Spherical Motor Design And Speed Detection For Attitude Control Of Agile Spacecraft

With the rapid development of aerospace industry,More and more attention has been paid to the research of multi-DOF motion motor which can achieve attitude control of spacecraft.To achieve agile and accurate attitude control of spacecraft,multi-DOF motion motors must have the characteristics of high torque density,low friction torque,high speed and controllable multi-degree-of-freedom speed.Compared with other multi-DOF motion motors,induction spherical motor has greater advantages in application and realization.However,due to its high nonlinearity and strong coupling,traditional motor modeling and motor parameter optimization methods cannot meet the requirements of multiple rapid iterative optimization designs.In addition,the traditional rotor support method and speed measurement method can not meet the high speed and multi-degree of freedom speed measurement demanded by the spacecraft for the induction spherical motor.Aiming at the above problems,based on the research of various spherical motors at home and abroad and practical application of attitude control for agile spacecraft,a novel structure of induction spherical motor is proposed,which adopts non-parametric modeling based on support vector machine(SVM).The mathematical model of inductive spherical motor is established,and the motor parameters are optimized by intelligent optimization algorithm.Then the spherical rotor maglev control system is established based on differential eddy current sensor,and the new spherical motor speed and azimuth measurement method is studied.It lays a foundation for agile attitude control applications on spacecraft for multi-DOF spherical motors.The main work and innovation of the paper are as follows:(1)A compact structure of induction spherical motor is proposed.The threedimensional electromagnetic field model of spherical motor is established by finite element method,and the torque model of spherical motor is established by analytic method.The influence of structure parameters and air gap size of the motor on the torque characteristics is analyzed,which provides a basis for subsequent SVM modeling and parameter optimization of the motor model.(2)An optimization method of motor design parameters based on finite element analysis results is proposed.Based on small sample space,the output torque of spherical motor is modeled and analyzed by SVM,and the parameters of SVM model are optimized by genetic algorithm.Finally,the interior point method is used to optimize the modeling results of support vector machine,and the optimal design parameters and corresponding output torque are obtained.(3)A magnetic levitation system based on Differential Eddy current sensor is proposed.A double PD controller is designed.The parameters of the magnetic levitation controller are obtained by pole placement method.The stability of the controller is proved by simulation analysis.(4)A surface spraying scheme for spherical rotors and a method of measuring the position and azimuth of spherical rotors by photoelectric encoder are presented.The theoretical modeling process is given,and the analytical method,Fibonacci method and genetic algorithm are used to calculate the optimal solution of the model,and comparative analysis is made.