Proposal for a New Design for Continuum Robots Suitable to Manipulate Tools in Higher Positions

Continuum robots do not contain rigid links and identifiable rotational joints. Their structure bend continuously along their length via elastic deformation and produce motion through the generation of smooth curves, similar to the tentacles or tongues of the animal kingdom. One technique to construct lightweight continuum devices with many degrees of freedom is to utilize remote actuation, and transfer motion into the structure via groups of antagonistic tendons. Independent tendon pairs or triads control the orientation of the backbone. Usually, continuum robots have a small working volume due to the fact that they need to bend their backbone in order to reach the aimed positions. This work proposes a new design for continuum robots with increased working volume by replacing the continuous backbone with a telescopic structure driven by wires and electric motors. Using this kind of design, it is possible to change the length of the robot. When attaching cable pairs to the end of the telescopic structure, it is possible to provide two axis bending using two mechanisms to exert tension on the cables in two horizontal orthogonal directions. To control the robot, a PLC was used, using an open loop control. The open control scheme works with the relation to he number of cycles of the DC motor that makes the end pole extremity reach a determined displacement. Applying such changes in the structure of a continuum robot, it is possible to build robots that could reach higher positions. This feature makes the robot more suitable for operations in inaccessible places, such as inspections of electric power transmission and distribution networks. To verify the efficiency of the proposal, a study case was adopted and a prototype was constructed, designated for wood cross-arms inspection. As a consequence, a robot was developed, much longer than any other continuum robot proposed, up to 9 meters high. Bearing in mind the importance of studying the deformation of the robot once the structure will bend in order to promote movements, it was analyzed, using the finite element method. The aim of the analysis is to find out how the structure would react to an external load caused by the tensile cables and to determine the amount of force that the mechanisms need to promote a specific displacement in the pole extremity. Finally, in order to validate the proposed design, a prototype has been developed, constructed and submitted to tests.