Development of a spherical tether-handling device with a coupled differential mechanism for tethered teleoperated robots

Tethered robots often experience entangling of their cables with obstacles in uncertain disaster environments. This paper proposes a spherical tether handling device that unfastens a robot's tether during surveys by releasing the tether and carrying it aside. By using a differential mechanism, the device drives shells and rollers that hold the tether. On flat surfaces, the device moves forward by driving the shells. When the device climbs over steps, the rollers are driven by the differential mechanism to pull the tether automatically. After prototyping the device, we confirm the surmountability of the proposed device against steps. The results show that the device can climb a height 90.9% of its diameter. We also demonstrate a scenario to handle the tether and untangle multiple tangles in an environment with several obstacles.