Research On Suspension Control Of Electric Vehicle With In-wheel Motor Based On Magnetorheological Damper Inverse Model

As people’s concept of environmental protection and energy conservation continues to strengthen,more and more consumers are choosing to purchase electric vehicles as the main means of transportation.Moreover,due to the support of national policies,the investment of major automobile manufacturers in the research and development of electric vehicles has increased year by year.As a development direction of electric vehicle,the in-wheel motor electric vehicle stands out from the development of electric vehicle because of its unique driving mode,compared with the traditional driving vehicle,which has the advantages of strong maneuverability,high integration and small space occupation.However,due to the introduction of the in-wheel motor,there are some negative effects of the increase in the unsprung mass and the excitation of the in-wheel motor of this type of electric vehicle.Therefore,using appropriate measures to improve the ride comfort of the in-wheel motor electric vehicle has theoretical research value and practical application significance.At present,for the ride comfort of the in-wheel motor electric vehicles,there are four main improvement measures: lightweight of the in-wheel motor,optimization of the traditional suspension,application of the dynamic vibration absorber and development of the intelligent suspension.The effects of the first three improvement measures are general or the application has limitations.This paper finally chooses to introduce the semi-active suspension to study the improvement of ride comfort of the in-wheel motor electric vehicle.A lot of research work has been carried out on the suspension control of in-wheel motor electric vehicle.However,most of the existing studies are based on quarter vehicle model,the plane model and the space model are few,and the rationality of the road excitation time domain model is not discussed.The adopted control strategy takes less consideration of the influence of the in-wheel motor excitation.And the combination with the actual control actuator is also less.Aiming at the problems faced by the research on ride comfort and suspension control of electric vehicle with in-wheel motor,relying on the key research projects of the China Automobile Industry Innovation and Development Joint Fund and the provincial-school joint project,this paper establishes a time-domain model of front and rear wheel road excitation based on Padé approximation and the four-degree-of-freedom plane model of automobile,simulates and analyses the influence of the order of Padé approximation on the ride comfort of the plane model,and finds the optimal order of the Padé approximation to establish the road excitation model for subsequent simulation.The forward model of magnetorheological damper is established,and its inverse model is established by NARX neural network.The plane model of in-wheel motor electric vehicle is established,and analyze the influence of motor excitation on passive suspension,skyhook control,goundhook control and skyhook-goundhook hybrid control.The better control strategy is selected and optimized adaptively by JADE algorithm and Fx LMS algorithm.The control effect is finally passed through the inverse model of the magnetorheological damper to reproduce.The main contents are as follows:(1)The basic principle of Padé approximation is studied,and the Padé approximation of exponential function and its time-domain general formula applied in hysteresis system are derived.Based on the filtered white noise description of the front wheel road excitation,a time domain model of the front and rear wheel road excitation is established.Based on the vehicle plane model and the proposed road excitation model,the time-domain and frequency-domain simulation methods of ride comfort are established.Under the 1-6 orders Padé_approximation.The simulation models of the front and rear wheel road excitation time-domain model and the vehicle four-degree-of-freedom plane model are developed.Based on the frequency domain simulation results,the comparison scheme is designed.The relative error and the relative error average are selected as the comparison indicators.The influence of the order of Padé approximation on the ride comfort is analyzed.The best order is found as the subsequent simulation input.(2)The mathematical description of the Bouc-Wen phenomenological model of magnetorheological damper is gived,and its simulation model is built.The response characteristics of the Bouc-Wen phenomenological model are analyzed from three aspects:displacement amplitude,excitation frequency and voltage intensity.The basic principle and MATLAB implementation of NARX neural network are summarized.The training samples are determined.A series of experimental schemes are designed.The root mean square value and correlation coefficient are selected as evaluation indicators to analyze the training test results of each scheme and find the best to establish an inverse model of the magnetorheological damper.(3)The excitation model of the switched reluctance motor and the plane model of the in-wheel motor electric vehicle including the passive suspension are established.The plane simulation model of the in-wheel motor electric vehicle including the passive suspension is developed.The influence of motor excitation on ride comfort evaluation indicators of in-wheel motor electric vehicle with passive suspension is simulated and analyzed.The principles of skyhook,goundhook and skyhook-goundhook hybrid control are expounded.The influence of motor excitation on the effects of three control strategies is simulated and analyzed.The JADE algorithm is introduced to adaptively optimize the skyhook-goundhook hybrid control strategy.And the simulation results show that the improvement of pitch angular acceleration is not ideal.Then,the Fx LMS algorithm is introduced to optimize the skyhook-goundhook hybrid control strategy.The simulation comparison results of the two adaptive optimization methods are given.(4)The plane model of the in-wheel motor electric vehicle with magnetorheological damper and its simulation model are established.The basic principle of the application of the magnetorheological damper inverse model is studied,and its evaluation scheme is established.The process of simulation of magnetorheological damper inverse model is expounded.The relative error is selected as the evaluation indicator to evaluate the application effect of the magnetorheological damper inverse model.The above research results show that the order of Padé approximation has a great influence on the road excitation model,and it is more important to select the appropriate order for simulation.The motor excitation has a great influence on the control strategy of the in-wheel motor electric vehicle suspension,so it is more realistic to consider the motor excitation.The adaptive optimization of the control strategy by JADE algorithm and Fx LMS algorithm,combined with the application of the magnetorheological damper inverse model,can provide some references of theory and method for the research of the suspension control of the in-wheel motor electric vehicle.