Novel 2-DOF Planar Ultrasonic Motor with Characteristic of Variable Mode Excitation

This paper presents a novel 2-DOF planar linear ultrasonic motor. The stator of the motor can be divided as two transducers and two isosceles triangular beams. The bending vibration modes and longitudinal vibration modes of the stator are superposed as three operation modes and generate elliptical trajectories of the driving foot in two planes to provide the thrust force along two dimensions. The operating principle of the motor and the formation of the elliptical trajectory of the driving foot are analyzed, and the variable mode excitation method is illustrated. A prototype was made and experiment investigation of the motor characteristics is presented. Testing results of the prototype shows that this motor can gain a maximum speed of 211.3 mm/s and its thrust force can reach 3.15 N under an exciting voltage of 400 V_P-P. The major feature of the motor is that the 2-DOF driving function can be achieved by using the method of variable mode excitation.