Mechanical characteristics calculation of 2-DOF spherical traveling-wave type ultrasonic motor

The mechanical characteristics calculation of traveling-wave ultrasonic motor with two degrees of freedom is investigated theoretically and experimentally. The space structure relations of traveling-wave ultrasonic motor with two degrees of freedom and the friction force on the contact surface of stator and rotor are analyzed. By using space position relations, the friction driving force and friction resistance at an arbitrary point on the contact surface of traveling-wave and spherical rotor are obtained through computation. Then the analytical expression of mechanical characteristics calculation is deduced on the basis of the axial force balance relation of traveling-wave stator when the motion is stable. The validity and veracity of the model is verified by theoretical and experimental analysis of the developed motor, and the influence of motor parameters on the output mechanical characteristics is analyzed. The maximum brake torque of developed motor reaches 0.10 Nm, the idle speed is 90 r/min. This research work lays a theoretical foundation for the next design, optimization and control of spherical traveling type ultrasonic motors.