Real-time Clamping Force Estimation of Brake-by-Wire System for Electric Autonomous Vehicles

Brake-by-wire systems are prevailing more than ever for electric autonomous vehicles owing to several advantages, such as faster clamping force response, more accurate clamping force control, and more convenient to be integrated with other vehicle active safety functions. This paper mainly focuses on Electro-Mechanical Brake (EMB) system. Due to high sensor costs and limited sensor installation spaces, wide applications of EMB systems are prevented currently. One such example is the clamping force sensor. To replace the clamping force sensor, an innovative clamping force estimation method, i.e., the Braking Force Separation Strategy, is proposed in this paper. Different from existing estimation approaches that model the clamping force as a nonlinear polynomial function of motor position and brake gap distance, the proposed approach estimates the clamping force without brake gap distance. The decoupling is achieved by the application of an unknown input observer that enables simultaneous states and inputs estimation. To demonstrate the effectiveness of the proposed algorithm, simulations are performed under different input scenarios with or without fictitious measurement noise. The results show that the clamping force can be accurately estimated by the proposed algorithm. It also demonstrates better performance by comparing with traditional method.