An artificial muscle for a human arm-like manipulator with high strain and high power density are under development,
and an SMA(Shape memory alloy) spring is a good actuator for this application. In this study, an artificial muscle
composed of a silicon tube and a bundle of SMA(Shape memory alloy) springs is evaluated. A bundle of SMA springs
consists of five SMA springs which are fabricated by using SMA wires with a diameter of 0.5 mm, and hot and cool
water actuates it by heating and cooling SMA springs. A faucet-like valve was also developed to mix hot water and cool
water and control the water temperature. The mass of silicon tube and a bundle of SMA springs is only 3.3 g and 2.25 g,
respectively, and the total mass of artificial muscle is 5.55 g. It showed good actuating performance for a load with a
mass of 2.3 kg and the power density was more than 800 W/kg for continuous valve switching with a cycle of 0.6 s. The
faucet-like valve can switch a water output from hot water to cold water within 0.3s, and the artificial muscle is actuated
well in response to the valve position and speed. It is also presented that the temperature of the mixed water can be
controlled depending on the valve position, and the displacement of the artificial muscle can be controlled well by the
mixed water. Based on these results, SMA spring-based artificial muscle actuated by hot and cool water could be
applicable to the human arm-like robot manipulators.
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