Adaptive Scheme for the Real-Time Estimation of Tire-Road Friction Coefficient and Vehicle Velocity

It is well known that both the tire-road friction coefficient and the absolute vehicle velocity are crucial factors for vehicle safety control systems. Therefore, numerous efforts have been made to resolve these problems, but none have presented satisfactory results in all cases. In this paper, cost-effective observers are designed based on an adaptive scheme and a recursive least squares algorithm without the addition of extra sensors on a production vehicle or modification of the vehicle control system. This paper has three major contributions. First, the front biased braking characteristics of production vehicles such that the front wheel brake torques are saturated first are exploited when estimating the tire-road friction coefficient. Second, the vehicle absolute speed is identified during the friction coefficient estimation process. Third, unlike the conventional method, this paper proposes using already available excitation signals in production vehicles. In order to verify the performance of the proposed observers, experiments based on real production vehicles are conducted, and the results reveal that the proposed algorithm can enhance the performance of any vehicle dynamics control systems.