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High Strain Shape Memory Alloy Actuators and their Control

D. Grant, V. Hayward The actuators consist of fibers woven in a specific pattern which achieves a large amount of displacement amplification with very small losses. In one prototype, twelve fibers are run in parallel resulting in a 16 mm diameter package weighing 6 grams and capable of pulling 4 N. In this configuration, the strain is about 20% and the rise time shorter than 100 ms for an antagonist set-up in ambiant air. Variable structure controllers are being investigated with the purpose of achieving the control of position, velocity, force, and combinations of these variables. Experimental performance results in the time domain demonstrate that this control can achieve very fast rise time, high rejection of disturbance, small tracking and steady state error, and quenching of limit cycles, despite their numerous nonlinear properties. [actuator.eps].50 A single NiTi actuator package, 16 mm accross.hayward:figure15

Thierry Baron
Mon Apr 7 12:54:24 EDT 1997