Optimal design of the TriVariant robot to achieve a nearly axial symmetry of kinematic performance

This paper revisits the optimal kinematic design of a 3-DOF parallel mechanism that forms the main body of a 5-DOF reconfigurable hybrid robot named the TriVariant. The dimensional synthesis of the 3-DOF parallel mechanism is carried out by introducing a tilt structure angle that enables to achieve a nearly axial symmetry of kinematic performance with respect to the configuration when the properly constrained active limb is vertically or horizontally placed. The results are then compared with those of the Tricept robot via an example. It concludes that for the same task workspace the modified version of the TriVariant has a very similar kinematic performance to that of the Tricept provided that they both have similar dimensions.