Traveling-wave ultrasonic motors (TWUSMs) have strong nonlinearity and uncertainty, which are sensitive to the environment, disturbances, and load changes. Thus, precision control of TWUSMs is hard to achieve with traditional methods for complex driving mechanisms. A nominal-model-based sliding-mode control strategy with strong robustness is proposed to achieve accurate speed control of TWUSMs. Firstly, a second-order nominal model of the speed difference and output torque was deduced to construct a nonlinear sliding-mode surface; then, a nonlinear sliding-mode controller was designed with the collaborative regulation of frequency and the amplitude of two-phase control voltages. The global asymptotic stability of the controller was proved under bounded disturbances and parameter uncertainty. Finally, the effectiveness and accurate control were testified to and verified by the simulations and experiments, which showed good robustness and a disturbance rejection of the strategy for TWUSMs, with strong nonlinearity and uncertainty.

Aiming at the problems of low control efficiency and great regulation difficulty of traveling wave ultrasonic motors (TWUSMs) caused by nonlinearity, strong coupling characteristics, and parameter uncertainty, this paper proposes a speed regulation scheme based on discrete contact modeling and monotonically increasing weighted nonlinear model predictive control (MIW-NMPC). On the basis of analyzing the existing TWUSM models, a discrete contact model of the motor is constructed, which reduces the modeling complexity while completely retaining the core dynamic characteristics of the motor’s operating mechanism. Based on this model, the MIW-NMPC algorithm for the precision speed control of TWUSM is designed, and its feasibility and stability are deduced and verified. Comparative simulations and experimental results demonstrate that the proposed discrete-model-based MIW-NMPC scheme can effectively enhance the precision and dynamic response of TWUSM speed control, offering a novel technical approach for its high-precision speed regulation applications.