks. The trackfiles will be identified as coming from the
FLD. (See FIG. 21, Track Report Generator Funcitons.)
[0384] Detection Processing PD and RGD
[0385] The PD and RGD are not as sophisticated as the FLD. The
clutter processing will be a simpler version of the FLD processing.
The detection process will also be a simpler version of the
Multi-Object Detection algorithm used in the FLD. The functional
design is shown in FIG. 32 and is discussed below.
[0386] Clutter Reduction
[0387] The Detection Processing module receives the 20 samples of
FFT'd data from the Interface boards. There can be up to 15 sets of
data. Each set of data will be clutter processed individually. The
clutter processing will have the same functions as described
earlier for the FLD but the functions will be adapted to the PD or
RGD requirements.
[0388] Threshold Computation
[0389] First the main difference is the clutter will have a
different spectral characteristic for each radar module view angle.
The forward looking radar modules will have similar clutter to the
FLD. The side looking sensors will have clutter which is lower in
frequency and for the radar modules closest to and viewing the side
of the road the clutter will be stronger. The rear modules will
have the most action from objects approaching the truck at low
speeds relative to the truck's speed. All of these specific
conditions will be addressed in the Threshold Computation Function
and the Road/Object Clutter Location Function.
[0390] The frequency domain signal will be analyzed and the clutter
removed individually for each sensor (see Equation 1). The clutter
is removed in four steps. The first step is to compute a threshold
versus frequency (speed) for the received spectrum. This set of
numbers (20, one for each sample) is computed from the speed of the
truck and the height of the sensor above the road. The frequency
spectrum of the clutter is related to the speed of the truck, the
distance to the road and the view angle of the radar module. The
height of the sensor will be the strongest return and it will be a
0 Hz in the spectrum. The 31 Hz return (1 MPH) will be from a
distance where the velocity component of the road is 1 MPH. The
next spectral bin will be from 2 MPH and so on. The distance to the
road for each frequency will be pre-computed and an equation for
clutter will use the resulting values (see Equation 2 except the
bin spacing is 31 Hz versus 38.75 Hz). The values in this equation
are sensor height and truck speed.
[0391] Rain Clutter Removal
[0392] Removal of weather related clutter will be done in steps two
and three. Rain clutter produces a distinct pattern in the
frequency spectrum. The 20-sample frequency spectrum will be
examined for this pattern. If found the threshold values at the
frequencies where rain is present will be adjusted for the presence
of rain.
[0393] Snow Clutter Removal
[0394] Snow will appear as colored noise. Several frequencies may
have more noise than others, but in general the average noise will
go up throughout the spectrum. The thresholds will be adjusted
accordingly.
[0395] Object Clutter Detection
[0396] Step four is the search for specific clutter from non-moving
objects. This will be done by flagging large returns (see Equation
4). Objects that are stationary will appear at specific frequencies
in the spectrum. Depending on the angle to the object the frequency
and amplitude will change. Objects on the side of the road at close
ranges will appear stronger in one sensor and at frequencies lower
than the speed of the truck. These objects and their frequencies
will be noted for processing later in the data fusion function.
[0397] Multi-Object Detection
[0398] After clutter reduction, the frequency spectrum, and clutter
thresholds will be fed into a Multi-Object Detection algorithm.
This algorithm will be-used to detect multiple objects in the
presence of road, snow and rain clutter. This algorithm will be
designed to offer up candidate detections, which when combined with
other sensor and truck data can be used to determine the actual
presence of an object.
[0399] Clutter Threshold Application
[0400] The first step is the application of the clutter thresholds
to the entire spectrum and the elimination of the colored clutter.
If a particular frequency bin exceeds the threshold it will be
stored for later processing as a detection candidate. If a certain
segment of frequency bins produces an excessive number of
detections the thresholds will be raised in that region and the
strongest detections will be reported.
[0401] Detection
[0402] The second step is to detect the threshold crossings (see
equation 5). For a detection to be declared a threshold crossing
must have occurred for one radar module. This step will output no
more than the two strongest candidate detections.
[0403] Pre-Tracker
[0404] The final step in the Multi-Object Detector is to eliminate
all but the 15 best detections. This algorithm is the first stage
of a tracker. The detections will be sorted by closing velocity,
SNR and radar module of origin. The objects that will most likely
reach the truck first will be given highest priority. If over 15
detections exist the pre-tracker will then sort the detections
further. The pre-tracker will compare the detection to objects
already being tracked from previous sensor cycles. Those detections
closest to existing tracks will receive priority within the
original sort. These detections will be "associated" with the
existing tracks (See the pre-tracker of the Signal Data Processing
Functions Section). More than one detection can associate with a
track. Up to 15 detections will be passed on. These detections will
be the objects that will reach the truck first and have been around
the longest. In all cases the shortest time to impact will be given
priority. Longevity will only be used to sort on detections that
have closing speeds within 10 mph and SNR's within 20 dB of each
other.
[0405] The Detection Processing module will output
detections/velocities, associated signal strengths, pulse timing
data, clutter estimates and clutter distribution.
[0406] Data Fusion
[0407] The Data Fusion algorithm will be designed to take inputs
from a N out of M tracker. This Data Fusion algorithm is
specifically designed to not require any specific set of sensors
and adapts as sensors are added using a lookup table of the new
sensor parameters and an indication of the number of and type of
sensors added. The Data Fusion Algorithm can also take into account
any data from the host vehicle supplied by various sensors. The
absence of data will not cause a problem with the algorithm,
however, the more data the better the performance. The purpose of
the Data Fusion Algorithm is to reduce all of the tracks and
detections down to a small set of object tracks representing the
objects surrounding the track. Each radar module and sensor set may
detect the same object. It is the task of the Data Fusion Algorithm
to sort this out. The algorithm uses a technique called Deepest
Hole to combine the data from multiple sensor and Kinematics
Combination to fuse this data together.
[0408] The Data Fusion functions are shown in FIG. 33. The purpose
of the Data Fusion Algorithm is to reduce all of the tracks and
detections down to a small set of object tracks representing the
objects surrounding the truck. Each radar module and sensor set
(FLD, PD, and RGD) may detect the same object. It is the task of
the Data Fusion Algorithm to sort all of this out. This algorithm
is described below.
[0409] Deepest Hole
[0410] The Deepest Hole function "associates" tracks from the
sensor sets with existing Fused Tracks. It is assumed that multiple
sensor sets may find the same object and that multiple radar
modules within a sensor set will often see and report on the same
object. The Deepest Hole function will resolve these redundant
tracks into a set of fused tracks, one per object. The output of
this function is a list of track links linking the tracks from
multiple radar modules together for each object.
[0411] The purpose of this function is to match new sensor data
with current tracks (multi-sensor track or MST). Matched sets of
MST and sensor data are found by operating on the agreement matrix
with a heuristic search algorithm. The agreement matrix contains
the normalized distances (referred to as "standard differences")
between shared state variables calculated for every possible
combination of sensor and MST track. The "deepest hole" search
algorithm finds the set of matches between rows and columns of the
agreement matrix to minimize the sum of matrix elements found at
the intersection of matched rows and columns.
[0412] The standard differences are calculated for every possible
combination of MST and sensor track. An agreement matrix is built
which contains MST tracks as the first index (rows) and sensor
tracks as the second index (columns). The standard difference for
each MST/sensor pair is put into the appropriate cross-index
position.
[0413] The standard difference is the sum of the squares of the
differences in shared state variables normalized by the sum of the
state variances and the number of variables shared by the two
tracks.
[0414] NOTE: Only the kinematic states NED and Rdot are queried for
use in the standard difference calculation; NED is North, East and
Down given by the sensor reporting the detection and the pointing
angle of the sensor. Down is set to zero. 5 DIFF = 1 N N i = 1 [ X
mst ( i ) - X sen ( i ) ] 2 [ V mst ( i ) + V sen ( i ) ] ( 7 )
[0415] where:
[0416] N=number of shared state variables
[0417] X.sub.mst=vector of MST track state variables shared with
sensor
[0418] X.sub.sen=vector of sensor track state variables shared with
MST
[0419] V.sub.mst=vector of MST track state variances corresponding
to X.sub.mst
[0420] V.sub.sen=vector of sensor track state variances
corresponding to X.sub.sen
[0421] DIFF=standard difference.
[0422] The most probable matches between new sensor data and
current MST tracks are found by searching through the agreement
matrix. A simple "deepest hole" heuristic algorithm, which closely
reproduces the results of exhaustive search algorithms, is used.
"Deepest hole" finds the set of matches between rows (MST tracks)
and columns (sensor tracks) in the agreement matrix which minimize
the sum of the standard differences residing at the intersection of
matched rows and columns. Matches are not allowed for matrix
elements (standard differences) greater than a user defined
limit.
[0423] The steps in Deepest Hole is as follows:
[0424] 1) If any matrix element is greater than MAX_DIFF, multiply
this element by MAX_DIFF and place it back into the agreement
matrix.
[0425] 2) If there are more rows than columns in the agreement
matrix, transpose the matrix. Note that the matrix needs to be
transposed again when processing is completed.
[0426] 3) Set up linked lists containing all unmatched rows and
columns.
[0427] 4) If there is only one row in the list of rows, loop
through linked list of columns to find the minimum value. Match
this row and column. If there are no more rows to process all
possible matches have been made.
[0428] 5) Loop through the linked list of rows. For each row
[0429] a) Loop through the linked list of columns to find the
minimum and next minimum values for this row.
[0430] b) Calculate the difference between minimum and next minimum
values in this row. Compare it with the largest value found so far
in this loop, and save the larger one.
[0431] 6) Remove the row with the largest difference, found in step
5b, from the linked list of unmatched rows. Match this row to the
column in which its minimum value was found. Remove that column
from the linked list of unmatched columns.
[0432] 7) Return to step 4.
EXAMPLE
Deepest Hole
[0433] Suppose the following agreement matrix was generated with
MST (rows) and sensor (columns) tracks. All possible standard
differences between the MST and sensor data are calculated and
placed into the matrix. For this example it will be assumed that
all standard differences fall below the limiting value (step 1).
Since this matdx contains more rows than columns, the matrix is
transposed (step 2). 6 Sensor Detections MST Tracks 1 2 3 1 1.7 2.0
2.7 2 1.8 2.5 5.4 3 3.1 2.7 1.5 4 2.3 6.2 1.9 transpose MST Tracks
Sensor Detections 1 2 3 4 1 1.7 1.8 3.1 2.3 2 2.0 2.5 2.7 6.2 3 2.7
5.4 1.5 1.9
[0434] The difference between the minimum and next minimum values
for each row is then calculated (step 5).
6 Row 1 Row 2 Row 3 (next min) - (min) A: 0.1 0.5 0.4
[0435] The largest value found (i.e. deepest hole) is 0.5
corresponding to Row 2 or Sensor Detection 2. This row is then
examined to find the corresponding column (MST track) which has the
minimum standard difference. The minimum is 2.0 corresponding to
column 1. The smallest value in row 2, 2.0 indicates that MST Track
1 is the closest to sensor detection 2. MST track 2 is the next
closest to sensor track 2, with a standard difference of 2.5. The
larger the distance between the standard differences the more
likely that the actual match is the minimum value found (2.0 in
this case). That is why the most probable match is determined from
the largest distance between standard differences. Therefore, it is
concluded that MST track 1 and sensor detection 2 are a probable
match. Row 2 and column 1 are now removed from the matrix (step 6)
and the entire procedure repeated on the reduced matrix (step 7).
The reduced matrix is: 7 MST Tracks Sensor Tracks 2 3 4 1 1.8 3.1
2.3 3 5.4 1.5 1.9
[0436] The difference between the minimum and next minimum values
for each row of the reduced agreement matrix is then calculated
(step 5).
7 Row 1 Row 2 Row 3 (next min) - (min) A: 0.5 -- 0.4
[0437] The "deepest hole" is found to be 0.5 corresponding to row 1
or sensor track 1. The minimum standard difference for this row is
1.8 corresponding to MST track 2, the next probable match. This row
and column are now removed. 8 MST Tracks Sensor Tracks 3 4 3 1.5
1.9
[0438] Now we need only find the most probable match between sensor
detection 3 and the remaining MST tracks. The minimum standard
difference is 1.5; hence, the last match pairs sensor detection 3
with MST track 3. Note that MST track 4 remained unpaired with any
new sensor data. The status of this track would be evaluated and
potentially changed. A summary of the resultant matches found in
this example is given below. 9 MATCHED TRACKS MST Sensor 1 2 2 1 3
3
[0439] Kinematics Combination
[0440] The track data from the tracks, which are linked, will be
merged in this function. The speeds from each track will be
averaged together. The SNR's will be averaged using a weighted
average considering radar module antenna gain (the FLD's and
potentially one RGD will have 15 to 20 dB more gain than the other
radar modules). The range estimate for the new merged track will be
handled by the Range Estimator Function. The ID will be merged
using the Probability of Correct ID and the ID Confidence.
[0441] The kinematics merge process consists of multiple passes,
one pass for each sensor being processed on a given cycle. The
algorithm acts as a sensor track combiner and does not provide
additional filtering to the sensor data. Given that only Radar
sensors with differing beamwidths are being considered the merge
process would behave as follows.
[0442] Let X(k) represent a state vector at cycle k. For brevity,
vector notation will be used. Thus X could be any of the vectors (N
Ndot).sup.T, (E Edot).sup.T, (D Ddot).sup.T, (R Rdot).sup.T where
the superscript T indicates transposition. To merge the sensor data
the following equation is used:
X.sub.M(k)=X.sub.M.sup.1(k)+W(k)[X.sub.S.sup.(E)(k)-X.sub.M.sup.(1)(k)]
(8)
[0443] where:
[0444] XM=the merged MST state vector
[0445] X.sub.M.sup.(1)=the MST state vector
[0446] W=weight vector
[0447] X.sup.(E).sub.S=sensor state vector extrapolated to current
MST time.
[0448] The weight vector W(k) is computed from the relation:
W(k)=P.sub.M.sup.(E)(k)[P.sub.M.sup.(E)(k)+P.sub.S.sup.(E)(k)].sup.-1
(9)
[0449] where
[0450] P.sub.M.sup.(E)=extrapolated covariance matrix of the MST
track
[0451] P.sub.S.sup.(E)=extrapolated covariance matrix of the sensor
detection
[0452] Note that the sensor data affects the MST track in inverse
proportion with the size of its errors.
[0453] The fusion process generates an MST track with lower
variances. The fused covariance matrix is given by:
P.sub.M.sup.(F)(k)=[I-W(k)]P.sub.M.sup.(E)(k) (10)
[0454] Range Estimation
[0455] Range Estimation consists of three steps. These steps are
designed to achieve maximum range resolution without using time
measurement as a tool. The estimator works using the principal
behind radar wave propagation. Radar signals are received in
relation to the transmitted power by range to the fourth power.
That is the radar signal drops in strength by range to the object
squared and on the return by range to the receiver from the object
squared. Thus when range goes from 300 feet to 100 feet there is an
increase in received power of 81 times. This change in power can be
measured and it is greater than the changes due to object size or
object perceived size (angle dependent). The range to a object can
be estimated by following the curve of the received power over
time. This is why tracks are formed in previous functions. The
tracks give a time history of the received signal which will be
used in the range estimate.
[0456] Multi-Hypothesis Automatic Difference Ranging (MADR)
[0457] To obtain range to the track an algorithm called MADR will
be used. The first step in MADR is to apply the SNR history to the
radar range curve fit program. An algorithm dubbed "Automatic
Ranging" will be used to establish this first range estimate. MADR
will estimate the starting range of a track based on the SNR
history. This starting range will be added to distance traveled (a
negative number for a closing object) and a current range estimate
will be computed. The MADR algorithm is discussed in detail
below.
[0458] A range estimate will be calculated from the signal strength
versus time and closing rate of each tracked object. Due to the
properties of radar, as an object changes its relative position to
the host vehicle, the signal strength will vary, by range to the
fourth power and by a scattering property called scintillation.
Combining this signal strength property with the distance traveled
by the object will yield the starting range and thus the current
range to the object. The distance traveled by the object is
computed in the sensors by combining time since the data collection
and tracking started, with the individual measured closing rates
versus time. Using multiple hypotheses the signal strengths versus
time will be inserted into an algorithm which matches the
hypothetical signal strength curve to a (range and distance
traveled)/(range to the fourth) curve. One hypothesis, a set of
points drawn through the returned signal levels over time, will
correspond to the correct starting range for the object given the
measured distance traveled. This hypothesis will provide the best
statistical match to a one over range to the fourth curve and will
be the range estimate provided. FIG. 34 shows an example of
multiple hypotheses through amplitude versus time data.
[0459] The multiple hypotheses will be sent into the Automatic
Ranging algorithm. Automatic Ranging is a technique first used by
the Navy in the late 1970's to passively estimate range to a
target. This application is substantially different but it can
still use the same principals.
[0460] Automatic Ranging (AR) is a technique that was originally
developed to determine the range and closing rate of an unknown
emitter passively for a fire control radar. Using only a receiver,
AR was able to determine the range and closing rate after the
emitter's signal strength had changed approximately 1 dB (about 11%
change in range). It's primary application was in determining range
to noise jammers whose purpose was to deny range information that
was required for missile firing equations. In order to do this, AR
made two major assumptions: 1) during the time that AR was ranging,
the emitters speed was constant, and 2) the emitters signal
strength did not vary appreciably. The basis of AR's ranging was
the fact that the emitters signal strength varies as range squared
(Range.sup.2). This non-linearity is exploited in AR's methodology
to determine where the emitter is. The key to AR is its
implementation which uses both known signal strength relationships
and the computational power of the digital computer. In general,
AR's ranging technique can be applied to any number of problems
where a measurable parameter varies in some non-linear manner while
other measurable or assumed parameters are linear. AR's basic
implementation concept and its application to the anti-collision
warning system is described in the following paragraphs.
[0461] The key to AR is converting the non-linear terms of the
problem to linear terms and then using the power of the computer to
find the correct answer. Converting the radar range equation
(either one way R.sup.2 or two way R.sup.4) to a linear equation
merely requires the use of log's (decibel's) so that the equation
becomes a series of linear operations. In simplified form, the
radar equation can be written:
S.sub.dB=(Some Constant).sub.dB-(2*Range.sub.dB) (or
(4*Range.sub.dB) for 2-way)
[0462] That is the simple part. The hard part is that we have one
equation with two unknowns (the constant and the Range). However,
that's where the digital computer comes in. What we do know, is
that as range changes the constant remains constant and the signal
strength increases or decreases (depending on whether you are
closing or opening). We also know (assume) that the range change
per unit of time is constant. However, this doesn't help because by
making the equation linear (taking the log of everything) we can't
use the idea of delta range directly. What we need is the actual
range. The solution is to assume an initial range and a speed. If
we assume the correct initial range and speed, then the equation
will remain linear over time (as range changes). The assumed
initial range allows us to solve for the "constant" and use that in
subsequent calculations. If we assume the wrong range or speed or
both, then the equation will become progressively more incorrect
over time. This is what AR does. Calculations for a series of
initial ranges and a series of speeds are done. By using a linear
regression to do a curve fit, only four terms are required to be
saved for each range/speed combination. The linear regression
allows calculation of the "slope" of the curve fit line. Since
we've made the equation linear, over time the correct combination
will have a "slope" of 1 and all other combinations will have
slopes greater than or less than 1 (as the curve fits become
progressively worse).
[0463] The application of AR to the anti-collision system requires
only a one dimensional solution, since closing rate is known and
only the initial range is calculated using a series of assumed
initial ranges. As in all uses of AR, the accuracy of the AR
depends on a variety of parameters. These parameters include:
signal strength measurement accuracy, signal strength variations
(due to scintillation, aspect changes, system non-linearity's), the
amount of range change, the number of signal strength measurements,
and the number (granularity) of the initial guesses which are
calculated (every 5 feet, every 10 feet, etc.). It should be noted
that while AR solves for initial conditions, calculation of the
current position is straightforward since the time and speed from
the initial position are known.
[0464] Constant Cross Section Ranging (CCSR)
[0465] The second method is to assume a constant radar cross
section for an object. The RCS will be derived from a look-up table
and the track ID. The SNR time history curve will be smoothed.
Using the estimated RCS and the measured speed an estimate of range
will be determined. Assuming a constant K for the losses and gains
in the radar sensor the range is given by:
R.sub.j={K*RCS.sup.2/S.sub.j}.sup.1/4 (11)
[0466] Where R.sub.j is the CCSR range estimate
[0467] RCS is the guess for radar cross section
[0468] S.sub.j is the j.sup.th track smoothed signal.
[0469] Range Estimate Resolution
[0470] The final step will be to resolve the two range estimates.
The resolution will be dependent on the history of range estimates
for the subject track, the ID of the track, the quality of the SNR
history (noise on the SNR curve) and the quality of the track ID.
10 = ( ( R ar ( t ) ) MAX ( R ar ( t ) ) ) .beta.=1-.alpha.
R.sub.j=.alpha.*R.sub.arj+.beta.*R.sub.ccsj
[0471] Where RCS(t) is the series of Radar Cross Section estimates
versus sensor cycles
[0472] .sigma. is the standard deviation
[0473] R.sub.ar is the range estimate using automatic ranging
versus sensor cycle
[0474] R.sub.ccs is the Constant Cross Section range estimate.
[0475] Situation Report Generator
[0476] The final stage of the processing is the Situation Report
Generator. This algorithm is the interface to the Display Driver.
The output from this algorithm will depend on the mode of the
detectors and the detectors installed on the track. This algorithm
will output detected objects in the truck's path as well as objects
immediately adjacent to the truck. The design goal for the false
alarm rate for reporting to the driver will be less than one per
day.
[0477] This algorithm receives trackfiles from the Data Fusion
algorithm and range estimates from the Range Estimator. This data
is compared to the reporting criteria established by a lookup table
in the CM. The lookup table will be mode and RM/sensor system (FLD,
PD, RGD) dependent. Depending on the RM(s) reporting and updating
the Fused Trackfile, the lookup table will determine whether the
track should be formatted and reported. This lookup table will be
created and updated by ATI. The format for the table is shown
below:
8 Alarm Threshold Warning Threshold Range FLD <3 feet <10
feet Range front PD <3 feet <6 feet Range rear PD/RGD (fwd
gear) -- <6 feet Range rear PD/RGD (rev gear) <.5 feet <2
feet Range Side PD/RGD (turning) <12 feet <24 feet Time to
Impact FLD <3 seconds <6 seconds Time to impact rear PD/RGD
<3 seconds <6 seconds
[0478] When the vehicle is in reverse, the data from the rear of
the truck will be used to provide the transverse angle to an object
behind the vehicle. If the object is a point source such as a pole
the transverse position will be stable and resolvable into eight
increments. Wide objects such as a loading dock cannot be located
in the transverse direction. The data fusion algorithm will output
the data necessary to provide the transverse location.
[0479] Built In Test
[0480] The Built In Test (BIT) function will be performed in the CM
on all of the system's components. The BIT software will be
designed to exercise the sensors such that a known preset
performance can be measured. If a fault occurs, the faulty
component will be recycled and retested. If the fault persists, a
permanent record of the condition and the associated component will
be stored in flash memory in the CM and the condition routed to the
display processor by the BIT software. The other CM functions will
always assume a fully functional system unless BIT informs it of a
faulty component. This fault detection will be at a 50-millisecond
rate for the FLD and a 333-millisecond rate for the PD and RGD.
[0481] Each RM has a distinct clutter response from the surface and
an identifying code in its digitized signal being fed to the CM.
BIT initiate will cause the BIT software to poll each RM for the
FLD, PD and RGD. If an individual RM is faulty, the BIT software
will identify the faulty RM through a comparison of the clutter
return to the expected clutter return. If the faulty RM is in the
FLD, BIT will inform the Object Data Processing module that
specific RM is no longer functional. The Object Data Processing
module will then revert to a degraded mode. If the faulty RM is in
the PD or RGD, BIT will inform the Detection Processing module,
which will revert to a degraded mode.
[0482] If BIT detects a fault in each of the RM responses connected
to a specific interface board or if no response is received from a
specific interface board, then BIT will assume that interface board
has failed. The failure of the FLD Interface Board will result in
complete loss of the FLD capability and this will be reported to
the Object Data Processing module. The failure of a PD or RGD will
be reported to the Detection Processing module, which will revert
to a degraded mode.
[0483] BIT will inform the Display Processor of all failures and
their severity, so that the operator is aware of the system
status.
[0484] Master Clear
[0485] The CM initiates the Master Clear function. On receipt of
the Master Clear discrete, the FLD, PD and RGD will reinitialize
all functions. All signal processing will cease and be restarted.
The A/D and FFT functions will continue to operate. A watch Dog
timer set to 1 second will be used to detect a reset condition in
the RMs. Upon receiving a time out (no serial request from the CM
in the last second) the microcontroller will be reset. All message
formatting will stop and any existing but unsent messages will be
cleared.
[0486] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement which is calculated to achieve the
same purpose may be substituted for the specific embodiments shown.
This application is intended to cover any adaptations or variations
of the present invention. Therefore, it is intended that this
invention be limited only by the claims and the equivalents
thereof.
* * * * *