Design and modelling of a flexure-based bistable gripper powered by shape memory alloys

Abstract Due to increased demand for compact grippers in applications such as drone deliveries or cleanroom pick and place robots, bistable grippers powered by shape memory alloys (SMAs) are an elegant solution for replacing the traditional pneumatic grippers. But due to their complex behaviour, they are difficult to size and are, thus, rarely used in industrial applications. In this paper, a bistable flexure-based SMA-driven parallel gripper is presented that is lightweight, compact and resistance to friction and wear. The bistability is created by a buckled beam, designed using analytical modelling based on Euler–Bernoulli beam theory. The gripper actuation is performed by a pair of antagonistic SMA coils. The novel design methodology is validated using a functional gripper prototype with a total volume of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>110</mml:mn> <mml:mo>×</mml:mo> <mml:mn>34</mml:mn> <mml:mo>×</mml:mo> <mml:mn>26</mml:mn> </mml:mrow> </mml:math> mm 3 , a maximum stroke of 2.5 mm for each jaw and a maximum gripping force of 1.4 N.