Super-resolution velocity reconstruction and control of ultrasonic motors.

Accurate and fast velocity feedback signal is essential for the velocity control of ultrasonic motors (USMs). However, the low operating velocity of USMs results in a long velocity detection dead time (VDDT) of incremental encoders, which seriously restricts the dynamic control performance of USMs. Therefore, this paper presents a super-resolution velocity control (SRVC) scheme based on the velocity reconstruction for the USM. Firstly, the mathematical model of the USM is derived by the mechanical characteristics and the electromechanical coupling characteristics. Then, the velocity reconstruction method is proposed by combining the model estimated velocity and the encoder measured velocity. The closed-loop control scheme using the reconstructed velocity is implemented by a self-designed driving circuit. Experimental results show the velocity reconstruction method not only can break through the limitation of the encoder resolution to reduce the VDDT, but also has a high velocity accuracy. Furthermore, compared with the existing encoder based control scheme, the proposed SRVC scheme has faster velocity response under different loads.