COMPACT, PIEZO-DRIVEN, VACUUM COMPATIBLE ROTATION DEVICE

A new, vacuum compatible piezo-driven rotation device (piezo-rotor) ba sed on inertial sliding has been developed. The piezo-rotor has one de gree of freedom, nanoradial resolution, and unlimited range. As a resu lt of the simple configuration and the use of piezo-actuators, the pie zo-rotor is extremely compact. It is well suited for specimen rotation in the vacuum chamber of a transmission electron microscope because t he piezos do not create a magnetic field. Although the piezo-rotor has been designed to work in a vacuum, it can be used in many other rotat ion and positioning applications. To test the performance of the piezo -rotor, a simple, easy-to-manufacture setup was used, whose dimensions are larger than we wanted in our application. Nevertheless, scaling l aws show that further miniaturization will not affect the working of t he piezo-rotor, so it can be used as an alternative in some volume-cri tical applications. The tested configuration has a maximum rotation sp eed on the order of 1 rad/s at drive frequencies of some kHz. Torques on the order of 10(-3) Nm have been measured. The positioning resoluti on depends on the drive electronics, the quality of the bearing surfac es, and the rotor dimensions. Theoretically, the highest angular resol ution is 1 mad. The spindle speed or torque can be optimized by studyi ng the friction process, the application of special coatings, the vari ation of the wave form frequency, its amplitude, and the axial preload . The piezo-rotor has been shown to be reliable and robust. (C) 1995 A merican Institute of Physics.