Дисертації з теми "Perturbation externe"

Ce travail doctoral poursuivait deux objectifs : D'une part, proposer une triple contribution méthodologique à l'analyse de la coordination motrice. Cette contribution consiste premièrement à analyser la sensibilité des résultats d'une procédure de dynamique inverse à la qualité des données d'entrée anthropométriques et à proposer une recommendation quant à la méthode d'estimation des BSP à utiliser pour déterminer au mieux les moments musculaires nets. Deuxièmement, une évolution d'un modèle biomécanique associant des données périphériques de différente nature (cinématique, anthropométrie, torseur dynamique externe, EMG) dans une procédure d'optimisation numérique et permettant d'estimer les moments développés par les groupes musculaires agoniste et antagoniste de l'articulation du genou est présentée. Les évolutions apportées visent à prendre en compte la baisse de capacit'e de production de force du groupe musculaire dûe à la fatigue en se basant sur une analyse fréquentielle du signal EMG réalisée par une transformée en ondelettes. Troisièmement, une méthode d'estimation des tensions musculaires est développée avec pour objectif une prédiction optimale de l'activité musculaire antagoniste. D'autre part, analyser la coordination musculaire lors d'une tâche de "squat" réalisée en présence d'une perturbation interne ou externe des conditions de réalisation de la tâche. L'ajout d'une charge supplémentaire modifiait les conditions externes de réalisation de la tâche tandis que la présence d'une fatigue musculaire représentait une perturbation interne. Les résultats de l'analyse de la coordination musculaire montrent une exploitation de la redondance musculaire orientée vers la stabilité de l'articulation et la production de mouvements coordonnés. De plus, la gestion de cette redondance en présence de fatigue diffère de celle observée lors de l'ajout d'une charge. Le Système Nerveux Central exploite donc différemment, mais toujours de manière optimale, la redondance musculaire pour faire face à une perturbation.

Le maintien de l’équilibre orthostatique est une activité motrice primordiale parce qu’elle permet de préserver l’autonomie de chaque individu. Les études présentées dans cette thèse traitent comment diverses contraintes influencent les mécanismes de contrôle impliqués lors du maintien de l’équilibre en station debout. Cette thèse a donc pour objectifs de vérifier : (1) Les effets de la fatigue de certains muscles impliqués dans le contrôle du maintien orthostatique. (2) Les effets d’une douleur expérimentale sur les mécanismes de régulation de l’équilibre orthostatique. (3) Les effets d’une perturbation externe pouvant causer une perte d’équilibre. (4) La validité d’un modèle mathématique démontrant l’importance d’une troisième variable nécessaire pour prédire la stabilité en station debout : le temps de développement du moment de force aux chevilles. En conclusion, cette thèse permet d’éclaircir l’implication des mécanismes adaptatifs du système nerveux dans différents contextes. Premièrement, le système nerveux s’adapteraient à la fatigue des triceps suraux en augmentant la fréquence des ajustements posturaux afin d’éviter des déplacements plus excentriques du centre de masse du corps ou en augmentant les propriétés mécaniques des articulations (i.e. la rigidité). Deuxièmement, une stimulation des nocicepteurs altère principalement les processus sensori-moteurs du système de contrôle postural. La détérioration de la stabilité est fonction de la localisation et de l’intensité de la stimulation douloureuse. La perception de la douleur nécessite des ressources attentionnelles qui ne nuisent pas au contrôle du maintien de l’équilibre en station debout. Troisièmement, l’incertitude reliée à l’avènement probable d’une perturbation provoque une altération des processus de contrôle du maintien de l’équilibre dans les situations sans perturbation et avec perturbation. Quatrièmement, le temps de développement du moment de force aux chevilles contraint la capacité d’une personne à retrouver l’équilibre en station debout suite à une déstabilisation vers l’avant. En ajoutant cette variable à un modèle mathématique, celui-ci permet de prédire 73.3 % des chutes et 73.3 % des stabilisations observées expérimentalement.

Chaque année dans le monde on rapporte plusieurs accidents liés aux foules denses. Ces accidents peuvent entraîner des blessures et même des décès dans les cas les plus extrêmes. Les chutes dans les foules denses ont été observées comme l’un des éléments déclencheurs possibles de ces accidents. De telles chutes résultent des difficultés de recouvrement de l’équilibre postural dans ce contexte particulier. Cependant, les connaissances concernant l’équilibre postural dans ce contexte sont très limitées en raison de la nature complexe des environnements liés aux foules denses. Dans cette thèse, nous proposons une approche expérimentale pour étudier le rétablissement d’équilibre postural suite à des perturbations externes dans des environnements de foules humaines avec différents niveaux de densité. En particulier, comme les perturbations peuvent survenir de n’importe quelle direction dans les foules, nous étudions dans un premier temps la réaction d’individus isolés à des perturbations externes provenant de plusieurs directions. Nous proposons ensuite une méthode permettant de prédire les stratégies de recouvrement d’équilibre des participants sur la base d’informations cinématiques uniquement. Des expériences impliquant plusieurs individus sont par la suite étudiées. En particulier, nous avons étudié l’effet de la densité de la foule sur l’initiation et les caractéristiques des pas de récupération d’équilibre. Finalement, un nouveau paradigme expérimental a été proposé pour étudier l’équilibre postural en conditions réelles lors d’événements impliquant des foules denses. Cette approche a ensuite été utilisée au sein de foules durant des concerts de musique punk rock. Les résultats fournissent de nouvelles informations concernant la nature des interactions physiques et les stratégies de récupération d’équilibre utilisées dans ce contexte
Every year, several crowd accidents are reported around the world. These accidents can result in injuries and even fatalities. One of the triggering element of these accidents has been reported to result from falls associated with loss of standing balance in this dense crowd context. However, knowledge regarding human standing balance in dense crowd is very limited due the complex nature of this environment. In this thesis we proposed an experimental approach to study standing balance recovery of individuals following external perturbations in environments with different crowd density. In particular, as perturbation may occur from any direction in dense crowds we first study the reaction to single individuals to external perturbations arising from different directions. Based on the data collected during of this experiment, we were able to propose a method to predict participants’ recovery strategies following external perturbations based on kinematic information. Experiment involving multiple individuals were then considered. In particular, we study the effect of the crowd density on the initiation and the characteristics of recovery steps. Eventually, a novel experimental paradigm was proposed to study standing balance during real crowded events. This approach was then used within punk rock concert crowds. Results provided new insights regarding the physical interactions and recovery strategies observed in this context

Le matériel roulant du RER, MI 79, construit en 1979 pour desservir la ligne B SNCF/RATP reliant Roissy Charles de Gaulle à St-Remy-les-Chevreuse a perturbé, dès sa mise en service, la réception des émissions radiophoniques des riverains. L'exploitation du matériel a provoqué le rayonnement vers l'extérieur d'un niveau de bruit dépassant la norme prescrite par les organismes intéressés (TDF). Une première tentative de parade a consisté à placer une série de condensateurs de filtrage à haute fréquence aux points du circuit juges les plus favorables. Mais, une contrepartie inattendue s'est manifestée, sous forme de perturbations internes à la rame. Ceci a justifié l'engagement du présent travail et a permis d'en définir les objectifs: 1) localiser les sources et les modes de propagation des perturbations électromagnétiques sur les rames, 2) optimiser les valeurs et les emplacements des condensateurs sur une rame, 3) proposer un ensemble de spécifications RATP, en matière de perturbations électromagnétiques auquel devrait satisfaire toute rame avant sa mise en exploitation, le but étant: 1. De limiter le niveau de perturbation a sa source, 2. D'immuniser les circuits sensibles par la mise en œuvre de protections adéquates. La première étape a consisté à caracteriser expérimentalement le niveau et la bande de fréquences des perturbations. Des mesures sur les composants de puissance de la rame ont été nécessaires en vue d'établir les bases d'une simulation numérique de la propagation des perturbations sur la rame. Ensuite, des mesures de perturbations sur la rame ont permis de comparer les résultats théoriques et expérimentaux. La portée de ce travail ne se limite pas à la résolution des problèmes actuels; en effet, il est important d'avancer quelques propositions visant à assurer dès la conception, la compatibilité électromagnétique dans le domaine du matériel ferroviaire, car l'utilisation future des circuits de traitement numérique a microprocesseur ne peut qu'accroitre les difficultés actuelles.

Mechanisms underpinning motor control of standing balance post-stroke remain unclear. Following stroke, ankle plantarflexor muscles demonstrate impairment associated with asymmetrical postural control and decreased balance. Stroke also results in increased attentional demands during challenges to standing balance. This thesis examined motor control impairment post-stroke from medial gastrocnemius motor units to the tri-muscle plantarflexor complex. Investigation of motor, kinematic and kinetic parameters of postural control during external perturbations in standing and associated levels of physiological arousal have furthered understanding of balance impairment post-stroke. Methods: Medial gastrocnemius motor units were recorded in controls (Chapter 2) and people post-stroke (Chapter 3) in standing as perturbations were sequentially applied at the pelvis under conditions of increased anteriorly-directed challenge. In both studies, motor unit firing rate was calculated during dynamic response to perturbation, and maintenance of steady state between perturbations. Joint kinematics, surface electromyography and movements of the centre of pressure were assessed. In Chapter 4, this methodology was expanded to cross-correlation analysis of electromyography activity of the three plantarflexor muscles with anterior-posterior centre of pressure during steady state. In Chapter 5, attentional demands surrounding timing of external perturbation were manipulated to investigate effects of stroke on physiological arousal and postural reactions. Results: In healthy subjects, medial gastrocnemius utilized primarily motor unit recruitment to maintain standing with a modest increase in motor unit firing rate only during the dynamic response to external perturbations. The paretic medial gastrocnemius also primarily used motor unit recruitment; however, lacked firing rate modulation during the dynamic response, albeit firing rate was related to kinematic variables of postural control. In people post-stroke, the three plantarflexors demonstrated asymmetrical motor control of postural sway between-legs but symmetry was improved under conditions of increased challenge to standing balance. Finally, knowledge of timing of perturbations did not decrease the heightened anticipatory postural strategy and level of physiological arousal exhibited post-stroke. Conclusions: This dissertation provides new understanding of motor control of standing balance post-stroke and reveals anticipatory postural strategies adopted post-stroke under conditions challenging balance. These findings implicate the importance of introducing challenge to standing balance post-stroke in the assessment and rehabilitation of postural control post-stroke.
Medicine, Faculty of
Graduate

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Introdução: A manutenção da postura emprega mecanismos de controle preditivos e reativos. Indivíduos com doença de Parkinson (DP) apresentam declínio no controle postural, principalmente na presença de perturbações externas. O uso de informações adicionais sobre a perturbação postural parece ser eficiente para melhorar o controle postural de idosos neurologicamente sadios, porém, na DP ainda é pouco conhecido. Objetivos: a) comparar as respostas dos ajustes posturais preditivos e reativos em idosos neurologicamente sadios (GC) e com DP (Estudo 1); b) verificar o efeito do fornecimento de informações adicionais nos ajustes posturais preditivos e reativos (Estudo 2). Metodologia: Participaram do Estudo 1, 39 (19 com DP e 20 GC) e do Estudo 2, 36 (17 com DP e 19 GC) selecionados na comunidade. Os indivíduos ficaram em pé sobre um equipamento que provocou a perturbação pelo deslocamento da base de suporte com intensidade de 15 cm/s e deslocamento de 5 cm. A perturbação inesperada foi apenas a primeira tentativa e, posteriormente, foram realizadas mais 15 tentativas em que apenas 5 ocorreram a perturbação de maneira imprevisível para análise da habituação à tarefa (Estudo 1). Para o Estudo 2 foram realizadas 20 tentativas com o fornecimento de informações adicionais sobre a perturbação, visual, verbal e somatossensorial do músculo requerido. Os dados EMG e CoP na condição inesperada foram analisados por meio de ANOVA one-way e nas perturbações imprevisíveis (Estudo 1 e 2) por meio de ANOVAs two-way. Resultados: Na perturbação inesperada, os idosos com DP apresentaram maiores valores nos parâmetros da EMG e do CoP em relação ao GC. Na habituação à perturbação, os idosos com DP adaptaram os padrões nos ajustes posturais reativos de forma tardia quando comparados ao GC. Em relação ao efeito das informações adicionais no controle postural, os idosos com DP apresentaram menor oscilação do CoP nos ajustes posturais preditivos em todas as condições de informações quando comparados ao GC. Já o GC aumentou a oscilação do CoP nos ajustes preditivos, considerando as mesmas condições. Nos ajustes posturais reativos, ambos os grupos apresentaram efeitos positivos das informações verbais e somatossensoriais, diminuindo os parâmetros temporais, de amplitude da EMG e espaciais do CoP em relação ás tentativas sem o seu fornecimento ou com o as demais informações (sobre a perturbação e visual). Além disso, os idosos com DP apresentaram controle postural mais adequado quando fornecida informação somatossensorial em relação às demais informações. Por fim, apesar das alterações positivas nos ajustes reativos, os idosos com DP apresentaram maior coativação muscular e tempo para recuperar a posição estável em relação ao GC. Conclusão: Idosos com DP possuem pior controle postural em situações com perturbações externas inesperada e imprevisível, evidenciando alterações temporais, na amplitude da EMG e espaciais do CoP. Além disso, idosos neurologicamente sadios e com DP conseguem alterar os padrões dos ajustes posturais com a exposição de perturbações externas, porém, na DP essa habituação é mais atrasada. As informações adicionais somatossensoriais parecem ter efeito positivo no controle postural dos idosos, principalmente na DP, diminuindo os parâmetros EMG e do CoP nos ajustes preditivos e reativos.
Introduction: Predictive and reactive postural mechanisms are necessary to maintain the posture. Patients with Parkinson's disease (PD) have a decline in postural control, mainly when occur an external perturbation. The use of additional information about the postural perturbation seems to be efficient to improve the postural control of neurotypical older people, but in PD it is still unclear. Aims: a) To compare the predictive and reactive postural adjustments responses in the neurotypical older people (CG) and the PD patients (Study 1); b) To verify the effect of additional information on predictive and reactive postural adjustments (Study 2). Methods: Participated thirty-nine (19 with PD and 20 GC) in the Study 1 and 36 (17 with PD and 19 GC) in the Study 2, selected in the community. The individuals stood on equipment that caused the perturbation by the displacement of the support base with the velocity of 15 cm/s and the range of 5 cm. The unexpected perturbation was the first trial, and 15 trials were realized in which in just 5 occurred the unpredictably perturbation to analyze the habituation to the task (Study 1). In the Study 2, 20 trail were realized with the additional information about the perturbation characteristics, visual, verbal, and somatosensory of the required muscle. The EMG and CoP data in the unexpected condition were analyzed by ANOVA one-way and in the unpredictable perturbations (Study 1 and 2) by the ANOVAs two-way. Results: In the unexpected perturbation, the PD patients presented higher temporal, range of EMG and spatial of CoP in relation to the CG. For the habituation to the perturbation, the patients with PD adapted the patterns in the reactive postural adjustments of delayed form when compared to the GC. In relation to the effect of the additional information on postural control, the PD patients presented lower CoP oscillation in the predictive postural adjustments in all the information conditions when compared to the CG. The GC increased the CoP oscillation in the predictive adjustments, considering the same information conditions. Both groups presented positive effects of verbal and somatosensory information in the reactive postural adjustments, decreasing temporal, range of EMG and spatial parameters of CoP in relation to trial without the information or with other information (about perturbation and visual). In addition, the PD patients presented more adequate postural control when somatosensory information was provided in relation to the other information. Finally, despite of the improvement in the reactive adjustments, patients with PD have a greater muscular coactivation and time to recover the stable position in relation to the CG. Conclusion: Patients with PD have worse postural control in situations with unexpected and unpredictable external perturbation, evidencing changes in the temporal, range of EMG and spatial of CoP parameters. In addition, neurotypical older people and PD patients can change the patterns of postural adjustments with the exposure of external perturbation, but in PD this habituation is more delayed. Besides that, somatosensory information seems to have a positive effect on the postural control of the older people, mainly in the PD, decreasing the EMG and CoP parameters in the predictive and reactive postural adjustments.
FAPESP: 2016/00503-0
CNPq: 159381/2015-0

In this project we have used Fourier transform infrared spectroscopy to study the photoresponse of two different types of quantum dot-in-a-well infrared photodetectors (DWELL QDIPs). The basic task was to compare the photoresponse of these two detectors, and to study the influence of external resonant laser pumping on the photoresponse. Series of measurements were done at 77K. In the first measurements we investigated the photoresponse for different applied voltages at 77K.

In a second run of experiments, we used a 1064 nm infrared semiconductor laser to resonantly

pump the fundamental transition of the quantum dots. The results show that by using this

additional illumination the photoresponse was dramatically increased by creating additional

charge carriers in the quantum dots. This could be used to increase the sensitivity of infrared

detectors based on QDs.

On considère l'évolution adiabatique des états vitreux sous perturbations extérieures. Bien que le formalisme que nous utilisons soit très général, nous nous concentrons ici sur les sphères dures en dimension infinie où une analyse exacte est possible. Nous considérons perturbations de la frontière, notamment compression ou cisaillement simple et nous calculons la réponse des états vitreux à ces perturbations : pression et contrainte de cisaillement. Nous constatons un dépassement des deux quantités avant que l'état vitreux ne devienne instable à un point spinodal, où il fond dans le liquide (ou cède). Nous estimons également la limite d'élasticité du verre. Enfin, nous étudions la stabilité des bassins vitreux vers la rupture en sous-bassins, correspondant à une transition de Gardner. Nous constatons que près de la transition dynamique, les verres subissent une transition de Gardner après une perturbation infinitésimale. Nous étudions ensuite le régime de haute pression et haut cisaillement au-delà de la transition de Gardner
We consider the adiabatic evolution of glassy states under external perturbations. Although the formalism we use is very general, we focus here on infinite-dimensional hard spheres where an exact analysis is possible. We consider perturbations of the boundary, i. e. compression or (volume preserving) shear-strain, and we compute the response of glassy states to such perturbations: pressure and shear-stress. We find that both quantities over shoot before the glass state becomes unstable at a spinodal point where it melts into a liquid (or yields). We also estimate the yield stress of the glass. Finally, we study the stability of the glass basins towards breaking into sub-basins, corresponding to a Gardner transition. We find that close to the dynamical transition, glasses undergo a Gardner transition after an infinitesimal perturbation. We then study the high-pressure and high-strain regime beyond the Gardner transition

L'usage intensif de composants complexes comme les microprocesseurs dans des automatismes, permet aujourd'hui de realiser des systemes compacts et puissants. Cependant, on sait peu de choses sur le comportement de tels systemes lorsqu'ils sont immerges dans un environnement electromagnetique. Du fait de leurs complexites, l'origine des dysfonctionnements dont ils sont l'objet peuvent etre difficile a localiser voire impossible. Compte tenu de la complexite des microprocesseurs, il n'est pas envisageable de leur etendre les modeles electromagnetiques determiner pour les composants de base que sont la diode, le transistor bipolaire et le transistor a effet de champ. Cette these propose une approche experimentale pour l'etude de la susceptibilite electromagnetique d'un microprocesseur. Elle est axee sur la comprehension des mecanismes d'erreurs sur les informations (adresses/donnees) echangees par un microprocesseur et une memoire externe; et ce suite a l'impact d'une perturbation electromagnetique. Pour tester la susceptibilite du microprocesseur, nous avons opte pour une approche harmonique bien que la majorite des perturbations soient de type transitoire; ceci parce qu'il n'existe aucune correlation temporelle entre l'instant d'apparition de la perturbation et celui de validation des adresses et/ou des donnees. Essentiellement deux types de perturbations ont ete etudiees: 1) la perturbation par injection de courant; 2) la perturbation par injection de tension. Cette etude a montre que l'origine des erreurs, sur les adresses et les donnees en injection de tension, est essentiellement liee a la perturbation des etats statiques. Alors qu'en injection de courant, les erreurs obtenues sur l'adresse peuvent, sous certaines conditions, etre etroitement liees a la valeur initiale de la tension sur l'etat haute impedance ayant precede l'apparition de l'adresse. La quasi-totalite des erreurs observees, tant sur les adresses que sur les donnees, sont de type fugitives. Il est par consequent necessaire de determiner leur evolution (probabilite d'apparition) en fonction de l'amplitude et de la frequence d'un perturbateur donne. Une etude statistique sur un nombre important de sequences adresse-donnee a montre qu'en presence d'une perturbation en injection de tension, par exemple, et pour des composants de technologie cmos, les erreurs sur les donnees apparaissent avant celles sur les adresses; et ce bien que ces informations se succedent sur le bus multiplexe du microprocesseur.

Thesis (Ph. D.)--Georgia State University, 2007.
Title from thesis title screen. Author's name from thesis title screen. Jerry C. Smith, committee chair; Kathryn Grant, Stuart Allison, committee members. Electronic text (148 p. : ill. (some col.)) : digital PDF file. Description based on contents viewed October 5, 2007. Includes bibliographical references (p. 124-148).

The molecular basis of the potent transdermal enhancement activity of a series of iminosulfuranes, structure provided where X = H, Cl, Br, and I, is being investigated skin models. It has been shown (J. Lipid Res. 46(2005), 2192-2201.) that correlations exist between the activity of the aforementioned transdermal penetration enhancers (TPE) and the extent to which these agents bind to DMPC vesicles and perturb the gel to liquid crystal phase transition measured by calorimetry. The degree to which the perturbation of these compounds extends into the bilayer interior in contrast to surface activity is unclear. To gain insight into this issue, the 31P NMR resonance from DMPC and DMPC-cholesterol unilamellar vesicles have been split by the slowly penetrating paramagnetic metal ion Pr+3. The extent to which this perturbation is attenuated by transdermal penetration enhancers has been investigated as a function of Pr+3 exposure time and iminosulfurane concentration. The effect of these iminosulfuranes on bilayer integrity is also being explored by monitoring the induced release of carboxyfluorescein from DMPC and DMPC- cholesterol unilamellar vesicles.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
With advancing age, the human body suffers morphological and functional changes, which lead the postural instability in elderly people. And an important factor in this, are linked to the inappropriate uses of postural adjustments strategies: anticipatory postural adjustment (APA) and compensatory postural adjustments (CPA). Such strategies deal with an ability to respond effectively to a possible loss of balance and minimize the negative consequences of it. Although the difficulties in maintaining balance in the elderly to be known, strategies of postural adjustment, in the face of external perturbations are still scarce. Therefore, the aim of this study was to investigate the APAs and CPAs and their inter-relationships in groups of elderly with and without falls. For this purpose, two groups of 20 elderly participants (with and without history of falls) and 20 young subjects received external perturbations of posture in the frontal plane, through the impact of a pendulum on the right shoulder of the individuals in the standing position, under two conditions: unpredictable and predictetable. The electromyography activity (EMG) of lateral ventral and dorsal postural muscles by recording and integrated (∫EMG) in the typical windows for these strategies, and displacement of body center of pressure (COP). The postural disturbance occurred in the medial-lateral direction, through the impact of a pendulum on the right shoulder of individuals under two conditions: unpredictable and predictable. The results showed the elderly groups (with and without falls) had, in general, smaller amplitude activation (∫EMG) of the CPAs to the dorsal and lateral studied in the unpredictable conditions. The elderly showed changes in the pattern of synergistic lateral muscles compared to the group of young individuals. There was a greater COP displacement in the predictable condition provided for groups of elderly patients with falls compared to the young. The results of this study indicate that the decrease in muscle activity in the elderly groups against disturbances of posture, especially the lateral muscles, may leave these individuals susceptible to falls. Therefore, research and training programs/training or treatment designed to restoring balance in the elderly by improving the activation of the lateral muscles must be developed.
Com o avançar da idade, o corpo humano sofre alterações morfológicas e funcionais, que acarretam grande instabilidade postural em idosos. E um fator importante desta, esta vinculada ao uso inadequado das estratégias de ajustes posturais: o ajuste postural antecipatório (APA) e compensatório (APC). Essas estratégias tratam da capacidade de um indivíduo em responder efetivamente a uma possível perda de equilíbrio. Embora, a dificuldade na manutenção do equilíbrio em idosos seja conhecida, estudos sobre as estratégias de ajuste postural frente a perturbações externas da postura nessa população ainda são escassos. Portanto, o objetivo desse estudo foi investigar os APAs e CPAs e suas inter-relações em idosos com e sem quedas. Para tanto, dois grupos de 20 idosos cada (sem e com histórico de quedas) e 20 indivíduos jovens receberam perturbações externas da postura no plano frontal, através do impacto de um pêndulo no ombro direito dos indivíduos na posição em pé, sob condições não prevista e prevista. As atividades eletromiográficas dos músculos posturais laterais, ventrais e dorsais foram registradas e integradas (∫EMG) nas janelas de tempo típicas para as estratégias de ajuste postural assim como o deslocamento do centro de pressão corporal (COP). De forma geral, os dois grupos de idosos apresentaram, menor amplitude de ativação (∫EMG) muscular nas janelas dos APCs para os músculos laterais e dorsais na condição não prevista. Idosos também apresentaram alteração no padrão sinérgico dos músculos laterais quando comparados ao grupo de indivíduos jovens. Houve um maior deslocamento do COP na condição prevista para os grupos de idosos com quedas quando comparados aos jovens. Os resultados desse estudo indicam que a diminuição da atividade muscular nos grupos de idosos frente a perturbações da postura, especialmente dos músculos laterais, podem deixar esses indivíduos suscetíveis a quedas. Portanto, investigações e programas de treinamento/tratamento que visam treinar ou restabelecer o equilíbrio em idosos melhorando a ativação dos músculos laterais devem ser desenvolvidos.

E objeto digital es la tesis de Misael Maguiña en version PDF
Se estudio la dinámica de interacción de solitones perturbados de la ecuación no lineal de Shrödinguer (nonlinear Schrödinger equation-NLSE), basado en la aproximación adiabática de los parámetros de la solución perturbada. La dinámica de un solitón se estudia aplicado dos perturbaciones: la primera con tasa de crecimiento y decrecimiento, la segunda con el potencial de oscilador armónico. En el primer caso de perturbación la amplitud del solitón encontrada varia exponencialmente, en el segundo caso la solución muestra un comportamiento oscilatorio. También se estudia a la dinámica de interacción para dos solitones y las fuerzas entre ellos. Sin perturbación la interacción de dos solitones en fase es atractiva y puede resultarse en formación de un estado ligado, esta solución tiene comportamiento periódico con oscilaciones de la amplitud y velocidad de solitones. Fuera de fase la interacción de solitones es repulsiva, no formando un estado ligado. El potencial de oscilación armónica mantiene los solitones confinados dentro del potencial y evoca su interacción periódica.\\ En la investigaci\'{o}n encontramos la solución analítica del problema de interacción de solitones de la NLSE en los sistemas con pérdidas o ganancias distribuidas. Los resultados analíticos proporcionan un excelente control cualitativo y cuantitativo de los resultados de las simulaciones numéricas conocidas hasta ahora. El resultado no trivial y inesperado consiste en el hecho de que la separación relativa de solitones dependen de las ganancias o pérdidas de amplificación. Al utilizar la interacción complementaria entre los experimentos informáticos directos y la teoría generalizada de perturbación del solitón adiabático de Karpman-Solov'ev, encontramos fórmulas empíricas notables que describen completamente, cualitativamente y cuantitativamente, el impacto de las pérdidas distribuidas y la ganancia en los escenarios de interacción de los solitones del NLSE.
PNPC, CONACYT

Le sulfure de dimethyle (dms), produit par le plancton dans l'eau de mer, est emis dans l'atmosphere. Il y est alors soumis a l'attaque d'oxydants et ses produits d'oxydation participent a la formation de noyaux de condensation qui peuvent influencer le nombre et la taille des gouttelettes nuageuses, ayant ainsi une repercussion sur le climat. Ce travail s'est articule autour de deux campagnes de mesures : l'une dans la rade de toulon ou un cycle annuel de concentrations dans l'eau et de divers facteurs biologiques a ete etudie. L'autre dans le golfe du lion ou ces mesures dans l'eau ont ete accompagnees de mesures de dms dans l'air et de caracterisation chimique des aerosols. Les principaux resultats sont les suivants : un milieu separe du plein ocean par une jetee artificielle engendre une biomasse phytoplanctonique, des concentrations de chlorophylle et de dms dans l'eau augmentees. Aucune correlation n'a ete obtenue entre la chlorophylle et le dms. Les concentrations de dms sont moindres lorsqu'on s'eloigne des cotes. Le flux de dms calcule d'apres 4 parametrisations differentes a montre que les valeurs de flux obtenues sont dans l'ordre de grandeur des flux rencontres dans d'autres zones mais que l'incertitude sur ce flux reste importante. Les variations journalieres de dms atmospherique sont, dans le cas d'advection d'air continental aux caracteristiques anthropiques marquees, inversees par rapport a ce qui est habituellement rencontre en zone purement marine. Dans ce cas l'oxydation nocturne (supposee due au radical no 3) gouverne le cycle journalier du dms. Les sulfates en exces mesures sont essentiellement anthropiques, comme le prouve le faible rapport msa/nsss, et l'absence de correlation entre ces deux composes. L'acide sulfurique et le msa condensent sur les particules pre-existantes nombreuses en zone cotiere et semblent donc participer a leur croissance plutot qu'a nucleer.

Il progressivo invecchiamento della popolazione sta sempre più sottolineando la necessità di un’accurata comprensione del tema delle cadute. Ancora oggi per gli anziani esse rappresentano una delle maggior cause di comorbidità e morte. Il traporto pubblico è un’importante risorsa di inclusione sociale e autonomia personale per la popolazione anziana, tuttavia esso comporta anche una maggiore esposizione al rischio di caduta. Le donne, notoriamente più esposte al rischio di caduta rispetto la controparte maschile, risultano maggiormente colpite da questi incidenti. Il contributo delle nuove tipologie di allenamento “pertubation-based” potrebbero essere una valida soluzione per il miglioramento dei tempi e modalità di risposta del soggetto a perturbazioni esterne che possono comportare una perdita di equilibrio. Il presente studio ha incluso 36 donne suddivise in giovani e anziane con lo scopo di descriverne differenze e caratteristiche nella risposta reattiva quando esposte a perturbazioni esterne, come quelle che possono riscontrarsi sui mezzi pubblici. I risultati hanno evidenziato le potenzialità e i limiti dei protocolli di allenamento che fanno uso di “treadmill perturbativi”, e costituiscono un vero e proprio studio di fattibilità di questi nuovi metodi per la prevenzione delle cadute.

Cette thèse traite de l'identification des paramètres du point de vue de l'optimisation et du contrôle de suivi distribué des systèmes multi-agents d'ordre fractionnaire (FOMASs) en tenant compte des retards, des perturbations externes, de la non-linéarité inhérente, des incertitudes des paramètres et de l'hétérogénéité dans le cadre d'une topologie de communication fixe non dirigée / dirigée. Plusieurs contrôleurs efficaces sont conçus pour réaliser avec succès le contrôle de suivi distribué des FOMASs dans différentes conditions. Plusieurs types d'algorithmes d'optimisation de l'intelligence artificielle et leurs versions modifiées sont appliquées pour identifier les paramètres inconnus des FOMASs avec une grande précision, une convergence rapide et une grande robustesse. Il est à noter que cette thèse fournit un lien prometteur entre la technique d'intelligence artificielle et le contrôle distribué
This thesis deals with the parameter identification from the viewpoint of optimization and distributed tracking control of fractional-order multi-agent systems (FOMASs) considering time delays, external disturbances, inherent nonlinearity, parameters uncertainties, and heterogeneity under fixed undirected/directed communication topology. Several efficient controllers are designed to achieve the distributed tracking control of FOMASs successfully under different conditions. Several kinds of artificial intelligence optimization algorithms andtheir modified versions are applied to identify the unknown parameters of the FOMASs with high accuracy, fast convergence and strong robustness. It should be noted that this thesis provides a promising link between the artificial intelligence technique and distributed control

Диссертация на соискание ученой степени кандидата технических наук по специальности 05.13.03 – системы и процессы управления. – Национальный технический университет "Харьковский политехнический институт", Харьков – 2016. Диссертация посвящена разработке аналоговых и цифровых инвариантных систем наведения и стабилизации основного вооружения танков на основе создания математических моделей возмущенного движения танковой пушки относительно оси цапф и танковой башни с пушкой относительно оси поворота, а также имитационных моделей внешних возмущений, действующих на основное вооружение в каналах вертикального и горизонтального наведения. Показано, что повышение степени инвариантности замкнутой системы стабилизации к действию внешних возмущений, за счет объединения в стабилизаторе двух основных принципов управления – принципа управления по отклонению и принципа управления по возмущению, приводит к снижению запаса устойчивости замкнутой системы. Для сохранения требуемого запаса устойчивости предложено введение в систему дополнительного контура обратной связи по угловому ускорению объекта стабилизации. С использованием метода гармонической линеаризации нелинейностей решена задача отыскания амплитуд и частот автоколебаний рамок гироскопической платформы, используемой в качестве гироскопического датчика углов отклонения оси канала ствола танковой пушки от линии прицеливания, а также автоколебаний давления рабочей жидкости в гидросистеме стабилизатора канала вертикального наведения. Показано, что причиной возмущения автоколебаний в первом случае является нелинейная характеристика системы разгрузки гироплатформы и "сухое" трение в осях кардановых подвесов, а во втором случае – нелинейные характеристики предохранителей гидроклапанов. Сделан вывод о том, что такие автоколебания являются высокочастотной помехой, приводящей к снижению помехозащищенности замкнутой системы наведения и стабилизации. Рассмотрены особенности цифровой инвариантной системы стабилизации наведения и стабилизации танковой пушки, в частности, необходимость использование цифровых низкочастотных фильтров Баттеруорта и Ланцоша для фильтрации высокочастотных помех выходных сигналов датчиков. Доказано, что при построении цифрового стабилизатора танковой пушки целесообразно последовательно-параллельное использование цифровых фильтров Баттеруорта и Ланцоша. Разработана структура и осуществлен выбор варьируемых констант алгоритмов стабилизации, обеспечивающих инвариантность замкнутой системы наведения и стабилизации без существенного снижения её запаса устойчивости. Моделирование процессов наведения и стабилизации в замкнутой системе с последующим анализом этих процессов позволяет сделать вывод о значительном повышении точности отработки внешнего возмущения (в 1.8 – 1.9 раз) по сравнению со штатной.
The thesis for the degree of candidate of technical sciences, specialty 05.13.03 – Systems and management processes. – National Technical University "Kharkov Polytechnic Institute", Kharkov – 2016. The thesis is dedicated to development analog and digital invariant guidance systems and stabilize the main armament of tanks through the creation of mathematical models perturbed motion tank gun relative to the axis of the pins and the tank tur ret gun relative to the axis of rotation, as well as simulation models of external disturbances acting on the main armament channels vertical and horizontal guidance. It is shown that increasing the degree of invariance closed stabilization system to external perturbations lead to lower stability margin closed system. To maintain the desired stability margin suggested the introduction of the system of additional feedback path for the angular acceleration of the object of stabilization. The features invariant digital stabilization system tank gun, including the need to use a digital low-pass filter Batteruorta and Lanczos filtering high frequency noise output signals of sensors. It is proved that the construction of a digital stabilizer tank cannon appropriate series-parallel use of digital filters Batteruorta and Lanczos. The structure created and the choice of variable constants stabilization algorithms was made that provide an invariance closed system of guidance and stabilization without significantly reducing its stability margin. Modeling of guidance and stabilization in a closed system with subsequent analysis of these processes suggests a significant increase in accuracy working off of external perturbation (at 1.8 – 1.9 times) compared with the standard.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.13.03 – системи і процеси керування. – Національний технічний університет "Харківський політехнічний інститут", Харків, – 2016. Дисертація присвячена розробці аналогових і цифрових інваріантних систем наведення і стабілізації основного озброєння танків на основі створення математичних моделей збуреного руху танкової гармати відносно вісі цапф і танкової башти з гарматою відносно вісі повороту, а також імітаційних моделей зовнішніх збурень, що діють на основне озброєння в каналах вертикального і горизонтального наведення. Показано, що підвищення ступеня інваріантності замкненої системи стабілізації до дії зовнішніх збурень приводить до зниження запасу стійкості замкненої системи. Для збереження потрібного запасу стійкості запропоновано введення до системи додаткового контуру зворотнього зв'язку за кутовим прискоренням об'єкту стабілізації. Розглянуті особливості цифрової інваріантної системи стабілізації танкової гармати, зокрема необхідність використання цифрових низькочастотних фільтрів Баттеруорта і Ланцоша для фільтрації високочастотних завад вихідних сигналів датчиків. Доведено, що при побудові цифрового стабілізатора танкової гармати доцільне послідовно-паралельне використання цифрових фільтрів Баттеруорта і Ланцоша. Розроблена структура і здійснений вибір варійованих констант алгоритмів стабілізації, які забезпечують інваріантність замкненої системи наведення і стабілізації без суттєвого зниження її запасу стійкості. Моделювання процесів наведення і стабілізації в замкненій системі з подальшим аналізом цих процесів дозволяє зробити висновок про значне підвищення точності відробки зовнішнього збурення (в 1.8 – 1.9 рази) у порівнянні зі штатною.
The thesis for the degree of candidate of technical sciences, specialty 05.13.03 – Systems and management processes. – National Technical University "Kharkov Polytechnic Institute", Kharkov – 2016. The thesis is dedicated to development analog and digital invariant guidance systems and stabilize the main armament of tanks through the creation of mathematical models perturbed motion tank gun relative to the axis of the pins and the tank tur ret gun relative to the axis of rotation, as well as simulation models of external disturbances acting on the main armament channels vertical and horizontal guidance. It is shown that increasing the degree of invariance closed stabilization system to external perturbations lead to lower stability margin closed system. To maintain the desired stability margin suggested the introduction of the system of additional feedback path for the angular acceleration of the object of stabilization. The features invariant digital stabilization system tank gun, including the need to use a digital low-pass filter Batteruorta and Lanczos filtering high frequency noise output signals of sensors. It is proved that the construction of a digital stabilizer tank cannon appropriate series-parallel use of digital filters Batteruorta and Lanczos. The structure created and the choice of variable constants stabilization algorithms was made that provide an invariance closed system of guidance and stabilization without significantly reducing its stability margin. Modeling of guidance and stabilization in a closed system with subsequent analysis of these processes suggests a significant increase in accuracy working off of external perturbation (at 1.8 – 1.9 times) compared with the standard.

Le but de ce travail est de proposer des mécanismes pour les drones multirotors qui permettent d'une part de tolérer des fautes sur le drone, et d'autre part de prendre en compte les effets du vent en extérieur. Les fautes visées comportent des fautes d'actionneurs, de capteurs, mais également des fautes logicielles sur les algorithmes de fusion de données. Dans nos travaux, nous avons développé un contrôleur robuste et un observateur des perturbations extérieures capables de coopérer avec la méthode de reconfiguration des commandes, pour tolérer de façon simultanée les défaillances de moteurs et les perturbations extérieures du vent par des techniques de tolérance aux fautes active. Egalement, nous avons proposé une nouvelle technique de tolérance aux fautes des actionneurs pour un drone octorotor coaxial. Cette technique est basée sur une loi de commande robuste avec des gains reconfigurables "self tuning sliding mode control (STSMC)", où les gains de contrôle sont réajustés en fonction de l'erreur détectée afin de maintenir la stabilité du système. Des expériences à l'intérieur ont été menées pour montrer et comparer notre solution avec deux autres techniques de tolérances aux fautes. L'efficacité et le comportement de chaque méthode ont été étudiés après des injections de fautes successives dans les actionneurs. Les principaux avantages et inconvénients de chaque méthode sont déduits en analysant les résultats obtenus. En outre, nous proposons une approche pour la tolérance aux fautes des capteurs et mécanismes logiciels de fusion de données du drone. Cette approche est basée sur la redondance des capteurs et la diversification des composants logiciels
The aim of this work is to propose mechanisms for multirotor drones that allow, on the one hand, to tolerate faults on the drone, and on the other hand to take into account the effects of the wind outdoors. The faults targeted include fault in actuators, sensors, but also software faults on the data fusion algorithms. ln our work, we have developed a robust controller and an exterior disturbance observer capable of cooperating with th, contrai reconfiguration method, to simultaneously tolerate motor failures and exterior wind disturbances through active fault tolerance techniques… We have also proposed a new technique for tolerating actuator faults for a coaxial octorotor drone. This technique is based on a robust command law with reconfigurable "self tuning sliding mode control (STSMC)" gains, where the control gains are readjusted according to the detected error in order to maintain the stability of the system. lndoor experiments are conducted to show and compare our solution with two other fault tolerance techniques. The efficiency and behavior of each method are studied after successive fault injections into the actuators. The main advantages and disadvantages of each method are deduced by analyzing the results obtained. Additionally, we provide an approach for fault tolerance of drone data fusion sensors and software mechanisms. This approach is based on the redundancy of sensors and the diversification of software components

Робота виконана на кафедрі аерокосмічних систем управління Національного авіаційного університету Міністерства освіти і науки України та у Публічному акціонерному товаристві «Науково-виробниче об’єднання «Київський завод автоматики».
Дисертаційна робота присвячена науковому обґрунтуванню та розробці алгоритмів компенсації внутрішніх похибок та зовнішніх збурень у Коріолісовому вібраційному гіроскопі, а також удосконаленню його складових частин (резонатора, чутливого елементу). Автором розроблено методику та обладнання для робочого місця безелектродного вимірювання динамічних параметрів металевого резонатора після його виготовлення, розроблено конструкцію приладдя для приклеювання п’єзоелектродів до резонатора нової конструкції, методику та обладнання робочого місця для балансування мас. Розроблено та відпрацьовано на експериментальному зразку КВГ методики температурної корекції фаз сигналів квадратури та кутової швидкості, багатопараметричної корекції дрейфу нуля і масштабного коефіцієнту, що призводить до збільшення точності виміру кутової швидкості в умовах дії температурних градієнтів.
In the thesis the following new scientific results are obtained: 1. For the first time, a multi-parameter method of CVG scale factor correction is developed and implemented, which can be used during the CVG operation in the rate and in the differential modes. Ukraine patent have been obtained for this method. 2. Scientifically grounded analysis of a new design of a cylindrical resonator with holes on the walls of a cylinder having higher vibration resistance was first developed and carried out. 3. The multiparameter bias correction algorithm has been developed and implemented, which has advantages over the existing ones by accuracy. 4. For the first time experimental researches were carried out on a manufactured experimental sample of CVG with developed metal cylindrical resonator made of elenvar elloy, which showed high accuracy scale factor and bias drift correction under the action of temperature gradient, as well as high shockvibration resistance of the sample. The practical significance of thesis results are: − comparison of two designs of metallic cylindrical resonators with holes on the bottom and on the wall of the cylinder and by calculations and computer simulation the advantages of the second design over the first one in the part of shock resistance have been substantiated; − аn analysis of the different geometries of the holes has been made. Their influence on the resonant oscillation frequencies of a cylindrical resonator is revealed. Recommendations for the geometry of the resonator and its elements have been developed; − improved design of the base on which the newly designed resonator with holes on the wall of the cylinder is installed; − the choice of electrodes used for oscillation excitation and measurement of the signals is experimentally substantiated; − the technique and equipment for workplace electrodeless measurement of metallic resonator dynamic parameters after its manufacture have been developed; − the influence of frequency mismatch, wave angle and positioning errors of the electrodes on the CVG bias and scale coefficient have been evaluated; − a new accessory design has been developed to attach the electrodes to the new resonator design; − the technique and equipment of the workplace for balancing the mass of the resonator on the fourth harmonic of the unbalance to reduce its frequency mismatch have been developed. The technique was tested in the manufactured ample of CVG; − the technique of measuring the angles of non-orthogonality of the sensitive axis to its mounting surface has been developed and implemented in the experimental sample of CVG; − the use of CVG to improve the accuracy of armament stabilization was analyzed; − improved CVG standing wave control algorithm block diagram, which provides a fast start of the gyroscope when it is turned on at any temperature in the range of operating temperatures; − the techniques for temperature correction of quadrature and angular rate phases, multiparameter correction of CVG bias and scale factor have been developed and tested on experimental sample of CVG, which leads to an increase in the accuracy of measuring angular rate under temperature gradients; − the experimental results showed that the CVG with a metallic resonator is resistant to multiple shocks with amplitude 100 g and its bias is slightly dependent on the shock amplitude and does not exceed 5×10−3 deg/s. The bias sensitivity to vibration perturbations is 2.5×10−3 deg/s/g.
Диссертация посвящена научному обоснованию и разработке алгоритмов компенсации внутренних погрешностей и внешних возмущений в Кориолисового вибрационном гироскопе, а также совершенствованию его составных частей (резонатора, чувствительного элемента). Автором разработана методика и оборудование для рабочего места безэлектродного измерения динамических параметров металлического резонатора после его изготовления, разработана конструкция приспособления для приклеивания пьезоэлектродов к резонатору новой конструкции, методику и оборудование рабочего места для балансировки масс резонатора. Разработано и отработано на экспериментальном образце КВГ методики температурной коррекции фаз сигналов квадратуры и угловой скорости, многопараметрической коррекции дрейфа нуля и масштабного коэффициента, что приводит к увеличению точности измерения угловой скорости в условиях действия температурных градиентов.

碩士
淡江大學
資訊工程研究所
83
There are two kinds of grasping analyses in robotics researches: find the grasping force distribution among the fingers when given the contact points as well as find the points of contact when given the shape of the object. Each kind of problems is associated with optimality and stability analysis. In this paper, we start from analyzing the stability and optimality aspects of the grasping analysis under external perturbations and find a guantitative measurement that could evaluate the performance of different grasping configurations when grasping a given object. This property actually determines which grasping configuration is better hence give a solution to the two kinds of grasping analysis problems. We proof some rotation and displacement geometry model to derive a formula that describes the change of equilibrium grasping forces under the influence of external forces. Using this formula, we present a new concept, called the force mapping closure, that plays the central role of stability analysis. A minimum finger grasping force required for a non-slip contact under given external perturbation can be determined using the force mapping closure curve. Hence a method against any external perturbations is developed to construct a stable grasp. An optimal grasp can be guaranteed using the method we discussed if the external perturbations is not exceed some threshold value. In the paper, the planar cases and spatial cases is discussed, respectively, and a example of three-fingered planar grasp is provided.

博士
國立清華大學
光電工程研究所
102
In the dissertation, stability analysis and four-wave mixing (FWM) analysis are applied to investigate the characteristics of the relaxation oscillation of the quantum dot (QD) and the quantum well (QW) semiconductor lasers and their responses to the weak external perturbation, respectively. The FWM analysis can also be utilized to extract the intrinsic parameters of the semiconductor lasers, which apparently influence the dynamical behaviors. Through the modifications of strong external perturbations on the intrinsic parameters, the dynamical behaviors of the lasers can be investigated thoroughly. The linear stability analysis has been applied on the solitary and injection-locked lasers of QD and QW structures. By deriving the characteristic equations from the small internal fluctuations, the relaxation frequencies and the damping rate can be obtained. From the damping rates of the lasers with different bias currents, linewidth enhancement factors, injection strengths, and detuning frequencies, the QD lasers show better stability than the QW lasers. Moreover, the stability and excitability of the QD laser subject to optical feedback are also numerically discussed. To investigate the responses on small external perturbations in the FWM analysis, the rate equations of the solitary and injection-locked lasers of QD and QW structures are derived for the analytical solutions. Moreover, the FWM mixing analysis on the QD lasers subject to optical feedback is also derived. All the analytical models are carefully verified with the numerical simulations. FWM analysis has been applied on a QD laser to simultaneously obtain the linewidth enhancement factor and other intrinsic laser parameters. By fitting the experimentally obtained regenerative and amplitude modulation spectra at different detuning frequencies with the respective curves analytically calculated from the rate equations, parameters including the linewidth enhancement factor, the carrier decay rate in the dots, the differential gain, and the photon decay rate can be determined simultaneously under the same operating conditions. The sensitivity and accuracy of the parameter extracted by the FWM analysis are presented. Moreover, how each parameter alters the shapes of the regenerative and amplitude modulation spectra is also discussed. Moreover, a simplified rate equation model is utilized for the FWM analysis on QD lasers subject to optical injection. The regenerative and amplitude modulation spectra of the QD laser with different intrinsic laser parameters and external injection conditions are investigated. By curve fitting the regenerative and amplitude modulation spectra experimentally, the intrinsic laser parameters of a commercial single-mode QD laser under different injection conditions are extracted. The linewidth enhancement factor at different injection levels and detuning frequencies are shown, where a reduction of about 40% from its free-running value is demonstrated. By increasing the injection strength, the linewidth enhancement factor can be further reduced to minimize the chirp in optical communications. To comprehensively investigate the characteristics of QD laser subject to external perturbations, the model for the FWM analysis on the QD laser subject to optical feedback is also developed analytically. The modifications with different feedback conditions on the regenerative and amplitude modulation spectra are discussed. Also, how the regenerative and amplitude modulation spectra vary with each intrinsic parameter is discussed. Based on the theoretical prediction, we successfully extract the intrinsic parameters of the QD laser subject to optical feedback experimentally and the linewidth enhancement factor is found to increase with optical feedback.

Balance is critical for human posture control when standing upright and during cyclic locomotor tasks such as walking or running, as well as for acyclic tasks such as gait initiation or complex sport movements. In the course of evolution, Homo sapiens developed an upright posture for bipedalism, thus freeing the upper limbs (arms) to interact with objects. Human upright stance is characterized by two straight legs and the center of mass (COM) is located above the hip, thus maximizing potential energy (due to high COM position) enabling great maneuverability for fast re-orientation of the body axis and re-direction of movement direction in space. Nevertheless, bipedalism is mechanically much more challenging (e.g. regarding stability) compared to other body morphologies in legged animals such as a quadrupedal leg configuration. This evolutionary innovation does not only provide benefits (such as those mentioned above), but also makes control functions difficult, which might involve instability of the whole mechanical system with segments arranged like an upside-down chain. To achieve the stable upright human stance and to prevent collapse, it is fundamental to continuously balance all segments above the feet by introducing appropriate joint torques and continuously adjusting the orientation of the ground reaction forces (GRF). Nevertheless, human motor control during tasks such as standing and walking provides stability in the case of external perturbations. Thus, humans are able to respond to external perturbations, such as changing ground level, different ground properties as well as pushes and pulls at different body regions, in order to keep their balance and maintain an upright posture. Given the current biomechanical understanding of human balance and posture control, it is still not well understood which neuro-muscular control mechanisms contribute to maintaining balance in response to external perturbations. In particular, it is not clear, how the contributions to recover from perturbations are organized at different levels, e.g. muscle mechanical response, spinal reflexes, and higher control contributions (e.g. from cortical areas in the brain). The present work focuses on improving this understanding by investigating human movement and posture control in response to different external perturbations. This thesis describes how healthy humans respond to unexpected external perturbations and identifies underlying neuro-muscular mechanisms enabling the motor system to cope with such challenges during locomotion and upright standing through passive and active strategies (e.g. tendon and muscles response, changed muscle activation). The first part of the thesis presents previous research results in a systematic review thus providing insights into how leg function responds to external perturbations in selected motion tasks. It is shown that humans adjust their movements not only to the environmental context (e.g. when walking on even ground vs. slopes or climbing stairs) but also dependent on the state of their motion (i.e. current phase of gait, COM position) and in relation to the type of perturbation like changes in ground or external forces. In the following part of the thesis, human standing experiments were designed to address the ability to cope with external perturbations with respect to axial and rotational leg function. Axial leg function described forces and displacements along the leg axis, pointing from the contact point of the foot to the COM. In contrast, rotational leg function described corresponding forces and displacements perpendicular to leg axis in sagittal plane. As predicted by biomechanical leg models, the results show that biarticular muscles strongly contribute to the redirection of the GRF in order to maintain an upright posture. In a second experimental study on human hopping, the ability to adapt leg stiffness (representing the axial leg function) in order to maintain cyclic movements in response to vertical ground level perturbations was investigated. The findings demonstrate a robust leg function, reflecting the ability of the human neuro-muscular system to cope with unexpected perturbations such as moving ground during hopping. An increase in leg stiffness was found in response to an upward surface acceleration. This thesis describes and analyses the ability of the human body to respond to external perturbations leading to robust movement patterns. By translating the observed coping strategies into biomechanical and motor control models, new approaches for the design and control of legged systems (e.g. for assistive and rehabilitation devices) can be derived.