Clamping-Force Estimation Method for Electro-Mechanical Brake Actuator Based on Enhanced Adaptive Extended State Observer

Electro-Mechanical Brake (EMB) is a highly promising development direction for brake-by-wire technology. The signal of the force sensor is the key to system control. However, force sensors are expensive and their stability decreases after frequent braking. One of the urgent problems to be solved is to obtain the force signal of EMB actuator without a force sensor. This article proposes a clamping-force estimation method for EMB actuator based on an enhanced adaptive extended state observer. Firstly, the extended state of the system was defined by simplifying the motor torque balance equation, and an adaptive extended state observer (AESO) was designed. In order to ensure the estimation accuracy when there is a significant change in clamping-force, a dual gain adaptive adjustment method for the observer based on estimation error is designed. When the estimation error is large, the adaptive gains are increased to enhance the estimation ability of disturbance, that is, to enhance the estimation ability of clamping-force, when the estimation error is small, the adaptive gains are reduced to improve the performance of noise suppression. The stability of the observer was proved through Lyapunov theorem. The AESO estimation method was compared with the Extended Luenberger Observer estimation method. The results show that AESO has higher estimation accuracy and stronger anti-disturbance ability through the gain adaptive adjustment method of observer based on estimation error, especially ensuring the estimation accuracy when the clamping-force continuously changes and undergoes large sudden changes, which helps to improve safety under conventional braking conditions and emergency braking conditions.