Abstract: A new type of standing -wave ultrasonic motor which consists of a ring plate with projections is only excited by one group of piezoelectric ceramics. The tops of the projections form the oblique displacement motion, so the projections provide the driving force for the motor. The driving principle of this type of motor is introduced. The curves about the main dimensions of the elastic body versus its natural frequency of the vibrator by FEM are given. The B₁₄ mode natural frequency of the vibrator is also calculated. Moreover the characteristics of the prototype in speed are measured and its feasibility is verified.

Key words: ultrasonic motor, standing wave, ring plate