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.

In the healthy young, stimulation of superficial peroneal nerve (SPn) cutaneous afferents at the ankle during walking has been shown to elicit functionally relevant neural and mechanical responses that contribute to obstacle avoidance during swing and have been referred to as stumble corrective responses. However, specific age-related differences in the stumble corrective response induced by electrically evoked cutaneous stimulation have yet to be determined. As a confounding contributor to age related changes in dynamic stability during locomotion, neural and mechanical changes in the stumble corrective response may result in a decreased ability to recover from a destabilizing incident and provide key markers of neuromuscular decline. Therefore the purpose of this study was to compare age-dependent differences in responses to electrically evoked stimulation of the superficial peroneal nerve at the ankle during walking in healthy young and elderly groups. Electromyograms (EMG) of the tibialis anterior (TA), soleus (Sol), medial gastrocnemius (MG), biceps femoris (BF) and vastus lateralis (VL) were recorded along with gait kinematics including joint displacement and angular velocity at the ankle and knee as well as toe clearance relative to the walking surface. Overall, the stumble corrective response was preserved in the elderly as evident by significant responses in kinematics and muscle activity that were similar in sign and phase to those seen in the healthy young. However, the magnitude of the kinematic responses and resulting toe clearance in older adults were significantly smaller than in the young. Further, during the swing phase of unstimulated walking cycles, there were reduced knee flexion, plantarflexion and toe clearance in the elderly with corresponding differences in muscle activity. Therefore, smaller kinematic responses to stimulation, in the elderly, superimposed on a different undisturbed gait profile, resulting in reduced toe clearance, reflects early degradation of the stumble corrective response. This early degradation is likely a prodromal sign of increased fall risk. This supports the potential use of cutaneous reflexes in quantifying degradation of neuromuscular control and its contribution to fall risk. / Graduate / 0317 / 0758 / rbrodie@uvic.ca

No description available.

Networks at various levels of the nervous system coordinate different motor patterns such as respiration, eye or hand movements and locomotion. Intrinsic rhythm-generating networks that are located in the spinal cord generate motor behaviors that underlie locomotion in vertebrates. These networks give a continuous and measurable coordinated rhythmic motor output and are referred to as locomotor central pattern generators (CPGs). Characterization of the mammalian locomotor CPG and its molecular control is depending on the identification of participating neurons and neuronal populations. In this thesis I present work where we have studied the significance of subpopulations of neurons in the formation and function of the left-right circuitry. In summary, we show that the axon guidance receptor DCC has a central role in the formation of spinal neuronal circuitry underlying left-right coordination, and that both Netrin-1 and DCC are required for normal function of the locomotor CPG. Commissural interneurons (CINs), which send their axons across the ventral midline in the spinal cord, play a critical role in left–right coordination during locomotion. A complete loss of commissural axons in the spinal cord, as seen in the Robo3 null mutant mouse, resulted in uncoordinated fictional locomotor activity. Removing CIN connections from either dorsal or ventral neuronal populations led to a shift from alternation to strict synchronous locomotor activity. Inhibitory dI6 CIN have been suggested as promising candidate neurons in coordinating bilateral alternation circuitry. We have identified that Dmrt3, expressed in inhibitory dI6 CINs, is a crucial component for the normal development of coordinated locomotor movements in both horses and mice. We have also concluded that the prominent hopping phenotype seen in hop/hop mice is a result of abnormal developmental processes including induction from the notochord and Shh signaling. Together, these findings increase our knowledge about the flexibility in neuronal circuit development and further confirm the role of dI6 neurons in locomotor circuits.

This thesis investigates walking patterns in healthy young people and in people with an increased risk of falling, and determines the physiological contributions to walking stability. First, a review of the relevant literature on techniques for assessing walking stability, age-related changes in balance and gait, and the contributions of vision, vestibular function, peripheral sensation and strength was undertaken. In response to a critical analysis of these findings, a new technique and protocol for the assessment of walking stability was developed. This involved measuring and analysing head and pelvis accelerations while subjects walked on a level surface and an irregular surface. Gait patterns were studied in 30 young healthy subjects and two groups known to be at increased risk of falling - 100 subjects over the age of 75, and 30 subjects with diabetic peripheral neuropathy. A series of vision, sensation, strength, reaction time and balance tests were also undertaken to identify subjects??? physiological abilities and risk of falls. Acceleration patterns of the head and pelvis differed according to physiological risk of falling, particularly when walking on the irregular surface. Those with a high risk of falling walked with a reduced velocity, cadence and step length, and exhibited less rhythmic acceleration patterns at the head and pelvis. Gait patterns were significantly associated with leg strength, peripheral sensation and reaction time. It is concluded that subjects with a high physiological risk of falling exhibit characteristic patterns of walking that indicate an impaired ability to control the movement of the pelvis and head, which may predispose to loss of balance.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2008. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Licentiatavhandling (sammanfattning) Skara : Sveriges lantbruksuniversitet, 2005. / Härtill 2 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 281-287). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.