Research Of Electric Controlled Hydraulic Power Steering System

With the development of vehicle control technology and people's requirements getting higher and higher in driving safety and comfort,hydraulic power steering system can not meet the new requirements because of its inability to achieve active control and steering power characteristics not adjusted.Although the electric power steering system can solve the above problems,there is power shortage defect in EPS applications of the medium or heavy vehicles.Therefore,the research of electric controlled hydraulic power steering system has important significance.In this paper,a new type of electric controlled hydraulic power steering system is designed based on the relevant research at home and abroad.On the basis of establishing the system dynamics model and studying the control strategy,the prototype is developed and the corresponding hardware in the loop simulation platform is designed and built,and the steering tests are carried out to provide theoretical and experimental references for the application of electric controlled hydraulic power steering system with steering active control.The main contents include:(1)Study the traditional hydraulic power steering system with rotary valve as its core component and analyse the system response characteristics and power characteristics.A new type of hydraulic power steering system based on servo proportional solenoid valve is designed,and the dynamic model of the system is established.The pressure feedback method is put forward to control the displacement of the valve core,which can control the hydraulic power,and realize the active control of the steering system and improve the power performance.(2)According to the control target of the steering system,the characteristic curve of the target hydraulic power is designed considering the influence of vehicle speed.In view of the nonlinear characteristics of the system,the active control strategy based on fuzzy adaptive PID control is developed,and the CarSim/MATLAB joint simulation model is established.Through the comparative analysis of the simulation results under different speed,theoretically verify the established system can realize the active control of road sense with the change of vehicle speed and improve the portability of steering control at low speed and stability at high speed compares to the traditional hydraulic power steering system.(3)According to the structure of the system,a prototype is developed.Based on the dSPACE real-time simulation system,combined with TTC60 controller,CarSim/MATLAB simulation model,and steering resistance torque simulation test bench,design and build the ECHPS hardware in the loop simulation platform.The hydraulic power steering tests are carried out to verify the simulation results,which provide theoretical and experimental references for the practical application of the new steering system.(4)Based on the new electric controlled hydraulic power steering system,this paper also concerns the possible lateral disturbance in the process of vehicle driving.In MATLAB/CarSim simulation environment,the system control strategy based on pressure compensation is established to realize the goal of keeping the vehicle in a straight line under lateral wind disturbance and reducing the load of the driver.The study of lateral disturbance control verifies the effectiveness and practicability of the established system in active control of steering.