Comparative evaluation of straight and curved beam flexures for selectively compliant mechanisms

In this paper, a quantitative comparison is made between straight beam and curved beam flexures for application on selectively compliant mechanisms. Following a general procedure previously described in the literature, the closed-form compliance equations for both flexural hinges are firstly derived. Then, the two morphologies are compared in terms of maximum achievable rotation and selective compliance (i.e. capability of providing low stiffness along a single desired direction). In particular, the performance of each design solution is quantified by means of purposely defined quality indexes, analytically computed on the basis of the hinges compliance matrix. Finally, the potentials of these types of flexures for the optimal design of compliant robotic fingers are critically discussed.