Design of a Precision Linear-Rotary Positioning Actuator

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