Position Analysis and Path Planning of the S-(nS)P U-SP U and S-(nS)PU-2SP U Underactuated Wrists

Abstract

In a previous work, this author showed that ten topologies for underactuated parallel wrists can be generated from a fully parallel wrist (FPW). Three of them are obtained by simply replacing a spherical pair (S) with a nonholonomic spherical pair (nS). The S-(nS)P U-SP U and S-(nS)PU-2SP U wrists are two among these three. The position analysis of these two wrists is studied here. In particular, all the four position-analysis problems, which are necessary for implementing their path planning, are addressed and solved in closed form. Despite their different topology, the position analysis of these two wrists can be practically solved by using the same formulas and algorithms. Based on the deduced formulas, a path-planning algorithm is proposed. The obtained results make the studied wrist topologies able to replace “ordinary” wrists in the manipulation tasks which do not require tracking.