Minimalist Dynamic Climbing

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