Redundant manipulator self-motion topology under joint limits with an 8-DOF case study

Abstract

The paper investigates the topology of self-motion manifolds for serial redundant manipulators with revolute joints in the presence of joint limits. It is known that the preimages of singular taskpoints divide the configuration space into regions where self-motion manifolds are homotopic, Initially, the authors describe how self-motion manifolds rupture as one moves from one region to the next. The influence of joint limits on those topologies is investigated next. This analysis led to the discovery of the semi-singularity, a new type of singularity introduced by the presence of joint limits in redundant manipulators. A 3-DOF planar robot is used to illustrate the phenomena and a case study explores the concepts in more detail. This is an important analysis for global redundancy resolution and path planning because it describes the connectivity as well as the general form of self-motion manifolds.