| With the increase of the speed of the rail vehicle,the stability and riding comfort during the vehicle operation have both attracted more attention from experts and scholars.As the research object of this article,Hydraulic shock absorber plays an important role in improving the dynamic performance of vehicle during operation.In particular,the introduction of the anti-snake shock absorber has greatly improved the critical speed of the vehicle.Therefore,it is of great engineering application value to carry out research on the hydraulic shock absorber of railway vehicles.Firstly,investigate external damping characteristics exhibited by the shock absorber by analyzing the internal structure.The existence of various types of valves inside the shock absorber causes the unloading phenomenon when the piston speed of shock absorber reaches a certain value,so the shock absorber shows nonlinear damping characteristics.When the piston operates at low frequency and high amplitude,the stiffness of dynamic hydraulic,the stiffness of the rubber joint at the both ends,and the stiffness of the mounting seat can't be ignored.And the damping characteristics of the shock absorber need to be described as the series connection of the damper and the spring;therefore,there is a phase difference between the speed of the shock absorber piston and the damping force.With the Damper module in the MTS hydraulic inspection system design the hydraulic shock absorber test,and the test material is the shock absorber that is replaced during the four-level maintenance of EMU.The purpose of the test is to check whether the dynamic and static characteristics of shock absorber conform to the application requirements of the actual circuit,to avoid the occurrence of maintenance transition and under-maintenance in the full life cycle of the shock absorber,and to provide valuable reference for the study of the visual maintenance or prolonging the maintenance cycle of shock absorber.According to the analysis result of the damping characteristic curve between the static damping force and the piston velocity of the anti-snake-type shock absorber replaced during the four-level maintenance of EMU,we can know when the piston speed is low,the damping force of some shock absorbers is beyond the tolerance range of the damping value of three-level maintenance,in addition,in the unloading interval the damping force of the anti-snake shock absorber meets the tolerance range of the damping value of three-level maintenance,meanwhile the general working interval of the anti-snake shock absorber is in the unloading area.Comparing the damping force of the shock absorber during three-level maintenancewith that in four-level maintenance,it can be found that the damping value of the shock absorber of the four-level maintenance is significantly lower than that in the three-level maintenance;and by exploring the evolution of the damping characteristics of the shock absorber with the increase of loading times,it can be found that the consumption of energy of the shock absorber each working period show downward trend with the increase of loading times,at the same time,the fullness of the indicator diagram show downward trend with the increase of loading times under the same load displacement condition.When the number of loading times of the shock absorber test is very high,there will be a sudden change in the indicator diagram of the shock absorber,the damping force of the shock absorber is mutated,and it can be caused by abrasion inside the shock absorber.Based on the analysis of static characteristics,dynamic characteristics and damping characteristics of shock absorbers,establish the model of dynamics model of the vehicle system with dynamics simulation software to evaluate the impact of the damping value of the shock absorber on the vehicle dynamic performance,vibration and transfer ratio of vibration.These researches provide a valuable reference to the reliability analysis and identification of suspension parameter for the latter research.Finally,briefly introduce the recursive least squares method with forgetting factor ? in the shock absorber damping value identification applications,build the "input-output" model of vehicle shock absorber damping value identification,and by using the vehicle model which established with Simpack software,extract the input state data and output observation data which is needed in the "input-output" model.Finally,using recursive least squares method to complete parameter identification of shock absorber damping values.In addition,separately analyze how do the variable forgetting factor ?,initial value of assessment parameters ?,algorithm of forecast error variance matrix P level of initial value,the different speed and different lines in the algorithm impact on the final result of parameter identification. |
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