Study of a fully compliant U-joint designed for minirobotics applications

The paper proposes the study of the kinetostatic behavior of a flexible universal joint for minirobotic applications. A closed-form formulation of joint's compliance is obtained for linear elastic material and small displacements. It is also presented a numerical study that considers the joint realized with a superelastic shape memory alloys (SMA) material (Ni–Ti alloy); in this case, a finite element (FE) approach is used to overcome the strong nonlinearities arising from both the superelastic constitutive law and the large displacements. Besides the compliance properties of the joint, also kinematic performances are investigated, since the instantaneous rotation axis is expected to be floating around its ideal position because of parasitic elastic deformations.