Geometry and Constraint Based Design of Metamorphic Parallel Mechanisms

Abstract

This paper presents two general metamorphic kinematic units which employ only revolute joints. The two kinematic units with reconfigurability are mapped from independent set of line vectors with different geometry. The underlying principle of the metamorphosis of this kind of reconfigurable kinematic units is unraveled by investigating the dependency of corresponding screw system comprised with line vectors. Limb structure that can be used for constructing new parallel mechanisms is proposed. Subphases of the limb are enumerated accompanying to the phase change of the embodied metamorphic units and constraints corresponding to each phase are analyzed based on reciprocity of screws. Two metamorphic parallel mechanisms which can change their configuration from fully 6-DOF phase to 3-DOF translational subphase and 3-DOF spherical subphase are proposed according to geometric conditions that must be met by limbs. The mobility changes of the platform induced by phase change of limbs are addressed.