Vehicle Velocity and Road Friction Coefficient Estimation for Anti-lock Braking System

摘要

Many studies take the slip as the major input for anti-lock braking system (ABS) controller. However, slip can only be calculated by vehicle velocity and wheel speed. The vehicle velocity cannot be measured by low cost sensors. In this paper, a vehicle velocity estimation and a friction coefficient estimation methods are proposed. The vehicle velocity estimation just requires wheel speed, wheel deceleration, brake pedal flag, and ABS enable flag. During the estimation, the friction of the road can also be obtained. The methods have been applied to real car ABS test data. There are four different road surface conditions including uniform low friction ($mu$), high $mu$, and $mu$ jump from both low to high and the opposite. According to the results, the deviation between estimated velocity and the ground truth is at maximum 1.57 m/s on $mu$ jump road surface which is from high $mu$ to low $mu$. As for other road surfaces, it provides more accurate outcome. The corresponding estimation of friction coefficient is close to reality. Moreover, the results show that the transition of road condition can be detected quickly. The proposed methods are proved effective for velocity estimation and friction coefficient estimation, which are beneficial for ABS control.