This paper discusses the design and experimental results of the improved fuel-powered compact SMA actuator system and its comparison with the first-generation design. The K-alloy SMA strip (12 mm × 0.9 mm), actuated by a forced convection heat transfer mechanism, is embedded in a rectangular channel. In this channel, a rectangular piston, with a slot to accommodate the SMA strip, runs along the strip and prevents mixing between the hot and cold fluid in order to increase the efficiency of the system. The main energy source is fuel, such as propane, in order to achieve high energy and power densities of the system. Numerical analysis was performed to determine optimal channel geometry and to estimate maximum available force, strain and actuation frequency of the SMA actuator. The combustor/heat exchanger was designed to achieve higher heat transfer rates to the hot fluid from the energy source. The SMA actuator system is composed of pumps, valves, bellows, radiator, combustor/heat exchanger and control unit. The experimental testing of the SMA actuator system resulted in 735 N force with 2.5% strain and 0.25 Hz actuation frequency in closed-loop operation.
This work discusses the numerical analysis, the design and experimental test of the fuel-powered compact SMA actuator along with its capabilities and limitations. Convection heating and cooling using water actuate the SMA element of the actuator. The energy of fuels, having a high energy density, is used as the energy source for the SMA actuator in order to increase power and energy density of the system, and thus in order to obviate the need for electrical power supplies such as batteries. The system is composed of pump, valves, bellows, heater (burner), control unit and a displacement amplification device. The experimental test of the first designed SMA actuator system results in 150 M Pa stress (force: 1560N) with 3 percent strain and 0.5 Hz actuation frequency. The actuation frequency is compared with the prediction obtained from numerical analysis. For the first designed fuel-powered SMA actuator system, the results of numerical analysis were utilized in determining design parameters and operating conditions.