Équilibre statique (physiologie)

Chez l'humain, l'équilibre statique dépend des réactions d’équilibre et des réactions de protection, et implique une interaction complexe entre les systèmes vestibulaire, proprioceptif, visuel et moteur. Description Dans le développement de l’enfant, l’acquisition de cette habileté favorise l’émergence de la station debout et d’autres habiletés motrices de haut niveau. On parle d’équilibre dynamique lorsqu’il s’agit de maintenir son équilibre en étant en mouvement alors que l’équilibre statique consiste à maintenir son équilibre tout en restant immobile. L’équilibre statique est sollicité plusieurs fois dans la journée d’une personne, et ce, de manière inconsciente. Par exemple, il permet de se tenir en position assise ou debout sans bouger à travers des tâches comme couper des légumes pour une préparation de repas, prendre une douche, écouter en classe Evaluation L’équilibre statique peut être évalué par des ergothérapeutes, psychomotri

Postural Control and Consciousness and Their Applications to Lower-Limb Exoskeletons

Jemina Fasola

Human postural control requires high coordination and is distributed over the whole musculoskeletal and nervous systems. Hence, postural balance can be impaired due to various pathologies. Efficient rehabilitation programs and technological solutions are therefore needed to alleviate the burden due to the risk of falls and lack of mobility. In this thesis, I have sought for solutions to improve postural balance with two different approaches. One approach is based on the application of neuroscience principles, while the other relies on engineering. With the emergence of exergames for balance training, it is essential to understand how the central nervous system integrates augmented visual feedback. Research in motor learning has demonstrated the need of experiencing errors to adapt to the environment and learn new skills. Hence, studies have proposed to visually amplify trajectory errors to promote learning. As this strategy demonstrated promising results for upper limb rehabilitation, I investigated whether visual error augmentation promotes motor adaptation during a balance task. Based on the observer model, I also investigated whether there is a link between sensorimotor learning and a conscious experience of movements known as the sense of agency. Our results suggest that visual error augmentation may promote balance learning and that the optimal gain may be influenced by the sense of agency. Moreover, our results illustrate that humans monitor their actions in an effector-independent manner. Although motor learning is different from neurorehabilitation, these studies help to understand cognitive components of motor learning that are of scientific and clinical relevance. Patients with severe balance deficits need engineering solutions to stand up and walk. We developed a lower-limb exoskeleton, called TWIICE, with the goal to give back autonomy to people with a complete spinal cord injury. Most exoskeletons require that the user manages balance while walking or standing with the help of crutches. To facilitate the interaction with the environment while standing, we developed the first postural controllers enabling patients with complete paraplegia to stand in a low-actuator count exoskeleton without the need for crutches. This could have important implications for the independence of individuals with paraplegia, their inclusion in social activities and their potential inclination to use an exoskeleton on a daily basis for the associated health benefits.

EPFL2020

Biologically inspired kinematic synergies enable linear balance control of a humanoid robot

Auke Ijspeert

Despite many efforts, balance control of humanoid robots in the presence of unforeseen external or internal forces has remained an unsolved problem. The difficulty of this problem is a consequence of the high dimensionality of the action space of a humanoid robot, due to its large number of degrees of freedom (joints), and of non-linearities in its kinematic chains. Biped biological organisms face similar difficulties, but have nevertheless solved this problem. Experimental data reveal that many biological organisms reduce the high dimensionality of their action space by generating movements through linear superposition of a rather small number of stereotypical combinations of simultaneous movements of many joints, to which we refer as kinematic synergies in this paper. We show that by constructing two suitable non-linear kinematic synergies for the lower part of the body of a humanoid robot, balance control can in fact be reduced to a linear control problem, at least in the case of relatively slow movements. We demonstrate for a variety of tasks that the humanoid robot HOAP-2 acquires through this approach the capability to balance dynamically against unforeseen disturbances that may arise from external forces or from manipulating unknown loads.

2011

Biologically Inspired Kinematic Synergies Provide a New Paradigm for Balance Control of Humanoid Robots

Auke Ijspeert

Nature has developed methods for controlling the movements of organisms with many degrees of freedom which differ strongly from existing approaches for balance control in humanoid robots: Biological organisms employ kinematic synergies that simultaneously engage many joints, and which are apparently designed in such a way that their superposition is approximately linear. We show in this article that this control strategy can in principle also be applied to balance control of humanoid robots. In contrast to existing approaches, this control strategy reduces the need to carry out complex computations in real time (replacing the iterated solution of quadratic optimization problems by a simple linear controller), and it does not require knowledge of a dynamic model of the robot. Therefore it can handle unforeseen changes in the dynamics of the robot that may for example arise from wind or other external forces. We demonstrate the feasibility of this novel approach to humanoid balance control through simulations of the humanoid robot HOAP-2 for tasks that require balance control on a randomly moving surfboard.

2007

Postural Control and Consciousness and Their Applications to Lower-Limb Exoskeletons

Jemina Fasola

EPFL2020