Feedback Control Using Shape Memory Alloy Actuators
- 1 April 1998
- journal article
- research article
- Published by SAGE Publications in Journal of Intelligent Material Systems and Structures
- Vol. 9 (4), 242-250
- https://doi.org/10.1177/1045389x9800900402
Abstract
Shape memory alloy (SMA) has been considered as an actuator for applications that require large force and displacement. Two factors have hampered the usefulness of such actuators: a hysteretic input-output relation and bandwidth limitations. This paper considers the hysteresis phenomenon from a control point of view. Instead of directly compensating for the hysteresis, which requires an accurate model, we use a closed loop approach which considers the feedback control of the beam strain. A simple lumped temperature and SMA force/displacement model is used for stability analysis. We show that with the SMA wire fixed between rigid surfaces, a proportional force feedback would render the closed loop stable. However, when SMA is coupled to a flexible structure, the resulting system can exhibit instability. We then show that a proportional position feedback is stabilizing, but there would be steady-state error. An adaptation scheme can be further added to remove the steady-state error. The analysis is verified experimentally in a simple experimental setup consisting of a flexible aluminum beam and a Nitinol shape memory alloy wire that applies a bending force to the end of the beam.Keywords
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