Research on lateral deflection in inchworm piezoelectric actuator of TianQin’s test mass release mechanism

Abstract

The TianQin project aims to detect gravitational waves from space using a constellation of satellites, each carrying test masses (TMs) as inertial references. A critical subsystem is the grabbing, positioning and release mechanism (GPRM), which must release the TM with extreme precision. A key challenge is the lateral deflection of the inchworm piezoelectric actuator that drives the GPRM, which may compromise release accuracy. This study combines ground experiments, dynamic modeling, and finite element simulation to investigate the origin and characteristics of these deflections. Experimental results show significant lateral displacements during axial motion, which are attributed to force imbalances caused by inconsistent step lengths among piezoelectric legs. The dynamic model reveals that asymmetric driving forces induce rotational torque, leading to lateral deflections. Finite element simulations confirm this mechanism and accurately reproduce the three-axis motion. These findings provide critical insight into the actuator’s non-ideal behavior, supporting the optimization of the GPRM for reliable on-orbit operation and the success of the TianQin project.