Research On Road Sense Simulation Control Method Of Vehicle Steer-by-wire System

As a new type of electronic control steering system,automotive steer-by-wire system can improve the steering stability of driving and make the internal space layout more flexible,which is also conducive to the integration of other functions of intelligent driving and unified control.The steer-by-wire system uses advanced technologies such as drive motors,controllers,and multiple sensors to replace the mechanical connection between the steering wheel and the steering mechanism of the traditional mechanical steering system.In the movement of the vehicle with steer-by-wire system,the road condition information obtained by the driver is generated by the simulation of a road feel motor.For this purpose,the quality of road feel simulation is extremely important to the steer-by-wire system.This study combines the school-enterprise cooperation project "Development of Automotive Steer-by-wire System" to conduct out the study on the road feel simulation algorithm and control method of the automotive steer-by-wire system based on two-way control.The main work contents are as follows:(2)According to the composition of automotive steer-by-wire system,the dynamic differential equation of the steer-by-wire system is established.At the same time,each detailed mechanism model of the steer-by-wire system is established by using relevant software,while an entire vehicle model with a steer-by-wire system is successfully established by combining the 27-degree-of-freedom vehicle model in professional vehicle simulation software.Through using the traditional steering vehicles in mature simulation software and making simulation comparisons under the same working conditions,the rationality and effectiveness of the established vehicle model can be verified.(2)The road feel simulation algorithm of the steer-by-wire system is studied.In detail,the two-way control system and road feel simulation method are analyzed to study the road feel of the steer-by-wire system by using the two-way control system.In this way,based on the method of measuring the current of the steering actuator to simulate the mechanical road sense,the road feel of the steer-by-wire system is designed.According to different steering conditions and driving conditions,the limit torque,friction compensation torque and damping compensation torque are designed to improve the road feel simulation algorithm of the steer-by-wire system,making the final road feel can be more in line with the driver’s expectations.By using typical test conditions,the designed road feel simulation algorithm is simulated and analyzed.According to the results,it can be indicated that the steering lightness can be improved at low speeds,and a clearer road feel can be obtained at high speeds,which will both improve the stability and safety of vehicle driving.(3)In order to ensure that the road feel motor can realize the functions of road feel simulation and steering wheel return quickly,the control methods of the two processes of steering and return are studied.Taking into account the influence of external interference and the changes of the system parameters during the driving,a fuzzy adaptive PI control method is designed to control the road feel simulation of the steering process,and the simulation is compared with the traditional PI control.The simulation results show that the designed control method can realize the road feel simulation function faster and more stably.Then,a new fast non-singular terminal sliding mode control method based on fast power reaching law is designed to control the steering wheel return process,and the simulation is compared with traditional PI control and sliding mode control.The simulation results indicate that the designed steering wheel return control method can avoid the phenomenon of insufficient return at low speed and overshoot at high speed,and improve the ability of steering wheel return.Simultaneously,the two-way coordinated control of the road feel motor and the steering execution motor is simulated.The results show that the steering execution motor can realize stable steering,and the road sensing motor can realize the road sensing simulation according to the driver’s expectations.(4)A hardware-in-the-loop test platform is established for automotive steer-by-wire system according to the requirements of road feel simulation control.After that,the typical test conditions are selected to carry out the hardware-in-the-loop simulation test on the automotive steer-by-wire system.The test results show that the road feel simulation control method designed in this study can meet the requirements of the driver’s smooth hand sense and real-time road feel.The return control method can achieve steering wheel control well and has good robustness.