Dissertations / Theses on the topic 'Human locomotion'

Arboreal travel for large apes is energetically demanding and risky due to the complexity of the forest canopy. Careful selection of supports is therefore essential for safe and efficient locomotion. This thesis investigates the factors involved in route and support selection in bonobos (Pan paniscus) and in modern human (Homo sapiens) tree climbers. Naturalistically housed bonobos were given a choice of two ropes, one that provided easy access and another that required more demanding postures, with which to access a hard-to-reach food goal. The bonobos selected a rope based on its distance from the goal and its flexibility. Decision making in human tree climbers was investigated using a novel combination of qualitative (participant interviews) and quantitative (observations of behaviour) data. Participants were asked to collect goals from within a tree crown three times each. Interviews revealed that participants either considered risk avoidance or ease/efficiency as the main factor influencing their decisions whilst climbing. Those considering risk took longer to complete each climb, but became quicker after their first climb. These studies demonstrate that the demands of the arboreal environment require knowledge of the functional properties of supports and that memory of specific routes may increase the efficiency of arboreal locomotion.

Includes bibliographical references. The thesis on CD-ROM includes Animate, GaitBib, GaitBook and GaitLab, four quick time movies which focus on the functional understanding of human gait. The CD-ROM is available at the Health Sciences Library.

Human locomotor economy and efficiency are highly variable. This study investigated the role that stature plays in this variation, by evaluating metabolic and respiratory responses to walking and running at speeds set relative to one's stature. Four groups of subjects: male, high V0₂ max (n = 11); male, average V0₂ max (n = 10); female, high V0₂ max (n = 10); and female, average V0₂ max (n = 11) were habituated to treadmill locomotion prior to the measurement of maximal oxygen consumption (V0₂ max). The V0₂ max test entailed 1 km.h⁻¹ increases per min from 3 to 6 km.h⁻¹ walking, and 7 - 17 km.h⁻¹ running then 1% grade increments per min until exhaustion. On each of four other occasions, the subject walked or ran at 6 of a variety of relative speeds - walking at 0.5, 0.7, 0.9, 1.1, 1.3; running at 1.5, 1.7, 1.9 and for selected subjects 2.1, 2.3 and 2.5 statures.s⁻¹ ,and grades - 0%, +3%, -3%. Steady-state respiratory and metabolic responses, and treadmill speed were monitored by an on-line computer system developed for this study. Cadence and RPE were also monitored. All subjects demonstrated an exponential relationship between V0₂ and walking relative speed (st.s⁻¹) (RS) . V0₂ (ml.kg⁻¹.min⁻¹ ) = 4.747 * e(1.371*RS) During running this relationship was essentially linear . The variability of economy at relative speed (9.08%) and absolute speed (9. 01%) did not differ. Male and female subjects did not differ in response to absolute speed but females were more economical at relative speeds (p<0.05). Those with high and average aerobic capacity did not differ in locomotor economy at relative speed. Higher freely-chosen stride length was associated with a higher V0₂ response as velocity increased. The V0₂ of uphill walking was 1.4 times greater than that for downhill walking (running: 1.28 times) . Stride length decreased with increasing speed in uphill locomotion but the reverse was the case for downhill. The economy and efficiency of walking was greater than that of running. Walking economy was maximal between 0.7 and 0.9 st. s⁻¹. Running economy remained essentially unaffected by increased velocity. The setting of locomotor velocity relative to stature does not minimize inter-subject variability in metabolic and respiratory response .

Kyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第18353号
人博第666号
新制||人||160(附属図書館)
25||人博||666(吉田南総合図書館)
31211
京都大学大学院人間・環境学研究科共生人間学専攻
(主査)准教授 神﨑 素樹, 教授 森谷 敏夫, 准教授 久代 恵介, 教授 小田 伸午
学位規則第4条第1項該当

Thesis (M.S.)--George Mason University, 2009.
Vita: p. 29. Thesis director: Zoran Durić. Submitted in partial fulfillment of the requirements for the degree of Master of Science in Computer Science. Title from PDF t.p. (viewed Oct. 11, 2009). Includes bibliographical references (p. 27-28). Also issued in print.

Sensory systems are believed to take advantage of the properties of natural stimuli. Natural images, for example, follow normality and a power-law which are reflected in the dynamics of visual cells. In order to better understand the vestibular system we examined natural human motion. We measured torso and head angular velocities of human subjects who walked, jogged, and climbed a staircase. Angular velocity distributions of the head and torso were fit well by Cauchy distributions, while power spectral densities did not follow a power law. We found that neither a power law nor a two-line-segment fit were sufficient to fit power spectral densities of angular velocity. Increases in power at the gait frequency and its harmonics are not well fit by lines. Differences between torso and head motion show a more evenly distributed reduction of angular velocities, presumably by the neck, in the semicircular canal frame of reference. Coherence between torso and head angular velocity did not show a linear relationship over all frequencies, but did suggest a linear relationship at the fundamental gait frequency and its harmonics. Reduction in angular velocity between the torso and head was then modeled by an adaptive linear filter. Results were mixed and depended on subject, condition, and axis. Qualitatively, predictions of angular velocity were good, capturing both the amplitude and periodicity of the actual head velocity. Finally, initial results were replicated while normalizing gait cycles using linear length normalization. Natural walking and running conditions were compared to treadmill walking and running. Subjects showed significantly different peak velocities during natural and treadmill conditions despite similar movement speeds. Coherence was also different between natural and treadmill conditions. These results provide evidence that natural and treadmill locomotion are treated differently, possibly due to the lack of visual input during treadmill locomotion. Subjects also walked with their heads turned to either the left or right, separating direction of motion and direction of the head. Angular velocity during these conditions show that head direction is not important for stabilizing the head, suggesting that efference copies play a role in head stabilization.

In ambito di ricerca (clinica e sportiva), la necessità di sviluppare un approccio ‘multilaterale’ (qualitativo e quantitativo) che caratterizzi matematicamente la traiettoria tri-dimensionale di una variabile fisica assolutamente importante ma spesso dimenticata, quale il centro di massa corporeo (CMC) (ovvero, il punto immaginario assimilabile al corpo umano in cui si suppone che tutte le masse corporee stiano concentrate), diviene oggi sempre più impellente e quanto mai urgente. Pertanto l’obiettivo di questo dottorato, perseguito tramite un differente utilizzo delle classiche metodologie biomeccaniche, è rappresentare le grandezze cinematiche che descrivono il movimento dei segmenti corporei e del suddetto CMC nel tempo e nello spazio. Per conseguire questo traguardo si sono pensati e realizzati due diversi progetti. Con il primo progetto si sono previsti: a) lo sviluppo di un metodo matematico quantitativo (Serie di Fourier) per descrivere e rappresentare graficamente la traiettoria tri-dimensionale del CMC durante la locomozione su treadmill (la cosiddetta Impronta Digitale Locomotoria, specifica per soggetto/popolazione); b) la caratterizzazione della simmetria nella traiettoria del CMC (il cosiddetto Indice di Simmetria); infine, c) la costituzione di un database di valori normali (coefficienti di equazioni) in un insieme piuttosto esteso di condizioni, al variare di sesso (maschi versus femmine), età (dai 6 ai 65 anni), tipologia di locomozione (marcia versus corsa), velocità e pendenza (piano, salita e discesa). Questo database iniziale rappresenta il parametro principale di riferimento per la locomozione sana. Attraverso questo studio è stato ampiamente dimostrato che la locomozione umana risulta genericamente asimmetrica. Nello specifico: 1) tra maschi e femmine non si sono riscontrate differenze significative; 2) indipendentemente da età e pendenza, le velocità più basse, meno naturali e comuni, sono caratterizzate da pattern di Impronte Digitali Locomotorie più variabili. Viceversa, un aumento di velocità è accoppiato con un progressivo e continuo innalzamento del CMC; 3) l’asimmetria destra e sinistra del passo è molto probabilmente correlata sia con l’anatomia (lunghezza della gamba) che con la predominanza dell’arto; in linea con l’ipotesi iniziale, 4) mediamente, la corsa è più asimmetrica della marcia; infine, 5) i bambini e gli anziani presentano maggiori asimmetrie (marcia e corsa): questo è dovuto alla progressiva maturazione del ciclo del cammino (nei bambini) ed alle caratteristiche muscolari e scheletriche dell’apparato locomotore (negli anziani). Pertanto, attraverso una caratterizzazione matematica della traiettoria tri-dimensionale del CMC, si è potuto: a) quantificare il suo spostamento nel tempo e nello spazio; b) individuare l’Impronta Digitale Locomotoria specifica di sesso, età, tipologia di locomozione, velocità e pendenza. Questo importante traguardo permetterà, in un immediato futuro, la comparazione con la situazione di normalità di condizioni di locomozione compromessa o impedita (ad esempio, bambini con paralisi cerebrale infantile, obesi e amputati). Infine, la stima della principali variabili biomeccaniche è risultata fondamentale sia nel descrivere la meccanica di marcia e corsa che nel caratterizzarne la corrispondente impronta locomotoria. Le nostre misure di tali variabili (semplici e complesse), ottenute con metodo discreto (ciclo per ciclo), con l’impiego di una funzione matematica continua (Serie di Fourier) e con l’applicazione di un’equazione predittiva (misura indiretta), soddisfano completamente ed addirittura ampliano la letteratura già esistente. Nel secondo progetto, partendo da uno studio sulla performance dei cavalli, si è cercato di verificare se esiste una correlazione tra simmetrie corporee (statiche e dinamiche) ed economia nella corsa anche in corridori umani variamente allenati (classificati in tre gruppi sulla base del loro miglior tempo nella maratona). Inoltre: a) si sono sviluppati metodi di analisi bi- e tri-dimensionale delle Risonanze Magnetiche per Immagini (regione pelvica ed arti inferiori), impiegate come riferimento per le simmetrie statiche; b) attraverso sia l’Impronta Digitale Locomotoria che l’Indice di Simmetria si sono caratterizzate le simmetrie dinamiche; infine c) l’economia della corsa è stata espressa attraverso il suo reciproco, ovvero il costo metabolico. L’analisi sia bi- che tri-dimensionale delle immagini ha evidenziato differenze davvero esigue in base al livello di allenamento. Positivamente ed indipendentemente dai corridori, si è dimostrato che ad una maggiore simmetria nella regione del ginocchio corrisponde una maggiore simmetria nella regione della caviglia. Inoltre l’analisi delle simmetrie dinamiche ha permesso di osservare che: 1) il CMC si solleva leggermente in funzione della velocità; 2) le asimmetrie destre e sinistre del passo sono principalmente marcate lungo la direzione di movimento e, contemporaneamente, ridotte lungo la direzione verticale. Esse sono strettamente dipendenti dall’anatomia e dall’arto dominante; 3) diversamente da quanto ci si aspettava, sono state comunque evidenziate solamente poche differenze tra i corridori. Negativamente, l’economia della corsa non mostra differenze significative tra i gruppi testati. Perciò, diversamente dall’ipotesi iniziale, non è stata evidenziata l’esistenza di alcuna relazione tra le simmetrie corporee e l’economia della corsa, quanto piuttosto solo la presenza di una discreta variabilità in simmetria statica e dinamica. Infine, l’analisi di bioenergetica (treadmill versus pista) e biomeccanica (variabili semplici/complesse e variabilità spazio/temporale del CMC) della corsa ha evidenziato la presenza solamente di poche differenze dovute al livello di allenamento dei soggetti studiati.
In both research laboratory and sport/clinical settings, it becomes very important to develop a ‘multilateral approach’ (qualitative and quantitative) to fully describe the individual behaviour of the centre of mass of the human body (BCOM) (i.e. the imaginary specific point at which the body behaves as if its masses were concentrated) over time and space. Consequently, the aim of this doctorate is to describe kinematic variables of the BCOM in varying locomotion conditions. This purpose, focusing on the BCOM as the investigation object fulfilling such a need, has been achieved through a different use of classic biomechanical procedures. In effect, two different studies were carried out. The first project sought: a) to develop a mathematical method (Fourier Series) which could describe and graphically represent each individual (subject or population) gait signature (i.e. Digital Locomotory Signature, a global index of the BCOM dynamics) during locomotion on a treadmill; b) to assess the symmetry (i.e. Symmetry Index) in each movement direction, along the BCOM trajectory, between the two stride phases; finally, c) to build up an initial comprehensive database of ‘healthy values’ (equation coefficients) in a set of different conditions considering gender (males versus females), age (from 6 to 65 years), gait (walking versus running), speed and gradient (level, uphill and downhill). Although only slight gender differences were found, human ‘healthy’ gait is rather asymmetrical. To be precise: 1) the lowest speeds have the most peculiar signature independently of age and gradient: indeed, these speeds are not so completely natural and common. However, if speed increases, the BCOM raises in such a way that its corresponding 3D contour becomes more regular; 2) right and left sides of the stride are quite asymmetrical (i.e. in the forward direction). Globally, this asymmetry is probably related both to anatomy (i.e. leg length) and which hand you use (i.e. right-handedness); 3) on average, the symmetry pattern is slightly lower in running gaits; and as expected, 4) young children and elderly adults are the most asymmetrical subjects, independently of testing conditions: while, during the early stages of life, this global asymmetry could be ascribed to the process of gait development, old age asymmetries are probably due to structural wearing down of the musculoskeletal system. Importantly, the mathematical methodology used here, by analysing even subtle changes in the 3D BCOM trajectory: a) characterizes its displacements over both time and space; b) quantitatively describes the individual gait signature; and c) represents the basis for the evaluation of gait anomaly/pathology (e.g. children with cerebral palsy, obese people and amputees). Finally, knowing the main biomechanical variables becomes fundamental both to fully describe the mechanics of walking and running and to extract and characterize the individual gait signature. In effect, our measurements (discrete method versus continuous mathematical function, and direct versus indirect measurement) of both simple and complex variables wholly confirm, complete and amplify previous literature data. Similarly to what previously demonstrated in horse performances, the second project tried: a) to verify both static anatomical and kinematic functional symmetries as important and relevant indicators of running economy (i.e. the reciprocal of metabolic cost) in humans featuring different running levels (i.e. occasional, skilled and top runners categorized primarily upon their best marathon time); b) to develop imaging based bi- and three-dimensional methods to analyse static symmetries recorded by Magnetic Resonance Imaging (lower limbs and pelvic area); c) to describe the kinematic symmetries defining both the Digital Locomotory Signature and the Symmetry Index; finally, d) to investigate running economy as a performance determinant. In effect, both the 2D/3D analysis of static symmetries highlight very few differences among runners; however, a strong relationship between ankle and knee areas has been underlined in all runners. Furthermore, independently of training ability: as expected, 1) the BCOM raises and lifts slightly as a function of running speed; 2) right and left steps are mostly asymmetrical in the forward direction and symmetrical in the vertical direction (i.e. combined action of gravity and ground reaction force); 3) differently to what was expected, slight differences have been found among runners. On the whole, the asymmetry is probably related both to anatomy and handedness. Other than that, no running economy differences were found. In conclusion, while a relationship between symmetries and running economy has not been found, significant results have however been underlined in each trial (static and dynamic symmetries). Finally, the deep investigation of both bioenergetics (treadmill versus over-ground) and biomechanics (simple/complex variables and spatial/temporal variability of the BCOM) of running has highlights only little (significant) differences among groups.

Made available in DSpace on 2018-08-02T00:02:04Z (GMT). No. of bitstreams: 1 tese_8979_[Cifuentes2015]Thesis20160322-161800.pdf: 19912329 bytes, checksum: 99cc718d614e10d2d6cce22fe9e19124 (MD5) Previous issue date: 2015-06-25
Neurological and age-related diseases affect human mobility at different levels causing partial or total loss of such faculty. There is a significant need to improve safe and efficient ambulation of patients with gait impairments. In this context, walkers present important benefits for human mobility, improving balance and reducing the load on their lower limbs. Most importantly, walkers induce the use of patients residual mobility capacities in different environments. In the field of robotic technologies for gait assistance, a new category of walkers has emerged, integrating robotic technology, electronics and mechanics. Such devices are known as robotic walkers, intelligent walkers or smart walkers One of the specific and important common aspects to the field of assistive technologies and rehabilitation robotics is the intrinsic interaction between the human and the robot. In this thesis, the concept of Human-Robot Interaction (HRI) for human locomotion assistance is explored. This interaction is composed of two interdependent components. On the one hand, the key role of a robot in a Physical HRI (pHRI) is the generation of supplementary forces to empower the human locomotion. This involves a net flux of power between both actors. On the other hand, one of the crucial roles of a Cognitive HRI (cHRI) is to make the human aware of the possibilities of the robot while allowing him to maintain control of the robot at all times. This doctoral thesis presents a new multimodal human-robot interface for testing and validating control strategies applied to a robotic walkers for assisting human mobility and gait rehabilitation. This interface extracts navigation intentions from a novel sensor fusion method that combines: (i) a Laser Range Finder (LRF) sensor to estimate the users legs kinematics, (ii) wearable Inertial Measurement Unit (IMU) sensors to capture the human and robot orientations and (iii) force sensors measure the physical interaction between the humans upper limbs and the robotic walker. Two close control loops were developed to naturally adapt the walker position and to perform body weight support strategies. First, a force interaction controller generates velocity outputs to the walker based on the upper-limbs physical interaction. Second, a inverse kinematic controller keeps the walker within a desired position to the human improving such interaction. The proposed control strategies are suitable for natural human-robot interaction as shown during the experimental validation. Moreover, methods for sensor fusion to estimate the control inputs were presented and validated. In the experimental studies, the parameters estimation was precise and unbiased. It also showed repeatability when speed changes and continuous turns were performed.

Cette thèse a été effectuée dans le cadre du projet européen Koroibot dont l'objectif est le développement d'algorithmes de marche avancés pour les robots humanoïdes. Dans le but de contrôler les robots d'une manière sûre et efficace chez les humains, il est nécessaire de comprendre les règles, les principes et les stratégies de l'homme lors de la locomotion et de les transférer à des robots. L'objectif de cette thèse est d'étudier et d'identifier les stratégies de locomotion humaine et créer des algorithmes qui pourraient être utilisés pour améliorer les capacités du robot. La contribution principale est l'analyse sur les principes de piétons qui guident les stratégies d'évitement des collisions. En particulier, nous observons comment les humains adapter une tâche de locomotion objectif direct quand ils ont à interférer avec un obstacle en mouvement traversant leur chemin. Nous montrons les différences entre la stratégie définie par les humains pour éviter un obstacle non-collaboratif et la stratégie pour éviter un autre être humain, et la façon dont les humains interagissent avec un objet si se déplaçant en manier simil à l'humaine. Deuxièmement, nous présentons un travail effectué en collaboration avec les neuroscientifiques de calcul. Nous proposons une nouvelle approche pour synthétiser réalistes complexes mouvements du robot humanoïde avec des primitives de mouvement. Trajectoires humaines walking-to-grasp ont été enregistrés. L'ensemble des mouvements du corps sont reciblées et proportionnée afin de correspondre à la cinématique de robots humanoïdes. Sur la base de cette base de données des mouvements, nous extrayons les primitives de mouvement. Nous montrons que ces signaux sources peuvent être exprimées sous forme de solutions stables d'un système dynamique autonome, qui peut être considéré comme un système de central pattern generators (CPGs). Sur la base de cette approche, les stratégies réactives walking-to-grasp ont été développés et expérimenté avec succès sur le robot humanoïde HRP-2 au LAAS-CNRS. Dans la troisième partie de la thèse, nous présentons une nouvelle approche du problème de pilotage d'un robot soumis à des contraintes non holonomes par une porte en utilisant l'asservissement visuel. La porte est représentée par deux points de repère situés sur ses supports verticaux. La plan géométric qui a été construit autour de la porte est constituée de faisceaux de hyperboles, des ellipses et des cercles orthogonaux. Nous montrons que cette géométrie peut être mesurée directement dans le plan d'image de la caméra et que la stratégie basée sur la vision présentée peut également être lié à l'homme. Simulation et expériences réalistes sont présentés pour montrer l'efficacité de nos solutions
This thesis has been done within the framework of the European Project Koroibot which aims at developing advanced algorithms to improve the humanoid robots locomotion. It is organized in three parts. With the aim of steering robots in a safe and efficient manner among humans it is required to understand the rules, principles and strategies of human during locomotion and transfer them to robots. The goal of this thesis is to investigate and identify the human locomotion strategies and create algorithms that could be used to improve robot capabilities. A first contribution is the analysis on pedestrian principles which guide collision avoidance strategies. In particular, we observe how humans adapt a goal-direct locomotion task when they have to interfere with a moving obstacle crossing their way. We show differences both in the strategy set by humans to avoid a non-collaborative obstacle with respect to avoid another human, and the way humans interact with an object moving in human-like way. Secondly, we present a work done in collaboration with computational neuroscientists. We propose a new approach to synthetize realistic complex humanoid robot movements with motion primitives. Human walking-to-grasp trajectories have been recorded. The whole body movements are retargeted and scaled in order to match the humanoid robot kinematics. Based on this database of movements, we extract the motion primitives. We prove that these sources signals can be expressed as stable solutions of an autonomous dynamical system, which can be regarded as a system of coupled central pattern generators (CPGs). Based on this approach, reactive walking-to-grasp strategies have been developed and successfully experimented on the humanoid robot HRP at LAAS-CNRS. In the third part of the thesis, we present a new approach to the problem of vision-based steering of robot subject to non-holonomic constrained to pass through a door. The door is represented by two landmarks located on its vertical supports. The planar geometry that has been built around the door consists of bundles of hyperbolae, ellipses, and orthogonal circles. We prove that this geometry can be directly measured in the camera image plane and that the proposed vision-based control strategy can also be related to human. Realistic simulation and experiments are reported to show the effectiveness of our solutions

The future where the industrial shop-floors witness humans and robots working in unison and the domestic households becoming a shared space for both these agents is not very far. The scientific community has been accelerating towards that future by extending their research efforts in human-robot interaction towards human-robot collaboration. It is possible that the anthropomorphic nature of the humanoid robots could deem the most suitable for such collaborations in semi-structured, human-centered environments. Wearable sensing technologies for human agents and efficient human-aware control strategies for the humanoid robot will be key in achieving a seamless human-humanoid collaboration. This is where reliable state estimation strategies become crucial in making sense of the information coming from multiple distributed sensors attached to the human and those on the robot to augment the feedback controllers designed for the humanoid robot to aid their human counterparts. In this context, this thesis investigates the theory of Lie groups for designing state estimation techniques aimed towards humanoid locomotion and human motion estimation. The abstract nature of Lie theory provides a unified approach to handle the three-dimensional machinery and the complex geometry required for modeling free-floating, highly articulated multi-body systems. It enables suitably appropriate methods to perform rigorous calculus over complex nonlinear spaces and to handle the notion of uncertainties in such spaces, which are important for an estimator design. Methods for loosely-coupled and tightly-coupled sensor fusion for floating base estimation of a humanoid robot are presented through the theory of averaging and filtering on Lie groups. The problem of human motion estimation through wearable sensing technologies is tackled through a combination of dynamical systems' theory-based Inverse Kinematics and filtering on Lie groups, demonstrated to be directly applicable also for humanoid state estimation. Experimental validations of the estimators for humanoid base estimation and human motion estimation have been carried out on simulated datasets and datasets collected from real-world experiments conducted on the iCub humanoid robot and Xsens Motion capture technology, respectively.

Thesis (M.S. in Electrical Engineering and M.S. in Systems Engeineering)--Naval Postgraduate School, June 2005.
Thesis Advisor(s): Xiaoping Yun. Includes bibliographical references (p. 93-95). Also available online.

Thesis (M.S. in Modeling, Virtual Environments and Simulation (MOVES))--Naval Postgraduate School, March 2009.
Thesis Advisor(s): Darken, Rudolph. "March 2009." Description based on title screen as viewed on May 6, 2009. Author(s) subject terms: Locomotion, Virtual Walking, Taxonomy, Virtual Environments Includes bibliographical references (p. 101-102). Also available in print.

Les travaux présentés dans cette mémoire visent à développer de nouvelles méthodes qui exploitent les propriétés de cyclostationnarité pour traiter des signaux de force de réaction du sol enregistrées au cours de la marche et la course à pied. Nous nous intéressons à l’analyse de la locomotion humaine dans trois domaines d´études: une étude liée à la pathologie, une deuxième liée directement à l’âge et une troisième relative à la fatigue. En effet, la détection du risque de chute chez les personnes âgées pour fin de prévention contre la chute constitue un enjeu majeur, car cette chute entraine d’une part un nombre de décès important et d’autres part se traduit par un cout élevée de la santé publique. Par ailleurs, l’étude de la fatigue musculaire en particulier pour l’amélioration des performances des sportifs de haut niveau a fait l’objet de nombreux travaux de recherche & développement. La recherche et le développement de nouvelles méthodes et d’indicateurs dans le domaine de traitement de signal dans le but de caractériser la locomotive humaine, permettrait des avancées intéressantes dans les enjeux évoqués ci-dessus. La complexité des signaux GRF est définie par le système neuromusculaire qui génère ce signal. Une meilleure connaissance de ce système nécessite le développement des méthodes de séparation de sources et des outils avancés de traitement du signal pour mieux décrire le système considéré. En effet, nous montrons dans cette thèse que les signaux GRF peuvent être modélisés dans un cadre cyclostationnaire élargi. Les composantes de signal GRF (contribution active et passive) sont séparées par de nouvelles techniques de séparation de sources. Cette modélisation ouvre de nouvelles perspectives pour la décomposition et identification des sources individuelles. D'autre part, on exploite les caractères cyclostationnaire des signaux dans le cadre de la méthode d'analyse en composantes morphologique (MCA). Cet algorithme nous permet de séparer avec succès les composantes d’ordre 1 et d’ordre 2 des signaux considérés. Finalement, nous nous proposons un nouveau modèle utile pour l'étude et la caractérisation de cyclostationnarité. Il présente l'effet de la variation aléatoire de la pente sur le spectre du signal cyclique. Nous appelons ce modèle (modèle cyclostationnaire à pente aléatoire). Nous appliquons ce modèle pour l'étude des signaux biomécaniques où nous considérons la pente comme une mesure spécifique extraite des forces de réaction du sol. Les résultats montrent que la pente et les polynômes à coefficients aléatoires du pic passive peuvent jouer un rôle important et fournir des informations intéressantes concernant la fatigue et concernant la performance de marche et course à pied
The research work presented in this dissertation, involves the development of novel methodologies and methods, for the exploitation of cyclostationarity properties and for the treatment of ground reaction force signals, recorded during walking and running. We are especially interested in the analysis of human locomotion in three fields of interest: a study relating to pathology, a study directly related to age, and a study of muscle fatigue. Indeed, the detection of risk of falling among the elderly for the prevention of falls is of major concern. This is because falling on the one hand leads to a large number of deaths and secondly, resulting in higher costs of public health.Study the muscle fatigue in particular has occupied taken a big share out of this research due to the importance of such events like strenuous level of sports. Research and development of new methods and indicators in the field of signal processing for better characterizing the human locomotion, would allow interesting advances in the aforementioned issues. The complexity of GRF signals is defined by the neuromuscular system which generates this signal. Improved knowledge of this system requires developing source separation methods and advanced signal processing tools to better describe the system under consideration. Indeed, we will endeavor to show in this dissertation that GRF signals can be modeled within an enlarged cyclostationary framework. The GRF signal components (active and passive contribution) are separated by means of new source separation techniques. This modeling opens new perspectives for the decomposition and identification of individual sources. On the other hand, we exploit the cyclostationary characters of signals in the context of Morphological component analysis (MCA) method. Such algorithm enables us to successfully separate the first and second order components of the signals under consideration. Finally, we provide a new model useful for studying and characterizing cyclostationarity. It presents the impact of random slope variation on the cyclic spectrum of the signal. We call this model the random slope modulation (RSM). We apply this model for studying biomechanical signals where we consider the slope as a specic measure extracted from the vertical ground reaction forces. The results show that the slope and polynomial random coefficients of passive peaks can play important role and provide interesting information concerning fatigue and concerning running / walking performance

Muscle and joint force during locomotion is estimated according to available formulations consistent with available methods of solving the indeterminate problem. In the case of the knee joint direct comparisons of results between several optimization methods proposed in the literature presents difficulties due to largely varying model formulation, input data, algorithms and other issues. The application presented here introduces a new optimization program which includes linear and non-linear techniques allowing greater flexibility in problem formulation. It also increases the variety of cost functions under a unified solution which allows for direct evaluation of factors such as optimization criteria and constraints. The method demonstrates that nonlinear solutions lead to more synergistic activity and in contrast to linear formulations, allows antagonistic activity. Nonlinearity also improves concurrence of EMG activity and predicted forces. Higher joint force predictions are resulting as expected from improved predictions of synergistic-antagonistic activity. The formulation allows for relaxation of the requirement that muscles resolve the entire intersegmental moment which in turn maintains muscle synergism in the nonlinear formulation while relieving muscle antagonism and reducing the predicted joint contact force. These methods allow for more possibilities for exploring new optimization formulations and in comparing the solutions to previously reported formulation. The present study based its input data on healthy subjects volunteering for a variety of walking tasks involving normal walking and turning during walking. Muscle and joint contact forces agree with other published results and the lateral: medial bony contact force distribution is calculated as 1: 2.5.

Every movement has a goal. For reaching, the goal is to move the hand to a specific location. For locomotion, however, goals for each step cycle are unclear and veiled by the automatic nature of lower limb control. What mechanical variables does the nervous system "care" about during locomotion? Abundant evidence from the biomechanics literature suggests that the force generated on the ground, or endpoint force, is an important task variable during hopping and running. Hopping and running are called bouncing gaits for the reason that the endpoint force trajectory is like that of bouncing on a pogo stick. In this work, I captured kinematics and kinetics of human bouncing gaits, and tested whether structure in the inherent step-to-step variability is consistent with control of endpoint force. I found that joint torques covary from step to step to stabilize only peak force. When two limbs are used to generate force on the ground at the same time, individual forces of the limbs are not stabilized, but the total peak force is stabilized. Moreover, passive dynamics may be exploited during forward progression. These results suggest that the number of kinetic goals is minimal, and this simple control scheme involves goals for discrete times during the gait cycle. Uncovering biomechanical goals of locomotion provides a functional context for understanding how complex joints, muscles, and neural circuits are coordinated.

The kinematic motor redundancy of the human legs provides more local degrees of freedom than are necessary to achieve low degree of freedom performance variables like leg length and orientation. The purpose of this dissertation is to investigate how the neuromuscular skeletal system simplifies control of a kinematically redundant system to achieve stable locomotion under different conditions. I propose that the neuromuscular skeletal system minimizes step to step variance of leg length and orientation while allowing segment angles to vary within the set of acceptable combinations of angles that achieves the desired leg length and orientation. I find that during human hopping, control of the locomotor system is organized hierarchically such that leg length and orientation are achieved by structuring segment angle variance. I also found that leg length and leg orientation was minimized for a variety of conditions and perturbations, including frequency, constrained foot placement, and different speeds. The results of this study will give valuable information on interjoint compensation strategies used when the locomotor system is perturbed. This work also provides evidence for neuromuscular system strategies in adapting to novel, difficult tasks. This information can be extended to give insight into new and different areas to focus on during gait rehabilitation of humans suffering from motor control deficits in movement and gait.

Thesis (Ph. D.)--University of Oregon, 2006.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 124-134). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (M.S. in Modeling, Virtual Environments and Simulation)--Naval Postgraduate School, March 2005.
Thesis Advisor(s): Rudolph Darken. Includes bibliographical references (p. 59-61). Also available online.

In the past decade and more than any time before, new technologies have been broadly applied in various fields of interaction between human and machine. Despite many functionality studies, yet, how such technologies should be evaluated within the context of human computer interaction research remains unclear. This research aims at proposing a mechanism to evaluate/predict the design of user interfaces with their interacting components. At the first level of analysis, an original concept extracts the usability results of components, such as effectiveness, efficiency, adjusted satisfaction, and overall acceptability, for comparison in the fields of interest. At the second level of analysis, another original concept defines new metrics based on the level of complexity in interactions between input modality and feedback of performing a task, in the field of classical solid mechanics. Having these results, a set of hypotheses is provided to test if some common satisfaction criteria can be predicted from their correlations with the components of performance, complexity, and overall acceptability. In the context of this research, three multimodal applications are implemented and experimentally tested to study the quality of interactions through the proposed hypotheses: a) full-body gestures vs. mouse/keyboard, in a Box game; b) arm/hand gestures vs. three-dimensional haptic controller, in a Slingshot game; and c) hand/finger gestures vs. mouse/keyboard, in a Race game. Their graphical user interfaces are designed to cover some extents of static/dynamic gestures, pulse/continuous touch-based controls, and discrete/analog tasks measured. They are quantified based on a new definition termed index of complexity which represents a concept of effort in the domain of locomotion interaction. Single/compound devices are also defined and studied to evaluate the effect of user’s attention in multi-tasking interactions. The proposed method of investigation for usability is meant to assist human-computer interface developers to reach a proper overall acceptability, performance, and effort-based analyses prior to their final user interface design.

Notre motivation est de comprendre la locomotion humaine pour un meilleur contrôle des systèmes virtuels (robots et mannequins). La locomotion humaine a été étudiée depuis longtemps dans des domaines différents. Nous considérons la locomotion comme le déplacement d'un repère attaché au corps humain (direction et orientation) au lieu de la trajectoire articulaire du corps complet. Notre approche est basée sur le fondement calculatoire de la locomotion humaine. Le but est de trouver un modèle qui explique la forme de la locomotion humaine dans l'espace. Pour ce faire, nous étudions tout d'abord le comportement des trajectoires au sol pendant la locomotion intentionnelle. Quand un humain marche, il met un pied devant l'autre et par conséquence, l'orientation du corps suit la direction tangente de la trajectoire. C'est ce qu'on appelle l'hypothèse de comportement nonholonome. Cependant, dans le cas d'un pas de côté, l'orientation du corps n'est plus semblable à la direction de trajectoire, et l'hypothèse n'est plus valable. Le comportement de la locomotion devient holonome. Le but de la thèse est de distinguer ces deux comportements et de les exploiter en neuroscience, robotique et animation graphique. La première partie de la thèse présente une étude qui permet de déterminer des configurations de comportement holonome par un protocole expérimental et par une fonction qui segmente les comportements nonholonomes et holonomes d'une trajectoire. Dans la deuxième partie, nous établissons un modèle unifiant comportements nonholonomes et holonomes. Ce modèle combine trois vitesses générant la locomotion humaine : tangentielle, angulaire et latérale. Par une approche de commande optimale inverse nous proposons une fonction multi-objectifs qui optimise des trajectoires calculées pour les rendre proches des trajectoires humaines naturelles. La dernière partie est l'application qui utilise les deux comportements pour synthétiser des locomotions humaines dans un environnement d'an imation graphique. Chaque locomotion est caractérisée par trois vitesses et est donc considérée comme un point dans l'espace de commande 3D (de trois vitesses). Nous avons collecté une librairie qui contient des locomotions de vitesses différentes - des points dans l'espace 3D. Ces points sont structurés en un nuage de tétraèdres. Quand une vitesse désirée est donnée, elle est projetée dans l'espace 3D et on trouve le tétraèdre qui la contient. La nouvelle animation est interpolée par quatre locomotions correspondant aux quatre sommets du tétraèdre. On expose plusieurs scénarios d'animations sur un personnage virtuel.

Le travail présenté dans ce mémoire s'inscrit dans les recherches en biomécanique entreprises au sein du L. A. M. I. H. Dans le cadre de la médecine, de l'ergonomie et des transports. Deux voies complémentaires ont été développées. La première consiste à réaliser une modélisation biomécanique modulaire du corps humain, obtenue par une description originale de la structure corporelle et d'un code de calcul auto-adaptatif qui repose sur les lois de la mécanique des systèmes articulés. Cet ensemble fournit aux expérimentateurs des informations qu'ils ne peuvent ni observer ni mesurer: les forces et les couples articules. La seconde conduit tout d'abord à définir une ou plusieurs références du mouvement optimal à partir d'une analyse multi-dimensionnelle des données qui le caractérisent puis a définir une métrique permettant d'évaluer la distance entre un sujet et ces références. Ces distances sont ensuite représentées graphiquement et hiérarchiquement de façon a aider l'expérimentateur a focaliser son analyse sur les variables les plus informatives. Cette double démarche est appliquée à la problématique médicale et tente de résoudre un des problèmes rencontres par les thérapeutes qui travaillent dans le domaine de la rééducation et la réadaptation fonctionnelle: le suivi et l'évaluation de la rééducation de la marche. Enfin dans un cadre plus général, la proposition de la structure et des fonctionnalités d'un atelier dédié à l'analyse, à la simulation et à l'optimisation des mouvements est décrite

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

Cette thèse traite du problème de la locomotion des robots humanoïdes dans le contexte du projet européen KoroiBot. En s'inspirant de l'être humain, l'objectif de ce projet est l'amélioration des capacités des robots humanoïdes à se mouvoir de façon dynamique et polyvalente. Le coeur de l'approche scientifique repose sur l'utilisation du controle optimal, à la fois pour l'identification des couts optimisés par l'être humain et pour leur mise en oeuvre sur les robots des partenaires roboticiens. Cette thèse s'illustre donc par une collaboration à la fois avec des mathématiciens du contrôle et des spécialistes de la modélisation des primitives motrices. Les contributions majeures de cette thèse reposent donc sur la conception de nouveaux algorithmes temps-réel de contrôle pour la locomotion des robots humanoïdes avec nos collégues de l'université d'Heidelberg et leur intégration sur le robot HRP-2. Deux contrôleurs seront présentés, le premier permettant la locomotion multi-contacts avec une connaissance a priori des futures positions des contacts. Le deuxième étant une extension d'un travail réalisé sur de la marche sur sol plat améliorant les performances et ajoutant des fonctionnalitées au précédent algorithme. En collaborant avec des spécialistes du mouvement humain nous avons implementé un contrôleur innovant permettant de suivre des trajectoires cycliques du centre de masse. Nous présenterons aussi un contrôleur corps-complet utilisant, pour le haut du corps, des primitives de mouvements extraites du mouvement humain et pour le bas du corps, un générateur de marche. Les résultats de cette thèse ont été intégrés dans la suite logicielle "Stack-of-Tasks" du LAAS-CNRS
This thesis covers the topic of humanoid robot locomotion in the frame of the European project KoroiBot. The goal of this project is to enhance the ability of humanoid robots to walk in a dynamic and versatile fashion as humans do. Research and innovation studies in KoroiBot rely on optimal control methods both for the identification of cost functions used by human being and for their implementations on robots owned by roboticist partners. Hence, this thesis includes fruitful collaborations with both control mathematicians and experts in motion primitive modeling. The main contributions of this PhD thesis lies in the design of new real time controllers for humanoid robot locomotion with our partners from the University of Heidelberg and their integration on the HRP-2 robot. Two controllers will be shown, one allowing multi-contact locomotion with a prior knowledge of the future contacts. And the second is an extension of a previous work improving performance and providing additional functionalities. In a collaboration with experts in human motion we designed an innovating controller for tracking cyclic trajectories of the center of mass. We also show a whole body controller using upper body movement primitives extracted from human behavior and lower body movement computed by a walking pattern generator. The results of this thesis have been integrated into the LAAS-CNRS "Stack-of-Tasks" software suit

The ability to perform a healthy walking gait can be altered in numerous cases due to gait disorder related pathologies. The latter could lead to partial or complete mobility loss, which affects the patients’ quality of life. Wearable exoskeletons and active prosthetics have been considered as a key component to remedy this mobility loss. The control of such devices knows numerous challenges that are yet to be addressed. As opposed to fixed trajectories control, real-time adaptive reference generation control is likely to provide the wearer with more intent control over the powered device. We propose a novel gait pattern generator for the control of such devices, taking advantage of the inter-joint coordination in the human gait. Our proposed method puts the user in the control loop as it maps the motion of healthy limbs to that of the affected one. To design such control strategy, it is critical to understand the dynamics behind bipedal walking. We begin by studying the simple compass gait walker. We examine the well-known Virtual Constraints method of controlling bipedal robots in the image of the compass gait. In addition, we provide both the mechanical and control design of an affordable research platform for bipedal dynamic walking. We then extend the concept of virtual constraints to human locomotion, where we investigate the accuracy of predicting lower limb joints angular position and velocity from the motion of the other limbs. Data from nine healthy subjects performing specific locomotion tasks were collected and are made available online. A successful prediction of the hip, knee, and ankle joints was achieved in different scenarios. It was also found that the motion of the cane alone has sufficient information to help predict good trajectories for the lower limb in stairs ascent. Better estimates were obtained using additional information from arm joints. We also explored the prediction of knee and ankle trajectories from the motion of the hip joints.

Thesis (M.Phil.)--City University of Hong Kong, 2009.
"Submitted to Department of Computer Science in partial fulfillment of the requirements for the degree of Master of Philosophy." Includes bibliographical references (leaves [152]-163)

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 51).
The biomechanics of lower limb locomotion is a yet unknown mixture of neurological control and physical parameters. The current study explored attaching a rehabilitative anklebot to subjects walking on a treadmill and observed duration, kinematic, and electromyography data to determine the biomechanical response to the asymmetric loading. The present report identified various gait cycle parameters that changed as a response to the asymmetric loading. Notably, significant differences in the stride time of the legs occurred under loading, while contralateral stride times also adjusted to remain equal to those of the loaded legs. Symmetry index analysis led to the conclusion that, while the asymmetric loading of the lower limbs had some effects on temporal gait parameters, the body adjusted to minimize any temporal asymmetry. However, goniometer data demonstrated kinematic changes in response to loading as knee flexion peaked earlier in the gait cycle.
by Wesley D. McDougal.
S.B.

Die Notwendigkeit, sich über unebene, sich ständig verändernde Gelände zu bewegen, gehört zu unserem täglichen Leben. Das zentrale Nervensystem muss daher eine erhöhte Menge an Information integrieren, um mit der Unvorhersehbarkeit äußerer Störungen zurechtkommen zu können. Die Folge dieser erhöhten Beanspruchung könnte eine flexible Kombination der modularen Organisation von Bewegungssteuerung sein. Auf Kosten der Genauigkeit der Bewegung wäre es so möglich, dass das System reagiert, indem es die Robustheit (Fähigkeit mit Fehlern umzugehen) seiner Steuerung erhöht. Jedoch sind die Strategien, die das zentrale Nervensystem zur Organisation der Bewegung verwendet, immer noch schlecht verstanden. Eine Möglichkeit besteht darin, dass Bewegungen zustande kommen durch eine kleine Anzahl linear kombinierter Aktivierungsmuster (Muskelsynergien). Unter den verschiedenen Möglichkeiten der Bewegungsstörung sind das Weglassen von Schuhen und die Verwendung von unebenen Oberflächen zwei gebräuchliche Optionen. In einem ersten Schritt habe ich eine gründliche Analyse der Methoden durchgeführt, die nützlich sind für a) die Auswertung von raumzeitlichen Gangparametern mithilfe von Daten der plantaren Druckverteilung und b) die Extraktion von Muskelsynergien mittels nicht-negativer Matrixfaktorisierung. Anschließend habe ich die modulare Organisation von c) beschut und barfuß Laufen und d) Laufband Gehen und Laufen über ebener und unebener Oberfläche analysiert. Im Vergleich zum gestörten Zustand zeigte das Barfußlaufen eine zeitlichen Verschiebung der zeitabhängigen Muskelaktivierungspatterns (Motor Primitives) und eine Reorganisation der zeitunabhängigen Koeffizienten (Motor Modules). Zusammenfassend, konserviert Fortbewegung über unebener Oberfläche, im Vergleich zu ebener, Motor Modules, während Motor Primitives im Allgemeinen breiter werden. Diese Ergebnisse unterstützen die Idee einer erhöhten Robustheit in der motorischen Kontrolle während der instabilen Fortbewegung.
The need to move over uneven, continuously changing terrains is part of our daily life. Thus, the central nervous system must integrate an augmented amount of information in order to be able to cope with the unpredictability of external disturbances. A consequence of this increased demand might be a flexible recombination of the modular organisation of movement creation and control. At the expense of motion’s accuracy, it is possible that the system responds by increasing its control’s robustness (i.e. ability to cope with errors). However, the strategies employed by the central nervous system to organise movement are still poorly understood. One possibility is that movements are constructed through a small amount of linearly combined patterns of activations, called muscle synergies. Amongst the several possibilities of perturbing locomotion, the removal of footwear and the use of uneven surfaces are two valid options. In a first step, I conducted a thorough analysis of the methodologies useful for a) the evaluation of spatiotemporal gait parameters using plantar pressure distribution data and b) the extraction of muscle synergies using non-negative matrix factorisation. Afterwards, I analysed the modular organisation of c) shod and barefoot running and d) walking and running over an even- and an uneven-surface treadmill. The modular organisation of locomotion, assessed through the extraction of muscle synergies, changed when perturbations were introduced. Compared to the shod condition, barefoot running underwent, mostly due to the different foot strike pattern, a reorganisation of the time-independent coefficients (motor modules) and a time-shift of the time-dependent muscle activation patterns (motor primitives). Uneven-surface locomotion, compared to even-surface, conserved motor modules, while motor primitives were generally wider, confirming the idea of an increased robustness in motor control during unsteady locomotion.

Exoskeletons have the ability to improve locomotor performance for a wide range of individuals: they can improve the economy of normal walking, aid in load carriage for soldiers, assist individuals with walking disabilities, and serve as gait rehabilitation tools. Although it may seem obvious how exoskeletons should be developed to provide a benefit to the user, the complexity of the human neuromuscular system makes developing effective exoskeleton assistance strategies a challenge. Rather than using intuition to guide our attempts at the design and control of ankle exoskeletons, we need to garner a deeper understanding of how ankle exoskeletons affect locomotor coordination and utilize such findings to facilitate effective interaction between the device and the human. This thesis details an iterative approach towards the development of ankle exoskeleton assistance strategies. We first performed a controlled experiment to observe the human response to specific assistance techniques. We then sought to explain the reasons for the observed responses by estimating muscle-tendon mechanics and energetics at the assisted joint using simulations of a musculoskeletal model. Through experimentation and simulation we found that individuals change and adapt their coordination patterns when walking with ankle exoskeletons, often in unexpected ways. Based on these findings, we developed and tested a novel ankle exoskeleton assistance strategy that adjusts exoskeleton behavior online in response to measured changes in the user. Such individualized, adaptive control approaches seem promising for discovering effective exoskeleton assistance strategies. Eventually we want to apply such strategies to populations with gait disabilities, but only once we have a better understanding of the mechanisms driving gait impairments. To that end, we designed and are conducting an experiment to investigate the relationship between features of post-stroke gait and energy economy. We expect our experimental findings to aid in the development of more accurate predictive models of human locomotion and to motivate new methods for developing assistive and rehabilitative techniques using robotic exoskeletons.

The neural control of human locomotion is not fully understood. As current experimental techniques provide only partial and indirect access to the neural control network, our understanding remains fragmentary with large gaps between detectable neural circuits and measurable behavioral data. Neuromechanical simulation studies can help bridging these gaps. By testing a hypothesized controller in neuromechanical simulations, one can evaluate the plausibility of the controller and propose experimental studies which can further investigate the hypothesis. Better understanding the control of human locomotion will change the way we design rehabilitation treatment and engineer assistive devices. This thesis first investigates how much of human locomotion control can be explained by spinal reflexes using neuromechanical simulations. It is known that the spinal control is essential in generating locomotion behaviors in humans, which leads to two central questions: “how does the lower layer controller in the spinal cord generate the motor stimulations?” and “how is this lower layer controller modulated by the higher layer brain control to realize different locomotion tasks?” To investigate these questions, we propose a hierarchical control model with two layers, where the lower-layer control consists of spinal reflexes, and the higher-layer sends a few commands to modulate this lower layer control. In neuromechanical simulations, this model can generate diverse human locomotion behaviors, including walking and running, adapting to slopes and stairs, and changing locomotion directions and speeds. Furthermore, its reactions to a range of unexpected disturbances during normal walking are remarkably similar to those observed in human experiments. The simulation results suggest following answers to the central questions: “the motor stimulations of many human locomotion behaviors can be generated by chains of reflexes” and “different locomotion behaviors can be realized by a reflex-based unified controller that is modulated by the higher-layer control.” The latter part of this thesis presents three studies of using the neuromechanical control model either as a simulation testbed for studying human locomotion or as a robotic controller for legged machines. First, the neuromechanical model is used to study human foot biomechanics. The walking simulations with different foot designs suggest that the windlass mechanism in human feet saves metabolic cost during walking, and this saving does not come from the compliance of the feet, which is one component of this mechanism. Second, the age-related skeletal, muscular, and neural changes are applied to the model to investigate why the metabolic cost increases and the regular walking speed reduces in elderly people. The increase of metabolic cost of the elderly model is mostly attributed to weakened muscles, and we find muscle fatigue as a plausible performance criterion that suggests slower walking speed for the elderly model. In the last study, we adapt the neuromechanical model for a bipedal robot ATRIAS. With the controller, ATRIAS could walk on a rough terrain with unknown height changes of +_20 cm in a sagittal plane physics simulation.

The mechanics of locomotion classically take into account the work done by muscle force to raise and accelerate the body center of mass and to accelerate limbs with respect to it at each step. This last component, named Internal Work (W_INT), considers only the cost to overcome segment inertia, inherently assuming frictionless joints. Thus, the unavoidable damping opposing segmental oscillation due to anatomical structures within or around the pivoting centers has never been measured so far. The frictional coefficient (b, N.m.s.rad-1) of such a biological rotational damper has been here assessed by sampling the time course of passive oscillation (with respect to the vertical axis) of upper and lower limbs and by analyzing its motion. This experiment (straight pendulum) was performed to assess joint energy dissipation during the swing phase of locomotion. A custom mathematical model, leading to a 2nd Order Non-Linear Ordinary Differential Equation, allowed to infer b values for upper (bUU = 0.39 ± 0.08) and lower (bUL = 2.24 ± 0.56 N.m.s.rad-1) limbs in 16 healthy males. Phase planes ensured that no muscle activity was involved. In the same population, the passive swing of a lower limb, behaving as an inverted pendulum after a push (body upside-down), was also sampled while loading the leg as to replicate the compressive stress to which the hip joint is exposed during stance phase. Loads ranged from 0 N (mass of leg only) to 118 N. Damper values (b) for the inverted swing of a loaded lower limb increased with the load and ranged from 4.89 ± 1.29 to 8.92 ± 1.74 N.m.s.rad-1. The influence on locomotion mechanics has been here evaluated. In walking, for instance, each step includes 3 'passively' swinging, unloaded segments (2 upper limbs and the swinging lower limb with joints under tensile stress) and 1 'actively' oscillating, almost fully loaded segment (stance lower limb, joint under compressive stress). The actual experimental results have been combined to provide an estimate of the internal mechanical work due to tissue and joint damping. In walking that is comparable (and should be added) to the estimate obtained by means of a kinematics-based model (Minetti, 1998) and experimental data from the literature of the traditional ‘kinematic’ W_INT. In the discussion, the potential overestimation and underestimation of those two types of internal work are presented, together with the implications of the presented additional work (and its metabolic equivalent) to the energy balance and efficiency of human locomotion.