Lift Generation by a Miniature Piezoelectric Ultrasonic Motor-Driven Rotary-Wing for Pico Air Vehicles

Actuators are key components for further miniaturization of insect-scale microrobots. It is challenging to create a new miniature actuator suited for rotary-wing pico aerial vehicles (PAVs), which have a wing span of a few centimeters and a mass of a few grams. In this paper, we propose a miniature piezoelectric ultrasonic motor that permits high-speed rotation at a sufficient torque to achieve the flight of the simplest device comprising the proposed motor and rotor blades. The prototype motor, which employs a bending vibration mode as a principle, measures 1.6 mm $\times1.6$ mm $\times2$ mm and weighs 25 mg. The experimental results show that the miniature motor rotates rotor blades having a length of 20 mm with an angular velocity of over 1800 rad/s. The thrust force generated from this system exceeds its total mass of 110 mg and successfully lifts the system. Although the flight is tethered, the set of the proposed motor and rotor blades demonstrates a takeoff that represents the possibility of rotary-wing PAVs.