Method and apparatus for wheel condition and load position sensing

• US 20020036567A1
• Filed: 09/06/2001
• Published: 03/28/2002
• Est. Priority Date: 08/09/2000
• Status: Active Grant

• Current Assignee: International Truck Intellectual Property Co. LLC (Volkswagen AG)
• Original Assignee: International Truck Intellectual Property Co. LLC (Volkswagen AG)
• Inventors: Larson, Gerald L.
• Granted Patent: US 6,426,694 B1
• Time in Patent Office: Days
• US Class Current: 340/442
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00

Abstract

A system and a method for detecting compromised vehicle wheel and tire operating characteristics includes detection for out of round new tires, under pressure tires, poor front wheel alignment and off center line loads. The instantaneous rotational velocity signal generated for each wheel by an existing antilock braking system (ABS) provides data for the basic comparison of wheel speed is against an instantaneous indication of vehicle speed. Once calibrated, the system provides operational monitoring of the wheels includes initializing the trip odometer, collecting wheel speeds, and sampling vehicle speed. Tire radius and tolerance data as a function of estimated wear and tire temperature. Tire temperature is in turn a function of ambient temperature and trip distance. The rotational velocities for the wheels are estimated as functions of vehicle speed and the updated tire radius data. Wheels rotational velocity is compared to estimated velocity and the difference is compared to the allowed, updated tolerances. A possible pressurization error is indicated if one wheel departs outside of the updated tolerances from estimated rotational velocity.

Claims

1. Apparatus for monitoring the condition of each of a plurality of wheels of a vehicle, the apparatus comprising:

a computer;

a wheel rotational velocity sensing system generating wheel rotational speeds respective to each wheel, coupled to the computer to apply rotational velocity signals for each wheel to the computer;

a vehicle speed signal generator;

computer memory in which is stored data relating to tire wear rates for tires mounted on each wheel, tire mileage since installation, current trip mileage, running average wheel rotational velocities, and a scaling factor for estimating wheel speed based on the vehicle speed signal; and

a stored program for execution on the computer for referencing the stored data in determining out of tolerance wheel speeds indicative of compromised operating conditions.

2. Apparatus as claimed in claim 1, further comprising an input/output interface allowing an operator to enter data relating to newly installed tires.

3. Apparatus as claimed in claim 2, further comprising:

an ambient temperature sensor; and

the stored program further referencing ambient temperature in determining out of tolerance wheel speeds.

4. Apparatus as claimed in claim 3, further comprising:

a global positioning sensor; and

a stored program for execution on the computer for calibrating measured vehicle speed against changes in position of the vehicle determined by the global positioning sensor.

5. Apparatus for detecting compromised vehicle wheel and tire operating characteristics, the apparatus comprising:

wheel rotational velocity sensors mounted on the vehicle in relation to each wheel and generating an instantaneous rotational velocity signal for each wheel;

a vehicle instantaneous speed signal generator;

an odometer indicating distance traveled on the tires currently mounted on the wheels;

a trip odometer indicating distance traveled since a current trip began;

computer memory storing and wheel and tire condition monitoring algorithm and data including the instant distance indications, wheel by wheel scalars for the currently mounted tires relating rotational velocity to vehicle speed, tire wear profile data and recent average vehicle speed; and

a computer coupled to the computer memory for reading and writing the data and executing the wheel and tire condition monitoring algorithm for detecting compromised wheel and tire conditions.

6. Apparatus as claimed in claim 5, further comprising:

an operator interface allowing entry of data relating to the newly mounted tires including running radius and running radius tolerances at rated pressure.

7. Apparatus as claimed in claim 6, wherein the wheel and tire condition monitoring algorithm further comprises:

means for calibrating newly mounted tires determining if each newly installed tire is within tolerances and generating a scalar relating wheel rotational velocity to straight line vehicle speed;

means for indicating a possible out of alignment condition for any wheel varying out of tolerance during calibration;

means for recording all calibrations on operator entered data;

means for operational monitoring of the wheels including means for initializing the trip odometer, means for collecting wheel speeds and means for collecting vehicle speed;

means for updating tire radius and tolerance data as a function of estimated wear and estimating wheel rotational velocity as a function of vehicle speed;

means for comparing wheel rotational velocity to estimated velocity and comparing the difference to the allowed, updated tolerances; and

means for indicating possible pressurization error if one wheel departs outside of the updated tolerances from estimated rotational velocity.

8. Apparatus as claimed in claim 7, the wheel and tire condition monitoring algorithm further comprising:

means utilizing the running averages for wheel rotational speeds for detecting side to side variation in wheel rotational speeds;

threshold means responsive to detection of side to side variation in wheel rotational speeds for deciding if the variation in wheel rotational speeds indicates onset of a turn; and

duration means responsive to detection of side to side variation in wheel rotational speeds for determining if the variation indicates an out of balance load.

9. Apparatus as claimed in claim 8, further comprising:

a thermometer coupled to the computer to apply ambient temperature signals thereto;

the means for updating tire radius and tolerance data as a function of estimated wear being further responsive to the ambient temperature signal.

10. Apparatus as claimed in claim 9, further comprising:

a global positioning sensor;

means for calibrating the vehicle instantaneous speed signal and the odometer and trip odometer indications based on comparison with estimates of speed and distance traveled derived from position readings supplied by the global positioning sensor.

11. Apparatus as claimed in claim 10, wherein the vehicle speed signal generator takes wheel rotational speed as inputs calibrated by position readings from the global positioning sensor.

12. Apparatus as claimed in claim 11, wherein the vehicle speed signal generator is a tachometer counting rotations of a drive shaft from the output end of a transmission.

13. Apparatus as claimed in claim 12, wherein the wheel rotational velocity sensors comprises a vehicle anti-lock braking system.

15. A method as claimed in claim 14, further comprising the steps of:

measuring ambient temperature and modifying the tire radius and tolerance data as a function in ambient temperature.

16. A method as claimed in claim 15, further comprising the steps of:

using a global positioning sensor repeatedly to determine position;

calculating vehicle speed from positions determined by the global positioning sensor; and

calibrating distance traveled and speed measurements based on the vehicle speed calculated from the positions.

18. Apparatus as claimed in claim 17 wherein the source of the calibration value includes a tire calibration algorithm operating on data inputs including initial tire size and tread depth.

19. Apparatus as claimed in claim 18, wherein the source of the calibration value includes a tire calibration algorithm operating on data inputs including initial tire size and tread depth.

20. Apparatus as claimed in claim 17, where the rotational velocity signal generator includes a means for comparing the rotational velocity of any one wheel against an average speed of the remaining wheels and eliminating any one wheel if its rotational velocity departs from the average by more than allowable deviation.

14. A method for detecting compromised vehicle wheel and tire operating characteristics, the method comprising the steps of:

generating an instantaneous rotational velocity signal for each wheel;

generating an instantaneous indication of vehicle speed;

calibrating newly mounted tires determining if each newly installed tire is within tolerances and generating a scalar relating wheel rotational velocity to straight line vehicle speed;

tracking distance traveled on the tires currently mounted on the wheels;

tracking distance traveled since a current trip began;

keeping wheel by wheel scalars for the currently mounted tires relating rotational velocity to vehicle speed, tire wear profile data, and recent average vehicle speed;

means for indicating a possible out of alignment condition for any wheel varying out of tolerance during calibration;

means for recording all calibration an operator entered data;

means for operational monitoring of the wheels including means for initializing the trip odometer, means for collecting wheel speeds, means for collecting vehicle speed;

updating tire radius and tolerance data as a function of estimated wear and estimating wheel rotational velocity as a function of vehicle speed and the updated tire radius data;

comparing wheel rotational velocity to estimated velocity and comparing the difference to the allowed, updated tolerances; and

indicating possible pressurization error if one wheel departs outside of the updated tolerances from estimated rotational velocity.

17. Apparatus for determining speed for a vehicle, comprising:

auto lock brake system including rotational velocity signal generators for each wheel;

a rotational velocity signal averager for producing a raw average speed; and

a source of calibration value for adjusting the raw average signal to produce a velocity signal for the vehicle.