SINGULARITY-CONSISTENT PATH PLANNING AND MOTION CONTROL THROUGH INSTANTANEOUS SELF-MOTION SINGULARITIES OF PARALLEL-LINK MANIPULATORS

The newly proposed singularity-consistent path tracking approach is ap plied to nonredundant parallel-link manipulators. We analyze the singu larities of such manipulators under the assumption that the output-lin k moves on a pre-defined and parameterized path. Special attention is paid to the so-called instantaneous self-motion type singularity. We p ropose a velocity-command generator type closed-loop controller that g uarantees asymptotic stability when tracking paths through such singul arities. As a comprehensive analytical example we use a planar five ba r mechanism. Results from computer simulations with the five bar mecha nism and the HEXA parallel robot are also presented. (C) 1997 John Wil ey & Sons, Inc.