A Nonlinear Characteristics Identification and Compensation Control Method for Electromechanical Brake System

Clamping force control in Electromechanical Brake (EMB) systems must overcome various nonlinear characteristics, such as motor distorted voltage, Back Electromotive Force (EMF), and actuator friction disturbances. Therefore, modeling and parameter identification of these nonlinearities are necessary. This paper first proposes a motor parameter identification method based on the mathematical model of a Permanent Magnet Synchronous Motor (PMSM). A combination of the Least Square Method and Particle Swarm Optimization (PSO) is used to stepwise identify both the electrical and mechanical parameters of the motor. The accuracy of the identified parameters is validated by comparing simulation results with test bench responses. The identified parameters are applied to design the motor Back EMF compensation module, the distorted voltage compensation module, and to tune the current loop parameters. Next, a lumped parameter friction model suitable for closed-loop clamping force control in EMB systems was established, and specific operating conditions for identifying friction parameters were designed. The feasibility of this identification was validated through simulation analysis. Finally, a closed-loop clamping force control strategy based on friction compensation was developed. The proposed method is applied to the clamping force control system of a vehicle equipped with four-wheel EMB. Experimental results demonstrate that the stepwise parameters identification method for both motor and actuator effectively improves the response speed and accuracy of EMB clamping force control.