No description available.

Many animals interact with the air-water interface during locomotion. Such location either involves moving through the water's surface or moving atop the water surface. This dissertation aims to investigate both of these forms of locomotion in frogs. First we quantified the kinematics of skittering, jumping on top the water's surface without sinking, in two species of frog, Acris crepitans and Euphlyctis cyanophlyctis. We found that what was described as "skittering" locomotion in Acris crepitans is actually more akin to porpoising. A. crepitans begins and ends each jump during their interfacial behavior under the water surface. These frogs may be unable to perform true skittering locomotion due to not being able to retract their hindlimbs fast enough. E. cyanophlyctis, however, does stay above the water surface during this mode of locomotion. We found that Euphlyctis is highly maneuverable during skittering locomotion compared to other inertial based water-surface traversing animals. Not only can they turn up to 80° between subsequent jumps, they also perform this behavior in close proximity to each other without collision. Next, we investigated control mechanisms used by frogs when jumping from water. Prior research has identified frogs of the genus Euphlyctis as high jumpers. But previous studies only considered their maximal performance. Here, we investigated how these frogs modulate propulsive force in order to control their jump height. We linked the frog limb kinematics to the jump force by modeling the added mass produced by the foot's motion. / Doctor of Philosophy / There are many animals that move across or through the water's surface. Most of them are very small and light and can thus be supported by surface tension. Larger animals instead must produce the force needed to stay afloat by moving quickly. Previous research has looked at the physics involved in running on the water surface in basilisk lizards and grebes. However, the ability of frogs to jump on the water surface (a behavior known as "skittering") has never been studied. In this dissertation, we examine the water-surface traversal of two frog species, Acris crepitans and Euphlyctis spp., using high-speed videography. Unlike previous human observations in the literature, we found that Acris does not stay atop the water's surface during its jumping behavior and instead begins and ends each jump under the water. This is similar to porpoising in animals like dolphins. Euphlyctis, however, does stay above the water during this jumping behavior. We found that these frogs can turn sharply between jumps which has not been observed in any other large water-runners. Additionally, we studied the ability of Euphlyctis to jump high in the air starting from floating on the water surface. These frogs are interesting to study because they can jump unusually high compared to other species of similar size and shape. We found that when shown insects at different heights, these frogs can control their jump height and only jump as high as necessary. By tracking the frogs' limbs during jumping we investigated several possible ways these frogs controlled their jump height.

Dans cette thèse, nous nous intéressons à la plasticité des voies réflexes chez l'homme, induite par l’adaptation du contrôle moteur de la marche suite à une perturbation mécanique. Nous formulons l’hypothèse que cette plasticité, induite dans les voies réflexes, peut être étudiée dans le but de mieux comprendre les mécanismes adaptatifs mis en place par le système nerveux central. Cependant, l’étude des modifications des voies neuronales empruntées par les réflexes exige une analyse à la fois sensible et robuste et une description détaillée de ces réponses, ce que ne permettent pas les approches classiques jusqu’ici utilisées. Dans une première étude présentée dans cette thèse, nous avons développé une méthode robuste de traitement de signal pour identifier et extraire les réflexes cutanés de manière précise et systématique. L’approche proposée est basée sur une analyse unitaire des réflexes, qui implique la détection et la caractérisation de chaque réponse individuelle à la stimulation. Dans l’étude 2, nous avons montré que l’adaptation de la marche à un champ de force impliquait des mécanismes de plasticité pré-motoneurale. Pour approfondir l’étude de ces mécanismes impliqués pendant l’adaptation du contrôle moteur à un champ de force, dans la troisième étude, nous avons analysé les changements réflexes obtenus lors de la stimulation de trois nerfs différents convergeant sur le même pool de motoneurones (Tibial Antérieur). Les résultats de cette étude ont montré que les circuits neuronaux empruntés par chacun de ces trois nerfs se réorganisent de façon spécifique et que cette spécificité est potentiellement due à une réorganisation au niveau des interneurones spinaux, suggérant ainsi que ces derniers constitueraient un site important de la plasticité induite par l’adaptation à un champ de force. Pour tendre vers un contexte réel de réadaptation, nous avons également comparé, dans une 4eme étude, les changements dans les réflexes cutanés après la vibration du corps chez des personnes ayant subit une lésion médullaire et des participants en santé. Les résultats de cette étude ont montré que les changements observés dans les voies réflexes diffèrent chez ces deux populations, mais semblent avoir dans les deux cas, un effet fonctionnellement positif sur la marche.

Effective locomotion and maneuvering in aquatic environments is important for survival for marine fauna. The ability to move quickly, change direction, and tune energy consumption for long migrations is critical for escape from predators and pursuit of prey. This controlled propulsion in terms of varying speed, turning rates, and actuation effort is of interest for the next generation of underwater vehicle design. Integration of biological functional simplicity, robustness, and superior performance enables robotic vehicles to successfully complete difficult and dynamic operational goals. Gelatinous animals known as Cnidarians employ a wide variety of propulsive methods, ranging from the simple but efficient propulsion of large jellyfish to the rapid and highly maneuverable multi-jet propulsion of colonial animals known as siphonophores. This dissertation studies how these two extremes of underwater soft body propulsion are able to achieve simple yet effective control and locomotion, and thus inform the design of effective vehicle propulsion control and actuation. Two large single bell jellyfish robots, Cyro 2 and Cyro 3, were designed and constructed to implement the simple body form and propulsive methods of large jellyfish to study the unique locomotive characteristics and fluid interactions that generate straight swimming and turning maneuvers. The other extreme of small soft-body colonies moving by multi-jet propulsion was subsequently investigated in-depth, starting with a characterization of the biological fluid jetting actions and gaits. The results of these performance capabilities were then applied to an experimental robotic model with bio-inspired construction and controls to verify an elegant but highly functional neurological control scheme and the kinematic capabilities from varying jetting gait patterns. / PHD / The ability to move rapidly in any direction is a primary characteristic of successful animal species. Evasion of predators, as well as pursuit of prey, is paramount for survival. Jellyfish are excellent examples of animals that have thrived for millions of years with varied methods of moving in their diverse environments. However, the propulsion methods of large jellyfish in straight swimming and turning have not been well understood until recent years. This dissertation focuses on the fundamental understanding of the locomotion and fluid interaction that jellyfish use for propulsion. A large jellyfish robot, named Cyro 2 (“Cy” for the species Cyanea, “ro” for robot, and the second generation of the design), was constructed to explore the role of various structural and fluidic parameters on the locomotion characteristics of the largest jellyfish species Cyanea. The successor Cyro 3 was designed to mimic the complex motions of large jellyfish during maneuvering. Motion tracking and fluid analysis of the robot during turning was utilized to explain how jellyfish dynamically control their orientation. These results inspired further study of a unique relative of jellyfish, the siphonophore, which can swim with a modular chain of soft pumping bodies that coordinate without a central nervous system. This unique control strategy and method of movement underwater was studied by analyzing specimens of the siphonophore Nanomia. Development and modeling of elegant control techniques inspired by this species is presented and implemented on an experimental model that uses this unique propulsion method to validate and expand upon observations of live specimens. Combined, the results obtained in this dissertation open the possibility of designing advanced underwater vehicles.

For humans, walking is the principle means of locomotion, or moving from one point to another. While upright locomotion is a human characteristic, the way humans direct their locomotion has not been studied extensively. Prior to the late 1940's, little research or scholarly thought was published regarding locomotion. In 1950, J. J. Gibson published one of the first texts on visual perception, which included theories and research on how humans interpret and react to a world of movement, even as they move within that world. Published research on the topic has been sporadic since then, especially when compared to the volume of work on eye-hand coordination and other eye-brain perception issues. Very little work has been documented on humans moving in a "real world" setting, not laboratory settings or under very specific timing requirements. This study begins by proposing a heuristic framework of human navigation, a description of how humans move from point to point, navigating over and across navigation hazards in the walking path. The heuristic model provides an engineering perspective for the safe design of pedestrian areas, allowing sufficient area for visual recognition of hazards. Two observational studies were performed, one with four different navigation hazards humans come in contact with and the other one with two different hazards that humans pass without contacting. These two classes of hazards involve different perceptual principles. The studies examined the effects of ambient lighting available affected the time required for high attention, fine navigation when approaching a navigation hazard. Specific comparisons between types of navigation hazards were not contemplated, since the perceptual and motor requirements varied considerably among the hazards. Low ambient light levels, representing twilight and night conditions, increase the amount of time required for fine navigation. Analysis of variance (ANOVA) showed a statistically significant difference in the fine navigation time to contact a navigation hazard for stairs travelling down, a 900 turn in the path, and walking downhill with a step midway. ANOVA also showed a significant difference in the fine navigation time to pass a navigation hazard for two different hazards. Under all conditions, post hoc analysis showed Night lighting levels were different from Day lighting levels. Practical applications of this research are in the facilities planning and safety design fields. The individual's locomotion speed combined with the fine navigation time required determines the distance needed for visual recognition of the hazard and preparatory locomotor changes. With extensive research, formalized guidelines and standards can be developed for the safe planning, design and redesign of pedestrian walkways. The human factors engineer could interact knowledgeably with other professional designers to assure that walking paths are designed to meet the human's requirements for safe locomotion. / Master of Science

Approved for public release, distribution is unlimited / This thesis investigates user interfaces for locomotion in virtual environments (VEs). It looks initially at virtual environments and user interfaces, then concentrates on locomotion interfaces, specifically on the Omni-Directional Treadmill (ODT) (Darken and Cockayne, 1997) and a new virtual walking device, LocoX, which was developed at the MOVES Institute, Naval Postgraduate School. It analyzes and compares the ODT and LocoX in terms of the application of human ability requirements (HARs). Afterwards, it compares the results of the analysis of the ODT and LocoX to real-world locomotion. The analysis indicates that LocoX, a new way of exploring virtual environments (VEs), provides a close match to real locomotion on some subtasks in VEs-- compared to the ODT--and produces relatively closer representation on some subtasks of real world locomotion. This thesis concludes that LocoX has great potential and that the locomotion provided is realistic enough to simulate certain kinds of movements inherent to real-world locomotion. LocoX still requires maturation and development, but is nonetheless a viable locomotion technique for VEs and future game-based simulations. / Lieutenant Junior Grade, Turkish Navy

Title: Phylogenetical consequenses of human locomotion realizated during the schoulder girdle Objectives: Description of phylogenetic context of human locomotion realized through the shoulder girdle Methods: Study and analysis of the available literature Analytic-synthetic comparison of the current knowledge of evolution Study of available sources of phylogeny of locomotion in terrestrial vertebrates Results: It was found similarity in the basic control of human bipedal locomotion to control of quadrupedal locomotion of other animals and similarity in the specific form of human locomotion to locomotion of non-human primates Keywords: Bipedal locomotion, quadrupedal locomotion, control of locomotion, interlimb coordination

A diversity of animals move on and bury within dry and wet granular media, such as dry desert sand or rainforest soils. Little is known about the biomechanics and neural control strategies used to move within these complex terrains. Burial and subsurface locomotion provides a particularly interesting behavior in which to study principles of interaction because the entire body becomes surrounded by the granular environment. In this dissertation, we used three model organisms to elucidate control principles of movement within granular substrates: the sand-specialist sandfish lizard which dives into dry sand using limb-ground interactions, and swims subsurface using body undulations; the long-slender shovel-nosed snake which undulates subsurface in dry sand with low slip; and the ocellated skink, a desert generalist which buries into both wet and dry substrates. Using muscle activation measurements we discovered that the sandfish targeted optimal kinematics which maximized forward speed and minimized the mechanical cost of transport. The simplicity of the sandfish body and kinematics coupled with a fluid-like model of the granular media revealed the fundamental mechanism responsible for neuromechanical phase lags, a general timing phenomenon between muscle activation and curvature along the body that has been observed in all undulatory animals that move in a variety of environments. Kinematic experiments revealed that the snake moved subsurface using a similar locomotion strategy as the sandfish, but its long body and low skin friction enabled higher performance (lower slip). The ocellated skink used a different locomotor pattern than observed in the sandfish and snake but that was sufficient for burial into both wet and dry media. Furthermore, the ocellated skink could only reach shallow burial depths in wet compared to dry granular media. We attribute this difference to the higher resistance forces in wet media and hypothesize that the burial efficacy is force-limited. These studies reveal basic locomotor principles of burial and subsurface movement in granular media and demonstrate the impact of environmental interaction in locomotor behavior.

Ce mémoire présente le développement de l’architecture et des algorithmes de commande d’une interface de locomotion utilisant un mécanisme parallèle à câbles. Cette interface de locomotion permet d’améliorer l’expérience de la réalité virtuelle en recréant la topologie du monde virtuel. Tout d’abord, une revue de littérature sur les interfaces de locomotion est présentée. Par la suite, l’architecture globale du système est présentée. Les définitions de base sous-jacentes à la compréhension des algorithmes de commande ainsi que l’analyse cinématique du mécanisme sont ensuite présentées. L’architecture logicielle et les algorithmes de commande sont enfin présentés. Des améliorations au point de vue des mécanismes à câbles sont aussi présentées. Ces améliorations permettent d’améliorer la précision de la commande en position des mécanismes à câbles. Enfin, les résultats présentent l’aboutissement des travaux en montrant le fonctionnement d’un prototype à trois degrés de liberté de l’interface de locomotion réalisé. / Québec Université Laval, Bibliothèque 2019

In this dissertation, we developed predictive models for legged and limbless locomotion on dry, homogeneous granular media. The vertical plane Resistive Force Theory (RFT) for frictional granular fluids accurately predicted the reaction forces on intruders (with complex geometries) translating and rotating at low speeds ( < 0.5 m/s). Using RFT and multibody simulation, we predicted the forward moving speed of legged robots. During the locomotion of lightweight robots and animals where instantaneous limb penetration speed can reach values greater than ~0.5 m/s, a Discrete Element Method (DEM) simulation was developed to capture the limb-ground interaction. We demonstrated that hydrodynamic-like forces generated by accelerated particles can balance the robot weight and inertia, and promote the rapid movement on granular media. Forces from the environment can not only determine locomotion dynamics, but also affect the locomotion strategy. We studied and simulated the limbless locomotion of snakes in a heterogeneous environment and demonstrated how touch sensing was used to adjust the movement pattern. In heterogeneous environments, the long-term locomotion dynamics is also poorly understood. We presented a theory for transport and diffusion in such settings.