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 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 50Ns−1, and highly accurate position control with steady-state errors below the resolution of the position encoder.