DEVELOpmENT Of fAST, STIff AND HIgH-RESOLUTION pIEzOELEcTRIc mOTORS wITH INTEgRATED bEARINg-DRIVINg fUNcTIONALITy

To meet the higher accuracy, stiffness and speed demands of positioning systems of machine tools and measuring instruments, two motor concepts are developed with an integrated bearing-driving functionality. For both concepts, piezoelectric technology is used as actuator principle. In the first concept, the limited stroke of piezoactuators is overcome by a travelling-wave principle, which assures an intrinsically smooth motion so that the controller requirements for this motor do not limit the speed. Because of their high resolution and stiffness, travelling wave motors are suited for an accurate positioning system where multiple degrees of freedom are integrated. The second concept is based on the combined drive principle. Here, a motor module is designed to work in a high-resolution slow stepping-operation mode, as well as in a lower resolution highspeed ultrasonic-operation mode. A planar prototype has shown the potential to effectively integrate multiple degrees of freedom. An experimentally verified motor model was developed to investigate the effect of resonance on the motor-performance and on the heat dissipation of the piezoactuators. A resonant motor allows for higher speeds, while a quasi-static motor is more compact and robust. Heat dissipation in piezoactuators can be significantly reduced by working in a resonance mode. It was shown that the optimal working frequency regarding heat dissipation lies between the resonance and the antiresonance frequency.