US6508102B1
Expired / Lapsed
US
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Near real-time friction estimation for pre-emptive vehicle control
Assignee: Aisin Corp
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Filing: 1999-08-26
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Granted: 2003-01-21
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Expires: 2019-08-26
Abstract
Abstract An improved estimator is provided for road/tire friction. The friction estimator provides near-real-time friction estimation, even while the car is accelerating, braking or turning. It is desirable to have an instantaneous and continuous estimate of the road/tire friction, but an estimate that occurs over several wheel rotations is more realistic. The estimate relies on easily measured signals such as yaw rate, lateral acceleration, wheel speed, etc. The estimate can be used to give the driver or a closed-loop controller an advanced warning when the tire force limit is being approached.
Inventors
- 👤 Donald L. Margolis
- 👤 Cornelis Jen Belltawn
- 👤 Alan Yasuji Arai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 04:57
CPC Classifications
B; B60; B60T; B60T8/00; B60T8/17; B60T8/172; B60T2210/00; B60T2210/10; B60T2210/12
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
107 words
A method of estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising the steps of: providing as a computational model an adaptive vehicle model, either non-linear or linear, that receives at least one vehicle control input and calculates at least one quantity describing a state of the vehicle; during an adaptation period, adapting the vehicle model to achieve close agreement of at least one physical measurement and a calculated output of the vehicle model during predictable driving conditions; and outside the adaptation period, using a difference between the physical measurement and the calculated output of the vehicle model to estimate road/tire friction.
Claim 2
Independent Claim
107 words
A method of estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising the steps of: providing as a computational model an adaptive vehicle model, either non-linear or linear, that receives at least one vehicle control input and calculates at least one quantity describing a state of the vehicle; during an adaptation period, adapting the vehicle model to achieve close agreement of at least one physical measurement and a calculated output of the vehicle model during predictable driving conditions; and outside the adaptation period, using a difference between the physical measurement and the calculated output of the vehicle model to estimate road/tire friction.
Claim 3
Dependent Claim
44 words
The method of claim 1 , wherein during the adaptation period, the step of adapting the vehicle model comprises the step of adjusting at least one of the following physical parameters: center of gravity location, vehicle mass, vehicle rotational inertia, and tire force characteristics.
Claim 4
Dependent Claim
34 words
The method of claim 1 , wherein at least a difference between a physical measurement of wheel speed and a calculated wheel speed output of the vehicle model is used to estimate road/tire friction.
Claim 5
Dependent Claim
18 words
The method of claim 1 , wherein a road/tire friction estimate is input to the adaptive vehicle model.
Claim 6
Dependent Claim
46 words
The method of claim 1 , wherein the at least one quantity describing the state of the vehicle is applied torque which is calculated using substantially the following equation: τ w = ( R × m 2 + J w R ) U . ·
Claim 7
Dependent Claim
19 words
The method of claim 5 , wherein total applied torque is evenly divided between the driven wheels during acceleration.
Claim 8
Dependent Claim
26 words
The method of claim 5 , wherein during braking, torque is estimated for each wheel assuming a predetermined torque ratio between front wheels and rear wheels.
Claim 9
Dependent Claim
17 words
The method of claim 5 , wherein a torque estimate is input to the adaptive vehicle model.
Claim 10
Dependent Claim
16 words
The method of claim 1 , wherein estimating is performed using Proportional, Integral and Derivative control.
Claim 11
Dependent Claim
42 words
The method of claim 1 , wherein said physical measurement is measured using at least one of the following: a longitudinal accelerometer, a lateral accelerometer, a yaw rate sensor, a wheel speed sensor, a wheel torque sensor, and a longitudinal velocity sensor.
Claim 12
Dependent Claim
16 words
The method of claim 1 , wherein the predictable driving conditions comprise a dry road test.
Claim 13
Dependent Claim
23 words
The method of claim 1 , further comprising a vehicle dynamics controller using the road/tire friction estimate as part of a control system.
Claim 14
Dependent Claim
14 words
The method of claim 12 , wherein the control system is a feedback/feedforward system.
Claim 15
Dependent Claim
18 words
The method of claim 12 , wherein road/tire friction is estimated on a per-tire basis for multiple tires.
Claim 16
Dependent Claim
18 words
The method of claim 14 , wherein a control algorithm accounts for available traction at multiple different tires.
Claim 17
Independent Claim
100 words
A method of estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising the steps of: providing as a computational model a vehicle model that receives as inputs at least one vehicle control input and a measure of forward velocity and that calculates at least one quantity describing a state of the vehicle; and using a difference between one physical measurement and the at least one quantity describing the state of the vehicle calculated by the vehicle model to estimate at least road/tire friction, a resulting estimate of road/tire friction being input to the vehicle model.
Claim 18
Independent Claim
100 words
A method of estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising the steps of: providing as a computational model a vehicle model that receives as inputs at least one vehicle control input and a measure of forward velocity and that calculates at least one quantity describing a state of the vehicle; and using a difference between one physical measurement and the at least one quantity describing the state of the vehicle calculated by the vehicle model to estimate at least road/tire friction, a resulting estimate of road/tire friction being input to the vehicle model.
Claim 19
Dependent Claim
28 words
The method of claim 16 , wherein the vehicle model calculates at least one of the following: lateral and longitudinal accelerations, lateral velocity, yaw rate, and wheel speed.
Claim 20
Dependent Claim
13 words
The method of claim 16 , wherein the vehicle model calculates wheel speed.
Claim 21
Dependent Claim
24 words
The method of claim 18 , wherein the vehicle model calculates at least one of lateral and longitudinal accelerations, lateral velocity and yaw rate.
Claim 22
Dependent Claim
103 words
Apparatus for estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising: a computational unit including a vehicle model that receives as inputs at least one vehicle control input and a measure of forward velocity and that calculates at least one quantity describing a state of the vehicle; and means for forming a difference between one physical measurement and the at least one quantity describing the state of the vehicle calculated by the vehicle model, the computational unit using the difference to estimate at least road/tire friction, a resulting estimate of road/tire friction being input to the vehicle model.
Claim 23
Dependent Claim
103 words
Apparatus for estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising: a computational unit including a vehicle model that receives as inputs at least one vehicle control input and a measure of forward velocity and that calculates at least one quantity describing a state of the vehicle; and means for forming a difference between one physical measurement and the at least one quantity describing the state of the vehicle calculated by the vehicle model, the computational unit using the difference to estimate at least road/tire friction, a resulting estimate of road/tire friction being input to the vehicle model.
Claim 24
Dependent Claim
28 words
The apparatus of claim 20 , wherein the vehicle model calculates at least one of the following: lateral and longitudinal accelerations, lateral velocity, yaw rate, and wheel speed.
Claim 25
Dependent Claim
13 words
The apparatus of claim 20 , wherein the vehicle model calculates wheel speed.
Claim 26
Dependent Claim
24 words
The apparatus of claim 20 , wherein the vehicle model calculates at least one of lateral and longitudinal accelerations, lateral velocity and yaw rate.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2006-01-20 | 2006-07-22 | 2007-01-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2010-01-20 | 2010-07-22 | 2011-01-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2014-01-20 | 2014-07-22 | 2015-01-21 | $7700.00 | Window Closed / Lapsed |