Design and analysis of a new parallel grasper having spherical motion

A new parallel grasper mechanism having 3-DOF spherical motions is proposed. The mechanism consists of one parallel four-bar chain and four serial sub-chains that are connected in parallel to the four-bar chain. Particularly, all joint axes of the mechanism are placed to have a common intersection point securing that all joint motion spaces of the mechanism are confined within the 3-DOF spherical motion spaces. Thus, the mechanism can not only grasp irregular shaped objects by changing configuration of its four-bar chain, but also exhibit 3 DOF spherical motions after grasping. The position analysis and kinematic analysis of the mechanism are performed. Also, its kinematic characteristics are investigated through simulation in aspects of three kinematic design indices. Lastly, a prototype was developed and tested through motion tracking and grasping experiments.