Flextensional ultrasonic piezoelectric micro-motor.

This paper presents the experimental design, construction, and operational characteristics of a new type of standing wave piezoelectric ultrasonic micro-motor. The motor uses a composite stator, consisting of a metallic flex-tensional mode converter, or "cymbal", bonded to a 2-mm-square piezoelectric plate. The cymbal converts contour-mode vibrations of the plate into oscillations in the cymbal, perpendicular to the stator plane. These are further converted into rotational movement in a rotor pressed against the cymbal by means of an elastic-fin friction drive to produce the required rotary actuation. The motor operates on a single-phase electrical supply, and direct control of the output speed and torque can be achieved by adjusting the amplitude and frequency of the supply voltage. Noncontact optical techniques were used to assess the performance of the developed micro-motor. The operational characteristics were developed from the acceleration and deceleration characteristics. No-load output speed (11 rev s(-1)) and stall torque (27 nNm) were derived using high-speed imaging and image analysis. Maximum efficiency was 0.6%.

Flextensional ultrasonic motor using the contour mode of a square piezoelectric plate.

This paper presents the design, fabrication, and characterization of a new type of standing wave piezoelectric ultrasonic motor. The motor uses a metallic flextensional amplifier, or cymbal, to convert the contour mode vibrations of a square piezoelectric ceramic plate into flexural oscillations, which are further converted to produce rotary actuation by means of an elastic-fin friction drive. The motor operates on a single-phase electrical supply. A beryllium copper rotor design with three-fin configuration was adopted, and the geometry was varied to include different material thicknesses, fin lengths, and inclinations. The best stall torque and no load speed for a 25-mm square motor were 0.72 Nmm and 895 r/minute, respectively. The behavior of the stator structure was analyzed by ANSYS finite element software using harmonic and modal analyses. The vibration mode estimated by finite element modeling (FEM) was confirmed by laser Doppler vibration measurements.