Design and experimental performance of a novel piezoelectric inchworm actuator based on screw clamping principle

The requirements of large thrust in bidirectional motion, high specific power (power/weight ratio), reliable self-locking at power off state, and compact size envelope for various applications of existing piezoelectric actuators are still urgent. To address these challenges, this study makes full use of the piezoelectric material's excellent dynamic performance, robust force output, and high energy density to propose a novel inchworm piezoelectric actuator, which relies on the alternate clamping of two nuts independently rotated by two ultrasonic motors on a feed-screw in accordance with a piezoelectric stack (piezo-stack) excitation to accumulate the piezo-stack's electric field-induced strain periodically and realize power output. The operation principle and design process of the presented actuator were elaborated, and a prototype was fabricated and experimented. Results indicate that the actuator has achieved an expected bidirectional motion for powering the tensile load and compressive load, attained a micrometer-sized step resolution, produced a 3.08 mm/s free speed, a 700 N stall load, and a 1.34 W/kg specific power, and shown a favorable prospect for further development.