Design and experimental investigation of a bidirectional stick-slip piezoelectric actuator inspired by the gait of starfish tube feet

Abstract

Most existing stick-slip piezoelectric actuators cannot actively suppress backward motion during operation, which degrades output performance and positioning accuracy. This study proposes a bidirectional stick-slip piezoelectric actuator inspired by the gait of starfish tube feet. The actuator combines a symmetric flexure-hinge structure with four PZT stacks and a tube-foot attach-pull-switch (TF-APS) control sequence. During each sequence, the driving side first establishes effective contact with the slider through its normal PZT stack and then advances the slider tangentially. The opposite side subsequently locks the slider and takes over load support before the driving side disengages and resets. This sequence maintains effective contact on at least one side, thereby reducing return-stage backward motion and enabling stable bidirectional stepping. An equivalent mechanical model of the flexure-hinge mechanism was established, and a direct FEM parameter scan was used to evaluate key geometric parameters and determine the structural dimensions. A prototype was then fabricated and tested to characterize its output, bidirectional motion, and return-stage backward-motion suppression. Its performance was also compared with that under a conventional stick-slip sequence. The actuator achieved a maximum speed of 4.31 mm s−1. The TF-APS sequence markedly reduced return-stage backward displacement and enabled stable bidirectional motion. At 150 V and 100 Hz, the actuator maintained stable motion at approximately 1.7 mm s−1 under a carrying load of 10 N.