A Class of Parallel Robots Practically Free of Parallel Singularities

Abstract

This paper presents a class of 6-DOF three-legged parallel robots that are practically free of parallel singularities. The robots of this class have legs with a characteristic passive pair of prismatic and spherical joints, the first being directly attached to the platform. First, the direct kinematics of this class is solved, showing that for a certain arrangement there exists only one assembly mode. Then, the robot singularities are derived, showing that they practically do not exist in this structure. The advantages of this class of robots are hence simple direct kinematics and no need of singularity calculations.