Stiffness modeling and analysis of a novel 5-DOF hybrid robot

This paper deals with the stiffness modeling and analysis of a novel 5-DOF hybrid robot named TriMule which is composed of a 3-DOF positioning parallel mechanism plus a 2-DOF wrist. The robot is especially designed as a compact yet rigid module suitable for large part on-site machining. Mainly drawing on screw theory, a semi-analytic stiffness model of the robot is formulated by taking into account the component compliances associated with the elements of both the parallel mechanism and the wrist, resulting in the Cartesian stiffness matrix that can explicitly be expressed in terms of the compliance matrices down to the joint and link level. The stiffness distributions of the tool head over a prescribed task workspace are predicted and the contributions of joint/link compliances are evaluated using a set of global indices.