To design and fabricate a robot finger joint based on a hybrid multi-Degree-of-Freedom (multi-DOF) piezoelectric ultrasonic motor. The motor′s stator consists of a multi-layered piezoelectric longitudinal vibrator and a sandwich bending vibrator. The multi-layered vibrator can produce large longitudinal vibration displacement in the z-direction at low driving voltage. The sandwich vibrator is composed of two lead zirconate titanate rings and four-divided bronze electrodes, and is driven by phased voltages to excite the bending vibration in two orthogonal directions. The synthesis of the longitudinal and bending vibrations can make a ball rotor rotate in three directions. An orthogonal bearing holding mechanism is introduced to hold the ball rotor without preventing the multi-DOF motions of the robot finger joint. The motions of the finger are demonstrated and evaluated experimentally.

multi-Degree-of-Freedom(multi-DOF)； ultrasonic motor； multilayered vibrator； robot finger′s joint