Design and Optimization of Miniature Climbing Robots using Flat Dry Elastomer Adhesives

This thesis describes novel methods dealing with problems that arise when utilizing elastomer adhesives as an attachment method for miniature climbing robots. Our work was motivated by the need of inspecting outer surfaces of airplanes and inner and outer surfaces of buildings. Our investigation of existing technologies have shown the elastomers to have significantly superior characteristics, such as the adhesion when the roughness is less than a few mum, the power consumption when the robot is loitering, imperfection traversal when there is a discontinuity on the surface compared to the other attachment methods. In this work we defined a set of boundaries for elastomer adhesives to be employed as an attachment technique and characterized to obtain the essential attributes to utilize for attachment purposes, we emphasized that the hysteresis of the elastomer adhesives can be employed to attach the robot on a surface using the proposed novel force transfer technique. This technique uses the detachment force of the elastomer adhesive to reattach on a surface in an infinite loop. In this way, the attachment mechanism can be kept on a surface as much as desired. We optimized a framework that facilitates a specific robotic transportation device and an elastomer whose desired performance metrics can be specified externally to optimize payload carrying, steering, surface transitioning, obstacle traversal, and loitering performances. We evaluated the performance of the built robots by measuring the steepest angle they can climb, the total payload that they can carry, the total power they consume during loitering and moving, the types of surface transitions they can make, and the maximum obstacle height they can traverse. A key aspect of the work stated herein is that it integrates the flat, bulk elastomer based attachment method with a novel force transfer mechanism utilizing the hysteresis of the elastomer adhesives.;We manufactured two climbing mechanisms called the 4-bar robot and Tankbot. Both of them employ the same force transfer technique in different ways. It is modeled and experimentally verified that the adhesion and preload on the adhesive footpads saturate after a few steps. We developed a model to estimate the total time of being stationary before failure. Moreover, our developed technique extends the time period of being stationary. The 4-bar robot is the first inverted climbing robot utilizing elastomer adhesives as an attachment method with a payload carrying capacity of more than its own weight and with an extended loiter time. Our second climbing robot design, Tankbot, is able to climb in any direction on commonly encountered vertical surfaces, such as painted walls, painted bricks, wooden doors, and metal cabinets, where the surface roughness is less than a few mum. Tankbot is the first climbing robot which climbs on various common surfaces with a payload carrying capacity, obstacle traversal, and surface transitioning capability using elastomer adhesives as an attachment method. In summary, we revealed that the legged robots, which employ a force transfer mechanism, can carry more payload than wheeled robots on an inverted smooth surface, however, wheeled robots are superior on relatively rough surfaces due to the continuous force transfer mechanism. This research draws upon, and has implications in a wide variety of engineering applications utilizing elastomer adhesives when the surface roughness is below a few mum.