Continuous path tracing by a cable-suspended, under-actuated robot: The Winch-Bot

Abstract

A simple, under-actuated robotic winch, called the "Winch-Bot," is developed for surface inspection of a large object. The Winch-Bot, placed over an object surface, has only one actuator for tracing a free geometric path in a vertical plane. The cable length is controlled in relation to the direction of the cable so that the inspection end-effecter hanging at the tip of the cable can follow the path dynamically despite the lack of full degrees of freedom. We analyze the tracing dynamics, address under what conditions a given geometric path can be traced (traceability conditions), and prove under what conditions the tracing motion is repetitive. A controller utilizing partial feedback linearization is proposed, and simulations are used to validate the explored traceability criteria and to confirm the controller's performance improvement.

Winch driven active heave compensation for load transfer in overhead crane system

“…Zhang et al have developed a nonlinear controller, based on partial feedback linearization for the underactuated gantry crane system [6]. Cunningham and Asada have proposed a method for continuous path tracing by a cablesuspended underactuated robot, or "winch-bot" [7]. They suggested controlling the cable length of the crane by utilizing the partial feedback linearization technique with respect to the cable direction, and thus ensuring that the endeffector is capable of free geometric path tracing in a vertical plane.…”