Highly-Compact SMA Actuators A Feasibiltiy Study of Fuel-Powered and Thermoelectric SMA Actuators

摘要

In this work, a compact fuel-powered (FPC) SMA actuator and a compact thermoelectric (TEC) SMA actuator has been designed, fabricated and tested. An FPC-SMA actuator system has been developed utilizing high energy density of fuels. The final FPC-SMA actuator system is composed of an SMA strip, two pumps, valves, two bellows, a multi-channel combustor/heat exchanger, a micro-tube heat exchanger (radiator) and a control unit. The SMA Strip is embedded in a rectangular channel. This channel also contains a rectangular piston with a slot, such that the piston can move along the SMA strip and prevent mixing between the hot and cold fluids. The final FPC-SMA system can generate 250 N force of 2.0 % strain at 1.0 Hz actuation frequency under closed-loop test conditions. The second actuator is a solid-state, compact, TEC-SMA actuator utilizing the thermoelectric effect. The TEC-SMA system is currently able to produce lOOMPa stress with 1.5% strain under 0.5Hz actuation frequency. Work on the TEC- SMA actuator includes development of a basic experimental setup to characterize and optimize actuator bandwidth, stroke, output power and energy density. Design and development of a fixture for improved contact between the SMA and the thermoelectric elements and a test matrix for evaluation of actuator bandwidth, stroke, power and energy densities with respect to commercially available TE modules. This feasibility study shows that to further optimize both the power density and efficiency of the TEC-SMA actuator, SMA surface area to volume ratio needs to be increased while maintaining heat sinks at low temperatures and minimizing contact resistances.