Research On The Key Techniques Of Long-Stroke Ultra-low Frequency Horizontal Electromagnetic Vibrator

Based on National Science and Technology Infrastructure Program "Establishment of national ultra-low frequency standard vibration device", the key techniques of a long-stroke ultra-low frequency horizontal vibrator were researched. This dissertation was arranged as follows.In chapter1, the destination and significance of the dissertation were presented. First, the vibration sensors and their calibration methods were given. Secondly, the general situation of development on the vibration calibration device at home and abroad was reviewed. Then the present research status on the ultra-low vibrator was analyzed and its challenge was pointed out. Finally, the main research content and aim of the dissertation was addressed.In chapter2, a kind of double-magnetic circuit for an ultra-low frequency horizontal vibrator was studied. Considering that a uniform distribution of magnetic flux density (MFD) in the long air gap (LAG) can not be realized through a traditional single-magnetic circuit, a double-magnetic circuit (DMC) composed of two oppositely-magnetized permanent magnets was proposed. Then the DMC was simulated by the finite element software. To enhance the uniformity of the MFD, the improved DMC with uneven air-gap was proposed and the MFD in the LAG was optimized. Finally, the magnetic flux leakage on the vibration table was analyzed.In chapter3, the design of the motion assembly in an ultra-low frequency horizontal vibrator was researched. The static characteristics and stability of the aerostatic slideway in the motion assembly were analyzed theoretically based on a simplified model, and the influence of different structure parameters of the aerostatic slideway on its performances were analyzed. In the end, the modal of the moving component was analyzed by the finite element software, which showed that its first modal frequency had been high enough to meet the requirement proposed by the operating frequency range of the vibrator. In chapter4, the motion control strategy for an ultra-low frequency horizontal vibrator was researched. Based on the transfer function of the vibrator, the PID control system with displacement feedback was designed. Then the parameters of a PID controller were set with the genetic algorithm. In the end, a closed-loop control system based on the displacement feedback was developed to achieve the high stability and precision of the output waveform from the vibrator.In chapter5, the performance of a developed ultra-low frequency horizontal vibrator was tested. The experimental contents included the magnetic flux leakage density on the working platform, total harmonic distortion of output acceleration waveform, transverse vibration ratio and stability, etc. Results showed that the performance of the long-stroke vibrator has met the expectation and it can be adopted as the standard vibrator in the ultra-low frequency vibration calibration system.In chapter6, the achievements of the dissertation were summarized briefly and the further research work need to be done was expected.