Research on ultra-low speed driving method of traveling wave ultrasonic motor for CMG.

The single-gimbal of control moment gyro (SGCMG) servo system needs high stability, high precision and low speed operation. Therefore, a novel driving approach of ultrasonic motor, called the superposition pulse driving method, is proposed in the present study by prolonging the turn-off time of the conventional micro-stepping driving method. Then, three types of contact models are proposed with the variable of pre-pressure between stator and rotor. Moreover, a theoretical analysis is carried out according to the classical friction binomial law. Results of the performed experiment show that, applying the superposition drive method may lead to the significant reduction of periodic vibration's adverse effect caused by mechanical system's inertia on the motor speed. Furthermore, it is found that the proposed method not only eliminates the alternating oscillation of the motor speed with large amplitude period, but also it significantly reduces the velocity volatility. It is found that compared with the micro-stepping method, the velocity volatility reduces four groups of different average velocity by about 200% thereby effectively improving the stability of the system. This implies the feasibility of the proposed scheme and ensures a precise adjustment of the satellite attitude by the SGCMG.