A Precise Clamping Force Control Strategy for Electro-Mechanical Braking System Based on Nonlinear Characteristics Compensation

Abstract

<div class="section abstract"><div class="htmlview paragraph">Electro-Mechanical Braking (EMB) system, which completely abandons the traditional hydraulic device, realizes complete human-vehicle decoupling and integrates various functions without adding additional accessories, could meet the requirements of the future intelligent driving technology for high-quality braking control. However, there are significant internal interference of nonlinear characteristics such as mechanical friction and system variable stiffness during the actual working process of EMB, and these make the accuracy and rate of the clamping force control decline. This paper proposes a precise clamping force control strategy for EMB based on nonlinear characteristics compensation. First, we systematically analyze the working principle of EMB, and establish the mathematical model of EMB system including motor, transmission mechanism and friction. At the same time, some typical experiments are designed to identify internal parameters of friction model. Next, in order to establish the precise clamping force control for EMB, we apply the Proportional-Integral (PI) theory to a clamping force-speed-current cascade controller. Considering simple PI theory is difficult to overcome the nonlinear characteristics faced by EMB in the clamping force control process, the inverse gain function linearization and load feedforward compensation are utilized to deal with the variable stiffness characteristics of the EMB system. On this basis, we jointly use identified friction model to dynamically compensate EMB nonlinear characteristic interference. Finally, we construct a hardware-in-the-loop (HiL) platform based on dSPACE to compare the designed strategy with traditional clamping force control method. The test results demonstrate the designed strategy could more effectively overcome the interference of EMB nonlinear characteristics, and significantly improve the rate and accuracy of clamping force control.</div></div>