The basic mechanics of bipedal walking lead to asymmetric behavior

Abstract-This paper computationally investigates whether gait asymmetries can be attributed in part to basic bipedal mechanics independent of motor control. Using a symmetrical rigid-body model known as the compass-gait biped, we show that changes in environmental or physiological parameters can facilitate asymmetry in gait kinetics at fast walking speeds. In the environmental case, the asymmetric family of high-speed gaits is in fact more stable than the symmetric family of lowspeed gaits. These simulations suggest that lower extremity mechanics might play a direct role in functional and pathological asymmetries reported in human walking, where velocity may be a common variable in the emergence and growth of asymmetry

Correction to: Cluster identification, selection, and description in Cluster randomized crossover trials: the PREP-IT trials

An amendment to this paper has been published and can be accessed via the original article

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

Minimalistic Dynamic Climbing

No official endorsement should be inferred. Keywords: Climbing robots, Dynamic locomotion, Minimalism, Nonlinear analysis, Openloop, Dynamics in locomotion is highly useful, as can be seen in animals and is becoming apparent in robots. For instance, chimpanzees are dynamic climbers that can reach virtually any part of a tree and even move to neighboring trees, while sloths are quasistatic climbers confined only to a few branches. Although dynamic maneuvers are undoubtedly beneficial, only a few engineered systems use them, most of which locomote horizontally. This is because the design and control are often extremely complicated. This thesis explores a family of dynamic climbing robots which extend robotic dynamic legged locomotion from horizontal motions such as walking, hopping, and running, to vertical motions such as leaping maneuvers. The motion of these dynamic robots resembles the motion of an athlete jumping and climbing inside a chute. Whereas this environment might be an unnavigable obstacle for a slow, quasistati

Interacting with Obstacles Using a Bio-Inspired, Flexible, Underactuated Multilink Manipulator

With the increasing demand for robotic manipulators to operate in complex environments, it is important to develop designs that work in obstacle-rich environments and can navigate around obstacles. This paper aims to demonstrate the capabilities of a bio-inspired, underactuated multilink manipulator in environments with fixed and/or movable obstacles. To simplify the system design, a single rotational actuator is used at the base of the manipulator. We present a modeling method for flexible, multilink underactuated manipulators, including their interaction with obstacles. We also demonstrate how to plan a trajectory for the manipulator in environments with fixed obstacles. The robustness of the manipulator is examined by analyzing the effects of uncertainty in its initial state and the position of obstacles. Next, we demonstrate the performance of the manipulator in environments with movable obstacles and show the advantages of controlling the obstacles’ radii and positions. Lastly, we showcase the process of picking up an object in workspaces with obstacles. All the findings are supported by simulations as well as hardware experiments

DSAC – dynamic, single actuated climber: Local stability and bifurcations

Abstract — This paper investigates a novel mechanism, calle

A Dynamic Single Actuator Vertical Climbing Robot

Abstract — A climbing robot mechanism is introduced, which uses dynamic movements to climb between two parallel vertical walls. This robot relies on its own internal dynamic motions to gain height, unlike previous mechanisms which are quasistatic. One benefit of dynamics is that it allows climbing with only a single actuated degree of freedom. We show with analysis, simulations and experiments that this dynamic robot is capable of climbing vertically between parallel walls. We introduce simplifications that enable us to obtain closed form approximations of the robot motion. Furthermore, this provides us with some design considerations and insights into the mechanism’s ability to climb. I