Abstract
A hybrid transducer type ultrasonic motor consists of a torsional vibrator (TV) and a multilayered piezoelectric actuator (MPA). MPA vibrates longitudinally in the axial direction and controls the timing of contact between the rotor and the stator, while TV generates the rotational force. Applying sinusoidal voltages of the torsional resonance frequency to both parts with a certain phase difference, the rotor is driven to rotate at almost the same angular velocity as the torsional vibration. If we apply a DC voltage to TV, the angular position of the rotor can be displaced precisely.
Making use of these two ways of operation and the merits of the motor such as a high output torque at low speed, a large braking torque without energy consumption and a quick response, this paper presents a precise angular positioning control system. First we drive the rotor by the hybrid vibration of the stator to reach near the given end point quickly. Then, applying a DC voltage, the error is reduced by the static twist of stator. The resolution of the proposed system was 4.85×10-6rad., which was equal to the resolution of the rotary optical encoder emplyed in this system.
