| Dynamic performance evaluation of high-speed EMU in on-orbit state,especially in high-speed operation,is the test basis of rail transit technology progress and the realistic demand of rail vehicle’s development of high-speed,heavy-duty and intelligent.The load spectrum reproduction test,using special equipments to simulate vehicle service conditions,has been widely used due to its diversified functions and high efficiency.Load spectrum refers to measurable information such as displacement,velocity,acceleration,etc.,which can reflect the change of physical parameters in specific spatial position of the research target.The goal of load spectrum reproduction test is to simulate and reappear vehicle operating conditions with high precision through bench,and its key technologies are equipments with high performance,accurate mathematical model of test system and effective reproduction method.In this paper,the key technologies mentioned above are taken as the research content and the load spectrum reproduction of high-speed EMU based on bogie test-bench is taken as the research goal.A special force measuring platform and electro-hydraulic servo control system of the bench which determine the load force measurement function and broadband excitation performance respectively are designed,the test methods of key bogie parameters are put forward.Based on system identification principle and iterative reproduction technology,with the test being combined with simulation,a loop iterative method with adaptive error coefficient is proposed,and the reproduction test of load spectrum with vertical acceleration of high-speed EMU body and bogie as the target is completed.The main work is as follows:1)The system composition of bogie test bench,pose motion spectrum system and test data analysis system are described.Vertical dynamic modeling is carried out for high-speed EMU vehicles and simulated half-car mass load spectrum reproduction system respectively,and the system response of vertical displacement of car body and bogie under the same excitation are simulated and analyzed by MATLAB/Simulink program.It is proved that simulated half-car mass load spectrum reproduction system can accurately reproduce the on-orbit running conditions of vehicles at medium and high speed,and its mathematical model is used as the model configuration basis of system identification.2)A special force-measuring platform which takes the load force at wheels of the bogie as the measurement target is proposed.Mechanical structure,strain gauge layout and measurement circuit are designed,and its scientificity and accuracy are verified from mechanical theoretical calculation and finite element simulation.Through calibration test,interdimensional coupling effect of three-dimensional force measurement is analyzed,and a numerical decoupling method based on least square theory is put forward.The test shows that the measurement accuracy of uniaxial and multiaxial load are able to meet requirements after numerical decoupling.According to the dynamic performance index of the test bench,static and dynamic design of the electro-hydraulic servo control system is carried out,and the selection of the main components such as hydraulic cylinder and servo valve and the correction of gain value of servo amplifier are completed.Stable broadband excitation performance of the test-bench is verified by frequency sweep test,modal simulation and experiment.3)Measuring methods of key bogie parameters such as bogie suspension stiffness,suspension damping,bogie center-of-gravity position coordinates and moment of inertia are designed: suspension stiffness parameters are measured by low-speed quasi-static triangular wave loading test,suspension damping parameters are measured by frequency-variable sine wave loading test with step-by-step scanning increment,bogie center-of-gravity position coordinates are measured by inclination test,and moment of inertia parameters are measured by constant-frequency sine wave loading test.In addition,according to the relationship among moment of inertia,center-of-gravity position and movement winding point,a kind of fitting test method with winding points presetted is proposed as a new method for measuring the height of the bogie center of gravity.These above methods for measuring bogie parameters have been verified by corresponding tests.4)Analytical expressions of power spectral density of track irregularity at home and abroad are studied,and the quality of China’s high-speed rail track spectrum and Germany’s high-low interference spectrum is compared.Inverse Fourier Transform is used to reconstruct China’s high-speed rail track,so as to provides target data for the subsequent track irregularity recurrence test.The test-bench posture motion spectrum calculation system is used to generate driving motion spectrum according to the track irregularity reconstruction sample data and the hydraulic flow demand of hydraulic actuators with different simulated vehicle speeds are calculated to prove the hydraulic driving ability.The posture measurement scheme of the bench is designed,which using laser displacement sensors to measure real-time displacement of the specific position of the movement platform,so as to calculate the spatial motion index.Tests of track irregularity recurrence of China’s high-speed rail are carried out,and the results show that the simulation of track irregularity recurrence can be accurately completed based on the bogie test bench with the medium and high simulated speeds.5)The data transfer of simulated half-car mass load spectrum reproduction test system is expressed as the series of two modules,namely,input data conversion and simulated half-car test device,and mathematical expression of transfer function are theoretically analyzed as the basis of system identification.Test method of system transfer function identification is designed.Band-pass white noise signal is used as the input signal,and the parameters of the optimized model are estimated by least square method.An iterative method combining simulation with experiment is proposed,and the system excitation meeting the precision requirement is obtained through computer simulation iteration and used as the initial input of test iteration to further approach recurrence target,the test efficiency is significantly improved via such means.According to the error correction coefficient which determines the iteration speed in the experiment,a strategy which can automatically optimize its own numerical value adapt to the recurrence error is designed.The experiment shows that the number of cycle iterations required is obviously reduced and the experiment efficiency is further improved.The research in this paper shows that,as a special bogie test equipment,the capability of the bogie test-bench meets performance index,and the accuracy of the load force measurement meets test requirements as well.Combined with various test methods,it can complete test determination of key bogie parameters,the parameter identification of the test system,and the cyclic iteration reappearance test with high test efficiency.As a result,the simulation of on-orbit running conditions of vehicles can be effectively completed.It is a successful equipment.Since its completion and operation,it has made great contributions to the technical progress of new bogies and rail transit industry in China. |
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