Study of the Equivalent Stiffness of a Non-Contact Piezoelectric Actuator’s Micro-Displacement Amplification Mechanism

To address the issues of mechanical wear and limited service life in conventional contact piezoelectric actuators, this study proposes a non-contact piezoelectric actuator employing compressed air for energy transmission; we elucidate its structure and operating principle. The working performance of the actuator is significantly affected by the amplification performance of its micro-displacement amplification mechanism, which itself is closely dependent on the mechanism's stiffness. Mathematical models for both the filleted straight-beam flexure hinge and the micro-displacement amplification mechanism are established. Analytical equations for calculating the equivalent stiffness of the hinge and the mechanism are derived. The variations in the hinge's bending stiffness and tensile stiffness, as well as the mechanism's equivalent stiffness with key structural parameters, are investigated. The stress distribution of the micro-displacement amplification mechanism is analyzed to evaluate the rationality and reliability of its structural design. A prototype is fabricated and equivalent stiffness tests are conducted. The theoretical calculation is basically consistent with the experimental results, verifying the accuracy of the stiffness model. The results show that flexure hinge tensile stiffness significantly exceeds the bending stiffness, permitting the simplification of the hinge stiffness model. Hinge minimum thickness and beam length critically affect mechanism stiffness; reducing thickness or increasing beam length lowers stiffness, boosting displacement amplification.