Comparative study and experimental verification of singular-free algorithms for a 6 DOF parallel haptic device

Although many singularity-free algorithms for kinematically redundant manipulators have been proposed, singularity-free algorithms for parallel haptic application have not been extensively discussed. In this paper, various singularity-free algorithms that are appropriate for parallel haptic systems will be discussed. A new 6 degree-of-freedom (DOF) parallel mechanism equipped with four sub-chains is designed and employed as the test device. To cope with the singularity problem, four task-priority algorithms and a redundant actuation algorithm are introduced and compared through simulation. In addition, experiments have been performed to show the effectiveness of those algorithms at the presence of singularity.