Resonant-type inertial impact motor with rectangular pulse drive

In this paper, a resonant-type piezoelectric inertial motor driven by rectangular pulse is developed. The rectangular pulse drive methodology is explained and its influence on output displacement of the stator is discussed in relation to four factors: frequency ratio, duty ratio, vibration amplitude ratio, and phase difference. A bending stator with second harmonics at its double fundamental resonant frequency is designed to generate saw-tooth type displacements under a rectangular pulse. It is composed of an aluminum plate (20 mm × 4 mm × 2 mm) sandwiched between two piezoelectric plates (10 mm × 4 mm × 0.73 mm). Experiments show that with optimized duty ratios, both the rotation speed and stall torque can be enhanced. The rotation direction of the rotor can be reversed by changing the duty ratio. The maximum no-load angular speed reaches 300 rpm with driving voltage of 60 Vpp at the fundamental resonant frequency of 35.3 kHz in both directions. Using a preload of 1.07 N, stall torque reaches 1220 μNm driven at 80 Vpp and 35.3 kHz. The maximum efficiency of the motor is 2.1%, which is higher than that of the previously reported piezoelectric inertial rotary motors. The proposed inertial motor features simple mechanical and electrical design, which makes it ideal for miniature electro-mechanical device applications.