Locomotives Multi-excitation Modal Test System Research

With the increasing velocity of locomotive train, the train vibration also has increased, thus the structure fatigue life is influenced. It is meaningful to study the vibration characteristics of structure, through which we can optimize the structure of vehicles, restrain the overlarge vibration and improve the performance of vehicles. Modal test is one of the major means to obtain structural vibration characteristics. Multi-point coordinated excitation modal test can accurately identify the modal parameters of railway vehicles and improve the modal purity at the same time. Taking the vehicle as the object of study, this paper developed a multi-point coordinated excitation system, and made the structural dynamic characteristics parameter testing.Chapter two introduced the principle of the multi-point coordinated excitation modal test technology, the applicability of multi-point coordinated excitation modal test on secondary suspension vehicles, and established the pure modal criterion and modal purity indicating functions of secondary suspension vehicles at the same time, then conducted the simulation on secondary suspension vehicle by applying the multi-point coordinated excitation modal technique.In chapter three, taking the secondary suspension model car as the object, taking the multi-point coordinated excitation theory as the basis and the Labview as the compiling platform, a multi-input and multi-output pure modal test system was developed. The system made an optimization design on the adjustable force interval of force signal via grid method; the feedback control of the system was achieved by using purity as the target function.At last, with the developed modal test system, multi-point coordinated excitation modal test was conducted on the secondary suspension model car, and the natural frequency and vibration mode of the model car was obtained. Comparing the result with the natural frequencies and vibration modes obtained via Ploymax parameter identification method, it indicated that the results of the two tests are in accordance with each other within an acceptable error, but the multi-point coordinated excitation method got a higher modal purity of each vibration mode.