Kinematic design and novel mobility analysis of a new 3D pantograph decoupled manipulator

A new decoupled 3D translational pantograph manipulator with symmetrical design is proposed. Since its three linear actuators are placed on/near the base, it possesses, to some extent, the advantages of parallel manipulators such as high speed, high stiffness and high accuracy. Since its structure is close to that of serial manipulators, its workspace to size ratio is high, comparable to that of serial manipulators. Moreover, the end-effector of the proposed manipulator has decoupled translation motions in three perpendicular directions with fixed orientation. Also, the manipulator has a linear input/output relationship for the positioning problem. Other possible architectures for the proposed manipulator are presented where the manipulator can have 4, 5 or 6 DOFs. The unconventional interconnected structure of the proposed manipulator does not allow the use of known mobility analysis methods. So, a novel method based on sketching the 3D velocity diagram is developed to derive the full-cycle mobility for general (serial, parallel or interconnected) manipulators. The kinematics, workspace, singularity and stiffness of the proposed manipulator are studied. The results show that the proposed manipulator outperforms the known translational decoupled Pantopteron manipulator regarding the workspace to size ratio. The proposed manipulator can also achieve configuration-independent and near-isotropic behaviors.