Independent Suspension Shimmy Control Based On Disturbance Estimation For Electric Vehicle

With the development and popularization of electric vehicles,safety problems and stability of electric vehicles have become the focus of research in the automotive industry.Vehicle steering system shimmy is a common phenomenon,which has poor stability when driving in straight line,aggravates the operation of the vehicle,and will cause vehicle accidents in serious cases.In this paper,the problem of front wheel shimmy is studied,and a new idea is provided to eliminate the shimmy of the vehicle by using the control theory.In the past,the research idea of eliminating automobile shimmy was to analyze the factors influencing the shimmy,such as optimizing parameters to solve the problem of shimmy.Because of wear and tear,the vehicle will still have the problem of shimmy after a period of use.In this paper,a nonlinear four-degree-of-freedom(DOF)independent suspension shimmy model for a domestic small vehicle is proposed.The control theory is used to design the controller based on the disturbance predictor to track the nonlinear factors which affect the shimmy of the front wheel,so that the shimmy can be eliminated quickly.The main research contents are as follows:1.Four degrees of freedom front wheel shimmy model construction and simulation analysis.Considering the lateral characteristics of the tire,dry friction gap and road shock,a DOF front wheel shimmy equation is constructed by using Lagrange equation.Numerical simulation of the model is earried out.The results show that there is forced vibration and self-excited vibration,and forced vibration appears in the process of high-speed driving,while self-excited vibration occurs in the low-speed and the resonance car speed is the most obvious in general.2.Design of active pendulum controller based on disturbance estimation.the control technology is used to eliminate shimmy.Based on the shimmy model of independent suspension,the disturbance observer strategy based on the current generation control theory is adopted,and the control module is designed based on Lyapunov stability analysis.Finally,the observer is combined with closed-loop system.Using real-time tracking to eliminate shimmy problem.At the same time,the sliding mode variable structure control system is designed to compare the advantages and disadvantages of the two controllers.3.Numerical simulation analysis based on MATLAB.And use MATLAB numerical simulation function to verify the four-degree-of-freedom pendulum model constructed based on independent suspension.The simulation results show that the pendulum model is basically in line with the actxial situation,and the lateral characteristics of wheels have a great impact oin the shimmy.At the same time,the closed loop system of the front wheel shimmy is simulated and analyzed.By comparing different working conditions,the simulation results show that the front wheel shimmy system with controller is obviously due to the system without controller.Compared with the pendulum system of sliding mode variable structure controller,the effect based on disturbance controller is better.4.Simulink-Carsim was used to simulate real cars.Some c-class vehicle parameters in the Carsim car library were selected as simulation objects.By comparing different working conditions,the accuracy of the model and the effectiveness of the controller based on disturbance estimation are further verified.