Thermodynamic Analysis for Control of Shape Memory Alloys.

Shape memory alloys (SMA) have significant potential for the actuation of small mechanisms. Control of SMA actuators is made difficult however by the need to heat and cool the metal to effect motion. A formal analysis of energy input, heat production and heat dissipation processes in SMA actuators is presented. Results of this analysis can be used in the design of actuator geometries, control algorithms and control circuitry to maximize actuator bandwidth. The production of joule heat in SMA actuators is analyzed and the relative rates of heat dissipation by convection, and radiation are compared. The effects of actuator geometry on heating and cooling are considered and methods for analog current and power control are presented.