An Adaptive Clamping Force Control Strategy for Electro-Mechanical Brake System Considering Nonlinear Friction Resistance 2024-01-2282

The Electronic Mechanical Braking (EMB) system, which offers advantages such as no liquid medium and complete decoupling, can meet the high-quality active braking and high-intensity regenerative braking demands proposed by intelligent vehicles and is considered one of the ideal platforms for future chassis. However, traditional control strategies with fixed clamping force tracking parameters struggle to maintain high-quality braking performance of EMB under variable braking requests, and the nonlinear friction between mechanical components also affects the accuracy of clamping force control. Therefore, this paper presents an adaptive clamping force control strategy for the EMB system, taking into account the resistance of nonlinear friction. First, an EMB model is established as the simulation and control object, which includes the motor model, transmission model, torque balance model, stiffness model, and friction model. Subsequently, a cascaded clamping force controller, consisting of clamping force loop, velocity loop, and current loop, is designed for EMB using Proportional-Integral (PI) control theory. On this basis, fuzzy theory is applied to adaptively adjust the PI control coefficients of the clamping force loop, and an Extended State Observer (ESO) is introduced in the current loop to dynamically estimate and compensate for the friction resistance of the EMB system. Finally, a simulation platform is established using MATLAB/Simulink for testing and validation. Simulation results demonstrate that ESO accurately estimates the friction torque in real-time, and the proposed adaptive clamping force control strategy effectively controls the EMB to overcome non-linear friction resistance, with a clamping force tracking error of less than 2% for an 8Hz sine wave input. Moreover, the controller exhibits good adaptability, maintaining high-quality control performance even after altering the simulated control object's friction characteristics.