|This paper presents a new control architecture for fast, accurate force
control of antagonistic pairs of shape memory alloy wires. The main
components are: a differential-mode controller which controls the
output force, an anti-slack mechanism, a rapid-heating mechanism
and an anti-overload mechanism. The closed-loop response is fast
and accurate, even in the presence of large external motion disturbances.
There is no sign of limit cycles, and the performance is unaffected
by large load inertias. This paper also presents an architecture
for position control, in which a position feedback loop is added to
the force control architecture. Experimental results show force control
accuracies as high as 1mN in a 3N range, force output rates
as high as 50Ns1, and highly accurate position control with steadystate
errors below the resolution of the position encoder.