Analysis and Design of a Novel Compact Four-Degree-of-Freedom Parallel Robot with unlimited rotation

Parallel robots are known for their high stiffness, excellent load capacity, and precision; however, their rotational capabilities are often limited. To address this challenge, we propose a novel compact four-degree-of-freedom (4-DoF) parallel robot, that can position a point P in space and perform an unlimited rotation about a specific axis passing through this point. The mechanism is intended to be used as a leg in a kinematically redundant parallel robot, with all actuators mounted on the base to minimize inertia and reduce potential collisions and singularities. This paper presents a comprehensive analysis of the robot's design, including its mobility, inverse kinematics, Jacobian matrices, workspace under mechanical constraints (with explicit identification of the region that admits unlimited rotation), and a CAD model of the robot.