Abstract
ABSTRACTIn this paper, an adaptive algorithm is developed which senses the road condition change and estimates a (time-varying) optimal braking slip ratio. This is conducted by two on-line simultaneously operating tire-road friction-curve slope calculators: one based on the accelerometer output and the other based on the wheel speed. The required vehicle speed is estimated using a robust sliding-mode observer. Enforcement of the online optimal braking reference is left to an adaptive sliding mode controller to cope with the system strong nonlinearity, time dependency and the speed and friction-coefficient estimation errors. The algorithm is applied to a half model car and the braking performance is examined. The results indicate that the proposed algorithm substantially reduces the stopping time and distance. The performance of the algorithm is verified using different vehicle initial speeds and especially non-uniform road condition where 8% improvement versus the nonadaptive optimal slip ratio algorithm is recorded.
Highlights
Antilock braking system (ABS) ensures safe stopping by regulating the brake torques to provide maximum wheel traction force
The performance of the algorithm is verified using different vehicle initial speeds and especially non-uniform road condition where 8% improvement versus the nonadaptive optimal slip ratio algorithm is recorded
The road condition dependent maximum brake traction force search is conducted using two measures, one based on the vehicle acceleration and another based on the wheel rotation speed
Summary
Antilock braking system (ABS) ensures safe stopping by regulating the brake torques to provide maximum wheel traction force This is conducted by estimating the optimal slip ratio, and enforcing it by a control technique. The braking discipline is enforced by an adaptive sliding mode controller to handle the system dynamic uncertainty and the estimators’ errors As it is expected, the proposed ABS reduces substantially the braking stop time and the stopping distance due to the employment of the adaptive slip ratio estimator. The proposed ABS reduces substantially the braking stop time and the stopping distance due to the employment of the adaptive slip ratio estimator This outstanding performance is verified by simulations considering various uniform and non-uniform road conditions and the vehicle initial speeds.
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