Design of an inchworm actuator based on a shape memory alloy wires

This paper presents a novel inchworm actuator, that is driven by shape memory alloy (SMA) wires. Contrary to common SMA-actuator concepts enables the inchworm concept to overcome the stroke restrictions of SMA. The presented actuator concept impresses with verry low production and material costs, compared to other inchworm actuator concepts. Especially, using polymer 3D-printing or injection molding and standardized NiTi-based SMA wires, prototype as well as series fabrication is simple and inexpensive. Another highlight is the considerably smaller geometry of the presented SMA-inchworm actuator, with a length of 75 mm, a width of 10mm and a height 20 mm. The actuator consists of three SMA-wires, where two are used for clamping and for the stroke. A peculiarity is the movement of the actuator in a channel, in contrast to the most concepts where a rod is moved by the actuator. The developed inchworm actuator exhibits moderate output force and large displacement, achieved by accumulating many small strokes based on the inchworm mechanism. In this paper the design and fabrication as well as the characterization like the achievable clamping force and the setting speed are shown. In addition, a comparison with commercial inchworm actuators is given.