Papers by Yannick Aoustin
IFAC-PapersOnLine, Jul 1, 2017
The control of the interaction between a robot and the environment is very important in the medic... more The control of the interaction between a robot and the environment is very important in the medical area. The control of this interaction can be realized with either a force control, which does not need human intervention, or co-manipulation, where the human operator moves the robot himself. This paper focuses on a simple hybrid external control scheme allowing these two applications by modelling the robot as a rigid structure interacting with the environment thanks to a spring representing the force sensor. Simulations were used to test the control system. Several experiments prove the accuracy of the control, for a one degree of freedom robot.
La locomotion des robots humanoides est essentielle pour le developpement de nouveaux systemes de... more La locomotion des robots humanoides est essentielle pour le developpement de nouveaux systemes de transport. Elle doit satisfaire des contraintes de moindre consommation d’energie afin d’accroitre l’autonomie energetique, et de respect des conditions de contact unilateral. Il faut aussi assurer la stabilite orbitale de la marche malgre les perturbations telles que les incertitudes de modele, les irregularites du sol, ou les interactions avec l’environnement. Pour rejeter ces perturbations, nous considerons des strategies de commande qui sont associees a la definition des mouvements de reference. Quelques strategies de commande de base et des elements d’analyse de la stabilite orbitale d’une marche cyclique de robots bipedes planaires et 3D sont presentes dans cet article.
Lecture Notes in Computer Science, 2023
HAL (Le Centre pour la Communication Scientifique Directe), May 6, 2019
This paper describes a sequential decomposition algorithm for single channel intramuscular electr... more This paper describes a sequential decomposition algorithm for single channel intramuscular electromyography (iEMG) generated by a varying number of active motor neurons. As in previous work, we establish a Hidden Markov Model of iEMG, in which each motor neuron spike train is modeled as a renewal process with inter-spike intervals following a discrete Weibull law and motor unit action potentials are modeled as impulse responses of linear time-invariant systems with known prior. We then expand this model by introducing an activation vector associated to the state vector of the Hidden Markov Model. This activation vector represents recruitment/derecruitment of motor units and is estimated together with the state vector using Bayesian filtering. Non-stationarity of the model parameters is addressed by means of a sliding window approach, thus making the algorithm adaptive to variations in contraction force and motor unit action potential waveforms. The algorithm was validated using simulated and experimental iEMG signals with varying number of active motor units. The experimental signals were acquired from the tibialis anterior and abductor digiti minimi muscles by fine wire and needle electrodes. The decomposition accuracy in both simulated and experimental signals exceeded 90% and the recruitment/derecruitment was successfully tracked by the algorithm. Because of its parallel structure, this algorithm can be efficiently accelerated, which lays the basis for its future real-time applications in human-machine interfaces, e.g. for prosthetic control.
In this paper, optimal cyclic reference trajectories are designed for three walking gaits of a qu... more In this paper, optimal cyclic reference trajectories are designed for three walking gaits of a quadruped robot, the curvet, the amble, the trot, taking into account the actuators characteristics and for a given motion robot velocity. The objectives of this study are multiple: • Automatic design of admissible reference trajectories, • Definition of the maximal speed of the robot for given actuators, • Study of the evolution of the torque cost for various motion velocities, • Comparison of three different gaits with respect to a sthenic criterion. For the gaits studied, during some phases the system is underactuated. The design of the cyclic gaits takes this fact into account. The optimization problem is solved with an algebraic optimization technique. The actuated joint evolution is chosen as a polynomial function of time. The coefficients of the polynomial functions are optimization parameters. The evolution of the passive joint is defined using the dynamic model to have admissible trajectory. During the optimization process, the constraints on the ground reactions, the validity of impact, the torques, the joints velocities of the robot are taken into account. Simulation results are presented for the three gaits. All motions are realistics. Curvet is the less efficient gait with respect to the criterion studied. For slow motion, trot is the more efficient gait. But amble permits the fastest motion with the same actuators.
HAL (Le Centre pour la Communication Scientifique Directe), 2018
HAL (Le Centre pour la Communication Scientifique Directe), 2017
Mechanisms and machine science, 2016
Underactuated robotic hands are becoming popular in complex robotic designs where mass and size a... more Underactuated robotic hands are becoming popular in complex robotic designs where mass and size are yet limited. Such designs require a tradeoff between versatility and simplicity. This is the case for prosthetic robotic hands, which need to imitate the human hand both in functionality and dimensions as closely as possible to achieve a natural feeling solution for the patient. This paper presents the initial mechanical analysis of the design of an anthropomorphic hand with 15 degrees of freedom using six electric motor actuators. A transmission system of cables and pulleys is used as the underactuated mechanism in order to propagate the motor torque over the three joints of each finger, and springs are used to provide the passive return actuation. The design has been validated according to its ability to stably grasp different cylindrical objects. The stability of the grasp has been judged according to the criterion of positive or zero contact forces being present at all points of contact between the hand and the object in a static case. A simulation of the grasping procedure where the contact forces are modeled over time has been developed in Matlab®. It has been shown that the design process requires iterative steps, as multiple factors such as spring stiffness, pulley radii, and motor torques will affect the stability of grasping of the hand and its effectiveness as a prosthetic device.
HAL (Le Centre pour la Communication Scientifique Directe), Jan 10, 2022
Real-time intramuscular electromyography (iEMG) decomposition, as an identification procedure of ... more Real-time intramuscular electromyography (iEMG) decomposition, as an identification procedure of individual motor neuron (MN) discharge timings from a streaming iEMG recording, has the potential to be used in human-machine interfacing. However, for these applications, the decomposition accuracy and speed of current approaches need to be improved. Methods: In our previous work, a real-time decomposition algorithm based on a Hidden Markov Model of EMG, using GPUimplemented Bayesian filter to estimate the spike trains of motor units (MU) and their action potentials (MUAPs), was proposed. In this paper, a substantially extended version of this algorithm that boosts the accuracy while maintaining real-time implementation, is introduced. Specifically, multiple heuristics that aim at resolving the problems leading to performance degradation, are applied to the original model. In addition, the recursive maximum likelihood (RML) estimator previously used to estimate the statistical parameters of the spike trains, is replaced by a linear regression (LR) estimator, which is computationally more efficient, in order to ensure real-time decomposition with the new heuristics. Results: The algorithm was validated using twenty-one experimental iEMG signals acquired from the tibialis anterior muscle of five subjects by fine wire electrodes. All signals were decomposed in real time. The decomposition accuracy depended on the level of muscle activation and was >90% when less than 10 MUs were identified, substantially exceeding previous real-time results. Conclusion: Single channel iEMG signals can be very accurately decomposed in real time with the proposed algorithm. Significance: The proposed highly accurate algorithm for singlechannel iEMG decomposition has the potential of providing neural information on motor tasks for human interfacing.
HAL (Le Centre pour la Communication Scientifique Directe), 2017
Robotikusu, Mekatoronikusu Koenkai koen gaiyoshu, 2007
IEEE robotics and automation letters, Jul 1, 2018
Robotics and Autonomous Systems, Feb 1, 2018
This paper seeks insight into stabilization mechanisms for periodic walking gaits in 3D bipedal r... more This paper seeks insight into stabilization mechanisms for periodic walking gaits in 3D bipedal robots. Based on this insight, a control strategy based on virtual constraints, which imposes coordination between joints rather than a temporal evolution, will be proposed for achieving asymptotic convergence toward a periodic motion. For planar bipeds with one degree of underactuation, it is known that a vertical displacement of the center of mass-with downward velocity at the step transitioninduces stability of a walking gait. This paper concerns the qualitative extension of this type of property to 3D walking with two degrees of underactuation. It is shown that a condition on the position of the center of mass in the horizontal plane at the transition between steps induces synchronization between the motions in the sagittal and frontal planes. A combination of the conditions for self-synchronization and vertical oscillations leads to stable gaits. The algorithm for self-stabilization of 3D walking gaits is first developed for a simplified model of a walking robot (an inverted pendulum with variable length legs), and then it is extended to a complex model of the humanoid robot Romeo using the notion of Hybrid Zero Dynamics. Simulations of the model of the robot illustrate the efficacy of the method and its robustness.
HAL (Le Centre pour la Communication Scientifique Directe), Aug 29, 2022
Ce travail est dédié à l'application de deux différentiateurs semi-implicites et homogènes pour e... more Ce travail est dédié à l'application de deux différentiateurs semi-implicites et homogènes pour estimer la vitesse de chacun des huit moteurs électriques du robot parallèle à câbles CRAFT à partir de l'enregistrement de la position angulaire de leur arbre de sortie respectif. Ces moteurs actionnent l'enroulement ou le déroulement de huit câbles pour déplacer la plateforme mobile du robot en translation et en rotation. Les résultats montrent que ces différentiateurs, dont les définitions sont fondées sur un et deux projecteurs, sont des outils performants pour estimer les vitesses angulaires des huit moteurs. Ces vitesses estimées sont beaucoup moins bruitées que leurs signaux de référence obtenus par différence arrière. Ces résultats laissent espérer un apport conséquent pour la commande du robot CRAFT.
HAL (Le Centre pour la Communication Scientifique Directe), Aug 26, 2019
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Mechanisms and Machine Science, 2016
The paper aim is to show theoretically the feasibility and efficiency of a passive exoskeleton fo... more The paper aim is to show theoretically the feasibility and efficiency of a passive exoskeleton for human carrying a load. Human is modeled using a mathematical model of a planar bipedal five-link anthropomorphic mechanism. This mechanism consists of a trunk and two identical legs; each leg consists of a thigh and shin with point-foot. The exoskeleton is considered also as a five-link anthropomorphic mechanism. The shape and the degrees of freedom of the exoskeleton are identical to biped (to human). If the biped is equipped with an exoskeleton, then the links of this exoskeleton are attached to the corresponding links of the biped and the corresponding hip-, knee-, and ankle-joints coincide. We compare the walking of a biped alone (without exoskeleton) and of a biped equipped with exoskeleton; both models are with a load. A ballistic walking gait is designed in both cases. During the ballistic walking of the biped with exoskeleton the knee of the stance leg of the exoskeleton (and as a consequence of the biped) is locked. The locking can be realized in the knee of each leg of the exoskeleton by any mechanical brake device with no energy consumption. There are not any actuators in our exoskeleton. Therefore, we call it passive exoskeleton. The walking of the biped consists of alternating single- and double-support phases. In our study, the double-support phase is assumed as instantaneous. At the instant of this phase, the knee of the previous swing leg is locked and the knee of the previous stance leg is unlocked. Numerical results show that during the load transport the human with the exoskeleton spends less energy than human alone.
Recherche, 2007
Cet ouvrage traite de différentes techniques pour la modélisation, la conception, la synthèse de ... more Cet ouvrage traite de différentes techniques pour la modélisation, la conception, la synthèse de la marche et la commande de robots marcheurs bipèdes. Des données générales sur la marche humaine sont accompagnées d'une brève présentation des réalisations actuelles ...
2022 16th International Workshop on Variable Structure Systems (VSS)
It is well-known that implicit-based and projectorbased differentiator schemes offer better perfo... more It is well-known that implicit-based and projectorbased differentiator schemes offer better performances, like reducing high frequency oscillations, compared to the corresponding explicit schemes. To keep the advantages of such implicit Euler approximations, when this approximation is applied in case of homogeneous differentiators, a semi-implicit Euler approximation has been recently proposed for secondorder systems. In this paper, a generalization to third order semi-implicit differentiation is proposed taking into account the attenuation of the noise considering advanced iterative projectors definition. Validation on experimental data is conducted to highlight the well-founded of the proposed differentiation strategy.
Uploads
Papers by Yannick Aoustin