Design And Research Of Control Of High Speed Rotor Of Control Moment Gyros Driven By Brushless Direct Current Motor

Control moment gyro is a kind of spacecraft attitude actuator,which is mainly used for spacecraft attitude control and rapid maneuver tasks.Utilizing the torque amplification effect,control moment gyro has the advantages of high torque amplification ratio and continuous output torque.Control moment gyro is composed of a momentum wheel and a frame.The performance of the momentum wheel system directly affects the performance of control moment gyro.This paper designs a momentum wheel system which has small size,light weight and can be used in microsatellites.Momentum wheel system is mainly composed of momentum wheel mechanical structure and brushless direct current motor drive control system.The mechanical structure design of momentum wheel includes the design of motor,high speed flywheel and auxiliary supporting mechanism.According to the differences of supporting modes,two kinds of general structures,cantilever structure and frame structure,are proposed.Brushless DC motor is selected to drive the high speed flywheel,the armature size and other motor size parameters are estimated on the basis of the relevant technical indicators,and two kinds of high speed flywheel which match with the motor are designed.The rotor dynamic model of momentum wheel is established and the characteristics of momentum wheel are studied.The design of direct current brushless motor drive control system is divided into hardware design and software design.In this paper,the working principle of brushless dc motor is studied.The process of motor commutation and starting is emphatically studied.The mathematical model of brushless DC motor is established to provide theoretical basis for the design of brushless DC motor drive control system.Based on digital signal processor,the drive control circuit is designed,and the drive control program matching with the hardware circuit is written.The performance of momentum wheel system is studied in this paper.Firstly,the open-loop output performance of momentum wheel system is tested.A discrete PID controller is designed to study the speed control characteristics of momentum wheel system.Experimental results show that the relative error can be controlled within plus or minus 0.25% of the working speed,and good control effect is obtained.Finally,the duty cycle–rotation speed transfer function of brushless DC motor is identified by the method of system identification.A digital internal model controller matching the transfer function is designed based on the sensitivity function shaping template.The simulation results show that the 1Hz band disturbance signal attenuates-25 db,performed by the controller.Experimental results show that the relative error can be controlled within plus or minus 0.20% of the working speed.