Research On Related Design Theory And Motion Control Technology For Ultralow-Frequency Standard Vibrators

Based on National Science and Technology Infrastructure Program "Establishment and research of national ultralow-frequency standard vibration device", the related design theory and motion control technology for the ultralow-frequency (ULF) standard vibrator were researched. This dissertation was arranged as follows.In chapter1, the significance and content of the dissertation were presented. Firstly, the contents and methods of vibration calibration were summarized. Then the significance of the ULF vibration calibration was analyzed. Secondly, the recent research on the vibration calibration at home and abroad was analyzed, especially on the ULF vibration calibration. Thirdly, the recent study status on the structure design and motion control of vibrators was analyzed. Then the significance and related technical challenge for developing an ULF standard vibrator were presented. At last, the main research content of the dissertation was addressed.In chapter2, the design theory for the uniform magnetic flux density (MFD) in the long air gap (LAG) of an ULF standard vibrator was researched. Firstly, aiming at the difficulty for a normal single magnetic circuit (SMC) in achieving the uniform MFD in the LAG, a novel closed-double-magnetic circuit (CDMC) was proposed. Then the two structures were analyzed theoretically. To strengthen the uniformity of the MFD in the LAG, the improved CDMC with uneven air gap and its design method were proposed:firstly, an uneven air gap structure expressed as a three-line-segment form was proposed and its optimization based on the traversing method was also conducted. Based on the optimized uneven air gap structure, the influence of slits in the outer magnetic yoke for practical application was analyzed. Then, another uneven air gap structure expressed as a polynomial form was proposed and its optimization based on the genetic algorithm was also conducted.In chapter3, the theory related with the compensation for the unevenness of guide rail in an ULF standard vibrator was researched. Firstly, based on a simplied theoretical model with uniform air film, the pressure distribution in the film of an aerostatic guide was analyzed. Secondly, a theoretical model with nonuniform air film of an aerostatic guide was established and analyzed in allusion to the practical existing unevenness of guide rails, which was demonstrated that the nonuniform air film resulted in asymmetric pressure distribution and caused the jounce of the moving component further. Thirdly, it was indicated that the sensitivity of the calibrated accelerometer would become higher or lower under the action of jouncing moving component and the relation between the geometric tolerance and the calibrated sensitivity deviation was also given. At last, a compensation method for the uneven guide rail was proposed and its effectiveness was verified experimentally.In chapter4, the theory related with the motion control of an ULF standard vibrator was researched. Firstly, the electromechanical model of an electromagnetic vibrator was established and its frequency response was also analyzed, then the model parameter identification method was proposed. Secondly, a special convert module was designed for a linear grating to realize the high-precision measurement of the displacement of a long-stroke vibrator. Then a displacement feedback system based on the linear grating was established and the effect of related paremeters on the total harmonic distortion (THD) of the vibrator output waveform was analyzed experimentally. Thirdly, based on the linear grating, an adjustable electro-viscoelastic-suspension device was further designed to replace the mechanical suspension device. The THD of the vibrator output waveform was further reduced and the effect of related parameters was analyzed experimentally. Fourthly, based on the self-sensing technology, a velocity extracting device was designed to get the velocity directly without any separate sensor. Then a velocity feedback system based on the velocity extracting device was established and the influence of related parameters on the THD of the vibrator output waveform was analyzed experimentally.In chapter5, the developed ULF standard vibration device was researched experimentally. An ULF standard vibrator was established based on the proposed theories and technologies in this dissertation related with the magnetic circuir design, the compensation for the uneven guide rail, the motion control. Based on the prototype, the MFD in the LAG and the magnetic flux leakage on the vibration table, the THD of the vibrator output waveform, the vibration calibration of an acceleration sensor in the ULF range were tested. The effectiveness of related theoretical research was verified.In chapter6, the achivements of this dissertation were summarized, and future research for further study was prospected.