SCG Rotor's Bearing System Research

The superconducting gyroscope (abbreviated as SCG) as an inertial instrument working on the Meissner effect of cryogenic superconducting materials has a promising prospect for its several advantages such as high precision, low power consumption and so on. The deep research of this dissertation emphasizes on the basic technologies and theorems of SCG rotor's bearing system, which is an essential department of preliminary research item 'Superconducting Gyroscope' of National Defense Science and Industry Committee in the Tenth Five-Year Program. The main works are as following:Based on the London equations and Maxwell equations, the electric and magnetic properties such as the penetrating depth, the magnetic field distribution, the magnetism and so on of the static superconducting rotor immersed in the external magnetic field are researched quantificationally by using the method of separated variables; Based on the London equations' Lorentz transformation, the electric and magnetic properties of the rotating superconducting rotor immersed in the external magnetic field are researched quantificationally too, and found the assumption that the cryogenic superconductor immersed in external magnetic field repulse the flux line completely when the external magnetic strength is less than the superconductor's critical magnetic strength is still right even though the rotor's rotation would decrease the superconductor's critical magnetic strength, the pure niobium is selected as the superconducting material coating the rotor and its performance parameters are ascertained. All these analytic results lay a solid foundation for the analysis on the properties of SCG's rotor levitated by superconducting maglev in spherical cavity, the formulae of maglev force and maglev stiffness are deduced, both the meams or schemes to realize the rotor's superconducting maglev and the superconducting maglev feature are presented.With the goals to control the rotor's position and enhance the maglev stiffness of the SCG rotor's bearing system, the active maglev system of rotor is presented.To overcome the bearing system's self-oscillation and forced-oscillation,a derivative feedback of drift is adopted to enhance the system's damping, the bearing system's open-loop frequency performance is improved and phase margin is enlarged by cascade phase-lag and phase-lead compensation according to frequency response method under the condition that all different cases of rotor's suspension been taken into account.lt is verified that the dynamic performance of the compensated system can satisfy the expected dynamic specifications of SCG bearing system and the specifications of the SCG's bearing system are presented originally in this dissertion. The negative effects of rotor's drift on gyroscope shift, rotor's position varieties measurement precision and superconducting state of rotor are analysed. Both the essentiality to measure the rotor's drift and the importance to control the rotor's position are illustrated clearly.The rotor's drift measurement scheme based on spherical differential capacitance is presented in this dissertation, the rotor's drift mathematical model is deduced and the compensation method is presented when the rotor's drift isn't micro-displacement. The rotor's drift measurement scheme and its parameters relationships are analysized, the eight-electrode distributing scheme is presented to guarantee the rotor's potential be zero, the negative factors affecting the measurement precision are analysed theoretically and the methods to eliminate their effects or the scope wherein the mathematical model is ideal are presented. The rotor's drift controlling scheme is also presented to control the rotor's position. To inspect the rotor's location on time, the absolute gap measurement scheme is presented and its negative effect on rotor's drift measurement is proved to be neligible.The exciting signal source circuit of the SCG rotor's bearing system based on direct digital synthesizer (DDS) and MCS-51 series single chip micyoco is designed to enhance the exciting signal's precision, stability and good waveform. It is proved that the exciting signal can meet the special need of SCG rotor's bearing system.All the schemes or methods presented in this dissertation are verified by simulation, the related electrocircuits are verified by testing circuits additionally.To make the simulation conditions resemble the actual SCG strongly, a simulation instrument is designed and manufactured especially to verify the feasibility of the rotor's drift measurement, a series of experiment results prove that all the schemes or methods presented in this dissertation are not only right but also feasible.This dissertation investigates SCG rotor's bearing system deeply, and figures out theoretically the problem of levitation, which is the most foundamental one of three major difficult problems-Levitation, Rotation and Detection for SCG research. It is very important and helpful for the research and development of high-precision SCG practically.