Research On The Characteristics Of The Electro-hydraulic Coupling Power Steering System And Lateral Motion Control For Commercial Vehicles

Commercial vehicles,which account for 77% of the freight traffic,driving safety and handling stability have an important impact on reducing traffic accidents.Meanwhile,intelligent vehicle is the trend of future freight development.The research on the characteristics of steering system and lateral motion control to improve driver safety and handling stability of commercial vehicle.In order to realize intelligent driving function,a new steering system that combines the EPS with the HPS for commercial vehicle is proposed,which is named electro-hydraulic coupling power steering(EHCPS)system.For improving the response bandwidth of EHCPS system closed-loop control and the tracking accuracy of lateral position of commercial vehicles,this paper designs the inner target angle tracking controller and the outer lateral automatic tracking controller.Meanwhile,a lateral nested motion control strategy composed of inner and outer layers is proposed.Simulation and test results show that control strategy adopted can improve the response bandwidth of EHCPS system closedloop control and the tracking accuracy of lateral position.The contents and results are summarized as follows.Firstly,EHCPS system dynamic model and vehicle 2DOF model are established,and the dynamic characteristics of EHCPS system are analyzed.Simulation and test analysis of the EHCPS system were carried out,and the analysis results were basically consistency.In addition,the original frequency domain dynamic performance analysis of EHCPS system is performed.The results show that the torsion bar torque lags the motor torque in phase under high-frequency inputtingSecondly,the paper developed a two-loop structure controller with main and compensate loop according to the dynamic model of the EHCPS system.Based on the transfer function from motor torque to handwheel angle,a leading correction controller is designed to improve the bandwidth of handwheel angle response to motor torque.The compensation control loop generates the desired handwheel angle according to the desired front wheel angle.The experimental and simulation results indicate that the two-loop control strategy proposed guarantees the good following of handwheel angle and the relationship between front wheel angle and handwheel angle.Thirdly,a control strategy of front wheel angle tracking based on fuzzy neural network model reference adaptation is proposed.The difference between the expected front wheel angle and the actual front wheel angle and the rate of change of the difference are applied to the EHCPS system through the fuzzy neural network controller.Experimental and simulation results show that the control strategy enables the actual front wheel angle follows the desired front wheel angle well.Fourthly,a lateral automatic tracking controller is designed for commercial vehicle.A two DOF vehicle control model with yaw and lateral motion was established,and a lateral automatic tracking controller was designed based on model predictive control.Simulation results show that commercial vehicle has a good path following performance under the controller.Lastly,a nested control strategy of lateral motion of commercial vehicle is proposed,which is formed the inner loop controller of EHCPS system and the outer loop controller.The simulation results show that the control strategy adapted improves the path tracking accuracy and response speed of EHCPS system.In this study,the EHCPS system dynamic model is established.A nested control strategy is proposed,which composed of inner target angle tracking control and outer lateral automatic tracking control.The control strategy adapted provides support for improving driving safety and realizing automatic tracking driving of commercial vehicle.