Study On Vibration Control Of Semi-active Suspension System For Railway Vehicle

As an important component of the vehicle system,the performance of suspension system affects the riding comfort and running stability directly.The optimization design for the vehicle suspension system is an effective method to improve the ride comfort of vehicle.At present,the semi-active suspension system based on magnetorheological damper(MR damper)has become one of the focal point of research in the field of vehicle suspension control.The control strategy of semi-active suspension system based on MR damper is studied deeply in this thesis.The classification of vehicle suspension system is introduced briefly,the working principle of MR damper is described,and the Sigmoid model of MR damper is established.On this basis,the influence of the variation of MR damper parameters on its characteristics is analyzed.At the same time,the American six level orbital spectrum is used as orbit excitation,the simulation model of passive suspension system and semi-active suspension system based on MR damper is established in MATLAB/Simulink.Finally,the vehicle performance evaluation index is introduced.Aiming at the problem of delay in the process of system control,the dynamic model of single-degree-of-freedom magnetorheological semi-active suspension system with time delay is established.The source of the time delay of the MR control system is introduced,and the influence of the time delay on magnetorheological semi-active suspension system is analyzed.Then the method of multiple scales is used to solve the differential equation of motion,and the characteristic curve equation of amplitude and frequency is obtained.The influence of the nonlinear stiffness coefficient,the magnetorheological semi-active damping coefficient and the time delay on the response curve of amplitude and frequency are analyzed by MATLAB programming.Finally,the numerical simulation of the system is carried out.The results shows that the reasonable semi-active damping coefficient and time-delay can effectively suppress the vibration of the system,however,if the parameters are not suitable,the vibration of the system will increase,and even lead to damage the system.The effectiveness of time-delayed feedback control to suppress vehicle vibration is verified.Combining with the motion status of vehicle system,a fuzzy control strategy based on the vehicle body acceleration and the speed difference between the body and the bogie as two input variables of the controller and MR damper current as output variable of the controller is designed.The simulation model of two-degree-of-freedom and six-degree-of-freedom semi-active suspension system based on fuzzy control are established in MATLAB/Simulink.The simulation results shows that the damping effect of the semi-active suspension system based on fuzzy control is better than the passive suspension system,and the riding comfort and running stability of the vehicle are improved effectively.Because of the parameters of fuzzy control strategy are obtained by the designer's experience,they are uncertain.Aiming at this problem,a fuzzy control strategy based on particle swarm optimization(PSO)is proposed,finding the optimal set of parameters to achieve better control effect through the optimization of quantized and scaling factor.Firstly,the principle and optimization process of particle swarm optimization algorithm are introduced,and the influence of parameter variation on the optimization effect is analyzed.Then the Simulink module of the PSO-Fuzzy control system is established.The simulation results shows that after the particle swarm optimization,the control effect of semi-active suspension system based on fuzzy control has been improved effectively.The overshoot and vibration fluctuation are reduced significantly,and the optimization of vehicle suspension system control has been achieved.