Research On Semi-active Suspension System Of High-speed Train Based On Magnetorheological Technology

Aiming at the problem that the vibration of the vehicle is increased after the running speed of the high-speed train is increased,the vehicle is prone to snake-shaped instability after the wheel and rail wear,and the lateral resonance of the vehicle body during the speedincreasing process,the semi-active suspension system of high-speed train based on magneto-rheological(MR)technology is developed.The research aims to improve the ride comfort and ensure the safety and the running stability of the high-speed train from the perspective of the suspension system.Magneto-rheological fluid(MRF)is a new type of intelligent material.Based on MR technology,a new semi-active shock absorber structure can be designed to equip high-speed trains with semi-active suspension systems with controllable parameter performance.The semi-active suspension can make the vehicle achieve the same vibration damping effect as the active suspension system,and has the advantages of simple structure,low energy consumption,fast response and high safety.However,there are still many scientific problems that need to be resolved in the semi-active suspension of high-speed trains based on MR technology.There are also large research gaps in the research on practical engineering problems such as high risk of instability and low stability encountered during high-speed train operation.Some theoretical and practical application issues still need to be further resolved.Based on this,the purpose of this paper is to reduce the vibration and improve the stability of high-speed trains.The method of combining theoretical analysis,simulation calculation and experimental research is used to study the design of controllable stiffness or damping MR damping device,semi-active suspension system and control strategy design,experimental testing and evaluation.The specific research work includes the following aspects:1.Research on the adaptability of variable stiffness(VS)suspension system for highspeed trains.As the running speed of the train increases,the track excitation frequency gradually increases.At a certain running speed,the track excitation frequency is equal to the natural vibration frequency of the vehicle,which causes the vehicle to resonate,and greatly threatens the running safety and reduces the ride comfortable of the vehicle.Because the lateral dynamic performance of the train is mainly studied,in order to better show the phenomenon of the lateral resonance of the vehicle,therefore,according to the parameters of a certain type of rail train,the classic lateral dynamics model of 17-degreeof-freedom of the rail vehicle with a VS-MR secondary system was established specifically by using the numerical calculation software Matlab/Simulink.An on-off switch control strategy to avoid lateral resonance of the vehicle body was designed.When the lateral resonance of the vehicle body occurs,the lateral stiffness value of the secondary suspension system is switched.Then,the lateral natural vibration frequency of the vehicle body is changed by changing the stiffness,thereby achieving the purpose of avoiding lateral resonance of the vehicle body.The results show that the VS secondary lateral suspension system can effectively avoid the lateral resonance of the train body and greatly reduce the lateral vibration transmissibility and the vibration acceleration of the vehicle.Compared with the passive suspension system,the RMS values of the lateral acceleration,yaw acceleration and rolling acceleration of the vehicle body are reduced by 40.41%,17.5% and 42.75%,respectively.2.Research on the adaptability of variable damping(VD)suspension system for highspeed trains.During the high-speed operation of the train,the vibration amplitude of the vehicle has increased significantly,and the safety and ride comfort have decreased.Moreover,due to the characteristics of high-speed railway lines in China,such as the variable curve lines and large line spans,the trains will also encounter the problems of reduced stability during the operation.Based on this,the research work of the VD secondary suspension system was carried out.In order to more realistically simulate the operation state of the rail vehicle,the multi-body dynamics software Simpack was used to establish the 46-degree-of-freedom dynamic model of the rail vehicle,and various nonlinear factors of the vehicle system and the measured track excitation were fully consider.The simulation results show that the high-speed train adopts VD anti-yaw damper and VD secondary lateral damper to control the changes of the anti-yaw damping and secondary lateral damping parameters,so that they can achieve excellent combined damping parameters,which can significantly improve dynamic performance of the vehicle.Compared with the standard damping parameters,the lateral acceleration of the vehicle body,stationarity index,derailment coefficient,wheel-rail lateral force and max wear power are reduced by 16.4%,14.0%,17.2%,3.9% and 85.4%,respectively.The nonlinear critical speed is up to 640 km/h.The VD anti-yaw damper can make the highspeed train better suited to different operating conditions,so that the vehicle always maintains good running performance.It can also better ensure the ride comfort and running safety of the vehicle,and reduce the yaw acceleration of the vehicle body,the lateral and yaw displacement of the bogie by 40%,29% and 51%,respectively.Aiming at the contradictory problem that anti-yaw damping should be appropriately increased as vehicle speed increases in a straight line condition,and as the curve radius is reduced,the anti-yaw damping should be appropriately reduced,and then the vehicle operating conditions are determined by monitoring vehicle dynamic parameters,and VD-MR antiyaw shock absorber is used to control the corresponding damping force according to different operating conditions,which can find a new way to resolve this contradiction.3.Adaptability study of variable stiffness and variable damping(VSVD)suspension system for high speed trains.The dynamic performance of the vehicle is different in different wheel-rail contact states.The anti-yaw shock absorber mainly affects the lateral dynamics of the vehicle and the stability of the yaw movement.Ordinary oil dampers may cause changes in anti-yaw stiffness and damping parameters due to factors such as oil pressure leakage and rubber node aging.And with the substantial increases in train operating speed(especially after over 300 km/h),the external disturbance frequency will increases and approach or exceed the natural frequency of the vehicle/track system,resulting in enhanced the wheel-rail interaction,train overal or local resonance,and bogie vibration instability,etc.Therefore,the adaptability of VSVD anti-yaw damper to wheel and rail wear was studied.A mathematical model of VSVD anti-yaw damper dynamics based on MR technology was established.Through the joint simulation of dynamic software Simpack and Matlab/Simulink,a fuzzy control algorithm which avoids the instability of the frame was designed.The results show that by controlling the stiffness and damping parameters of the anti-yaw damper,the running performance of the vehicle can be greatly improved when the wear wheel-rail contact is poor,ensuring that the frame does not suffer from yaw instability.Compared with the vehicle with passive suspension system,the lateral acceleration and yaw acceleration of the vehicle body are reduced by 22.4% and 25.5%,the lateral acceleration and yaw acceleration of the frame are reduced by 16.0% and 65.6%,and the derailment coefficient,wheel-rail lateral force,and wheelset lateral displacement are reduced by 53.9%,40.8% and 20.6%,respectively.4.Experimental study on the effectiveness of the variable stiffness(VS)suspension system for high-speed railway vehicles.In order to verify the effectiveness of the controllable stiffness secondary lateral suspension for high-speed trains,a 1/8-scale rail vehicle model was designed and manufactured,and two VS-MR dampers were designed and fabricated,firstly.Then,a VS semi-active suspension system that can be used for this vehicle model was also designed,and the vehicle vibration test platform was built.Subsequently,based on on-off switch and short-time Fourier transform(STFT)algorithm,the control strategy for avoiding lateral resonance of vehicle body was designed.Finally,the experimental research and evaluation were carried out.The test results show that the designed VS-MR damper has excellent stiffness controllability.When the coil current increases from 0 to 0.8 A,the equivalent stiffness coefficient increases by 3.7 times.And it breaks through the bottleneck of controllable damping parameters of general MR dampers.The designed VS semi-active suspension system and its control algorithm can effectively avoid the lateral resonance of the vehicle body.Compared with the passive suspension system,the vibration transmissibility is greatly reduced,especially near the resonance frequency.Under harmonic excitation and random excitation,the RMS value of the lateral acceleration of the car body has decreased by more than 22%.5.Design and experimental evaluation of a versatile variable stiffness and variable damping(VSVD)semi-active suspension system for high-speed trains.Firstly,the VSmagneto-rheological elastomer(MRE)isolator and the VD-MR damper were designed.Then,a VSVD semi-active suspension system was designed and manufactured,which includes four VS-MRE isolators and two VD-MR dampers.Subsequently,the control algorithm of the VSVD semi-active suspension was designed,including a VS controller based on on-off switch and STFT algorithm,and a VD controller based on Sky-hook.The test results show that the designed multi-function VSVD semi-active suspension can not only effectively avoid the lateral resonance of the vehicle body,but also greatly reduce the lateral vibration acceleration.In the case of harmonic vibration excitation,compared with passive(switch-off)suspension,the RMS values of passive(switch-on)suspension,VS suspension,VD suspension and multi-function VSVD suspension are reduced by 54.7%,41.6%,56.7% and 68.8%,respectively.The multi-function VSVD suspension has the best vibration attenuation ability and the minimum vibration transmissibility over a wide range of vibration frequencies,which effectively avoids lateral resonance of the vehicle body.In the case of random excitation,compared to the passive(switch-off)suspension system the RMS values of the VS suspension,VD suspension and VSVD suspension systems are reduced by 31.3%,44.2% and 55.7%,respectively.The versatile VSVD semi-active suspension system exhibits optimum vibration damping performance and is scalable for use in practical high-speed train suspension systems as well as high fail-safe reliability.