U.S. patent application number 10/359968 was filed with the patent office on 2003-06-26 for determination of wheel sensor position using radio frequency detectors in an automotive remote tire monitor system.
This patent application is currently assigned to Schrader Bridgeport International, Inc.. Invention is credited to Marguet, Emmanuel, Stewart, William David.
Application Number | 20030117276 10/359968 |
Document ID | / |
Family ID | 24226458 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030117276 |
Kind Code |
A1 |
Marguet, Emmanuel ; et
al. |
June 26, 2003 |
Determination of wheel sensor position using radio frequency
detectors in an automotive remote tire monitor system
Abstract
In a remote tire monitor system, radio frequency (RF) signals
including tire data are transmitted from a plurality of tire
monitors at wheels of a vehicle. At an RF receiver, the signals are
received and tire data is detected. The RF signals are detected at
a receiving RF detector associated with the transmitting tire
monitor. The receiving RF detector produces a transmission
indication in response to the received RF signals. A control unit
is coupled to the RF receiver and the RF detector. The control unit
receives the tire data and the transmission indication and
associates a position of the transmitting tire monitor with the
tire data in response to transmission indication. This permits
automatic update of the position of tire monitors on the
vehicle.
Inventors: |
Marguet, Emmanuel; (Arcon,
FR) ; Stewart, William David; (Antrim, IE) |
Correspondence
Address: |
John G. Rauch
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
Schrader Bridgeport International,
Inc.
|
Family ID: |
24226458 |
Appl. No.: |
10/359968 |
Filed: |
February 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10359968 |
Feb 5, 2003 |
|
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|
09557682 |
Apr 25, 2000 |
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6518876 |
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Current U.S.
Class: |
340/442 ;
340/447 |
Current CPC
Class: |
B60C 23/0433 20130101;
B60C 23/0416 20130101 |
Class at
Publication: |
340/442 ;
340/447 |
International
Class: |
B60C 023/00 |
Claims
1. A method for operating a remote tire monitor system, the method
comprising: at a transmitting tire monitor of a plurality of tire
monitors, transmitting radio frequency (RF) signals including tire
data; at a RF receiver, receiving the RF signals and detecting the
tire data; at a receiving RF detector of a plurality of RF
detectors each associated with a tire monitor, producing a
transmission indication; and at a control unit, receiving the tire
data and transmission indication and associating a position of the
transmitting tire monitor with the tire data in response to the
transmission indication.
2. The method of claim 1 further comprising: comparing the position
of the transmitting tire monitor with a stored position of the
transmitting tire monitor; and updating the stored position with
the position of the transmitting tire monitor when the position of
the transmitting tire monitor differs from the stored position.
3. The method of claim 1 wherein receiving the RF signals
comprises: demodulating the RF signals; decoding the tire data; and
conveying the tire data to the control unit.
4. The method of claim 3 wherein decoding the tire data comprises:
decoding a tire monitor identifier; and decoding tire pressure
data.
5. The method of claim 1 wherein producing a transmission
indication comprises: detecting an envelope of the RF signals; and
producing a wire line signal in response to the envelope of the RF
signals.
6. The method of claim 5 wherein producing a wire line signal
comprises: modulating a current in a conductor coupled with the
control unit.
7. The method of claim 6 further comprising: detecting modulation
of the current at the control unit to locate the transmitting tire
monitor.
8. A control unit for a remote tire monitor system of a vehicle,
the control unit comprising: a radio frequency (RF) receiver
configured to receive RF signals conveying tire data from at least
one transmitting tire monitor of a plurality of tire monitors
associated with wheels of the vehicle; and a RF decoder configured
to receive a transmission indication from at least one receiving RF
detector of a plurality of RF detectors associated with wheels of
the vehicle and identify a position of the transmitting tire
monitor on the vehicle in response to the transmission
indication.
9. The control unit of claim 8 further comprising: a memory; and a
controller configured to store in the memory position of the
plurality of tire monitors including the position of the
transmitting tire monitor.
10. The control unit of claim 9 wherein the controller is further
configured to compare the position of the transmitting tire monitor
with a stored position of the transmitting tire monitor store the
position of the transmitting tire monitor as the stored position
when the position of the transmitting tire monitor does not match
the stored position.
11. A radio frequency (RF) detector for use in association with a
tire monitor of a remote tire monitor system of a vehicle, the RF
detector comprising: an antenna to sense RF signals from the tire
monitor; an envelope detector coupled to the antenna; and an output
circuit coupled to the envelope detector.
12. The RF detector of claim 11 wherein the output circuit
comprises: at least one transistor to produce a wire line
signal.
13. The RF detector of claim 11 wherein the envelope detector
comprises: a circuit coupled with the antenna to detect an envelope
of electrical signals produced by the antenna in response to the RF
signals; and an amplifier.
14. The RF detector of claim 13 wherein the output circuit
comprises: at least one transistor which modulates a wire line
signal in response to the envelope.
15. A method for a remote tire monitor system, the method
comprising: receiving radio frequency (RF) signals including tire
data from a transmitting tire monitor associated with a wheel of a
vehicle; receiving a wire line indication from an RF detector
associated with the transmitting tire monitor; and identifying
position on vehicle of the transmitting tire monitor in response to
the wire line indication.
16. The method of claim 15 further comprising: storing position
data for a plurality of tire monitors of the remote tire monitor
system; and updating the position data for the transmitting tire
monitor when the position of the transmitting tire monitor varies
from a stored position for the transmitting tire monitor.
17. The method of claim 15 wherein receiving a wire line indication
comprises: detecting a modulated electrical signal on a wire
coupled to the RF detector near the transmitting tire monitor.
18. The method of claim 17 wherein detecting a modulated electrical
signal comprises: detecting current which has been modulated by an
envelope of the RF signals at the RF detector.
19. A remote tire monitor system comprising: a plurality of tire
monitors, each tire monitor being associated with a wheel of a
vehicle and configured to transmit radio frequency (RF) signals
including tire data; a plurality of RF detectors, each RF detector
being mounted on the vehicle proximate an associated tire monitor
to detect the RF signals from the associated tire monitor and
produce a transmission indication in response to detected RF
signals; a RF receiver to receive tire data in RF signals
transmitted by any tire monitor of the plurality of tire monitors;
and a control unit coupled with the plurality of RF detectors to
receive transmission indications and coupled with the RF receiver
to receive the tire data, the control unit being operative to
associate a position of a transmitting tire monitor with a received
transmission indication.
20. The remote tire monitor system of claim 19 wherein each RF
detector comprises: an envelope detector to detect an envelope of
the RF signals from the associated tire monitor; and an output
circuit to modulate an electrical signal on a conductor as the
transmission indication.
21. The remote tire monitor system of claim 20 wherein the output
circuit comprises: at least one transistor for modulating a current
in the conductor.
22. A method for automatically identifying positions of a plurality
of tire monitors on a vehicle, the method comprising: initiating
operation of the plurality of tire monitors upon operation of the
vehicle; receiving from the plurality of tire monitors radio
frequency (RF) signals containing tire information; receiving
wireline indications from a plurality of RF detectors, each RF
detector being associated on the vehicle with a tire monitor to
detect but not demodulate RF signals transmitted by the tire
monitor; and associating the tire information from each tire
monitor with an RF detector in response to the wireline
indications.
23. The method of claim 22 further comprising: at each tire
monitor, detecting motion of the tire monitor; and transmitting
local tire information in response to detection of motion.
24. The method of claim 23 wherein transmitting local tire
information comprises: transmitting tire pressure data.
25. The method of claim 24 wherein transmitting local tire
information further comprises: transmitting a tire monitor
identifier associated with the tire monitor.
26. The method of claim 22 wherein associating the tire information
from each tire monitor with an RF detector comprises determining an
identifier associated with a transmitting tire monitor in the tire
information; identifying a receiving RF detector which originated a
received wireline indication; and storing the identifier at a
memory location associated with the receiving RF detector.
27. The method of claim 22 further comprising: receiving subsequent
RF signals containing additional tire information; receiving
subsequent wireline indications from receiving RF detectors;
associating the additional tire information with the receiving RF
detectors; and verifying the tire information with the additional
tire information.
28. The method of claim 27 further comprising: after verification,
storing the tire information in a memory location associated with
the RF detector which is associated with the tire information.
29. A method for automatically updating a remote tire monitor
system of a vehicle, the method comprising: storing identification
information for each tire monitor of a plurality of tire monitors
of the vehicle; receiving an identifier transmitted by a
transmitting tire monitor; receiving a transmission indication from
a receiving radio frequency (RF) detector associated with the
transmitting tire monitor; and when the identifier does not produce
a match with the identification information, updating the
identification information using the identifier.
30. The method of claim 29 wherein receiving the identifier
comprises: receiving RF signals at an RF circuit; demodulating the
RF signals to receive tire information; and locating the identifier
in the tire information.
31. The method of claim 30 wherein receiving a transmission
indication comprises: detecting the RF signals at the receiving RF
detector; and without demodulating the RF signals, producing a
wireline indication in response to the RF signals; and at a control
unit, detecting the wireline indication as the transmission
indication.
32. The method of claim 31 further comprising: in response to the
wireline indication, reading the identification information from a
storage location in memory, the storage location being associated
with the receiving RF detector.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to a remote tire
monitoring system. More particularly, the present invention relates
to a method and apparatus for automatically updating position
information for tire monitors in such a system.
[0002] Systems have been developed to monitor a characteristic such
as tire pressure of a vehicle and to report the characteristic to a
receiver at a central monitoring station using radio transmissions.
A monitor is located at each tire and periodically takes a
measurement of the tire characteristic. The monitor then transmits
the results of the measurement in a radio frequency transmission to
the central monitoring station which produces an alarm or a display
in response to the measurement.
[0003] One problem with such systems has been the need to program
the location of the transmitters at the central station. To be
fully useful, the tire characteristic data is preferably associated
with the tire which originated the measurement when presenting a
display or alarm. Each monitor includes identification information
which can be transmitted with the measurement. The tire monitor is
preferably activated to produce this information and the
information is then conveyed to the central station and associated
with the position of the tire.
[0004] In the technique of U.S. Pat. No. 5,600,301, the tire
monitors each include a reed switch or other magnetic device. A
magnet is passed near the reed switch, causing the monitor to
transmit a radio frequency transmission that includes
identification data. A service technician repeats this process at
each wheel and then loads the identification and position
information into the central monitoring station. Another method
provides a printed bar code on each tire monitor which contains the
identification information and which may be read with a suitable
bar code reader.
[0005] In U.S. Pat. No. 5,880,363, an activation signal is provided
from the central controller to a low frequency transmitter at each
wheel well. The transmitter generates a low frequency signal to
activate the tire monitor. The tire pressure monitor responds by
generating a long wave identification signal and transmitting that
signal with tire pressure and identification data directly to the
control unit. The long wave identification signal is used to
identify the position of the tire by distinguishing this
transmission from other transmissions received by the
controller.
[0006] U.S. Pat. No. 5,883,305 discloses two-way communication of
data by radio signals. A tire pressure monitor is activated by a
radio frequency signal transmitted by an antenna in the wheel well
adjacent the tire. The tire pressure monitor transmits a second
radio frequency signal which is detected by the wheel well antenna.
The second signal is demodulated to detect that tire pressure
data.
[0007] These previous techniques have been limited in
effectiveness. The magnetic programming technique may be subject to
interference and crosstalk, for example in a factory where many
such tire monitors are being assembled with tires and vehicles. The
bar code label system requires a label at each tire which can be
lost or become dirty or illegible. The apparatus for transmitting a
long wave activation signal and generating a long wave
identification signal therefrom is too expensive for some
applications. The two-way data communication techniques requires
demodulation of the received radio signals at the wheel well and
coaxial cabling back to the central controller, both of which add
to the cost of the system.
[0008] A further limitation of some of these prior techniques is
the manual operation requiring activation by a service technician.
A system is desired which automatically conveys wheel position data
to the receiver. Such a system would be particularly useful after
any change in tire position, such as tire rotation or replacement
of a tire.
SUMMARY
[0009] By way of introduction only, a remote tire monitor method
and apparatus provide a central control unit in the cockpit or
trunk of a vehicle. The control unit includes a radio frequency
(RF) receiver and a controller. Tire monitors are located at each
wheel of the vehicle and periodically transmit tire data such as
tire pressure information, along with a tire monitor identifier.
Four small, inexpensive RF detectors are located near each wheel,
for example, in the wheel well. Each detector is connected to the
central control unit by a power line and a ground line.
[0010] When a tire monitor transmits data by emitting an RF
transmission, the RF detector that is closest to the transmitter
will detect the burst of RF energy. The RF detector responds to the
RF energy by modulating the power line to the control unit with the
envelope of the transmitted data. The control unit detects this
modulation on one of its power lines. Also, the RF receiver of the
control unit receives and demodulates the data transmitted by the
tire monitor. The control unit associates the received data with
the position indication provided by the modulation on the power
line. When the positions of the wheels on the vehicle are changed,
the control unit can determine the new position using the modulated
power line or by using the tire monitor identifier in the
transmitted data.
[0011] The foregoing discussion of the preferred embodiments has
been provided only by way of introduction. Nothing in this section
should be taken as a limitation on the following claims, which
define the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWING
[0012] FIG. 1 is a block diagram of a remote tire monitor system
shown in conjunction with portions of a vehicle;
[0013] FIG. 2 is a flow diagram illustrating an auto learn method
for the remote tire monitor system of FIG. 1; and
[0014] FIG. 3 is a flow diagram illustrating an auto learn method
for the remote tire monitor system of FIG. 1.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0015] Referring now to the drawing, it is a block diagram of a
remote tire monitor system 100 shown in conjunction with portions
of a vehicle 102. The vehicle 102 includes in this example four
tires 104. Other numbers of tires may be included, such as a fifth
tire as a spare or additional tires if the vehicle is a truck,
trailer or other multi-wheeled vehicle.
[0016] Associated with each of the tires 104 is a transmitter or
tire monitor 106. Each of the tire monitors 106 includes a battery
powered, radio frequency (RF) transmitter. Any suitable tire
monitor may be used. U.S. patent application Ser. No. 09/245,938,
entitled "Method And Apparatus For A Remote Tire Pressure Monitor
System," filed Feb. 5, 1999 in the name of McClelland et al., and
commonly assigned with the present application is incorporated
herein by reference and illustrates one suitable tire monitor for
use in the remote tire pressure monitor system 100. Each tire
monitor 106 includes a sensor such as a pressure sensor for
measuring a tire characteristic. The tire monitor 106 converts the
measured tire characteristic to tire data. The tire data is encoded
for transmission from the tire monitor 106.
[0017] The tire monitor further includes a transmitter configured
to transmit RF signals including the tire data. In some
embodiments, the transmissions are encoded or randomized to
minimize clashes at a receiver. For example, U.S. patent
application Ser. No. 09/245,577, entitled "Method For Communicating
Data In A Remote Tire Pressure Monitoring System," filed Feb. 5,
1999 in the name of Bailie, et al., and commonly assigned with the
present application is incorporated herein by reference. This
application shows a technique in which data words are transmitted
separated by a time delay. The time delay for each respective data
word is defined according to a repeating pattern common to the
tires so that data words are transmitted during a plurality of
aperiodic time windows. Transmission parameters such as modulation
techniques, transmission frequency and transmission power are
chosen according to local regulations and to assure reliable
reception of the RF signals.
[0018] The tire monitor 106 includes a motion switch 139. The
motion switch 139 closes upon detection of movement of the vehicle
100. The motion switch 139 provides a signal to the processor 124
indicating closure of the switch 139 and motion of the vehicle. In
response to closure of the switch, the tire monitor system 100
begins operating, for example, by transmitting tire data. In the
illustrated embodiment, during normal operation, the tire monitor
106 transmits supervisory tire pressure information once every
minute. Any suitable motion switch may be used for the switch
139.
[0019] The remote tire monitor system 100 includes a control unit
110 and a plurality of radio frequency (RF) detectors 112. In
alternative embodiment, the remote tire monitor system 100
additionally includes a user display for providing user information
such as tire pressure information and low tire pressure alarms. In
the illustrated embodiment, each RF detector 112 is mounted on the
vehicle 102 proximate an associated tire monitor 106 to detect the
RF signals from the associated tire monitor 106 and produce a
transmission indication in response to detected RF signals. Each of
the RF detectors 112 is electrically coupled by a conductor 114 to
the control unit 110. Structure and operation of the RF detectors
112 will be described in greater detail below.
[0020] The control unit 110 includes an RF receiver 120, an RF
decoder 122, and a controller 124. The RF receiver 120 is
configured to receive RF signals conveying tire data from at least
one transmitting tire monitor 106 of the plurality of tire monitors
106 associated with the wheels or tires 104 of the vehicle 102. Any
suitable RF receiver circuit may be used. The design and
implementation of the RF receiver 120 will depend on the type of
modulation used for the RF signals, transmission frequency for the
RF signals, and physical limitations such as permitted size, weight
and power dissipation.
[0021] The RF decoder 122 is configured to receive a transmission
indication from at least one receiving RF detector 112 of a
plurality of RF detectors 112 associated with wheels or tires 104
of the vehicle 102. Thus, a tire monitor 106 will transmit RF
signals which are detected by the RF detector 112 associated with
the transmitting tire monitor 106. The receiving RF detector 112
signals its detection of the RF signals by providing the
transmission indication on its associated conductor 114.
[0022] The RF decoder 122 is further configured to identify a
position of a transmitting tire monitor on the vehicle in response
to the transmission indication received from an RF detector.
Accordingly, the RF decoder 122 includes a plurality of input
circuits 123 coupled to the conductors 114 which are in turn
coupled to the RF detectors 112. A transmission indication
impressed on a conductor 114 is detected by an associated input
circuit 123. In the illustrated embodiment, there is a one-to-one
relationship between input circuits 123 and RF detectors 112. In
this manner, the RF detector 112 which originated the transmission
indication may be identified by the RF decoder determining which
input circuit 123 detects the transmission indication. In
alternative embodiments, the RF decoder 122 may include fewer than
four input circuits 123 which are multiplexed in some manner among
the plurality of RF detectors 112. For example, a single input
circuit 123 may be time shared among the plurality of RF detectors
112 to reduce the cost and complexity of the RF decoder 122.
[0023] The RF decoder 122 is electrically coupled with the RF
circuit 120. Upon receipt of RF signals at the RF circuit 120, the
RF signals are demodulated to extract the tire data contained
within the RF signals. In some applications, additional data
decoding may be required after demodulation. The tire data in one
exemplary embodiment includes a tire monitor identifier, or unique
identification code which uniquely identifies the tire monitor 106
which transmitted the RF signals. In addition, in this exemplary
embodiment, the tire data also includes tire pressure data related
to a sensed tire pressure of the tire 104 at which the transmitting
tire monitor 106 is located. Alternative tire data may be included
or substituted for the tire pressure data, such as a number of tire
revolutions, tire temperature, and so forth.
[0024] After extracting the tire data from the RF signals, the tire
data is conveyed from the RF receiver 120 to the RF decoder 122.
The RF decoder 122 associates the tire data with a position of the
transmitting tire monitor 106 on the vehicle 102. Position
information is determined using the input circuit 123 and a
transmission indication received over a conductor 114 from RF
detector 112. The tire data and associated tire position are
conveyed from the RF decoder 122 to the controller 124.
[0025] The controller 124 controls the operation of the remote tire
monitor system 100. The controller 124 is preferably a
microcontroller including a processor 128 and a memory 126. The
processor 128 operates in response to data and instructions stored
in the memory 126 to control overall operation of the system
100.
[0026] In the illustrated embodiment, the processor 128 stores
position data for a plurality of tire monitors 106 of the remote
tire monitor system 100. The controller 124 is electrically coupled
to the RF decoder 122 to receive tire data and position data from
the RF decoder 122. In the illustrated embodiment, when tire data
and position data are received at the microcontroller 124, the
processor 128 retrieves stored position data from the memory 126.
In one embodiment, the position data are stored in association with
a position on the vehicle, such as left front, left rear, right
front or right rear. The received position data is compared with
the stored position data. If there is no change, the position data
is not updated and further processing may occur using the received
tire data. However, the processor 128 updates the position data for
the transmitting tire monitor 106 when the position of the
transmitting tire monitor 106 varies from the stored position data
for the transmitting tire monitor. Thus, the controller 124
includes a memory 126 and a processor configured to store in the
memory 126 position of the plurality of tire monitors 106 including
the position of the transmitting tire monitor which originated the
received position data.
[0027] In an alternative embodiment, the memory 126 is not used for
storage of position data. Rather, the received tire data is
associated by the control unit 110 with the position information
provided by the transmission indication from a RF detector 112. The
tire data and the position information from the input circuit 123
are used together to produce a display or alarm, if appropriate, by
the system 100. Additionally, in still another embodiment, the tire
data omits any identifying information for the transmitting tire
monitor 106 and again, the tire data and the position information
from the input circuit 123 are used together to produce the
appropriate display or alarm.
[0028] Completing the identification of the elements in FIG. 1, the
vehicle 102 further includes a CAN driver 130, a voltage regulator
132, power line noise suppressor 134, and a battery 136. The
battery 136 provides operating power for electrical systems of the
vehicle 102 including the remote tire monitor system 100. The
battery 136 is a portion of the electrical power system of the
vehicle, which typically also includes an alternator and other
components. Such electrical power systems for vehicles are well
known. The power line suppressor 134 reduces noise on the power
line from the battery 136. Noise may originate in other electrical
components of the vehicle 102, such as the ignition system. The
voltage regulator 132 receives the battery voltage or other
operating voltage from the power line suppressor 134 and produces a
well regulated voltage for components such as the control unit 10
and CAN driver 130. The CAN driver 130 provides electrical
interface with other elements of a Controlled Area Network.
Controlled Area Network or CAN is a serial communication protocol
for data commonly used in automotive and other applications. The
CAN bus 138 accessed by the CAN driver 130 is used to interconnect
a network of electronic nodes or modules. The CAN bus operates
according to an adopted standard. In conjunction with a remote tire
pressure monitor system 100, the CAN bus 138 may be used to convey
tire monitor data to other locations in the vehicle 102. For
example, an alarm or a display (not shown) may be controlled to
provide a visual or audible indication to an operator of the
vehicle 102 that the tire data indicates an out-of-range condition,
such as low tire pressure.
[0029] In FIG. 1, the RF decoder 122 and the controller 124 are
shown as separate elements of the control unit 110. In alternative
embodiments, they may be combined in a single processor or logic
block or circuit. Any other illustrated elements or additional
elements included to enhance the functionality of the system 100
may be integrated or combined with other components of the system
100.
[0030] Further, the system 100 should not be restricted to use in
conjunction with a CAN bus. In alternative embodiments, any other
communications medium may be employed for interconnecting the
system 100 with other elements of the vehicle 102. For example,
communication buses in accordance with the J-1850 or USB standards
may be substituted, or the control unit 110 may be directly hard
wired with other elements of the vehicle 102. Still further,
external communications may be omitted entirely so that the system
100 is completely self-contained.
[0031] FIG. 1 further shows a detailed view of one embodiment of an
RF detector 112 for use in the remote tire monitor system 100. The
RF detector 112 includes an antenna 140 to sense radio frequency
(RF) signals transmitted from the tire monitor 106, an amplifier
142, an envelope detector coupled to the antenna 140 through the
amplifier 142 and an output circuit 146 coupled to the envelope
detector 144. The envelope detector 144 includes a filter 149, a
diode 150, a capacitor 152 coupled to ground and an amplifier 154.
The RF detector 112 is powered from a power line 156 and a ground
line 158 provided on the conductor 114 which couples the RF
detector 112 to the input circuit 123 of the RF decoder 122. To
isolate the operational circuitry of the RF detector 112 from noise
on the power line 156, the RF detector 112 further includes a
resistor 160 and a capacitor 162 to ground.
[0032] The envelope detector 144 responds to the input signals
received at the antenna and amplified by the amplifier 142 to
produce at the output circuit 146 data corresponding to the
envelope of the RF signals transmitted by the tire monitors 106.
Thus, the filter 148, diode 150 and capacitor 152 together form a
circuit coupled with the antenna 140 to detect an envelope of
electrical signals produced by the antenna in response to the RF
signals. The envelope is itself an electrical signal which is
amplified in the amplifier 154. The output signal from the
amplifier 154 is applied to the base of a transistor 164. In
response to this signal at its base, the transistor 164 modulates a
wireline signal on the conductor 114 in response to the envelope of
the RF signals received at the RF detector 112. That is, the
signals applied at the base of the transistor 164 control turn-on
of the transistor 164, conducting current from its collector at the
power node of the conductor 114 to its emitter at the ground node
of the conductor 114. As a result, the current in the conductor 114
will be modulated in response to the RF signals received at the
antenna 140 of the RF detector 112.
[0033] In one embodiment, to detect the modulated current, the
input circuits 123 of the RF decoder in the illustrated embodiment
may include a current mirror which duplicates the current drawn
from the input stage of the input circuit 123, coupled to the
conductor 114. The output current from the current mirror in the
input circuit 123 is provided to a resistor which converts the
current signal into a voltage signal which can be read by the
microcontroller 124. Suitable current mirror circuits are within
the purview of those ordinarily skilled in the art of circuit
design.
[0034] In this manner, then, the signal provided on the conductor
114 forms a transmission indication indicating that the tire
monitor 106 associated with the RF detector 112 has transmitted an
RF signal which was detected by the RF detector 112. Producing the
transmission indication includes detecting the envelope of the RF
signals transmitted by the tire monitor 106 and producing a
wireline signal on the conductor 114 in response to the envelope of
the RF signals. In particular, in the illustrated embodiment, the
wireline signal is produced by modulating a current in a conductor
114 coupled with the control unit 110. The control unit 110 detects
the modulation of the current to locate the transmitting tire
monitor 106.
[0035] Significantly, the RF detector 112 does not demodulate the
data transmitted by the tire monitor 106. Only the RF circuit 120
of the control unit 110 demodulates the data to extract the
contents of the RF signal 106. The RF detector only senses the
presence of the transmitted RF signals. This reduces the cost of
the RF detectors 112 and the overall cost of the remote tire
monitor system 100.
[0036] Also, by modulating the current in the conductor 114, the RF
detector's sensitivity to noise is reduced. Noise will occur in the
form of voltage spikes or pulses on the conductor 114. However,
this noise will have little effect on the operation of the RF
detector 112 and will have little effect on the current levels in
the conductor. As a result, the conductor 114 can be, for example,
a twisted pair of wire or any other inexpensive two-wire cable.
Coaxial cable or other shielded cable is not necessary for
implementing the system 100 using RF detector 112.
[0037] In alternative embodiments, the RF circuit 120 may be
omitted. In such an embodiment, the RF detectors 112 are used to
detect the variations in the radio frequency signals and modulate a
wire line signal on the conductors 114. The RF decoder 122 in such
an embodiment is configured to demodulate the data in conjunction
with the microcontroller 124. Current pulses on the conductor 114
are detected by the RF decoder 122 and converted to voltage pulses.
The voltage pulses can be read by the microcontroller 124. In this
manner, microcontroller 124 obtains the data from the RF detectors
and the RF decoder, without use of an RF circuit 120. This has the
advantage of eliminating the relatively expensive RF circuit.
Further, this permits reduction in the transmit power used by the
tire monitors 106 to transmit the radio frequency signals conveying
the entire data. In some jurisdictions, substantially attenuated
transmit power is required for applications such as tire monitors.
These low transmit power requirements may be satisfied while still
providing reliable performance in the remote tire monitoring system
100 by use of the RF detectors 112.
[0038] In still other embodiments, the functionality described
herein may be implemented using a programmed computer or other
processor operating in response to data and instructions stored in
memory. The processor may operate in conjunction with some or all
of the hardware elements described in the embodiments shown
herein.
[0039] The disclosed tire monitor system may be used to provide an
improved auto learn or auto train method for automatically
identifying positions of a plurality of tire monitors on a vehicle.
As noted above, previously devices such as a transponder or
magnetic activation tools were used in the car plant to train the
control unit of the remote tire monitor system with identifiers for
the wheel sensors or tire monitors. With the vehicle located in a
training booth or activation area at the factory, the wheel sensors
were activated in sequence and the control unit, expecting
activated pressure transmissions in a certain order, learned the
identification and position on the vehicle of the wheel sensors. So
as to prevent cross talk from other training booths, each
activation area is required to be RF shielded. Another method of
training the receivers was to use bar code readers to scan the
identifiers of the wheel sensors and input this data into the
receiver. All of these methods required an additional operation
either manually or by automatic readers. These operations add cost
and potential for downtime.
[0040] In the illustrated embodiment of FIG. 1, no such tools are
required. In the car plant at the end of the production line, a
standard one to two minute dynamic test is used to test and
calibrate steering, brakes etc. of the vehicle. For the illustrated
embodiment, positions and identities of the four tire pressure
monitor wheel sensors are automatically learned during this dynamic
test.
[0041] This is achieved by placing the control unit or receiver in
a "learn state" at a dynamic test booth. The wheel sensors transmit
either once a minute as in the normal mode, or in a special initial
mode corresponding to a brand new, right out of the box state,
transmitting more often, for example every 30 seconds, or every 10
seconds.
[0042] For example, when the wheel sensors leave the manufacturer's
production line, they are placed in off mode. This mode means that
each wheel sensor is dormant until it is activated by the closing
of its motion switch. Closing the motion switch is only achievable
through centrifugal force caused by spinning the tire monitor on a
rotating wheel. During normal operation, the wheel sensor, while
driving, transmits tire information including supervisory tire
pressure once every minute. However, in the illustrated embodiment,
for the driving periods during the first 16 activations of the
motion switch, the wheel sensor will transmit the supervisory
pressure data once every 30 seconds (to conform to United States
regulatory requirements) or 10 seconds outside the United States.
Other time intervals may be used. After the initial 16
transmissions, or any other suitable number, the transmission
interval is changed to its normal mode value, such as one minute.
This initial mode is known as factory test mode.
[0043] At the time of the dynamic vehicle test, the vehicle is
accelerated, causing the wheel sensors to activate with the
rotation of the wheels and associated closure of their motion
switches. When the wheel sensors begin transmitting tire pressure,
say once every thirty seconds, each sensor's identifier is
transmitted by the sensor and is received up by the RF circuit of
the control unit. In this initial unlearned state, the receiver
loads the new identifier into memory, associating the transmission
with one of the four RF detectors. Only data received which also is
synchronized to activity on one of the RF detector conductors is
regarded as valid. Over the one to two minute duration of the
dynamic test, each wheel sensor will transmit numerous times and
the control unit can verify the tire information, such as each
wheel sensor identifier, and associated wheel position. The control
unit can then load this data into non-volatile memory for
subsequent normal use.
[0044] Key advantages of this auto-learn technique is the lack of
any additional labor or equipment at the vehicle assembly plant,
and the lack of a need for a transponder component or magnetic
switch in the wheel sensor. Also there is no possibility of
learning the wrong wheels, from other vehicles due to cross talk or
of getting the wrong position. Thus, cost is reduced, operation is
simplified and reliability is increased. Using the illustrated
embodiment of the tire monitor system, no additional activation or
learning tools are required to train the control unit with the
wheel sensors' position on the vehicle. The only device required to
train the control unit is the standard dynamic vehicle test at the
end of line test in the vehicle assembly plant. Because the
training procedure can be carried out in parallel with the steering
and braking tests on the rolling road, and because of the factory
test mode feature, no extra time or cost is required to `auto
learn` the tire monitor system.
[0045] The illustrated embodiment further provides for automatic
update of tire monitor position information in the control unit
upon replacement of one of the tire monitors of the system. This
would occur, for example, if one of the wheels or tires of the
vehicle is replaced. Due to the nature of the current embodiment,
where the RF detectors are continuously indicating the position of
the wheel sensors, a wheel sensor may be replaced and detected by
the control unit without the need for user intervention. In this
case, where a new wheel sensor is put on a wheel, the control unit
initially realizes it is receiving a wrong identifier for the tire
monitor, but still getting RF detector pulses from a particular
wheel position. In addition, the control unit detects that the
previously stored identifier for that position is no longer being
received. Over a period of time, say ten minutes driving, the
receiver verifies it has stopped receiving a stored identifier and
is now receiving a new ID for that position. After verification,
the new identifier is stored for that position and operation
continues as normal.
[0046] The big advantage of this is the lack of need for user
intervention and elimination of the need for a service tool at each
service location. Tire monitor position and identification is
updated automatically.
[0047] FIG. 2 is a flow diagram illustrating an auto learn method
for the remote tire monitor system of FIG. 1. The method begins at
block 200. At block 202, one or more tires with new tire monitors
are mounted on a vehicle which includes a remote tire monitor
system. In this embodiment, the tire monitors are in unused, out of
the box condition from the manufacturer. The installation of block
202 may occur as part of the final assembly of the vehicle at the
factory. Alternatively, the installation may occur when new tires
are installed on the vehicle or when a remote tire monitor system
is added to the vehicle.
[0048] At block 204, the dynamic vehicle test is initiated and, in
response, at block 206, the tire monitors begin transmitting radio
frequency (RF) signals. The dynamic vehicle test is a test to check
proper functionality of the systems of the vehicle, including drive
train and brakes. Alternatively, any activity which causes the tire
monitors to begin transmitting may be substituted at block 204 to
initiate transmission at block 206. For example, the process of
driving the vehicle from the end of the assembly line to a storage
area or a final checkout area in block 204 may be adequate to begin
transmission at block 206. It is contemplated that the tire
monitors each include a motion switch which activates the tire
monitor in response to motion of the tire monitor on the wheel of
the vehicle.
[0049] Further, at block 206, the tire monitor begins transmitting
at a test mode interval, such as once every 30 or 60 seconds. This
aspect may be omitted but adds convenience for initializing the
tire monitor system. After initialization, the interval may be
reduced to reduce power drain from the battery which powers the
tire monitor.
[0050] After transmission of the RF signals at block 206, the RF
signals are received by a receiver of the remote tire monitor
system at block 208. The RF signals are demodulated, decoded and
otherwise processed to extract the data conveyed on the RF signals.
For example, the tire monitor may modulate a carrier signal using
data corresponding to pressure of the tire or a tire monitor
identifier. The receiver of the remote tire monitor system
demodulates the received RF signals to receive the data. At block
212, the data including a tire monitor identifier, if any, is
provided to a control unit of the remote tire monitor system.
[0051] Meanwhile, the same RF signals received and demodulated at
blocks 208, 210 are detected at block 214. In the preferred
embodiment, the RF signals are received without demodulation, for
example, using a detector of the type illustrated above in
conjunction with FIG. 1. Other suitable RF detectors may be used.
At block 216, in response to the detected RF signals, a
transmission indication is provided to the control unit. The
transmission indication indicates to the control unit which RF
detector of the vehicle detected the RF signals transmitted by the
tire monitor and received by the receiver at block 208.
[0052] At block 218, identification information associated with the
tire monitor is stored. In one embodiment, the data forming the
identifier transmitted by the tire monitor and received by the
receiver of the remote tire monitor system is stored in memory.
Other types and formats of identification information may be
stored. For example, the control unit may store an RF detector
indicator which indicates which RF detector detected the received
RF signals.
[0053] In this manner, the described method provides automatic
learn capability in a remote tire monitor system. No manual
intervention is necessary for the control unit to identify and
store the identities and locations of individual tire monitors on
the vehicle. This reduces time and cost associated with initiating
operation of the remote tire monitor system.
[0054] FIG. 3 is a flow diagram illustrating an auto learn method
for the remote tire monitor system of FIG. 1. The method of FIG. 3
starts at block 300.
[0055] At block 302, RF signals transmitted by a tire monitor
associated with a wheel of a vehicle are received by a receiver of
the remote tire monitor system. At block 304, the RF signals are
demodulated, decoded and otherwise processed to extract the data
conveyed on the RF signals. For example, the tire monitor may
modulate a carrier signal using data corresponding to pressure of
the tire or a tire monitor identifier. The tire monitor identifier
may be a serial number or other unique or nearly-unique data
associated with the tire monitor. For example, the tire monitor
identifier may be multiple bit data stored in the tire monitor at
the time of manufacture of the tire monitor. The receiver of the
remote tire monitor system demodulates the received RF signals to
receive the data. At block 306, the data including a tire monitor
identifier, if any, is provided to a control unit of the remote
tire monitor system.
[0056] Meanwhile, the same RF signals received and demodulated at
blocks 302, 304 are detected at block 308. In the preferred
embodiment, the RF signals are received without demodulation, for
example, using a detector of the type illustrated above in
conjunction with FIG. 1. Other suitable RF detectors may be used.
At block 310, in response to the detected RF signals, a
transmission indication is provided to the control unit. The
transmission indication indicates to the control unit which RF
detector of the vehicle detected the RF signals transmitted by the
tire monitor and received by the receiver at block 302.
[0057] At block 312, stored identification information is retrieved
from memory at the control unit. In the illustrated embodiment, the
identification information is stored at a memory location
associated with the transmission indication or RF detector. Thus,
the control unit receives a wireline indication from a receiving RF
detector that a transmission has been received. Using the wireline
indication, the control unit selects the memory location from which
previous identification information is retrieved.
[0058] At block 314, the control unit determines if the identifier
received from the transmitting tire monitor matches the stored
identification information. In this application, a match may mean a
bit-by-bit match of received and stored data or some other level or
association between the received data and the stored data. If the
data match, at block 316, the tire information such as pressure
data are updated. For example, in one embodiment, tire pressure
data are stored along with the identification information for the
tire monitor. If the received tire pressure data varies by a
predetermined amount from the stored tire pressure data, the
received tire pressure data is stored and an alarm or other user
indication is generated.
[0059] At block 318, if there is no match between the received
identifier and the stored identification information, the method
waits for receipt of an additional transmission associated with
this RF detector. Preferably, the tire monitor transmits pressure
data and a tire monitor identifier periodically, such as once per
minute. Upon receipt of a subsequent transmission, at block 320,
the method attempts to verify the previously received tire monitor
identifier. This is done by comparing the newly received tire
monitor identifier and the previously received tire monitor
identifier to determine if there was an error in communication of
the previously received tire monitor identifier. In some
embodiments, multiple subsequent transmissions may be received for
comparison. If there is no verification, at block 322, the
mismatched transmission received at block 302 is discarded. This
condition indicates that the same tire monitor continues to
transmit, and the mismatched transmission was received with an
error.
[0060] If at block 320 the newly received data verify the
previously received data, the identification information stored for
this RF detector is updated with the tire monitor identifier from
the received transmission. This condition indicates that the tire
monitor has been changed and is communicating reliably. In this
manner, the illustrated system and method provide automatic update
capability after a tire monitor has been changed. This may occur if
the tires of the vehicle are rotated or if one or more tires is
replaced. There is thus no need to manually intervene for the
remote tire monitor system to update the identities and locations
of the tire monitors on the vehicle.
[0061] From the foregoing, it can be seen that the present
embodiments provide a method and apparatus which automatically
conveys wheel position and data to a receiver in a vehicle. Even
after changes in tire position due to tire rotation or replacement
of a tire, the system automatically re-learns the position of the
tires on the vehicle. No external actuation is required.
Interference and cross talk are minimized by locating the RF
detectors in close proximity to the tire monitors. The required
components are relatively inexpensive and may be implemented at a
relatively low cost. Further, the system provides automatic learn
capability for learning and updating the identities of tire
monitors on the vehicle without manual intervention.
[0062] While a particular embodiment of the present invention has
been shown and described, modifications may be made. It is
therefore intended in the appended claims to cover all such changes
and modifications which fall within the true spirit and scope of
the invention.
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