Tire monitoring system

• US 6,696,935 B2
• Filed: 09/10/2001
• Issued: 02/24/2004
• Est. Priority Date: 09/10/2001
• Status: Expired due to Fees

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Bonardi, Timothy A., Chandler, Gregg A., Turnbull, Robert R., Knapp, Robert C., Schmidt, David J.
• Primary Examiner(s): Tweel, John
• Application Number:
  US09/949,955
• Publication Number:
  US 20030048178A1
• Time in Patent Office: 897 Days
• Field of Search: 340/447, 340/438, 340/635, 340/825.69, 340/825.72, 307/10.1, 307/10.2
• US Class Current: 340/447
• CPC Class Codes: B60C 23/0416 allocating a corresponding wheel position on vehicle, e.g. front/left or rear/right

Abstract

A tire monitoring (TM) system includes a peak detector signal filter that is configured to substantially prevent impulse noise from increasing a data slicer threshold, while simultaneously allowing the data slicer threshold to follow the variations in a received message attributable to signal fading. The TM system also automatically determines the location of a plurality of vehicle tires relative to the vehicle, utilizes a single receiver to receive messages of multiple lengths and masks an alarm when a missing ID code corresponds to a stored ID code associated with a flat tire.

Claims

1. A method for improving the ability of a data slicer to properly resolve data bits of a received message in the presence of high noise levels relative to the received message, the received message also exhibiting signal fading, the data slicer including a first input, a second input and an output, the method comprising the steps of:

providing a peak detector that includes a peak detector input and a peak detector output, wherein the peak detector input is coupled to the first input of the data slicer, and wherein the peak detector output provides a peak detector signal that corresponds to a peak of a received demodulated signal; and

providing a peak detector signal filter coupled between the peak detector output and the second input of the data slicer, wherein the peak detector signal filter is configured to substantially prevent impulse noise from increasing a variable data slicer threshold on the second input of the data slicer while simultaneously allowing the data slicer threshold to substantially follow the variations in the demodulated signal attributable to signal fading.

2. The method of claim 1, wherein the demodulated signal is in the form of a pulse width modulated (PWM) code.

3. The method of claim 2, wherein if a duty cycle of a bit of the demodulated signal is about thirty-three percent, a digital zero is indicated, and if the duty cycle is about sixty-six percent, a digital one is indicated.

4. The method of claim 1, wherein the received signal originates from a transmitter in a tire and the signal fading is due to wheel rotation.

5. A signal processing system for improving the ability of a data slicer that is coupled to a tire pressure receiver to properly resolve data bits of a received message in the presence of high noise levels relative to the received message, the received message also exhibiting signal fading, the data slicer including a first input, a second input and an output, the system comprising:

a peak detector that includes a peak detector input and a peak detector output, wherein the peak detector input is coupled to the first input of the data slicer, and wherein the peak detector output provides a peak detector signal that corresponds to a peak of a received demodulated signal; and

a peak detector signal filter coupled between the peak detector output and the second input of the data slicer, wherein the peak detector signal filter is configured to substantially prevent impulse noise from increasing a variable data slicer threshold on the second input of the data slicer while simultaneously allowing the data slicer threshold to substantially follow the variations in the demodulated signal attributable to signal fading.

6. The system of claim 5, wherein the demodulated signal is in the form of a pulse width modulated (PWM) code.

7. The system of claim 6, wherein if a duty cycle of a bit of the demodulated signal is about thirty-three percent, a digital zero is indicated, and if the duty cycle is about sixty-six percent, a digital one is indicated.

8. The system of claim 5, wherein the received signal originates from a transmitter in a tire and the signal fading is due to wheel rotation.

9. A method for automatically determining the location of a plurality of vehicle tires relative to a vehicle, comprising the steps of:

providing a plurality of sensors each located in a different one of the plurality of vehicle tires, and wherein each of the sensors provides an indicator of a rotation direction in a main rotation plane for the vehicle tire in which it is located; and

providing a plurality of transmitters each associated with a respective one of the sensors, wherein each of the transmitters is configured to transmit a unique transmitter identification code and the indicator of the rotation direction for the vehicle tire in which it is located to a receiver located in the vehicle, and wherein each of the sensors further provide another indicator of whether one of the plurality of vehicle tires has turned out of the main rotation plane.

10. The method of claim 9, wherein each of the sensors includes a two axis accelerometer that has a first axis aligned along the main rotation plane and a second axis aligned perpendicular to the main rotation plane.

11. The method of claim 9, wherein the sensor includes a single throw switch aligned along the main rotation plane, and wherein a switch closure represents a first direction of rotation and no switch closure represents a second direction of rotation that is opposite the first direction of rotation.

12. The method of claim 9, wherein the sensor includes a gyroscope aligned to determine the direction of rotation and any deviation from the main rotation plane.

13. A tire monitoring system including the capability of automatically determining the location of a plurality of vehicle tires relative to a vehicle, the system comprising:

a plurality of sensors each located in a different one of the plurality of vehicle tires, and wherein each of the sensors provides an indicator of a rotation direction in a main rotation plane for the vehicle tire in which it is located; and

a plurality of transmitters each associated with a respective one of the sensors, wherein each of the transmitters is configured to transmit a unique transmitter identification code and the indicator of the rotation direction in the main rotation plane for the vehicle tire in which it is located to a receiver located in the vehicle, and wherein each of the sensors further provides another indicator of whether one of the plurality of vehicle tires has turned out of the main rotation plane.

14. The system of claim 13, wherein the sensor includes a two axis accelerometer that has a first axis aligned along the main rotation plane and a second axis aligned perpendicular to the main rotation plane.

15. The system of claim 13, wherein the sensor includes a single throw switch aligned along the main rotation plane, and wherein a switch closure represents a first direction of rotation and no switch closure represents a second direction of rotation that is opposite the first direction of rotation.

16. The system of claim 13, wherein the sensor includes a double throw switch aligned along the main rotation plane, wherein a switch closure in a first direction represents a first direction of rotation and a switch closure in a second direction represents a second direction of rotation that is opposite the first direction of rotation.

17. The system of claim 13, wherein the sensor includes a gyroscope aligned to determine the direction of rotation and any deviation from the main rotation plane.

18. A method for utilizing a single receiver for receiving messages of multiple lengths, comprising the steps of:

receiving a message from a transmitter, the message including a plurality of bits, wherein a portion of the plurality of bits of a valid message correspond to a transmitter identification code;

providing a timeout indication when a bit is not detected in the received message for a timeout period;

providing a first indication when the number of bits in the received message is equal to a first number of total bits;

providing a second indication when the number of bits in the received message is equal to a second number of total bits that is greater than the first number of total bits; and

processing the message according to the first and second indications, wherein the first and second indications allow different length messages to be distinguished such that the single receiver can receive transmissions from transmitters that have different length messages.

19. The method of claim 18, further including the step of:

clearing the timeout, first and second indications when the length of the message exceeds a maximum frame length or the timeout indication is provided other than following receipt of the first and the second number of total bits.

20. A tire monitoring system for monitoring a plurality of vehicle tires associated with a vehicle, the system comprising:

a plurality of transmitters for transmitting messages, wherein one of the transmitters is located in each of the plurality of vehicle tires;

a processor;

a receiver coupled to the processor and in communication with the transmitters;

a memory subsystem coupled to the processor, the memory subsystem storing information and processor executable code for causing the processor to perform the steps of;

receiving transmitted messages, wherein each of the messages including a plurality of bits, and wherein a portion of the plurality of bits of a valid message correspond to a transmitter identification code;

providing a timeout indication when a bit is not detected in the received message for a timeout period;

providing a first indication when the number of bits in the received message is equal to a first number of total bits;

providing a second indication when the number of bits in the received message is equal to a second number of total bits that is greater than the first number of total bits;

processing the message according to the first and second indications, wherein the first and second indications allow different length messages to be distinguished such that the receiver can receive transmissions from transmitters that have different length messages;

storing a flat tire transmitter identification code;

determining whether a missing transmitter identification code corresponds to the stored flat tire transmitter identification code; and

masking an alarm when the missing transmitter identification code corresponds to the stored flat tire transmitter identification code;

a data slicer coupled to the receiver, the data slicer including a first input, a second input and an output;

a peak detector coupled to the first input of the data slicer, the peak detector providing a peak detector signal that corresponds to a peak of the message;

a peak detector signal filter coupled between the peak detector output and the second input of the data slicer, wherein the peak detector signal filter is configured to substantially prevent impulse noise from increasing a variable data slicer threshold on the second input of the data slicer while simultaneously allowing the data slicer threshold to substantially follow the variations in the demodulated signal attributable to signal fading; and

a plurality of sensors, wherein one of the sensors is located in each of the vehicle tires, and wherein each of the sensors provides an indicator of a rotation direction in a main rotation plane for the vehicle tire in which it is located, where the processor utilizes the indicator provided by each of the sensors to automatically determine the location of each of the vehicle tires relative to the vehicle.

21. A method for masking an alarm provided by a tire monitoring system when a transmitter equipped flat tire is replaced with a spare tire that does not include a transmitter, comprising the steps of:

storing a transmitter identification code associated with a flat tire;

determining whether a missing transmitter identification code corresponds to the stored transmitter identification code associated with the flat tire; and

masking an alarm when the missing transmitter identification code corresponds to the stored transmitter identification code associated with the flat tire.

22. A tire monitoring system for monitoring a plurality of vehicle tires associated with a vehicle, the system comprising:

a plurality of transmitters for transmitting messages, wherein one of the transmitters is located in each of the plurality of vehicle tires;

a processor;

a receiver coupled to the processor and in communication with the transmitters; and

a memory subsystem coupled to the processor, the memory subsystem storing information and processor executable code for causing the processor to perform the steps of;

receiving transmitted messages, wherein each of the messages including a plurality of bits, and wherein a portion of the plurality of bits of a valid message correspond to a transmitter identification code;

providing a timeout indication when a bit is not detected in the received message for a timeout period;

providing a first indication when the number of bits in the received message is equal to a first number of total bits;

providing a second indication when the number of bits in the received message is equal to a second number of total bits that is greater than the first number of total bits; and

processing the message according to the first and second indications, wherein the first and second indications allow different length messages to be distinguished such that the receiver can receive transmissions from transmitters that have different length messages.

23. A tire monitoring system for monitoring a plurality of vehicle tires associated with a vehicle, the system comprising:

a plurality of transmitters for transmitting messages, wherein one of the transmitters is located in each of the plurality of vehicle tires;

a processor;

a receiver coupled to the processor and in communication with the transmitters; and

a memory subsystem coupled to the processor, the memory subsystem storing information and processor executable code for causing the processor to perform the steps of;

storing a transmitter identification code associated with a flat tire;

determining whether a missing transmitter identification code corresponds to the stored transmitter identification code associated with the flat tire; and

masking an alarm when the missing transmitter identification code corresponds to the stored transmitter identification code associated with the flat tire.