Coupe sagittale | EPFL Graph Search

En anatomie, le plan sagittal, ou plan longitudinal, est un plan anatomique qui divise le corps en parties droite et gauche. Le plan peut être au centre du corps et le diviser en deux moitiés (plan médian) ou loin de la ligne médiane et le diviser en parties inégales (plan para-sagittal). Le terme anatomique sagittal a été inventé au par le traducteur Gérard de Crémone. Notes et références Catégorie:Lexique de l'anatomie

Experimental validation of a bio-inspired controller for dynamic walking with a humanoid robot

Allan Barrea, Luca Colasanto, Auke Ijspeert, Renaud Ronsse, Jesse van den Kieboom, Nicolas Benoît Dominique Van der Noot

Bipedal walking with humanoid robots requires efficient real-time control. Nowadays, most bipedal robots require to ensure local stability at every instant in time, preventing them from achieving the impressive human walking skills. At the same time, bio-inspired walking controllers are emerging, though they are still mostly explored in simulation studies. However, porting these controllers to real hardware is needed to validate their use on real robots, as well as adapting them to face the world non-idealities. Here, we implemented one of them on a real humanoid robot, namely the COMAN, by conducting dynamic walking experiments. More precisely, we used a muscle-reflex model producing efficient and humanlike gaits. Starting from an off-line optimization performed in simulation, we present the controller implementation, focussing on the additional steps required to port it to real hardware. In our experimental results, we highlight some discrepancies between simulation and reality, together with possible controller extensions to fix them. Despite these differences, the real robot still managed to perform dynamic walking. On top of that, its gait exhibited stretched legs and foot roll at some points of the gait, two human walking features hard to achieve with most robot gaits. We present this on a 50 steps walk where the robot was free to move in the sagittal plane while lateral balance was provided by a human operator.

IEEE2015

Balance Control Strategies during Standing in a Locked-Ankle Passive Exoskeleton

Romain Pierre François Baud, Hannes Bleuler, Mohamed Bouri, Jemina Fasola, Tristan Hubert Vouga

This paper investigates sensorimotor adaptation strategies of sagittal postural control in healthy subjects under kinematic constraints. A passive exoskeleton named CAPTUR, with locked ankle joints and legs motion restrained to the sagittal plane is used to restrict and measure participant's movements. The aim is to assess the role of the orientation of the shank and the trunk segments in maintaining the body center of mass above its support base, while the ankle strategy is inhibited. Five young healthy participants were asked to keep standing, while their balance was challenged by live experimental conditions. Participants mainly regulated quiet standing balance by flexing/extending the knees, in order to affect the shank and feet angles, and move the contact patch along the sagittal axis. In this case, the orientation of the trunk segment changes synchronously with the shank angle to keep an upright posture. Responses to more dramatic excursions of the center of pressure are ensured by changing the trunk tilt angle in opposition of phase with the shank angle These observations could be used to implement a bioinspired balance controller for such constrained lower-limb exoskeletons.

IEEE2019

Exploring the Contribution of Proprioceptive Reflexes to Balance Control in Perturbed Standing

Auke Ijspeert, Anne Daniëlle Koelewijn

Humans control balance using different feedback loops involving the vestibular system, the visual system, and proprioception. In this article, we focus on proprioception and explore the contribution of reflexes based on force and length feedback to standing balance. In particular, we address the questions of how much proprioception alone could explain balance control, and whether one modality, force or length feedback, is more important than the other. A sagittal plane neuro-musculoskeletal model was developed with six degrees of freedom and nine muscles in each leg. A controller was designed using proprioceptive reflexes and a dead zone. No feedback control was applied inside the dead zone. Reflexes were active once the center of mass moved outside the dead zone. Controller parameters were found by solving an optimization problem, where effort was minimized while the neuro-musculoskeletal model should remain standing upright on a perturbed platform. The ground was perturbed with random square pulses in the sagittal plane with different amplitudes and durations. The optimization was solved for three controllers: using force and length feedback (base model), using only force feedback, and using only length feedback. Simulations were compared to human data from previous work, where an experiment with the same perturbation signal was performed. The optimized controller yielded a similar posture, since average joint angles were within 5 degrees of the experimental average joint angles. The joint angles of the base model, the length only model, and the force only model correlated weakly (ankle) to moderately with the experimental joint angles. The ankle moment correlated weakly to moderately with the experimental ankle moment, while the hip and knee moment were only weakly correlated, or not at all. The time series of the joint angles showed that the length feedback model was better able to explain the experimental joint angles than the force feedback model. Changes in time delay affected the correlation of the joint angles and joint moments. The objective of effort minimization yielded lower joint moments than in the experiment, suggesting that other objectives are also important in balance control, which cause an increase in effort and thus larger joint moments.

FRONTIERS MEDIA SA2020

Exploring the Contribution of Proprioceptive Reflexes to Balance Control in Perturbed Standing

Auke Ijspeert, Anne Daniëlle Koelewijn

FRONTIERS MEDIA SA2020