Carbody Vibration Control And Strain Modal Analysis For EMU

The vibration of high-speed train directly influences its operation safety and passenger ride comfort in running process. Due to the lightweight design and high speed running of train, the safety and ride comfort issues caused by the vibration have become prominent.More attention should be paid to the elastic vibration of components, especially carbody,which can loose the connection structure, increase noise, and propagate the crack of structure.These would decrease the structure fatigue life sharply and affect the train operation safety seriously. Track irregularity is the source of train vibration, which is random and complex.So the vibration of vehicle has the feature of randomicity and complexity. Therefore, it is important to study the vehicle vibration characteristics of the elastic effect, vibration evaluation method and attenuation vibration method.Aiming at the elastic vibration problem in high-speed train system, the dynamic behavior of vehicle excitated by track irregularity is studied by establishing the models of two-dimensional Bernoulli-Euler beam and three-dimensional rigid-flexible coupling dynamics. Firstly, the vehicle dynamics model considered elastic carbody is established. The vehicle vibration characteristics and rules are analyzed in frequency domain. Secondly, the passive control method of the train suspension parameters optimization, the active control method of installing the smart piezoelectric component in carbody and the active control actuator in secondary suspension are analyzed, respectively. These methods can reduce vehicle vibration and improve ride quality. The main research work can be summarized as following,(1) Based on establishing the models of two-dimensional Bernoulli-Euler beam and three-dimensional rigid-flexible coupling dynamics, the vibration characteristics and transfer relationship under flexible effect are studied in frequency domain. Analysis results show that symmetrical mode response is zero and anti-symmetric mode response is the maximum in some specific wavelengths, and anti-symmetric mode response is zero and symmetrical mode response is the maximum in others. When the natural frequencies equal to excitation frequencies, the car body produces modal resonance. The resonance speed and resonance wavelength of first-order vertical bending vibration has significant impact on train operation.The correlated frequency response function acceleration transmissibility at first-order vertical bending vibration feequency is the maximum and has the largest contribution to the car body vibration. The higher speed, the higher first-order bending frequency is required.(2) The vibration acceleration transfer relationship is analyzed by the vibration acceleration data of line test. It is compared with the results of the vehicle vibration simulations. Their agreement demonstrates the correctness of simulation. The affection of primary suspension parameters, secondary suspension parameters and unning speed of the vehicle on running stability are analyzed. To improve the running stability, the min-max optimization approach is utilized to improve the train riding comfort with related 4 suspension parameters. The K-S function is applied to fit the objective function. The optimization analysis of a high-speed train is done. In order to reduce the vibration and improve the ride comfort, the method effectiveness and measures of the carbody natural frequency design, modal and local modal design, and transfer function design are studied,respectively.(3) The active vibration suppression of high-speed EMU carbody is studied by combined use of secondary suspension actuator and piezoelectric actuator. A vertical dynamics model is established considering the secondary suspension saturator and piezoelectric actuator. The optimal installation position of piezoelectric actuator and piezoclectric sensor are analyzed. The feedback controller based on the robust optimal control is designed. With the simulation method, the dynamic performances of vehicle with active control system are analyzed. Simulation results show that the robust control method based on secondary suspension actuator and piezoelectric actuator can reduce vehicle vibration and improve ride quality. The secondary suspension actuator can reduce carbody rigid vibration and piezoelectric actuator can reduce elastic vibration. The higher speed, the more obvious acceleration suspension effect is. Compared with the passive suspension system, the active vibration suspension system with robust controller can reduce the vehicle rigid and elastic vibration and improve the ride comfort.(4) In the structural strength design and damage diagnosis, the key is to obtain the stress state. The stress state can be obtained by the strain. Strain modal theory and its property are derived from displacement modal theory. The results show that it is more sensitive for strain modal than displacement modal through the simulation analysis of the carbody equivalent vertical model calculation. Strain modal difference curve can determine the structural damage location and damage degree. The vehicle FE model verifies this result. The strain and stress versus time history of carbody can be obtained by the mode superposition method.