Decoupled Parallel Manipulators Generating S-RS-US Structures: Type Synthesis and Position Analysis

Parallel manipulators (PMs) with decoupled kinematics can be obtained by combining a translational PM (TPM) with a spherical PM (SPM) either in multiplatform architectures or in integrated more-complex architectures. Some of the latter type are inspired by the 6-4 fully parallel manipulator (6-4 FPM), whereas others of the same type are deduced by suitably combining TPMs' limbs and SPMs' limbs into more cumbersome limbs which contain more than one actuated joint. The decoupled PMs (DPMs) presented here pursue an intermediate concept between the last two, which keeps all the actuators on or near to the base in a simplified architecture with only three limbs. These features preserve the lightness of the mobile masses, together with the associated good dynamic performances, and reduce the limitations on the workspace due to limb interferences. The type synthesis of these DPMs is addressed till to identify sixty-three architectures; then, the position analysis problems of the identified architectures are solved in closed form.