Singularity-consistent path planning and motion control through instantaneous self-motion singularities of parallel-link manipulators

Abstract

The newly proposed singularity-consistent path tracking approach is applied to nonredundant parallel-link manipulators. We analyze the singularities of such manipulators under the assumption that the output-link moves on a pre-defined and parameterized path. Special attention is paid to the so-called instantaneous self-motion type singularity. We propose a velocity-command generator type closed-loop controller that guarantees asymptotic stability when tracking paths through such singularities. As a comprehensive analytical example we use a planar five bar mechanism. Results from computer simulations with the five bar mechanism and the HEXA parallel robot are also presented. © 1997 John Wiley & Sons, Inc.