U.S. patent application number 13/400393 was filed with the patent office on 2013-08-22 for method and apparatus for determining a condition and relative location of an inner tire and an outer tire of a tire pair.
The applicant listed for this patent is David L. Juzswik. Invention is credited to David L. Juzswik.
Application Number | 20130218364 13/400393 |
Document ID | / |
Family ID | 48808726 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130218364 |
Kind Code |
A1 |
Juzswik; David L. |
August 22, 2013 |
METHOD AND APPARATUS FOR DETERMINING A CONDITION AND RELATIVE
LOCATION OF AN INNER TIRE AND AN OUTER TIRE OF A TIRE PAIR
Abstract
An apparatus determines a condition and relative location of an
inner tire and an outer tire of a tire pair. Each tire has an
associated tire-based sensor assembly that senses a tire condition,
senses acceleration, and transmits, in response to its associated
acceleration signal, having a unique tire identification and
associated sensed tire condition. A tire rotation sensor senses
rotation of the tire pair during vehicle movement and provides a
tire rotation signal indicative thereof. A vehicle-based controller
associates each of the unique identification signals with one of
the inner tire location and the outer tire location responsive to a
phase relationship between the received transmitted signals from
the tire-based sensor assemblies and the tire rotation signal.
Inventors: |
Juzswik; David L.; (Commerce
Township, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Juzswik; David L. |
Commerce Township |
MI |
US |
|
|
Family ID: |
48808726 |
Appl. No.: |
13/400393 |
Filed: |
February 20, 2012 |
Current U.S.
Class: |
701/1 |
Current CPC
Class: |
B60C 23/0416 20130101;
B60C 23/0489 20130101; B60C 23/0488 20130101 |
Class at
Publication: |
701/1 |
International
Class: |
G06F 7/00 20060101
G06F007/00 |
Claims
1. An apparatus for determining a condition and relative location
of an inner tire and an outer tire of a tire pair mounted on one
side of a vehicle, the apparatus comprising: tire-based sensor
assemblies, the inner tire and the outer tire each having an
associated tire-based sensor assembly, each tire-based sensor
assembly including (i) an associated tire condition sensor for
sensing a tire condition and providing a tire condition signal
indicative thereof and (ii) an associated acceleration sensor for
sensing acceleration and providing an acceleration signal as its
associated tire rotates, the associated acceleration sensor of the
inner tire and the associated acceleration sensor of the outer tire
of the tire pair each having an axis of sensitivity in a
predetermined orientation relative to each other, each tire-based
sensor assembly further including a tire-based transmitter coupled
to its associated tire condition sensor and associated acceleration
sensor for transmitting, in response to its associated acceleration
signal, a unique tire identification signal and its associated
sensed tire condition signal; tire rotation sensor mounted
externally of the tire pair for sensing rotation of said tire pair
during vehicle movement and providing a tire rotation signal
indicative thereof; and a vehicle-based controller for receiving
the transmitted signals from each tire-based transmitter of the
tire pair and the tire rotation signal, said vehicle-based
controller including means for associating each of the unique
identification signals with one of the inner tire location and the
outer tire location responsive to a phase relationship between the
received transmitted signals from the tire-based sensor assemblies
and the tire rotation signal.
2. The apparatus of claim 1 wherein said means for associating is
responsive to a lead/lag relationship between said received
transmitted signals relative to the tire rotation signal.
3. The apparatus of claim 1 wherein the associated acceleration
sensor of the inner tire and the associated acceleration sensor of
the outer tire are substantially circumferentially aligned.
4. The apparatus of claim 1 wherein the axis of sensitivity of the
associated acceleration sensor of the inner tire and the axis of
sensitivity of the associated acceleration sensor of the outer tire
are offset from one another by a predetermined amount.
5. An apparatus for determining a condition and relative location
of an inner tire and an outer tire of a tire pair mounted on one
side of a vehicle, the apparatus comprising: tire-based sensor
assemblies, the inner tire and the outer tire each having an
associated tire-based sensor assembly, each tire-based sensor
assembly including (i) an associated tire condition sensor for
sensing a tire condition and providing a tire condition signal
indicative thereof and (ii) an associated acceleration sensor for
sensing acceleration and providing an acceleration signal as its
associated tire rotates, the associated acceleration sensor of the
inner tire and the associated acceleration sensor of the outer tire
of the tire pair each having an axis of sensitivity in a
predetermined orientation relative to each other, each tire-based
sensor assembly further including a tire-based transmitter coupled
to its associated tire condition sensor and associated acceleration
sensor for transmitting, in response to its associated acceleration
signal, a unique tire identification signal and its associated
sensed tire condition signal; tire rotation sensor mounted
externally of the tire pair for sensing rotation of said tire pair
during vehicle movement and providing a tire rotation signal
indicative thereof; and a vehicle-based controller for receiving
the transmitted signals from each tire-based transmitter of the
tire pair and the tire rotation signal, said vehicle-based
controller including means for associating each of the unique
identification signals with one of the inner tire location and the
outer tire location responsive to a phase relationship between the
received transmitted signals from the tire-based sensor assemblies
and the tire rotation signal; wherein the axis of sensitivity of
the associated acceleration sensor of the inner tire and the axis
of sensitivity of the associated acceleration sensor of the outer
tire are offset from one another by a predetermined amount, and are
positioned so that, as the tire pair rotates, the two acceleration
signals are approximately 130 degrees out of phase relative to each
other as referenced from the tire rotation signal.
6. A method for determining a condition and relative location of an
inner tire and an outer tire of a tire pair mounted on one side of
a vehicle, the method comprising the steps of: sensing a tire
condition of the inner tire and providing a tire condition signal
indicative thereof; sensing acceleration of the inner tire and
providing an inner tire acceleration signal as the inner tire
rotates; transmitting from said inner tire a unique tire
identification and associated tire condition indication in response
to the inner tire acceleration signal; sensing a tire condition of
the outer tire and providing a tire condition signal indicative
thereof; sensing acceleration of the outer tire and providing an
outer tire acceleration signal as the outer tire rotates;
transmitting from said outer tire a unique tire identification and
associated tire condition indication in response to the outer tire
acceleration signal; sensing externally of the tire pair rotation
of said tire pair during vehicle movement and providing a tire
rotation signal indicative thereof; receiving the transmitted
signals from the inner tire, the outer tire, and the tire rotation
signal; and associating each of the unique identification signals
with one of the inner tire location and the outer tire location
responsive to a phase relationship between the transmissions from
the inner tire and the outer tire relative to the tire rotation
signal.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method and apparatus for
determining a condition and relative location of an inner tire and
an outer tire of a tire pair mounted on a vehicle.
BACKGROUND
[0002] Systems for sensing tire conditions and displaying sensed
tire condition information to a vehicle occupant are known. Often,
such systems are known as tire pressure monitoring ("TPM") systems
even though the system may sense tire conditions in addition to
pressure, such as tire temperature. Such TPM systems may include a
tire-based sensor assembly that senses, for example, the air
pressure and temperature inside its associated tire and transmits
the sensed tire condition information to a vehicle-based receiver,
i.e., a receiver mounted in the vehicle. The transmitted sensed
tire condition signal may be a coded radio frequency ("RF") signal.
The vehicle-based receiver is connected to a display located in the
vehicle cabin that can display, for example, a warning signal to
the vehicle operator when an under-inflated tire pressure condition
exists or an over-heated tire condition occurs.
[0003] Each tire-based sensor assembly may have a unique
identification ("ID") code associate therewith. The tire-based
sensor assembly may transmit a signal that includes its associated
unique ID code along with the sensed tire condition. The
vehicle-based receiver can associate the received tire signal and
unique ID with a particular tire location on the vehicle such as
front right ("FR"), front left ("FL"), rear right ("RR"), or rear
left ("RL"). By associating the tire ID with the tire location on
the vehicle, the vehicle-based receiver is able to display the
sensed tire condition information at each particular tire location
so the vehicle operator can identify which tire (i.e., tire
location) has a sensed, improper condition.
[0004] Associating a tire location with a tire-based transmitted ID
code for each of the tire locations may require a "learning"
process by the vehicle-based receiver. Methods have been proposed
to accomplish this learning function including using signal
interrogation in which each tire-based sensor assembly includes a
receiver that is separately interrogated from a transmitter located
outside of the tire using, for example, a low frequency ("LF")
interrogation signal. In response to receiving an interrogation
signal, the tire-based sensor assembly transmits a response signal
having its associated unique ID. Upon receipt of the response
signal from the tire-based unit, the vehicle-based receiver
associates that unique tire ID with that tire location since the
system "knows" which tire location was just interrogated. The
vehicle-based system stores tire-based sensor IDs and tire location
associations in memory for later use in its display operation.
[0005] Certain vehicles have multiple tires per side per axle. One
such vehicle is a pickup truck referred to as a "dually." A dually
pickup truck has four wheels/tires on the rear axle with two tires
on each side, i.e., multiple tires per axle per side. Other
vehicles, such as semi-trailers, may also have two tires per side
on certain axles. Two tires on one side of a vehicle on the same
axle are referred to herein as a tire pair.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to a method and apparatus
for determining a condition and relative location of an inner tire
and an outer tire of a tire pair mounted on a vehicle. In this way,
not only can a vehicle corner or axle location be identified for or
associated with the tire pair, but a particular tire-based
transmitter (unique tire ID) of a tire pressure monitor assembly
can be associated with either the inside tire or the outside tire
of the tire pair, i.e., the inner and outer tire relative location
can be determined
[0007] In accordance with an example embodiment of the present
invention, an apparatus is provided for determining a condition and
relative location of an inner tire and an outer tire of a tire pair
mounted on one side of a vehicle. The apparatus comprises
tire-based sensor assemblies, the inner tire and the outer tire
each having an associated tire-based sensor assembly. Each
tire-based sensor assembly includes (i) an associated tire
condition sensor for sensing a tire condition and providing a tire
condition signal indicative thereof and (ii) an associated
acceleration sensor for sensing acceleration and providing an
acceleration signal as its associated tire rotates. The
acceleration sensor of the inner tire and the acceleration sensor
of the outer tire of the tire pair each have an axis of sensitivity
in a predetermined orientation relative to each other. Each
tire-based sensor assembly further includes a tire-based
transmitter coupled to its associated tire condition sensor and
acceleration sensor for transmitting, in response to its associated
acceleration signal, a unique tire identification signal and its
associated sensed tire condition signal. The apparatus further
includes a tire rotation sensor mounted externally of the tire pair
for sensing rotation of said tire pair during vehicle movement and
providing a tire rotation signal indicative thereof. A
vehicle-based controller receives the transmitted signals from each
tire-based transmitter of the tire pair and the tire rotation
signal. The vehicle-based controller includes means for associating
each of the unique identification signals with one of the inner
tire location and the outer tire location responsive to a phase
relationship between the received transmitted signals from the
tire-based sensor assemblies and the tire rotation signal.
[0008] In accordance with another example embodiment of the present
invention, a method is provided for determining a condition and
relative location of an inner tire and an outer tire of a tire pair
mounted on one side of a vehicle. The method comprises the steps of
sensing a tire condition of the inner tire and providing an inner
tire condition signal indicative thereof, sensing acceleration of
the inner tire and providing an inner tire acceleration signal as
the inner tire rotates, and transmitting from said inner tire a
unique tire identification and associated inner tire condition
indication in response to the inner tire acceleration signal. The
method further includes the steps of sensing a tire condition of
the outer tire and providing an outer tire condition signal
indicative thereof, sensing acceleration of the outer tire and
providing an outer tire acceleration signal as the outer tire
rotates, transmitting from said outer tire a unique tire
identification and associated tire condition indication in response
to the outer tire acceleration signal, and sensing externally of
the tire pair rotation of said tire pair during vehicle movement
and providing a tire rotation signal indicative thereof. The
transmitted signals from the inner tire and the outer tire are
received, and the tire rotation signal is received. The method
further includes the step of associating each of the received
unique identification signals with one of the inner tire location
and the outer tire location responsive to a phase relationship
between the transmissions from the inner tire and the outer tire
relative to the tire rotation signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing and other features and advantages of the
present invention will become apparent to one skilled in the art
upon consideration of the following detailed description of the
invention along with the accompanying drawings, in which:
[0010] FIG. 1 is a schematic illustration of a vehicle having a
tire pressure monitoring system;
[0011] FIG. 2 is a schematic block diagram of the tire pressure
monitoring system of FIG. 1 showing a sensor arrangement associated
with one of the tires in greater detail;
[0012] FIG. 3 is a schematic block diagram of the tire pressure
monitoring system of FIG. 2 showing the tire-based sensor at two
rotational positions where signal transmission could occur;
[0013] FIG. 4 is a schematic block diagram of the tire pressure
monitoring system of FIG. 1 showing the tire-based sensor unit in
further detail;
[0014] FIG. 5 is a functional block diagram of the tire pressure
monitoring system of FIG. 1 showing the vehicle-based receiver in
further detail;
[0015] FIG. 6 is a flow chart depicting a control process to
correlate each tire-based sensor location with tire location on the
vehicle;
[0016] FIG. 7 is a schematic illustration of a vehicle with a
dually tire arrangement having a tire pressure monitoring system in
accordance with an example embodiment of the present invention;
[0017] FIG. 8 is a schematic block diagram of the tire pressure
monitoring system of FIG. 7 showing the sensor arrangement
associated with the two tires on one axle on one side of the
vehicle;
[0018] FIG. 9 is a tire condition sensor for the dually tire
arrangement of the vehicle of FIG. 7 showing the axis or
orientation of the two sensors in accordance with an example
embodiment of the present invention; and
[0019] FIG. 10 is a graphical representation of the sensors'
outputs during tire rotation for the dually tire arrangement shown
in FIG. 7.
DETAILED DESCRIPTION
[0020] To more easily appreciate the present invention, a
discussion is first presented showing an arrangement for
determining a tire condition and relative location of the tire
having a tire pressure monitor with unique identification on a
vehicle with a single tire per side per axle arrangement. This
system, shown in FIGS. 1-6, associates the front/rear/right/left
location of each of the vehicle tires (i.e., associates the unique
identification of each tire pressure monitor with tire location)
and the condition for each tire.
[0021] Referring to FIG. 1, a tire pressure monitoring ("TPM")
system 10 is shown mounted on a vehicle 12. The TPM system 10
includes a plurality of sensors 14 ("S1"), 16 ("S2"), 18 ("S3"),
and 20 ("S4") located at each of the four corners front right
("FR"), front left ("FL"), rear right ("RR"), and rear left ("RL"),
respectively, of the vehicle 12. As mentioned, the vehicle 12 (in
FIG. 1) includes one wheel and tire per side per axle.
[0022] It should be understood that the tire-based sensor units 14,
16, 18, and 20 are each mounted in their associated tires in any
one of several possible known arrangements. For example, each of
the TPM sensors can be mounted as part of a valve stem assembly,
mounted in a separate housing and attached to its associated wheel
rim, or mounted to a side wall of the inside of the tire itself.
Each of the tire-based sensor units 14, 16, 18, and 20 include a
sensor for sensing acceleration that occurs during tire rotation
and a sensor for sensing at least one condition of the tire, such
as pressure and/or temperature. Each of the tire-based sensor units
14, 16, 18, and 20 include an associated transmitter, such as a
radio frequency ("RF") transmitter, for transmitting the associated
sensed tire condition information along with a unique
identification ("ID") signal associated with that sensor.
[0023] The TPM system 10 further includes wheel rotation sensor
assemblies 22, 24, 26, and 28 located at the FR, FL, RR, and RL
corners of the vehicle, respectively, and mounted external of its
associated tire. Each external wheel rotation sensor assembly is
similar and, therefore, only one (wheel rotation sensor assembly
22) is described in detail.
[0024] The wheel rotation sensor assembly 22 includes a circular
toothed plate or disc 30 that is mounted so as to rotate with its
associated tire 54. A sensor 32 senses passing of each tooth of the
disc 30 as the tire rotates and provides an electrical signal
indicative thereof (e.g., a pulse is produced each time a tooth of
the disc 30 passes the sensor 32). The wheel rotation sensor
assemblies 22, 24, 26, 28 may be part of the vehicle's anti-lock
braking system ("ABS") and may also be referred to as wheel speed
("WS") sensors. The sensor portion of each of the wheel rotation
sensor assemblies is connected to an ABS electronic control unit
("ECU") 40.
[0025] The TPM system 10 further includes a vehicle-based
receiver/controller 44. The vehicle-based receiver/controller 44 is
connected to the ABS ECU 40 and receives wheel rotation signals
indicative of the incremental rotational position of each of the
wheels at the four corners of the vehicle via the sensor 32 and the
toothed disc 30. The vehicle-based receiver/controller 44 also
includes a receiving antenna 46 for receiving RF signals indicative
of tire condition information transmitted from each of the
tire-based sensor units 14, 16, 18, and 20. The vehicle-based
receiver/controller 44 is connected to a display 48 located within
the vehicle cabin for displaying tire condition information for
each of the tires at each of the vehicle corners. The display 48
can take any of several known forms including a liquid crystal
display ("LCD").
[0026] Referring to FIG. 2, a tire 54 located at the FR corner of
the vehicle includes the tire-based sensor unit 14 operatively
mounted to the tire 54 for sensing tire acceleration along a
predetermined axis of sensitivity as the tire rotates and tire
condition. The wheel rotation sensor assembly 22 has its toothed
disc 30 mounted so as to rotate with the tire 54. The sensor 32
provides an electrical signal (e.g., a pulse signal) when each
tooth of disc 30 passing by the sensor 32. By way of example, the
toothed disc has locations for seventy two teeth 56 to be equally
spaced about the disc 30. However, the disc 30 includes seventy one
teeth at these locations with one missing tooth at one of the
locations. Each time a tooth passes the sensor 32, a pulse is
provided. Any of several types of sensors could be used for sensor
32 such as an inductive sensor, a Hall Effect sensor, etc. If there
are seventy two teeth locations, a pulse is output from the sensor
32 every five degrees except when the missing tooth location 58
passes the location of the sensor 32. The missing tooth location 58
is designated as the zero wheel position and can function as a
reference point. In effect, if the missing tooth location being
aligned with the sensor 32 is referred to as the zero position,
then the ABS ECU controller can count the number of sensed pulsed
and determine an angular position of the tire 54 relative to the
zero position by knowing each received pulse represents a five
degree rotation of the tire 54.
[0027] The output from the sensor 32 is connected to the ABS ECU
40. The ABS ECU 40 monitors the output of the sensor 32 and
determines the angular position of the disc 30 relative to the zero
position of the disc 30 (i.e., the missing tooth position being
aligned with the sensor 32), and, in turn, determines the angular
position of the tire 54 relative to the zero wheel disc position.
It should be appreciated that, although no signal is generated as
the missing tooth location pace 58 on the disc 30 passes the sensor
32, the ABS ECU 40 receives an otherwise continuous stream of
pulses when the tire 54 is continuously rotating during normal
vehicle movement. When there is a missing pulse, the ABS ECU
"knows" that half way between the last pulse and the next received
pulse is the "zero position." The ABS ECU then "knows" that each
pulse received after the zero position is equal to five degrees of
tire rotation. The angle monitoring/determination continuous as the
disc 30 and tire 54 rotate with the zero position restarting the
angle determination upon each complete tire revolution. The ABS ECU
40 is connected to the vehicle-based receiver/controller 44.
[0028] The tire-based sensor unit 14 includes a TPM processing
circuit 60 (FIG. 4) that includes the tire condition sensor 82 and
a tire rotation sensor 68. As shown in FIG. 3, the tire-based
sensor unit 14 is arranged to transmit its tire condition RF signal
at two separated rotational positions of the tire 54 as the tire
rotates during normal vehicle movement, e.g., not parked but
moving.
[0029] Referring to FIG. 4, the tire-based sensor unit 14 includes
a TPM processing circuit 60. Those skilled in the art will
appreciate that the control functions of the TPM processing circuit
60 could be accomplished using a controller, such as a
micro-controller, by using discrete circuitry, a combination of
different types of circuitry, or an application specific integrated
circuit ("ASIC"), and can be embodied using either an analog or
digital circuitry or a combination of both. Each of the tire-based
sensor units 14, 16, 18, and 20 is constructed and operates in a
similar manner and, therefore, for ease of discussion, only one
tire-based sensor unit 14 is described in detail.
[0030] The tire-based sensor unit 14 includes an accelerometer 66
that take the form of a piezoelectric transducer ("PZT"). The
accelerometer 66 provides or generates a voltage signal that
changes in response to force/acceleration as the tire 54 rotates.
As described in detail below, the axis of sensitivity of the
accelerometer 66 is offset by 25 degrees relative to a tangent of
the tire rim to which the tire 54 is mounted. Two forces that the
accelerometer 66 experiences during tire rotation are centripetal
force and earth's gravitational force. As the accelerometer 66
travels in a circle during one tire rotation, it will experience
the earth's gravitation force change from +1 G to -1 G. If the
wheel/tire is rotating at a constant rate, the output of the
accelerometer will vary in a sinusoidal pattern over each
revolution of the tire. The centripetal force experienced by the
accelerometer 66 will either be of a consistent level, as would
occur when the vehicle is traveling at a constant velocity, or will
be slowly as vehicle speed changes as compared to the change
resulting from the earth's gravitational force experienced during
tire rotation. The signal from the accelerometer 66 is used to
control transmission of the tire condition signal and the
associated ID of the tire-based unit.
[0031] The output of the accelerometer 66 is connected to an
Analog-to-Digital Converter ("ADC") 64 that converts the analog
output signal from the accelerometer 66 to a digital signal for
further processing and analysis. The output of the ADC 64,
representing the sampled acceleration signal, is connected to a low
pass filter ("LPF") 70 that can be embodied as hardware or,
alternatively, the LPF function can be accomplished in software.
The LPF 70 aids in removing road noise from the accelerometer
output signal. The output of the LPF 70 is compared against a plus
threshold value in comparator 72 and a minus threshold value in
comparator 74 and also provides a signal reference level for use in
a data slicer 76. The output of the data slicer 76 is connected to
an edge detector circuit 78. The output of the edge detector is
connected to a microcomputer 80. The LPF 70, threshold comparators
72, 74, data slicer 76, and edge detector circuit 78 are arranged
so as to provide a first output signal when the sensed acceleration
value is at one value and a second output signal when the sensed
acceleration is at a second value. Furthermore, these components
are selected and arranged so that, effectively, the output of the
edge detector switches from the first signal to the second signal
and from the second signal back to the first signal at 180 degree
intervals of rotation of the tire. In other words, two signals are
provided for each 360 rotation of the tire with the signals
occurring at 180 degree intervals of rotation. As mentioned, the
signal from the edge detector is used to trigger the transmission
of the tire condition information and the associated tire-based
unit's ID.
[0032] The tire-based sensor unit 14 further includes a tire
condition sensor 82 for sensing tire pressure and/or tire
temperature and/or any other desired tire condition. The output of
the tire condition sensor 82 is connected to a signal processor
circuit 84 that converts the signal from the tire condition sensor
82 into a digital format and places the information into a digital
packet or word for ultimate transmission having information
regarding the sensed tire condition. The output of the signal
processor circuit 84 is connected to the microcomputer 80. As
mentioned, the tire condition sensor 82 can be a pressure sensor
for sensing tire pressure or can sense tire operating temperature
or both or any other desired tire condition.
[0033] The microcomputer 80 has stored in its internal memory its
associated, unique ID, e.g., sensor ID=S1 in this example for the
FR tire location. As mentioned, each tire has its own associated
unique tire ID different than the ID's of the other tire-based
sensor units. The microcomputer 80 assembles the digital
information packet or word for transmission including the sensed
tire condition information and sensor unit's associated ID. The
microcomputer 80 could include other data to be included as part of
the information packet assembled for transmission if desired such
as a wake-up portion, a check-sum portion, etc. The microcomputer
80, however, does not include as part of the information in the
data packet any angle information from the accelerometer 66 since
the angle of the tire is not known. The output of the microcomputer
80 is connected to a radio frequency ("RF") transmitter circuit 86
for transmission via an antenna 88 of the information packet having
the tire condition information and the ID of the tire-based sensor
unit. The microcomputer 80 includes internal timers that control
sample timing of the tire condition sensor 82 signal. Transmission
is controlled in response to the acceleration signal, which, as
mentioned, occurs twice per revolution of the tire, one
transmission each 180 degree rotation of the tire.
[0034] Referring to FIG. 5, the operation of the vehicle-based
receiver/controller 44 will be appreciated as well as the
transmission control followed by the tire-based sensor unit 14. The
vehicle-based receiver/controller 44 is connected to the output of
the ABS ECU 40 via an appropriate connection such as the vehicle's
controller-area network bus ("CAN-bus"). The vehicle-based
receiver/controller 44 monitors the pulse output associated with
each sensor/toothed disc unit of each of the vehicle's four
corners. From the pulse count and "knowing" when the zero tooth
location passes the associated sensor, the vehicle-based
receiver/controller 44 can determine angular position of each of
the wheels of the vehicle from each of the wheel rotation sensor
assemblies (also referred to as wheel speed sensors) 22, 24, 26,
and 28, also designated as WS FR, WS FL, WS RR, and WS RL,
respectively. The vehicle-based receiver/controller 44 also
includes an RF receiver 90 connected to a receiving antenna 46 for
receiving and demodulating the tire ID and condition information
from each of the transmitters associated with the tire-based sensor
units 14, 16, 18, and 20.
[0035] The received signals from each of the tire-based sensor
units 14, 16, 18, and 20 is referred to herein as message 1 when
the wheel or tire rotation is at the first position and message 2
when the wheel or tire rotation is at the second position, which is
approximately 180 degrees from the first position, as sensed by the
accelerometer 66. Recall that the vehicle based receiver/controller
does not "know" which position the tire is at when the transmission
occurred but only "knows" that the transmissions occur at 180
degree intervals of rotation.
[0036] An event graph 92 represents the occurrence of received tire
condition signals from one of the tire-based sensor unit 14 ID S1.
When each tire condition signal is received, the vehicle-based
receiver/controller 44 monitors the angular position of each of the
four wheels as determined from each associated ABS wheel speed
sensors 22, 24, 26, and 28. The tables 94 are the angle values in
degrees for the four wheels as determined from the ABS wheel speed
sensor signals each time an RF tire condition message is received.
These angular values are stored in memory as the angle values that
occurred when a message was received having a tire ID=S1.
Similarly, the wheel rotational positions are stored for each of
the tire-based units S2, S3 and S4 each time an RF signal from one
of their associated tire condition sensors is received.
[0037] The transmission of the RF signals from each tire based
unit, as mentioned, is controlled by the microcomputer 80. The
microcomputer 80 "knows" when tire rotation is occurring from the
signal output from the accelerometer 66. During a first ten minute
period after initial tire rotation begins, it may be desirable to
transmit a tire condition signal forty times. During forty
predetermined time slots over the ten minute period, the
microcomputer 80 monitors the tire condition sensor 82 and
transmits a tire condition signal when the edge detector indicates
the tire has reached the first rotational position or the second
rotational position where the first and second rotational positions
are 180 degrees apart. The microcomputer 80 can transmit the tire
condition signal in any of several patterns in response to the
detection of the first and second positions during tire rotation.
For example, the microcomputer 80 can transmit at a first of the
forty time slots when the tire position reaches position 1. During
the second of the forty time slots, the microcomputer 80 could wait
and transmit when the tire position reaches position 2, and so on.
The result would be tables 94 having a tire transmission pattern of
1, 2, 1, 2, etc. Any other desired pattern could be used by the
microcomputer 80. After a first 10 minute time interval of forty
transmissions, the microcomputer could change the transmission
timing to one time every minute. Also, the microcomputer 80 can
either maintain the same transmission pattern or could change the
transmission pattern.
[0038] The vehicle-based receiver/controller 44, after a sufficient
amount of data is collected (sufficient numbers of tables 94 are
filled), determines which tire angular positions correlate the best
with having received tire ID's and condition signals that would
have occurred commensurate with 180 degree rotational positions of
the tire. Assume that the microcomputer 80 was controlling the
transmitter circuit 86 to transmit in a 1, 2, 1, 2, pattern. Also
assume that the table 94 indicates that the FR ABS wheel speed
sensor (WS FR) always measured angles 102 and 282 degrees (180
degree interval), respectively, each time a tire condition signal
had a S1 ID. Then, the vehicle-based receiver/controller 44 could
assume that the tire ID S1 is located at the FR corner of the
vehicle. Once tire condition data and ID date transmissions
correlates with tire angular position as determined from the wheel
speed sensors with a confidence level above a predetermined
threshold, that tire ID for that vehicle tire location is stored in
an internal memory of the vehicle-based receiver/controller 44 for
later use in identifying the tire location when tire condition
information is to be displayed on the display 48, e.g., an under
inflated tire occurrence. The confidence level can be determined by
several different methods. One example is to determine that the WS
angle data in a table does not vary over a predetermined number of
samples by more than a predetermined amount.
[0039] Once the sensor ID's are correlated with the vehicle corner
locations, the pressure/temperature information portion of the
transmitted signal is monitored for each of the sensors, and the
tire condition information can be displayed along with the
associated determined vehicle tire location information for the
vehicle operator. As those skilled in the art will appreciate, the
display of tire condition information can be limited only to
abnormal tire conditions or can be continuous tire pressure and
temperature information, if so desired.
[0040] Referring to FIG. 6, a flow chart is shown depicting a
control process 150 for determining tire location in a TPM system.
The control process 150 starts at step 152 where initial
conditions, flags, appropriate values, etc., are set. At step 154,
the ABS signals indicative of the wheel angular position from each
of the vehicle tires is continuously captured and provided to the
vehicle-based receiver/controller 44. In step 156, the
vehicle-based receiver/controller 44 monitors for received RF tire
condition information signals from the tire-based units. In step
158, a determination is made whether RF signals have been received.
If negative, the process loops back to step 154 where wheel angular
position from the ABS wheel speed sensors is continued to be
captured. If the determination in step 158 is affirmative, the
wheel angles from all four wheels are temporarily stored in step
160 (table 94). In step 162, a determination is made as to whether
there has been a sufficient amount of data collected to make a
location determination. For example, it may be desired to have
10-20 samplings of data before a location determinations is made.
If there is not enough data, the process loops back to step 154
until a sufficient amount of data is received and stored.
[0041] In step 164, a determination of wheel location is performed
by correlating the angular wheel position that best corresponds to
the event of the received tire condition signals, e.g., wheel FR
rotates 180 degrees each time a tire condition signal having S1 ID
is received therefore correlating S1 with the FR location. In step
166, a determination is made as to whether the determined tire
location correlation has a confidence value greater than a
predetermined value. Assuming that the confidence level of the
determination is sufficient, the tire-based unit ID and determined
tire location information is stored in memory in step 168. If the
confidence value is not greater than a predetermined level, no
location information is stored, the process loops back to step 154,
and any previous stored location information is retained. The
vehicle-based receiver/controller 44 correlates the sensors S1, S2,
S3, and S4 with tire locations FR, FL, RR, and RL on the
vehicle.
[0042] Signal filtering is required even on smooth road surfaces.
Both passive and adaptive digital filtering techniques can be used
to smooth the signal over the frequency range of three to twenty
Hertz without undue signal attenuation or use of battery
energy.
[0043] Although the toothed disc, as described above, has a missing
tooth to establish a zero position of the wheel, the wheel position
at the time the vehicle is started can be designated the zero
position, knowing that every 72 pulses (assuming a disc with 72
teeth) returns the wheel to the "zero" position (i.e., start
position). Also, the tire-based sensor units could communicate via
RF to the ABS ECU 40 and that the ABS ECU 40 could perform the
correlation of tire-based units with vehicle corner location.
[0044] Referring now to FIGS. 7-10, one skilled in the art will
appreciate the method and apparatus 200 of the present invention
for determining a tire condition and relative location of a dually
tire pair (corner location and inside/outside position) on a
vehicle 202 with a tire pressure monitoring system. Recall that a
dually tire pair on a vehicle includes a multi-tire per side per
axle arrangement. Specifically, a vehicle, such as a pick-up truck,
may have two wheels located on each side of the rear axle 204 of
the vehicle 202. Such a vehicle is referred to as a "dually" since
each of the rear corner locations 206, 208 of the vehicle have dual
tires. Looking at the rear corner locations 206 and 208, the dual
tire pairs have inside tires 212, 214 and outside tires 216, 218,
respectively. The tires of the dual tire pair at the rear right
corner location 208 of the vehicle 202 are designated herein as
RR.sub.o for the rear right outside tire 218 and RR.sub.i for the
rear right inside tire 214. The tires of the dual tire pair at the
rear left corner location 206 of the vehicle 202 are designated
herein as RL.sub.o for the rear left outside tire 216 and LR.sub.i
for the rear left inside tire 212.
[0045] In accordance with the present invention, each of the rear
tires has an associated tire condition sensor 222, 224, 226, and
228, respectively. The RR.sub.o outside tire has an associated tire
condition sensor unit 228 providing a unique sensor ID signal
{S3.sub.o} and the RR.sub.i inside tire has an associated tire
condition sensor unit 224 providing a unique sensor ID signal
{S3.sub.i}. The RL.sub.o outside tire has an associated tire
condition sensor unit 226 providing a unique sensor ID signal
{S4.sub.o} and the RL.sub.i inside tire has an associated tire
condition sensor 222 providing a unique sensor ID signal
{S4.sub.i}.
[0046] The sensor units for each dually tire pair are mounted onto
the rear axle in a known relative angular position relative to the
sensor in the other associated tire of the dually pair. In
accordance with one example embodiment of the present invention,
tire condition sensor units 228 and 224 are aligned at
substantially zero degrees relative to each other and tire
condition sensor units 222 and 226 are aligned at substantially
zero degrees relative to each other. Such an alignment of the
sensors relative to each other is referred to as being "clocked" to
each other. FIG. 8 shows the tire pair at the rear left corner
location 206, where the RL.sub.o tire 216 is viewed looking at the
TPM tire condition sensor unit 226 from the outside looking into
the vehicle. The RL.sub.i tire 212 is viewed in the drawing looking
at the TPM tire condition sensor unit 222 from inside the vehicle
looking outward.
[0047] Each of the tire-based sensor units 222 and 226 has a 25
degree offset relative to a tangent of their rim mount and in
opposite directions. As the tire pair at the corner location 206
rotates, the output signals of their associated accelerometers will
be sinusoidal signals that are out of phase by 130 degrees (180
degrees--(the two 25 degree (i.e., 50 degree) offsets)). Thus, as
the dually tire pair at corner location 206 rotates, the output
signals from the associated accelerometer sensors of the tire
condition sensor units 222 and 226 will be as depicted in the graph
of FIG. 10. Although a zero degree relative alignment between the
two sensors is described, other predetermined alignments between
the two sensors could be used. The important thing is that the
sensors from each dually pair that is part of the valve stem
assembly are mechanically or manually synchronized (mechanically
aligned or clocked) such as within a few degrees of each other
(i.e., substantially aligned).
[0048] One of the inside tire or outside tire or both of the tires
of the dually pair can be used for the corner location as described
above. So, assume that only the inside tire 212 is used for corner
location determination as described above. After the tire 212 is
associated with the corner location at 206, the relationship
between the signals of the tire condition sensor units 222 and 226
are used to determine the relative location between the two tires,
namely the inside or outside location. This inside or outside
location determination is accomplished by monitoring the lead/lag
relationship of the transmitted signals which are offset by 130
degrees. For a given side of the vehicle, the inner or the outer
tire-based sensor units will always be leading in phase angle (on
one side of the vehicle, the inner tire signal leads the outer tire
signal, and on the other side of the vehicle, the inner tire signal
lags the outer tire signal). When the vehicle is moving in the
forward direction, the outer tire signal leads the inner tire
signal on the driver side (206) and the inner tire signal leads the
outer tire signal on the passenger side (208).
[0049] Again, it should be appreciated that, for the dually pair,
either one tire or both tires could be used for corner location by
correlating condition and ID transmissions with 180 degree
rotations monitored from the wheel speed sensors. The
inside/outside determination is made from the lead/lag relationship
of the transmitted signals.
[0050] The present invention has been described with regard to
example embodiments. Those skilled in the art will perceive
modifications and alterations. Such modifications and alterations
are contemplated and are intended to be covered by the claims set
forth below.
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