Design of a Precision Linear-Rotary Positioning Actuator

Abstract

We designed a prototype linear-rotary (<I>Z</I>-θ) dual-axis actuator for precision positioning in which an aluminum rotor (moving element) moves along and rotates around the axis (<I>Z</I>) of a ceramic cylinder (drive rod). The <I>Z</I>-θ actuator consists of a <I>Z</I>-piezoelectric actuator (<I>Z</I>-PZT) (maximum stroke: 12µm) for linear <I>Z</I>-motion, two θ-piezoelectric actuators (θ-PZTs) (maximum stroke: 9.1µm) for rotational θ-motion, a drive rod, and a rotor. θ-PZTs are attached to the drive rod via a clamp. The rotor’s inner side contacts the drive rod with a certain friction. <I>Z</I>-axis positioning uses a smooth impact drive to achieve a long stroke by applying periodic saw-toothed voltage to the <I>Z</I>-PZT. Sinusoidal voltage is applied to θ-PZTs for rotary positioning, not based on a smooth impact drive. The prototype actuator stroke along the <I>Z</I>-axis, limited by the drive rod length, is 10mm and rotary motion is unrestricted. Positioning resolution is a few nanometers and maximum speed in the <I>Z</I>-direction is approximately 2.4mm/s. The maximum revolution speed is 50rpm.