Analysis of a Piezo-Hydraulically Actuated Fixing Plate for High Precision Positioning

摘要

This paper presents the experimental investigation of a novel micro-positioning system. For precise positioning of heavy loads a hybrid system has been designed. It combines high forces and high precision of piezoelectric stack actuators with long strokes and high power of hydraulic cylinders. The actuation unit consists of a bidirectional piezo-hydraulic micropump with included fast-switching valves. For prototypic realization modular design and precise assembling strategy are demanded. After implementing, wide studies have been carried out to define the pressure dependent delivery characteristics of the piezo-hydraulic actuation unit. In this context interactions between fluid dynamics and output capacity of the pump module are considered. The dynamic drive of the pump module coupled with a hydraulic circuit of two hydraulic cylinders transforms the small strokes of the piezoelectric actuator into a continuous rotational movement of a fixing plate. In this way an autarkic micro-positioning system in form of an active fixing plate for implementation into machine tools is realized. The development and application of a capable control strategy are taken into account. Experimental results concerning the complemented active fixing plate characteristics show the outstanding positioning accuracy of +/- 0.25 μm of one piston.