An architecture for fast and accurate control of shape memory alloy actuators

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 distur-bances. There is no sign of limit cycles, and the performance is unaf-fected 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 con-trol accuracies as high as 1 mN in a 3 N range, force output rates as high as 50 N s1, and highly accurate position control with steady-state errors below the resolution of the position encoder. KEY WORDS—shape memory alloys, Acuators, force con-trol, position control 1