Real-time FEM Control System for Connected Piezoelectric Actuators
Daigoro Isobe*, Hiroshi Nakamura** and Ryuta Shimizu***
*Institute of Engineering Mechanics and Systems, University of Tsukuba, 1-1-1 Tennodai Tsukuba-shi, Ibaraki 305-8573 Japan
**Enterprise Server Division, Hitachi Ltd., 1 Horiyamashita Hatano-shi, Kanagawa 259-1392 Japan
***Yamaha Co., 10-1 Nakazawa-cho Hamamatsu-shi, Shizuoka 430-8650, Japan
In this paper, the Finite Element Method (FEM) and the previously proposed inverse theory for bimorph piezoelectric actuators are applied into a real time control algorithm of connected piezoelectric actuators. Most control schemes handle an entire system in series, which becomes a drawback when some elements lose their function in a higher redundant system. On the other hand, the FEM can handle the system in parallel by subdividing it into discrete finite elements, and can cope with flexibility in the change of form and material properties. Noncompatible finite elements are used to express the actuators in the control algorithm, and empirical formulae considering time-dependent characteristics such as creep and residual strain, are also implemented. A real-time FEM control system, which consists of a PC, a bipolar DC unit and a signal-distributing controller, is developed. The system is verified by experiments on quasi-static displacement control of connected piezoelectric actuators. The results show the possibility of highly accurate, realtime control of the actuators using the FEM.
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