High-Quality Clamping Force Control for Electro-Mechanical Brake Considering Nonlinear Disturbances

The Electro-Mechanical Brake (EMB) eliminates the traditional hydraulic pipeline arrangement through high-performance servo motor at the vehicles brake calipers. This provides a foundation for intelligent electric vehicles to achieve high-precision, fast response, and strong robustness in brake clamping force control. However, EMB faces some tricky nonlinear disturbances such as varying system stiffness disturbances, complex friction obstruction, etc., which leads to a decline in clamping force control performance. Therefore, this paper proposes a high-quality clamping force control for EMB considering nonlinear disturbances. First, we establish an EMB actuator model including the permanent magnet synchronous motor, mechanical transmission mechanism, and system stiffness characteristics. Next, the high-quality clamping force control strategy for EMB is designed. An outer-loop clamping force regulator is developed using Proportional-Integral-Derivative (PID) feedback control and feedforward control of the system stiffness fitting. In the mid-loop position regulator, an inversion sliding mode control is introduced, along with Karnopp friction dynamic compensation that includes static friction, viscous friction, and Coulomb friction. In the inner-loop current regulator, the PID feedback control with the target excitation axis current set as zero and voltage feedforward field weakening techniques are comprehensively applied to enhance the EMB’s dynamic response. Finally, testing and validation are conducted on the MATLAB/Simulink simulation platform. The experimental results demonstrate the proposed control method significantly improves the precision, speed, and robustness of EMB clamping force control compared to the traditional three-loop PID clamping force controller.