An extendable continuum robot arm using a flexible screw as a backbone to propel inside a confined space with discontinuous contact area

This paper proposes a concept of an extendable continuum robot arm having many moving plates along a flexible feed screw and deploying each of them at a certain contactable area. The mechanism aims to bear a practical working load by utilizing a bracing on surrounding walls. In general, a narrow and confined workspace of human labor is composed of many discontinuous areas instead. Therefore, the mechanism deploys intermediate plates at certain supportable areas, and pushes rest of plates forward. To bend the arm in such workspace, tendon-driving technique is employed. In this paper, a basic composition of the arm is proposed and its feasibility is demonstrated by using a planar prototype. Subsequently, a simple geometric calculation scheme to obtain a configuration of the arm to avoid two kinds of insufficient conditions, that result in the failure of the arm to bear neither the external load nor its own weight, is proposed. Achievability of the solution of the geometric calculation is then evaluated by a static simulation including feedback control loop, and several experimental results with a spatial prototype performed to demonstrate the feasibility of the proposed concept are finally presented and discussed.