Balancing speed-torque trade-off in a piezoelectric inchworm rotary actuator via amplified-torsional flexures

Abstract

A major challenge in designing piezoelectric inchworm rotary actuators is to balance rotational speed, load capacity, and output torque while retaining power-off self-locking capability and relaxed assembly tolerance. This study presents the design and experimental evaluation of a piezoelectric inchworm rotary actuator that achieves balanced rotational performance and integrated pre-tightening regulation through a hybrid amplified-torsional flexure stator. Double-output rhombus-type compliant clamping and driving mechanisms are combined with torsional flexures to increase the angular step size and provide self-locking functionality. A pre-tightening flexure mechanism is incorporated into a built-in architecture, with the entire rotary stator housed inside the rotor, thereby ensuring structural compactness and ease of assembly. A prototype with dimensions of Φ90 mm × 55 mm is fabricated and experimentally tested. The experimental results demonstrate a maximum velocity of 99.2 mrad s−1 at 40 Hz, an output torque exceeding 453.1 N·mm, and a vertical load capacity of up to 10 kg. In addition, a minimum rotary step of 2.66 μrad is obtained at a driving voltage of 0.06 V. Good bidirectional consistency is also achieved through the shortened actuation chain, demonstrating the promising performance enabled by the hybrid amplified-torsional compliant driving mechanism.