Study On The Servo-control Of Control Moment Gyro System

Taking the background of the applications of spacecraft attitude control, the control moment gyro (CMG) servo system was analyzed in this thesis. For the features that the flywheel subsystem need high steady, high-precision speed control; frame run in low speed, require for high steady, high-precision speed control, corresponding control method was presented to control the flywheel and frame servo system. The traditional PID and other control methods were also analyzed to apply to flywheel and frame system.Firstly, this thesis established a mathematical model of CMG flywheel subsystem, compared the advantages and disadvantages of the PID, integral separation and phase-locked loop (PLL) control methods. Then the simulink model and corresponding simulation results of the three control methods was given. Demonstrated the feasibility of PLL control method used in flywheel subsystem.Secondly, Stribeck friction model was proposed to analyze the impact of friction torque on the CMG frame motor. And simulated the impact of the friction when frame motor in low-speed. Then dither-smoothed method and phase-locked loop low-speed control method were introduced to compensate friction, and analyzed the effectiveness of this method.Later, the paper designed and realized a phase-locked loop control system, used 10 states dedicated PLL chip UC3633 to be the part of the core control in the system, TL494 chip was used for PWM signal generate and CPLD-EPM7064S was used to achieve motor commutation logic. The actual system operation proves that the design functions are well realized.Finally, Based on the design parameters of the steady speed flywheel control system, experiments were done at different rotation speeds set point, phase-locked loop circuits have achieved a good steady speed control, steady speed accuracy error of less than 0.1%. Verified the validity of a phase locked loop control system. According to the experiments, Optimized step-down, regulate voltage circuit, using advanced angle compensation methods were recommended for improvement.