Research On Control Method Of Direct Drive Vehicle Braking System

The requirements for the braking system of automobiles such as the advanced driver assistance system requires the braking force can be adjusted in real time and the braking force of each wheel can be controlled independently and the volume of the braking system should be as small as possible and the degree of integration should be high are becoming higher and higher with the intelligent development of automobiles.The automobile braking system with direct drive volume control system can meet these requirements.In this paper,the vehicle braking system with direct drive volume control system is studied.Firstly,the schematic diagram of the system is introduced.The parameters of the hydraulic pump,hydraulic cylinder and other components in the system are calculated according to the static index,which lays a foundation for the components selection and simulation.The direct drive vehicle braking system is modeled by AMESim,which can be divided into hydraulic part and permanent magnet synchronous motor part.The control method of dq axis current decoupling is adopted in PMSM.The modeling of the hydraulic part includes the dynamic mechanism model,the hydraulic controlled check valve model,the friction model and the nonlinear load.The transfer function of the system is obtained through linearization analysis method,and th e main factor affecting the characteristics of the research object are analyzed.Control strategy of direct drive vehicle braking system is formulated for the problem of nonlinear load in the system,the characteristics of brake disc load change because of wear and the residual braking force.In the force control part,feedback linearization is adopted to eliminate the nonlinear load,the time-varying nonlinear information of the load is updated by fading memory least square method,the residual braking force is eliminated by parallel structure of the position controller,the force controller and the velocity information of the hydraulic cylinder is obtained by tracking differentiator.The control block diagram is built in Simulink,the co-simulation with AMESim is realized and verify the validity of the control strategy.