Research On Sliding Mode Control Strategy Of Vehicle Steering-by-Wire Based On Nonlinear Disturbance Observer

With the deep integration of industrialization and informatization,the automobile industry is developing rapidly in the direction of intelligence and electrification.The development trend of the automobile industry is the automotive autonomous driving technology,in which the steer-by-wire system,as a key component of the autonomous driving technology,can effectively improve the vehicle handling stability,driving comfort and active safety,and increasingly becomes the focus of people’s attention and research.Steer-by-wire is structured to eliminate the mechanical connection between the steering wheel and the front wheels,steering and road sense feedback of the automobile are completely completed by the electronic control unit through the control of steering motor and feedback motor.Therefore,the design of a control strategy with strong robustness and high tracking accuracy is the key to ensure the stable operation of the steer-by-wire system.According to the sliding mode control has good control performance and strong robustness in nonlinear control,this thesis studies the control strategy of automobile steer-by-wire system based on sliding mode control theory and disturbance observer technology.Firstly,the working principle and structure of the steer-by-wire system are analyzed,and the second-order dynamics model of the steer-by-wire system is established.The lumped uncertainty mathematical model of the steer-by-wire system is established for parameter perturbation and external disturbance.Then,according to the control performance requirements of the steer-by-wire system,a fast terminal sliding mode control strategy is designed to ensure that the front wheel of the steer-by-wire system can track the steering wheel Angle accurately and quickly.The controller is designed from the point of view of discrete time to maintain consistency with the digital processor and achieve the performance of quantitative control.In this thesis,the model of the steer-by-wire system is discretized and a discrete fast terminal sliding mode control strategy is designed.A nonlinear perturbation observer is designed to estimate and compensate the lumped perturbation of the system,which improves the tracking accuracy and robustness of the system.Finally,according to the steering behavior of the vehicle in the actual driving process,several groups of comparative simulation studies are carried out from the two control strategies of continuous time and discrete time.The simulation results show that,compared with traditional linear sliding mode control and fast terminal sliding mode control,the discrete fast terminal sliding mode based on nonlinear disturbance observer technology proposed in this thesis can not only achieve fast and accurate tracking performance,but also exhibit stronger robustness and stability.