Minimalist Dynamic Climbing

<p>Dynamics in locomotion is highly useful, as can be seen in animals and is becoming<br>apparent in robots. For instance, chimpanzees are dynamic climbers that can<br>reach virtually any part of a tree and even move to neighboring trees, while sloths are<br>quasistatic climbers confined only to a few branches. Although dynamic maneuvers<br>are undoubtedly beneficial, only a few engineered systems use them, most of which<br>locomote horizontally. This is because the design and control are often extremely<br>complicated.<br>This thesis explores a family of dynamic climbing robots which extend robotic<br>dynamic legged locomotion from horizontal motions such as walking, hopping, and<br>running, to vertical motions such as leaping maneuvers. The motion of these dynamic<br>robots resembles the motion of an athlete jumping and climbing inside a<br>chute. Whereas this environment might be an unnavigable obstacle for a slow, quasistatic<br>climber, it is an invaluable source of reaction forces for a dynamic climber.<br>The mechanisms described here achieve dynamic, vertical motions while retaining<br>simplicity in design and control.<br>The first mechanism called DSAC, for Dynamic Single Actuated Climber, comprises<br>only two links connected by a single oscillating actuator. This simple, openloop<br>oscillation, propels the robot stably between two vertical walls. By rotating the<br>axis of revolution of the single actuator by 90 degrees, we also developed a simpler<br>robot that can be easily miniaturized and can be used to climb inside tubes.<br>The DTAR, for Dynamic Tube Ascending Robot, uses a single continuously rotating<br>motor, unlike the oscillating DSAC motor. This continuous rotation even further<br>simplifies and enables the miniaturization of the robot to enable robust climbing<br>inside small tubes. The last mechanism explored in this thesis is the ParkourBot,<br>which sacrifices some of the simplicity shown in the first two mechanism in favor<br>of efficiency and more versatile climbing. This mechanism comprises two efficient<br>springy legs connected to a body.<br>We use this family of dynamic climbers to explore a minimalist approach to locomotion.<br>We first analyze the open-loop stability characteristics of all three mechanisms.<br>We show how an open-loop, sensorless control, such as the fixed oscillation<br>of the DSAC’s leg can converge to a stable orbit. We also show that a change in<br>the mechanism’s parameters not only changes the stability of the system but also<br>changes the climbing pattern from a symmetric climb to a limping, non-symmetric<br>climb. Corresponding analyses are presented for the DTAR and ParkourBot mechanisms.<br>We finally show how the open-loop behavior can be used to traverse more<br>complex terrains by incrementally adding feedback. We are able to achieve climbing<br>inside a chute with wall width changes without the need for precise and fast sensing<br>and control.</p>