  Robotic manipulation of tethered tools is widely seen in robotic work cells.
They may cause excess strain on the tool's cable or undesired entanglements
with the robot's arms. This paper presents a manipulation planner with cable
orientation constraints for tethered tools suspended by tool balancers. The
planner uses orientation constraints to limit the bending of the balancer's
cable while the robot manipulates a tool and places it in a desired pose. The
constraints reduce entanglements and decrease the torque induced by the cable
on the robot joints. Simulation and real-world experiments show that the
constrained planner can successfully plan robot motions for the manipulation of
suspended tethered tools preventing the robot from damaging the cable or
getting its arms entangled, potentially avoiding accidents. The planner is
expected to play promising roles in manufacturing cells.
