| The vehicle suspension system is a key component to ensure the ride comfort and handling stability of the vehicle.The passive suspension has less improvement in ride comfort.Therefore,the active suspension is widely concerned with its real-time control response,wide frequency control range,and strong adaptive capability.Due to the use of the flexible components of the suspension system and the coupling of various components,the suspension exhibits strong nonlinear hysteresis characteristics.The study of nonlinear suspension and control strategy can make the suspension vibration characteristics closer to the actual suspension.Therefore,the research on the active control of nonlinear suspension is of great significance.Based on the established nonlinear model of suspension spring hysteresis,the vibration characteristics of the suspension are analyzed,and then the nonlinear optimal suspension is controlled by the preview optimal control algorithm.An improved optimization strategy is proposed for the optimal control of the preview.Finally,the improved effect of the proposed nonlinear control based on nonlinear suspension is verified by simulation.In this paper,based on the principle of vehicle dynamics,the suspension vibration equation with hysteresis nonlinearity of spring is established.The Bouc-Wen model is used to describe the hysteresis nonlinearity of the suspension spring.Based on the established single-side road spectral excitation model,the equivalent linearization and virtual excitation method are combined to solve the frequency domain response of the suspension directly in the frequency domain.And analyze the impact of different vehicle driving conditions and different nonlinear coefficients on the suspension response.The results show that the hysteresis nonlinearity of the suspension spring has a great influence on the response of the vehicle,and the frequency shift of the peak of the suspension vibration occurs.Based on the nonlinear model,the active suspension of the preview optimal control based on Kalman state estimation is established.After estimating the state of the system,the state space equation of the system is expanded by using the preview information of the front wheel.Finally,the optimal control algorithm is used to calculate the required control force.According to the established active suspension,the effectiveness of Kalman estimation,the suppression vibration effect of preview control,and the control effect of active suspension under different nonlinear parameters are analyzed.The simulation results show that the proposed optimal preview control can effectively suppress the effects of vibration on vehicle acceleration,suspension movement and tire dynamic load.Aiming at the complicated process of selecting the weight coefficient in the optimal control,a method for determining the weight coefficient based on the AHP-NSGA-III algorithm is proposed.The ratio of the response root mean square value of the active suspension to the root mean square of the response of the passive suspension is selected as the objective function.The initial range of the weight coefficient is given as the optimization interval by the AHP method with emphasis on the suspension.Under the constraints of the schedule and other conditions,a multi-objective optimization scheme based on NSGA-III is established.Finally,the local optimization is selected in the generated Pareto optimal solution set to determine the weight coefficient of the optimal control,and the method is applied to the linear active suspension and the nonlinear active suspension.The simulation results show that the preview optimal control after weight coefficient optimization has better performance than the traditional method to determine the weighted index predictive optimal control.Finally,in order to facilitate the further study of system parameters,a nonlinear active suspension performance calculation software based on hysteretic nonlinear suspension and active control method is developed.It provides response power spectrum analysis of nonlinear vehicle passive suspension and active suspension under different vehicle parameters,different nonlinear coefficients,different vehicle operating conditions and different grades of roads,which is convenient for users to develop different vehicles and simplify development Process.The related research results in this paper can provide reference for the development of active suspension of nonlinear suspension,and also provide a solution for nonlinear systems.It also provides a systematic method for determining the weight of optimal control algorithms. |
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