| Y. Wischnitzer Robotics Laboratory,
Department of Mechanical Engineering,
Technion—Israel Institute of Technology,
Technion City, Haifa 32000, Israel, N. Shvalb Department of Mechanical Engineering,
Faculty of Engineering,
Ariel University Center of Samaria,
Ariel 40700, Israel and M. Shoham Robotics Laboratory,
Department of Mechanical Engineering,
Technion—Israel Institute of Technology,
Technion City, Haifa 32000, Israel |
| In spatial designs of wire-driven parallel robots, collisions between
wires by limiting platform trajectories. The common practice for
avoiding collisions between wires is by limiting the moving platform
trajectories. However, as opposed to rigid links, wires may tangle and
the robot may still be functional. Hence, the purpose of this work is to
examine the possibility of permitting wire collisions and thus expanding
the workspace of the robot. Under the assumptions of negligible
wire mass and diameter and negligible friction between the wires, the
inverse kinematics of a robot with two colliding wires is formulated
and was solved numerically. In addition, linearization was performed
and found to be accurate excluding the initial steps of collision. To
resolve this, approximated systems were solved analytically (up to
univariate high-order polynomials) using an elimination method that
provides accurate results. An experimental setup with two motorized
wires was built and the theoretical and experimental results are presented.
Velocities and forces mappings for the wire-driven parallel robot
under wire collisions were also formulated. It should be noted that
unlike the collisions-free case, these two mappings are not identical. |
