Near real-time friction estimation for pre-emptive vehicle control
First Claim
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1. 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.
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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.
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Citations
23 Claims
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1. A method of estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising the steps of:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising the steps of:
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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. - View Dependent Claims (17, 18, 19)
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20. Apparatus for estimating road/tire friction between tires of a wheeled vehicle and a road surface, comprising:
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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. - View Dependent Claims (21, 22, 23)
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Specification