Study On Active Control Strategy For Suspension Systems Of Electric Vehicle

As energy shortage and environmental pollution,the development of electric vehicles(EVs)is an effective solution,and the NVH problem is also an important link in the process of research and development.In-wheel motor electric vehicle(IWM-EV)is regarded as the final drive form and has received widespread attention.The ride comfort and road holding stability of the IWM-EV are deteriorated due to the increase of unsprung mass and unbalanced force produced by the motor.The switched reluctance motor(SRM)has been widely applied to the IWM-EV due to its advantages including high starting torque,a wide operating speed range and high efficiency.Note that the unbalanced force produced by the SRM and the road disturbance may severely deteriorate the ride comfort of the IWM-EV equipped with a conventional passive suspension system.It is difficult to reduce the SRM unbalanced force by improving the manufacturing precision and assembly precision.Considering the advantages of active suspension systems,the design of the active suspension in a IWM-EV has some potential application prospect.It can simultaneously suppress the external disturbances including the SRM vertical force and the road roughness for improving the ride comfort and stability.The control algorithm is very important for the active suspension system.For the IWM-EV active suspension control design,the unbalanced electromagnetic force should be considered as an unknown external disturbance.At present,the research is relatively rare.The paper investigates the active suspension control strategies for the in-wheel switched reluctance motor electric vehicle(IWSRM-EV).The main works are as follows:A quarter-car suspension model with SRM is established,and the performances of the suspension are discussed under the SRM vertical force and the road disturbances.On this basis,a half-car active suspension is modeled by taking the SRM vertical force and the road unevenness as the external disturbances.The static output feedback control problem of the active suspension with information structure constraints is investigated.Moreover,a novel static output feedback control strategy is proposed.A variable substitution method is employed in the controller design such that the initial feasible solution with a sparsity constraint can be solved by a single-step linear matrix inequality(LMI).The state-feedback information is used for handling the initial infeasibility issue.Meanwhile,an optimization algorithm is also proposed to search for less conservative results.In chapter 3,the problem of robust non-fragile output-feedback control of vehicle active suspension systems with finite-frequency constraint is investigated.The ride comfort is improved within the given frequency range and the hard constraints are also guaranteed in the time-domain.For the robustness of the controller,a non-fragile ability is also considered.A new finite-frequency H∞ control theorem is introduced by using the Generalized Kalman Yakubovich Popov(GKYP)lemma.Furthermore,a non-iteration algorithm is proposed for solution.Different from the previous theorems,the design is effective and less conservative.Finally,a design example is given.In chapter 4,the finite-frequency control is applied to the EV active suspension system with road preview information.Firstly,an augmented active suspension system with road preview information is established.Secondly,a finite-frequency linear-parameter-varying(LPV)controller is designed.Finally,simulation and experimental results are given to shown the merits of the proposed method.The chapter 5 deals with the problem of static output-feedback H∞ control for vehicle active suspension systems with time-varying input delay.A new delay-range-dependent(DRD)H∞ control criteria is established by using double convex combination approach.The solution is directly derived by a single-step method,the design process is greatly simplified.In the end,the effectiveness is illustrated by numerical simulation.A novel sliding mode tracking control scheme for vehicle active suspension systems with matched and mismatched uncertainties is proposed based on super-twisting concept(STC).A novel trajectory function is proposed to adjust the suspension performances based on a negative acceleration feedback loop.The system uncertainties can be estimated by using a extended super-twisting disturbance observer(ESTDO).The control scheme requires only the suspension deflection and acceleration feedback and thus is easy to implement.Numerical and experimental results are given to show the effectiveness of the controller.Finally,the conclusions and outlooks are given.