Study Of Control Strategy On Vehicle Steer-By-Wire System With Time Delay

In the further development of automatic driving progress,Steer-By-Wire(SBW)system is a key element for highly automatic driving.The time delay caused by mechanical friction and signal transmission influences the system dynamics response.In this paper,the steer-by-wire system with delay time is modeled and the controller is designed to deal with the time delay.Firstly,the whole system is divided into the vehicle model,the road sense feedback model,the steering actuator model,the driver model and the time delay model.The time delay caused by signal acquisition,processing and transmission between the lower steering actuator system and the upper driver system is fully considered.More specifically,the time delay is comprised of three parts: delay generated by mechanical friction and damping in the lower steering actuator,delay generated by the driver's preview and reaction,delay generated by the signal processing or transmission between the driver system and the steering actuator system.Secondly,to cope with the delay generated by mechanical friction and damping in the lower steering actuator,Smith compensator is designed for delay compensation.To cope with delay generated by the driver system and signal transmission between the driver system and the steering actuator system,the two degree of freedom of internal model control is devised.Then MATLAB/Simulink in combination with CarSim software are used for the simulation verification of the lower steering execution and the upper system.The tracking accuracy and robustness of the designed controller are verified under a variety of working conditions like constant or random time delays.Compared with the conventional PID controller,the designed controller shows higher tracking accuracy under the random time delay and guarantees the better stability.Finally,dSPACE system is used for signal acquisition and controller construction in the steer-by-wire hardware in loop bench test.On the one hand,the angular tracking experiment verifies the nice tracking performance of the controller and the delay compensation is effectively carried out to improve the response tracking speed.On the other hand,under the time delay caused by mechanical friction and signal transmission,the vehicle displacement can reach the steady state in a very short time,and good front wheel angle tracking is achieved in the driver closed-loop test verification.In conclusion,the controller designed in this paper can compensate the constant and random type of delay time,improving the quality and reliability of steer-by-wire system.The results are both verified by simulation and hardware in the loop test.The maneuverability and dynamic performance of ship are closely related to its navigation safety and economy.Considering that time delay has a huge impact on the marine maneuvering and power system control performance,the method proposed in this paper can provide advice for the control of the marine system.