Study On The Vibration Reduction Strategies Of Lateral Suspension In Superconducting Electrodynamic Suspension Vehicle

Superconducting electrodynamic suspension(EDS)train is currently the only transportation tool which achieved the speed of 600 km/h,therefore,it is expected to be the main options of next generation of manned high-speed and ultra-high-speed transportation.The dynamic performance is one of the main challenges for commercial application of superconducting EDS train.Ride stability and comfort are important indexes to evaluate vehicle dynamic performance,and the main ways to improve the ride stability and comfort of the superconducting EDS train are to improve the line grade and the suspension system of the vehicle.Among them,the improvement of line grade will lead to the remarkable increase of the line construction cost.Therefore,the optimization and design of vehicle suspension system is a more efficient way to improve the stability and comfort of the vehicle.Based on the Newton-Euler equation,the lateral dynamics model of superconducting EDS vehicle was established in this thesis,which took the rolling pendulum motion into account.The time domain series of the guideway irregularity was obtained by numerical simulation based on Inverse Fourier transform,and then taken as the excitation input of vehicle.The response characteristics of vehicle lateral dynamics was studied.In order to improve the running stability of the superconducting EDS vehicle,firstly an active control model of superconducting EDS vehicle was established in this thesis.Based on the optimal control theory,a linear quadratic(LQ)optimal controller was designed.Aiming at the difficulty in selecting the weight coefficient of LQ optimal controller performance index,a method for selecting the weight coefficient of multi-level LQ optimal controller was proposed based on the analytic hierarchy process and genetic algorithm(AHP-GA).The influence of genetic algorithm parameters in this method on the vibration reduction performance of LQ optimal controller was also studied and analyzed.It is found that the population size,cross offspring ratio,elite number and maximum generation can affect the vibration reduction effect of LQ optimal controller.The effect of LQ optimal control method based on AHP and AHP-GA on the vibration control of the suspension system of superconducting EDS vehicle was compared from the time domain and frequency domain.The results show that the LQ optimal controller based on AHP and AHP-GA multi-level optimization weight coefficients can effectively improve the ride comfort and running stability of the vehicle.What’s more,the latter can significantly suppress the low-frequency vibration components near the first-order and second-order natural frequencies of the car body,and therefore is of a better control effect.Secondly,the semi-active control model of superconducting EDS vehicle was established.By studying the motion law of the velocity and acceleration of the car body and the bogie,an improved ON-OFF type skyhook damping semi-active control method was proposed.The advantages and disadvantages of ON-OFF type,continuous type and improved ON-OFF type of semi-active skyhook damping methods were compared from the aspects of control effect and control efficiency.The results show that the control efficiency of the improved ON-OFF type skyhook damping semi-active control method is between that of the ON-OFF type and the continuous type skyhook damping semi-active control method.Its vibration reduction performance is the best of the three methods,which can improve the running stability and ride comfort of the vehicle.Finally,in view of the challenge to establish an accurate model of superconducting EDS train with multiple dimension,strong-coupling and nonlinearity,an adjustable factor fuzzyimproved skyhook damping semi-active composite control method was proposed,using the improved ON-OFF type skyhook damping semi-active control method as the knowledge base of fuzzy control.The fuzzy-improved type skyhook damping and adjustable factor fuzzyimproved type skyhook damping semi-active composite control method were applied to the vibration control of suspension system of superconducting EDS vehicle.The vibration reduction effects of the two methods were studied and compared.The results show that the adjustable factor fuzzy-improved skyhook damping semi-active control composite method is of a better adaptive ability,so it is control effect.As a result,it can suppress the lateral vibration amplitude of the car body and bogie,reduce the lateral and vertical displacement variation of the bogie when the vehicle is in stable suspension,and broaden the frequency range of vibration control.The running safety and stability of the vehicle could be effectively improved with the help of it.