Stimulus System for Up:Manipulators
Analysis and Control
High Strain Shape Memory Alloy
Actuators and their Control
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 ambient air. A model of these actuators, which is relevant to
control design, has been developed. The model is sufficiently accurate
to allow controllers designed in simulation to be applied in practice without
tuning. Variable structure controllers have been investigated with the
purpose of achieving the control of position, force, and acceleration.
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. Patent granted. (Figure 6.14).
D. Grant, V. Hayward
Figure 6.14: A single NiTi actuator package, 16 mm accross.
Mon Jun 26 21:22:20 GMT 2000