Experimental analysis of Type II singularities and assembly change points in a 3UPS+RPU parallel robot

Parallel robots (PRs) have singular configurations where the robot gains at least one degree-of-freedom and loses control. Theoretically, such singularity occurs when Forward Jacobian-Matrix determinant becomes zero (Type II). However, actual PRs could lose control owing to Type II singularities for values near zero, but not because manufacturing tolerances introduce errors that are complex model due their low repeatability. Thus, using an 3UPS+RPU PR, this paper presents three contributions: i) a proximity detection index based on angle between two Output Twist Screws. The can identify which kinematic chains contribute singularity. ii) experimental benchmark study singularities. iii) PR proposed is Jacobian not. In last configuration, findings show unable handle external actions applied PR.