Research Of Variable Gain Control Method For Gyrowheelsystem

Gyro Wheel is an innovative component of the small spacecraft attitude control system,which integrates the functions of the actuator and sensor in the attitude control system at the same time.The volume,quality,and cost will be significantly reduced by using Gyro Wheel.Control issues of Gyro Wheel can be divided into axial motion control and tilting motion control while the tilting motion control is the emphasis of Gyro Wheel rotor control issues.In this paper,base on the tilting motion control issue as the research object,different variable gain control methods are studied and the control effect of variable gain controllers is verified according to the Gyro Wheel prototype.First,the complete nonlinear dynamical equations of Gyro Wheel is obtained by using Lagrange equations,then,the simplified model of Gyro Wheel is obtained based on some reasonable assumptions.The co-simulation model of Gyro Wheel is established by using MATLAB.Due to gyroscopic effect,there exist precession mode and nutation mode during the high speed operation of Gyro Wheel.The nutation instability will occur due to the serious phase lag in high frequency.The double-frequency jitter increases with the tilt angle of Gyro Wheel rotor,which may affect the accuracy of three-axis torque outputs;however,the stability of Gyro Wheel system isn't affected.Secondly,three kinds of variable gain control methods are desigened based on the simplified model of Gyro Wheel.In variable gain precession control,the precession characteristic of Gyro Wheel is used as the main transmission term and the control command is generated according to the cross-axis deviation signal.In variable gain feedforward matrix control,the variable gain feedforward matrix is uesed to increase response speed for the input of Gyro Wheel and reduce steady-state error.In variable gain cross feedback control,the variable gain cross link is used to compensate the phase lag and improve the stability of Gyro Wheel system.The decaying factor of variable gain cross link should be designed according to the parameters of Gyro Wheel and controller in order to suppress system instability.According to the simulation results,all of three variable gain control methods mentioned above can ensure the stability of Gyro Wheel.At last,the variable gain precession control and variable gain feedforward matrix control are studied experimentally based on the experimental platform of Gyro Wheel prototype.The parameters of Gyro Wheel prototype are identified by measuring the cross-axis frequency characteristic of Gyro Wheel rotor.The experiment results agree with the simulation results,which indicate the effectiveness and practicability of variable gain precession control and variable gain feedforward matrix control.