Research On ABS Control Of Vehicle Electronic Mechanical Braking System Based On Active Disturbance Rejection Control

With the transformation and upgrading of vehicle intelligence and electrification related industrial technologies,the rapid development of brake-by-wire technology has been promoted.With the advantages of fast braking response,precise braking torque control and easy integration of active safety functions,electronic mechanical braking(EMB)system is regarded as the most ideal development direction of brake-by-wire system.A slip rate tracking control strategy is designed on the basis of EMB system.It improves the control performance of anti-lock braking system(ABS).However,road adhesion information recognition and controller robustness are two key factors to improve ABS control effect.On the other hand,the problems of nonlinear and uncertain EMB system also need to be solved.Therefore,in order to improve vehicle stability and driving safety under emergency braking conditions,this paper proposes an ABS hierarchical control strategy based on active disturbance rejection control(ADRC)for EMB system.The main research contents of this paper are as follows:(1)A multi-stage closed-loop control strategy for electronic mechanical braking system is designed in view of the differences of the braking stages.Firstly,according to the functional requirements of the EMB system,the selection,design and verification of the driving motor and transmission mechanism of the EMB system are completed,and the mathematical model of the EMB system is established.Secondly,the working characteristics and differences of EMB system at each braking stage were investigated.Therefore,a multi-stage closed-loop control strategy was designed based on permanent magnetic synchronous machine(PMSM)vector control.Finally,the simulation results show that the designed multi-stage closed-loop control strategy of EMB system meets the design requirements and is feasible.(2)Aiming at the key problem that road adhesion information restricts vehicle braking control effect,and the characteristics that wheel angular velocity and braking torque can be obtained in the braking process of EMB system,a road identification algorithm based on extended state observer was proposed as the upper layer control of ABS hierarchical control strategy.Based on the EMB system,the second order nonlinear extended state observer is designed to estimate the road adhesion coefficient in real time,calculate the difference with each typical road adhesion coefficient,and determine the road information according to the minimum difference.Simulation results show that the proposed road identification algorithm has good recognition accuracy and real-time performance under single road condition and variable road condition,and meets the requirements of road identification accuracy and response time under emergency braking conditions.(3)Aiming at the nonlinear,time-varying and uncertain problems of ABS,and in order to improve the robustness of ABS controller,a slip rate tracking control strategy based on active disturbance rejection control was proposed as the lower layer control of ABS hierarchical control strategy.After the optimal slip rate is output by the upper control,the ADRC algorithm is applied to the ABS control system to track the optimal slip rate,considering the advantage that ADRC can actively estimate and compensate the unknown disturbance in the controlled system.The simulation results show that the designed ABS hierarchical control strategy based on active disturbance rejection control can improve the braking effect and control robustness,effectively shorten the braking distance and braking time,and has a strong adaptability to road conditions.(4)Complete the EMB system controller hardware and software design and motor bench construction.Firstly,the functional requirements of the EMB system controller are analyzed and the software and hardware design scheme is formulated.Secondly,complete the hardware circuit design and software program development of EMB system controller.Finally,the motor bench experimental scheme is formulated and the motor bench is built to carry out the motor test experiment.