Experimental investigations on permanent magnet based wheel mechanism for safe navigation of climbing robot

This paper presents excremental studies on permanent magnet based wheel mechanism for safe navigation of climbing robot on ferrous wall surface structures. Three types of wheel mechanism (Wheel 1, Wheel 2 and Wheel 3) are manufactured and compared for their working performance experimentally for climbing robot locomotion trials. The Wheel 1 mechanism with MS hub is very compact, simple in design with easy assemble/dissemble features, and having less manufacturing cost. However, the adhesion force of the prototype wheel is comparable with already reported permanent magnet based adhesion mechanism. Wheel 1 design is further improved by developing Wheel 2 and 3 versions by changing hub material from mild steel to Aluminum. These wheel mechanisms are light in weight and more powerful to achieve maximum adhesion force i.e., 210 N and 251 N with and without rubber grip, respectively, at only 200 gm wheel weight as compared to previously reported permanent magnetic adhesion mechanism. Thus, more payload carrying capacity climbing robot can be developed using these developed mechanisms for field trials of climbing robot. A comprehensive experimental study on the influence of rubber grip thickness, air gap, wheel tilt angle and test surface thickness variation on adhesion force of these developed wheel mechanisms have been reported. The influence of both static and kinetic coefficient of friction (COF) for vertical surface locomotion of climbing robot has also been investigated. These developed wheel mechanisms have been further demonstrated using a four-wheel differential drive prototype-climbing robot for safe navigation testing first on a 2-D framed plane wall structure and next on a 3-D framed wall structure. It is found from the laboratory trials that based on these wheel mechanisms, the climbing robot can safely navigate remotely on even surface for these chosen structures. (C) 2018 The Authors. Published by Elsevier Ltd.