Stabilité Posturale d’un Exosquelette Actif de Jambes

Vaiyee Huynh 1, 2
2 ReV - Robotique Et Vivant
LS2N - Laboratoire des Sciences du Numérique de Nantes
Abstract : The postural stability (or balance) of leg exoskeletons, no matter their purposes (medical, military or civil), is a real issue since the user is fastened to them. Indeed, in order to respect the will of the user and his movements to the maximum, we have to study the system balance. Therefore, the purpose of this thesis is to develop balance strategies for a leg exoskeleton designed for industrial applications such as static work. It is about assisting the balance of the coupled system { user + exoskeleton } by dealing with the exoskeleton’s balance subjected to the user’s action. We present a balance control which is inspired by control methods developed by CEA-LIST for the Hercule exoskeleton, as well as by human balance strategies. It is mainly based on the instanta- neous capture point concept. This concept is an efficient tool that can be used in both static and dynamic situations. But its most interesting characteristic is that it gives an information about the direction of the movement and this, in turn, helps anticipate some actions like stepping. The first contribution of this thesis is the application of a classical instantaneous capture point control scheme to a leg exoskeleton that assists a user. The user’s intention is first detected through the position of the instantaneous capture point. Then, depending on the location of this point within the support polygon, the assistance provided by the exoskeleton differs : we defined three control modes that goes from a simple weight compensation to a stepping assistance. It means that the exoskeleton adapts its behaviour to the user’s, and we suppose that the user lets himself be guided by the robot. The second contribution focuses on how we can distribute the effort to the legs. The experience of the « Master-Slave » control of CEA-LIST showed that the main difficulty, for a user, is to handle the weight transfer in order to take the swing leg off and make a step. We suggest a new leg distri- bution, based on the instantaneous capture point, that is able to anticipate perturbations or a step. The exoskeleton transfers the load from one leg to the other, thus easing the movement for the user. The last contribution is related to the underactuation of the exoskeleton (not all the joints are moto- rized) in the double support phase. We propose an optimization algorithm that aims at following the desired leg distribution, and at managing the interaction forces between the user and the exoskeleton. Only the leg distribution part was tested on the exoskeleton EMY-Balance of the CEA-LIST which is an underactuated exoskeleton. This allowed to partially validate experimentally the approach proposed in this thesis.
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Vaiyee Huynh. Stabilité Posturale d’un Exosquelette Actif de Jambes. Automatique / Robotique. Ecole Centrale Nantes, Université Bretagne Loire, 2017. Français. ⟨tel-01714461⟩

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