A Gravity-Assisted Piezoelectric Inertial Actuator for Bidirectional Smooth Drives by Single Excitation Source

The piezoelectric inertial actuator is one of the critical technologies for precision equipment. However, its inherent working mode makes it difficult to achieve smooth motion, further limiting broad commercialization. This work presents a gravity-assisted piezoelectric inertial actuator that can achieve bidirectional smooth drives by a single excitation source and improve bidirectional consistency in vertical assembly by actively leveraging the contact behaviors of the piezoelectric stack and flexure mechanism. Specifically, the strategy is to balance the forward displacement surge and the reverse backward motion using assisted gravity combined with the locking force regulation of the stator's parasitic motion. The operating process is clarified by kinetic modeling, the parametric design of the structure is completed by the finite element method, and experimental studies verify the concept's feasibility. Bidirectional displacement linear fitting correlation coefficients R-2 reach 0.9999 assisted by gravity, even at the dead weight of a moving object equivalent to a load thrust of 1.35 N (more than 3.3 times the current work). The maximum velocity and resolution achieve 304.73 mm/s and 5.3 nm, respectively. This novel design idea is especially suitable for the Z degree-of-freedom drive, which has been successfully applied to microscopic imaging.