Design And Research Of Steering Feel For Steer-By-Wire Vehicle Control System

The rapid development and maturity of related technologies of the auto industry,the higher requirements for safety and comfort of vehicle steering system earn more and more attention to the researchers.Compared with the traditional steering system,the steering-by-wire(SBW)system has many advantages.Firstly,it improves safety of vehicle by removing mechanical connected steering column,which avoids the damage of the steering column to the driver in a crash.Secondly,SBW improves driving characteristics and enhance maneuverability.Finally,improve the driver's convenience when driving the vehicle and the driver's road experience Finally,the driver's convenience and sense of road experience can be improved by steering feedback.The model and control methods of steering feel design for the SBW system have been studied in this thesis.A steering feel feedback model is constructed for SBW vehicles,which consists of returnability torque of the upper layer and road-to-tire torque of the lower layer.The terminal sliding mode control(TSMC)and the least squares(LS)were applied to obtain the uncertain parameters and design the control inputs.Then,the designed steering feel torque was feedback to the driver.The key problems to be solved can be concluded as the following:(1)Dynamic modeling of the steering feel feedback system for SBW vehicles can refer to the composition of the feedback torque in a traditional vehicle;(2)A TSMC method was designed for the returnability torque of the upper layer,which can guarantee the hand-wheel angle converges to the reference angle within a limited time,and the Lyapunov's theorem was used for its stability proof;(3)For road-to-tire torque,some parameters of the vehicle are very difficult to be measured or very expensive to obtain,so corresponding estimation methods are designed for these parameters firstly,then road-to-tire toque can be estimated.The software CarSim has advantages to simulate a complete vehicle model,and the characteristics of simulation and experiment environment also can be freely defined.The data generated by CarSim are imported into MATLAB/Simulink,which is mainly used to modeling and running the algorithms for real-time simulation experiments.In this thesis,a TSMC was firstly designed for the upper returnability torque,after the control law was proposed,the Lyapunov's theorem was used to prove the stability of the algorithm.The conventional PID and sliding mode control(SMC)methods were introduced as a comparison for TSMC.Simulation results show that TSMC achieved a faster convergence speed and stronger robustness.Then,for the lower part of the roadto-tire torque,the cornering stiffness was estimated according to the varies of the road condition,this guarantee the self-aligning torque includes the road information.The vehicle velocity,friction coefficient and hand-wheel steering angle were taken into consideration for simulations in this research,and the results verified that an excellent tracking performance has been achieved for the self-aligning torque.The steering wheel angle and the corresponding feedback torque can accurately reflect the actual situation.