PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, cilt.25, sa.1, ss.65-74, 2024 (SCI-Expanded)
Parallel
robots have many remarkable advantages over their conventional serial
counterparts. Highly accurate positioning capability and high payload-to-weight
ratio are among the main ones. The main factor underlying all these advantages
is their closed-loop construction. However, this constructional feature also
causes a special singularity problem, which constitutes their biggest
disadvantage. Characteristic singularities classified as Type II exist inside
their workspace, around which the magnitude of the inverse dynamic solution
grows unboundedly. This naturally yields the saturation of the actuators and
eventually in uncontrollability of the robot. Consequently, the whole workspace
becomes impossible to be used. In order to pass through a Type II singularity,
the consistency of the motion equations of the robot must be maintained at that
singularity. However, any Type II singular configuration can transform into a
high-order singularity, which, in order to be passed through, requires
additional conditions other than the consistency. Therefore, full utilization
of the whole workspace with a minimum number of conditions requires to avoid
high-order singularities. The present article contributes to the literature by
developing path and trajectory planning principles for preventing a
two-degree-of-freedom planar parallel robot with RPRPR structure from
experiencing high-order singularities.