Angled contact surface optimization and experimental verification of traveling wave ultrasonic motor with axial-bending coupled vibration

Beam-type ultrasonic motors (USMs) operating in bending modes generate axial coupled vibration, resulting in low motion performance since the actuation trajectory is not vertical to the friction surface. To improve output characteristics with a compact structure, angled contact surface optimization based on axial-bending coupled vibration is proposed. Theoretical analysis is performed to illustrate the operating principle and design the optimal conical angle. To assess the validity, a beam-type traveling wave USM with a dimension of Φ50 mm × 85 mm is designed and fabricated to analyze its vibration performances, impedance characteristics and output characteristics. Experimental results indicate that this USM achieved an output velocity of 201.2 rpm under the preload of 182 N, voltage amplitude of 300 V_p-p and exciting frequency of 21.4 kHz; the maximum torque reaches 1.0 N·m when the preload increases to 375 N; meantime, the output power under stable motion reaches up to 4.72 W. This work provides a novel approach to improve the performance of rotary USMs with compact structures.