Multi-closed-loop Pressure Control Strategy Considering Nonlinear Characteristics of Electro-booster Brake System

In order to solve the nonlinear characteristics, including the time-varying characteristic disturbance of the hydraulic system, the dynamic and static friction obstacles of the transmission mechanism, and the electromagnetic characteristics coupling of underlying servo motor, faced by the electro-booster brake system(Ebooster) during active braking, a multi-closed-loop pressure control strategy with a pressure, position, and current loop is proposed. First, analyze the working principle of Ebooster and establish an equivalent simplified model for controller design. Subsequently, the pressure loop is designed based on the active disturbance rejection controller, which compensated the disturbance of the time-varying characteristics of the hydraulic system; Robust sliding mode variable structure is used to design the position loop, taking into account the dynamic and static friction obstacles of the transmission mechanism, as well as the unmodeled disturbance of the system; The current loop is designed based on Lyapunov's stability theory, and solves the problem of dual-axis current coupling of permanent magnet synchronous motors. A hardware-in-the-loop bench is built based on dSPCAE equipment for algorithm test. The test results show that the proposed multi-closed-loop pressure control strategy can control Ebooster to realize the active braking function. The steady-state error of pressure tracking is within 0.2 MPa, and it shows good control effect under a variety of pressure following conditions. The research results provide a good solution to the various nonlinear disturbance problems faced by the mechanical-electric-hydraulic brake by wire brake system. © 2023 Editorial Office of Chinese Journal of Mechanical Engineering. All rights reserved.