The Braking Force Control Strategy Based On Road Identification Technology For Brake-by-wire System

With the increasing development of the new energy vehicle industry with electric vehicle as its main body, vehicles have become typical mechatronic system integration. In addition, the safety of modern vehicles have become increasingly demanding, automobile brake systems have been gradually moving towards the road of full electronic. Brake-by-wire as an advanced brake control system, is the future direction of the vehicle brake system. However, many new requirements have been put forward for the design of the control system, and the current studies are not yet mature. Therefore, the development of a stable, efficient and safe control systems have become key issues needed to solve. In this paper, in accordance with the requirements of the control-by-wire braking system, the braking force control strategy for brake-by-wire(BBW) was focused on, and the research will be conducted as following:The half-vehicle dynamic model, the tire model and the model of the electro-mechanical brake(EMB) system were established. The structure of the EMB system based on the slip ratio was designed, and the control system was divided into the braking intention recognition module, the braking condition identification module, the braking force distribution module, the braking force control module and the on-line sensing detection module.Through dimensionality reduction method, the longitudinal vehicle velocity observer and the longitudinal braking force observer based on Kalman filter were constructed, respectively. Based on the wheel slip ratio and the braking force coefficient as input, the optimal slip ratio identifier was designed based on the minimum braking force coefficient deviation. The simulation results indicate that the longitudinal vehicle velocity observer, the longitudinal braking force observer and the optimal slip ratio identifier have good observation precision and stability characteristics.The nonlinear characteristics of the EMB system were analyzed, and a fuzzy sliding mode controller(FSMC) for EMB systems was designed. The equivalent control law of sliding mode controller was designed on the basis of the state observation, while the switching control law was adjusted by the fuzzycorrector. The simulation results indicate that the fuzzy SMC strategy has the superior performance and better adaptability to various types of roads, as compared to PID control and SMC.A hardware-in-loop(HIL) experiment system for EMB control system was designed, the d SPACE real-time simulation model, the programs of the controller, the host online monitoring and data recording software were developed. The HIL experimental results verify the feasibility and effectiveness of the fuzzy sliding mode controller.