Abstract
This paper presents a novel Schönflies-motion Parallel Manipulator with Rotational Pitch motion (SPM-RP) based on a single-platform fully-parallel mechanism. The analysis of position, workspace, velocity, and singularity of the SPM-RP is carried out in detail, and a dimensionless Jacobian is proposed to evaluate the manipulability of the SPM-RP. It is shown that the SPM-RP is kinematically position-decoupled, which possesses a large singularity-free workspace and excellent manipulability. The SPM-RP is actuated by four parallel prismatic actuators, enabling the manipulator to provide identical kinematic performance at all generic cross-sections perpendicular to the prismatic joint axes within its workspace. This paper thus proposes a reduced design optimization formulation, where the traditional optimization over the entire workspace is reduced to one on a representative workspace cross-section of the SPM-RP. The design optimization of the SPM-RP has been carried out by maximizing its manipulability over the total orientation workspace, which is crucial for precision assembly. A SPM-RP prototype has been developed based on the achieved optimal design. The mobility, orientation capability, total orientation workspace, and repeatability are tested and verified for the developed SPM-RP prototype. Experiments show that the SPM-RP achieves a large total orientation workspace with excellent precision performance.