Abstract

This paper presents a shape memory alloy actuator design using a bimorph structure capable of high-speed actuation and low power consumption. Two active layers of shape memory alloy wires are separated by a passive layer of thermoplastic polyurethane. This structure results in a bending actuator when current is alternated between the two active shape memory alloy layers. Actuators of lengths 20, 25, 30, 35 and 40 mm were tested at peak current input of 110, 120, 130 and 140 mA. The 40 mm actuator was shown to have a natural frequency of 11.4 Hz with a bending displacement of 26.4 mm perpendicular to the neutral position and a power input of 0.78 watts (140 mA peak current input). A relationship between the input current and the resulting vibratory characteristics was found. As the current increases, the natural frequency decreases and the damping ratio increases. The experimental results are compared with an FEM vibration analysis and an Euler-Bernoulli cantilever beam equations.

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