The design of shape memory alloy (SMA) actuators typically compromises between force and stroke, the two properties being hard to achieve simultaneously. This paper presents a bow-like compliant SMA actuator aimed at improving the performance on both sides. Conceptually, the actuator is formed by two straight elastic beams hinged at the ends with an SMA wire pre-stretched in between. Heating of the alloy shortens the wire, which in turn makes the beams to buckle outward in a symmetric double-arched configuration. The transverse displacement of the beams amplifies the contraction of the wire while producing a favourable output force. The paper develops a simple, though accurate, analytical model of the actuator upon which a step-by-step design procedure is built. The numerical results for a case study are compared with the outcome of a finite element simulation.

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