Strong stiffness and high-resolution stepping for ultrasonic motors based on beat traveling wave pulse drive control method

Aiming at requirements in stepping motion of ultrasonic motors in space laser communication, a novel beat traveling wave pulse drive control (BTWPDC) method is proposed. Utilizing the special motion form of ultrasonic motors driven by the beat traveling wave, parameters are controlled so that the power-off speed is sufficiently low, and a pulse cycle is composed by setting a suitable excitation interval. An experimental platform based on FPGA is established to generate the required signals and verify the effect. The experimental data show that compared with the conventional pulse drive method, jitter in the stepping process, which has a maximum value above 15% of the step length, is effectively weak to realize almost jitter-free stepping under open-loop control. Meanwhile, the step resolution is significantly improved to stable 2 urad and even higher. This method solves the jitter in stepping motion and improves the step resolution for ultrasonic motors.