Research on control strategy of electro-mechanical braking system

The electro-mechanical braking system utilized in rail vehicles experiences braking judder and vibration during operation. It is imperative to enhance control accuracy and develop precise control algorithms for the accurate regulation of clamping force. This study introduces a staged, comprehensive control strategy that segments the operation process of the electro-mechanical braking system into three distinct stages: the idling travel stage, the braking pressure jump tracking stage, and the gap holding stage. During the idling travel stage, a speed-current dual closed-loop control strategy is implemented, with the target speed set at the maximum idling speed, thereby allowing the caliper to complete its idling travel in the minimal speed response time. The design of the current loop is informed by quadratic optimization within a model predictive control framework, aimed at enhancing the instantaneous tracking performance of the control current. In the braking pressure tracking stage, the strategy accounts for the motor load torque and braking force response speed, utilizing a pressure-current dual closed-loop control approach to facilitate rapid response times and adherence to the stability, which corresponds to the target braking pressure. An active disturbance rejection control (ADRC) strategy based on nonlinear PD feedforward fusion is designed for the clamping force loop to improve the tracking performance of the clamping force and the disturbance rejection ability during braking tracking. In the gap holding stage, the control strategy considers both braking pressure and motor load torque, implementing a position-speed-current triple closed-loop PI control strategy to achieve the highest accuracy in maintaining the braking gap. The validity and efficacy of the proposed algorithm have been substantiated through simulations and experiments conducted on a platform developed using MATLAB/Simulink and dSPACE. The results indicate that the proposed control strategy significantly enhances both the control accuracy and response speed of the braking force while demonstrating improved robustness.