Key Techniques And Their Realization In Developing Ultra-Low-Frequency Vibrator Calibration System

In this dissertation, the present research status of standard vibration metrology technique at home and abroad is introduced, and the significance of developing ultra-low-frequency standard vibration metrology is discussed as well. Systematic research has been done in developing ultra-low-frequency standard vibrator. Several key technical problems are solved in order to develop the calibration system of this kind of vibrator. This dissertation if arranged as follows.In chapter 1, the aims of the dissertation are presented. Firstly, the properties of vibration transducers and their calibration methods are given, and the significance of establishing ultra-low-frequency standard vibration calibration system is pointed out. Secondly, the present research status on standard vibration metrology at home and abroad is surveyed. Thirdly, some problems in the ultra-low-frequency standard vibration metrology and the future direction are pointed out. In the end, the main content of this dissertation is addressed.In chapter 2, based on the analysis of present vibrator's principle and structure, two kinds of transfer functions and frequency response curves of the vibrator, driven by voltage feedback power amplifier and current feedback amplifier, are given separately. And turnover frequencies between different frequency rangs are also given.In chapter 3, the mechanism of test table waveform distortion generated by factors of ultra-low-frequency standard vibrator is studies systematically. These factors include the nonlinearity of suspension spring, the nonlinearity of damping force and the nonlinearity of driving force, etc, in which suspension spring and damping force are main factors that influence the distortion of ultra-low-frequency vibrator.In chapter 4, control strategy for standard vibrator's test table waveform is studied. Based on the discussion of the nonlinearity of the vibrator, the mathematic model of ultra-low-frequency vibrator is established. Then, on the basis of the Ziegler-Nichols PID controller, PID control parameters aremodified according to the control requirements of object, and the computer simulation is done. Finally, Low-frequency feedback system is built up, which solves the problem of high distortion of the output of vibrator under ultra-low frequency.In chapter 5, the ultra-low-frequency vibration calibration system is developed. The hardware and software design methods of the system are discussed, and the methods that solve the problem under ultra-low frequency are emphasized, such as the design of ultra-low-frequency amplifier and the arithmetic of adjusting the vibrant level. In the end, many kinds of experiments prove the performance of total system.In chapter 6, the achievements of the dissertation are summarized and the further research work that needs to be done is put forward.