Peer-reviewed journal articles


2018

    Phantom-mobility-based prosthesis control in transhumeral amputees without surgical reinnervation: a preliminary study

    , , , , , , ,
    In Frontiers in Bioengineering and Biotechnology , volume 6 , 2018.

    Abstract

    Transhumeral amputees face substantial difficulties in efficiently controlling their prosthetic limb, leading to a high rate of rejection of these devices. Actual myoelectric control approaches make their use slow, sequential and unnatural, especially for these patients with a high level of amputation who need a prosthesis with numerous active degrees of freedom (powered elbow, wrist, and hand). While surgical muscle-reinnervation is becoming a generic solution for amputees to increase their control capabilities over a prosthesis, research is still being conducted on the possibility of using the surface myoelectric patterns specifically associated to voluntary Phantom Limb Mobilization (PLM), appearing naturally in most upper-limb amputees without requiring specific surgery. The objective of this study was to evaluate the possibility for transhumeral amputees to use a PLM-based control approach to perform more realistic functional grasping tasks. Two transhumeral amputated participants were asked to repetitively grasp one out of three different objects with an unworn eight-active-DoF prosthetic arm and release it in a dedicated drawer. The prosthesis control was based on phantom limb mobilization and myoelectric pattern recognition techniques, using only two repetitions of each PLM to train the classification architecture. The results show that the task could be successfully achieved with rather optimal strategies and joint trajectories, even if the completion time was increased in comparison with the performances obtained by a control group using a simple GUI control, and the control strategies required numerous corrections. While numerous limitations related to robustness of pattern recognition techniques and to the perturbations generated by actual wearing of the prosthesis remain to be solved, these preliminary results encourage further exploration and deeper understanding of the phenomenon of natural residual myoelectric activity related to PLM, since it could possibly be a viable option in some transhumeral amputees to extend their control abilities of functional upper limb prosthetics with multiple active joints without undergoing muscular reinnervation surgery.

    Characteristics of phantom upper limb mobility encourage phantom-mobility-based prosthesis control

    , , , , , , ,
    In Nature Scientific Reports , volume 8 , 2018.

    Abstract

    There is an increasing need to extend the control possibilities of upper limb amputees over their prosthetics, especially given the development of devices with numerous active joints. One way of feeding pattern recognition myoelectric control is to rely on the myoelectric activities of the residual limb associated with phantom limb movements (PLM). This study aimed to describe the types, characteristics, potential influencing factors and trainability of upper limb PLM. Seventy-six below- and above-elbow amputees with major amputation underwent a semi-directed interview about their phantom limb. Amputation level, elapsed time since amputation, chronic pain and use of prostheses of upper limb PLM were extracted from the interviews. Thirteen different PLM were found involving the hand, wrist and elbow. Seventy-six percent of the patients were able to produce at least one type of PLM; most of them could execute several. Amputation level, elapsed time since amputation, chronic pain and use of myoelectric prostheses were not found to influence PLM. Five above-elbow amputees participated in a PLM training program and consequently increased both endurance and speed of their PLM. These results clearly encourage further research on PLM-associated muscle activation patterns for future PLM-based modes of prostheses control.

    Movement-based control for upper-limb prosthetics: is the regression technique the key to a robust and accurate control?

    , , , ,
    In Frontiers in Neurorobotics Frontiers , volume 12 , 2018.

    Abstract

    Due to the limitations of myoelectric control (such as dependence on muscular fatigue and on electrodes shift, difficulty in decoding complex patterns or in dealing with simultaneous movements), there is a renewal of interest in the movement-based control approaches for prosthetics. The latter use residual limb movements rather than muscular activity as command inputs, in order to develop more natural and intuitive control techniques. Among those, several research works rely on the interjoint coordinations that naturally exist in human upper limb movements. These relationships are modeled to control the distal joints (e.g. elbow) based on the motions of proximal ones (e.g. shoulder). The regression techniques, used to model the coordinations, are various (Artificial Neural Networks, Principal Components Analysis, etc.) and yet, analysis of their performance and impact on the prosthesis control is missing in the literature. Is there one technique really more efficient than the others to model interjoint coordinations? To answer this question, we conducted an experimental campaign to compare the performance of three common regression techniques in the control of the elbow joint on a transhumeral prosthesis. Ten non-disabled subjects performed a reaching task, while wearing an elbow prosthesis which was driven by several interjoint coordination models obtained through different regression techniques. The models of the shoulder-elbow kinematic relationship were built from the recordings of fifteen different non-disabled subjects that performed a similar reaching task with their healthy arm. Among Radial Basis Function Networks (RBFN), Locally Weighted Regression (LWR) and Principal Components Analysis (PCA), RBFN was found to be the most robust, based on the analysis of several criteria including the quality of generated movements but also the compensatory strategies exhibited by users. Yet, RBFN does not significantly outperform LWR and PCA. The regression technique seems not to be the most significant factor for improvement of interjoint coordinations-based control. By characterizing the impact of the modeling techniques through closed-loop experiments with human users instead of purely offline simulations, this work could also help in improving movement-based control approaches and in bringing them closer to a real use by patients.

    Force, Impedance and Trajectory Learning for Contact Tooling and Haptic Identification

    , , , , ,
    In IEEE Transactions on Robotics , volume 35 , 2018.

    Abstract

    Humans can skilfully use tools and interact with the environment by adapting their movement trajectory, contact force, and impedance. Motivated by the human versatility, we develop here a robot controller that concurrently adapts feedforward force, impedance, and reference trajectory when interacting with an unknown environment. In particular, the robot’s reference trajectory is adapted to limit the interaction force and maintain it at a desired level, while feedforward force and impedance adaptation compensates for the interaction with the environment. An analysis of the interaction dynamics using Lyapunov theory yields the conditions for convergence of the closed-loop interaction mediated by this controller. Simulations exhibit adaptive properties similar to human motor adaptation. The implementation of this controller for typical interaction tasks including drilling, cutting, and haptic exploration shows that this controller can outperform conventional controllers in contact tooling.

    Can we achieve intuitive prosthetic elbow control based on healthy upper limb motor?

    , , , ,
    In Frontiers in Neurorobotics Frontiers , volume 12 , 2018.

    Abstract

    Most transhumeral amputees report that their prosthetic device lacks functionality, citing the control strategy as a major limitation. Indeed, they are required to control several degrees of freedom with muscle groups primarily used for elbow actuation. As a result, most of them choose to have a one-degree-of-freedom myoelectric hand for grasping objects, a myoelectric wrist for pronation/supination, and a body-powered elbow. Unlike healthy upper limb movements, the prosthetic elbow joint angle, adjusted prior to the motion, is not involved in the overall upper limb movements, causing the rest of the body to compensate for the lack of mobility of the prosthesis. A promising solution to improve upper limb prosthesis control exploits the residual limb mobility: like in healthy movements, shoulder and prosthetic elbow motions are coupled using inter-joint coordination models. The present study aims to test this approach. A transhumeral amputated individual used a prosthesis with a residual limb motion-driven elbow to point at targets. The prosthetic elbow motion was derived from IMU-based shoulder measurements and a generic model of inter-joint coordinations built from healthy individuals data. For comparison, the participant also performed the task while the prosthetic elbow was implemented with his own myoelectric control strategy. The results show that although the transhumeral amputated participant achieved the pointing task with a better precision when the elbow was myoelectrically-controlled, he had to develop large compensatory trunk movements. Automatic elbow control reduced trunk displacements, and enabled a more natural body behavior with synchronous shoulder and elbow motions. However, due to socket impairments, the residual limb amplitudes were not as large as those of healthy shoulder movements. Therefore, this work also investigates if a control strategy whereby prosthetic joints are automatized according to healthy individuals' coordination models can lead to an intuitive and natural prosthetic control.

2017

    Taxonomy based analysis of force exchanges during multi-digital object grasping and manipulation

    , , ,
    In Plos One Public Library of Science , volume 12 , 2017.

    Abstract

    The flexibility of the human hand in object manipulation is essential for daily life activities, but remains relatively little explored with quantitative methods. On the one hand, recent taxonomies describe qualitatively the classes of hand postures for object grasping and manipulation. On the other hand, the quantitative analysis of hand function has been generally restricted to precision grip (with thumb and index opposition) during lifting tasks. The aim of the present study is to fill the gap between these two kinds of descriptions, by investigating quantitatively the forces exerted by the hand on an instrumented object in a set of representative manipulation tasks. The object was a parallelepiped object able to measure the force exerted on the six faces and its acceleration. The grasping force was estimated from the lateral force and the unloading force from the bottom force. The protocol included eleven tasks with complementary constraints inspired by recent taxonomies: four tasks corresponding to lifting and holding the object with different grasp configurations, and seven to manipulating the object (rotation around each of its axis and translation). The grasping and unloading forces and object rotations were measured during the five phases of the actions: unloading, lifting, holding or manipulation, preparation to deposit, and deposit. The results confirm the tight regulation between grasping and unloading forces during lifting, and extend this to the deposit phase. In addition, they provide a precise description of the regulation of force exchanges during various manipulation tasks spanning representative actions of daily life. The timing of manipulation showed both sequential and overlapping organization of the different sub-actions, and micro-errors could be detected. This phenomenological study confirms the feasibility of using an instrumented object to investigate complex manipulative behavior in humans. This protocol will be used in the future to investigate upper-limb dexterity in patients with sensory-motor impairments.

    Classification of Phantom Finger, Hand, Wrist and Elbow Voluntary Gestures in Transhumeral Amputees with sEMG

    , , , , , ,
    In IEEE Transactions on Neural Systems and Rehabilitation Engineering , volume 25 , 2017.

    Abstract

    Decoding finger and hand movements from sEMG electrodes placed on the forearm of transradial amputees has been commonly studied by many research groups. A few recent studies have shown an interesting phenomenon: simple correlations between distal phantom finger, hand and wrist voluntary movements and muscle activity in the residual upper arm in transhumeral amputees, i.e., of muscle groups that, prior to amputation, had no physical effect on the concerned hand and wrist joints. In this study, we are going further into the exploration of this phenomenon by setting up an evaluation study of phantom finger, hand, wrist and elbow (if present) movement classification based on the analysis of surface electromyographic (sEMG) signals measured by multiple electrodes placed on the residual upper arm of 5 transhumeral amputees with a controllable phantom limb who did not undergo any reinnervation surgery. We showed that with a state-of-the-art classification architecture, it is possible to correctly classify phantom limb activity (up to 14 movements) with a rather important average success (over 80% if considering basic sets of 6 hand, wrist and elbow movements) and to use this pattern recognition output to give online control of a device (here a graphical interface) to these transhumeral amputees. Beyond changing the way the phantom limb condition is apprehended by both patients and clinicians, such results could pave the road towards a new control approach for transhumeral amputated patients with a voluntary controllable phantom limb. This could ease and extend their control abilities of functional upper limb prosthetics with multiple active joints without undergoing muscular reinnervation surgery.

    SITAR: a system for independent task-oriented assessment and rehabilitation

    , , , , , , , ,
    In Journal of Rehabilitation and Assistive Technologies Engineering , volume 4 , 2017.

    Abstract

    Introduction: Over recent years, task-oriented training has emerged as a dominant approach in neurorehabilitation. This article presents a novel, sensor-based system for independent task-oriented assessment and rehabilitation (SITAR) of the upper limb.Methods: The SITAR is an ecosystem of interactive devices including a touch and force–sensitive tabletop and a set of intelligent objects enabling functional interaction. In contrast to most existing sensor-based systems, SITAR provides natural training of visuomotor coordination through collocated visual and haptic workspaces alongside multimodal feedback, facilitating learning and its transfer to real tasks. We illustrate the possibilities offered by the SITAR for sensorimotor assessment and therapy through pilot assessment and usability studies.Results: The pilot data from the assessment study demonstrates how the system can be used to assess different aspects of upper limb reaching, pick-and-place and sensory tactile resolution tasks. The pilot usability study indicates that patients are able to train arm-reaching movements independently using the SITAR with minimal involvement of the therapist and that they were motivated to pursue the SITAR-based therapy.Conclusion: SITAR is a versatile, non-robotic tool that can be used to implement a range of therapeutic exercises and assessments for different types of patients, which is particularly well-suited for task-oriented training.

    Robotic prostheses: what do they actually mean for the patient?

    In Human Body In Motion Journal , volume 1 , 2017.

    Abstract

    Prostheses have undergone an accelerated development over the past few years, triggered by, amongst others, the conflicts in Iraq and Afghanistan. Indeed, with their share of wounded and amputees, these conflicts will undoubtedly have made a strong contribution to, putting the spotlight on this niche field of research. The technological sophistication of robotic prostheses gives free rein to the imagination. But what is the reality on the ground? As we speak more and more of the augmented man and body-machine fusion, what does this all actually mean for the patient? To shed some light on this matter, we put our questions to Nathanaël Jarrassé, a CNRS researcher at the Institute of Intelligent Systems and Robotics at the Pierre and Marie Curie University in Paris.

    Reachability and the sense of embodiment in amputees using prostheses

    , , , , , ,
    In Nature Scientific Reports , volume 7 , 2017.

    Abstract

    Amputated patients are hardly satisfied with upper limb prostheses, and tend to favour the use of their contralateral arm to partially compensate their disability. This may seem surprising in light of recent evidences that external objects (rubber hand or tool) can easily be embodied, namely incorporated in the body representation. We investigated both implicit body representations (by evaluating the peripersonal space using a reachability judgement task) and the quality of bodily integration of the patient’s prosthesis (assessed via questionnaires). As expected, the patients estimated that they could reach further while wearing their prosthesis, showing an embodiment of their prosthesis in their judgement. Yet, the real reaching space was found to be smaller with their prosthesis than with their healthy limb, showing a large error between reachability judgement and actual capacity. An overestimation was also found on the healthy side (comparatively to healthy subjects) suggesting a bilateral modification of body representation in amputated patients. Finally, a correlation was found between the quality of integration of the prosthesis and the way the body representation changed. This study therefore illustrates the multifaceted nature of the phenomenon of prosthesis integration, which involves its incorporation as a tool, but also various specific subjective aspects.

    Modifying upper-limb inter-joint coordination in healthy subjects by training with a robotic exoskeleton

    , , ,
    In Journal of NeuroEngineering and Rehabilitation , volume 14 , 2017.

    Abstract

    The possibility to modify the usually pathological patterns of coordination of the upper-limb in stroke survivors remains a central issue and an open question for neurorehabilitation. Despite robot-led physical training could potentially improve the motor recovery of hemiparetic patients, most of the state-of-the-art studies addressing motor control learning, with artificial virtual force fields, only focused on the end-effector kinematic adaptation, by using planar devices. Clearly, an interesting aspect of studying 3D movements with a robotic exoskeleton, is the possibility to investigate the way the human central nervous system deals with the natural upper-limb redundancy for common activities like pointing or tracking tasks.

    Spectral parameters for Finger tapping quantification

    , , , , , , ,
    In Facta Universitatis, Series: Electronics and Energetics , volume 30 , 2017.

    Abstract

    A miniature inertial sensor placed on fingertip of index finger while performing finger tapping test can be used for an objective quantification of finger tapping motion. Temporal and spatial parameters such as cadence, tapping duration, and tapping angle can be extracted for detailed analysis. However, the mentioned parameters, although intuitive and simple to interpret, do not always provide all the necessary information regarding the subject’s motor performance. Analysis of frequency content of the finger tapping movement can provide crucial information about the patient's condition. In this paper, we present parameters extracted from spectral analysis that we found to be significant for finger tapping assessment. With these parameters, tapping’s intra-variability, movement smoothness and anomalies that may occur within the tapping performance can be detected and described, providing significant information for further diagnostics and monitoring progress of the disease or response to therapy.

2016

    Upper-Limb Robotic Exoskeletons for Neurorehabilitation: A Review on Control Strategies

    , , ,
    In IEEE Reviews in Biomedical Engineering , volume 9 , 2016.

    Abstract

    Since the late 90s, there has been a burst of research on robotic devices for post-stroke rehabilitation. Robot-mediated therapy produced improvements on recovery of motor capacity; however, so far, the use of robots has not shown qualitative benefit over classical therapist-led training session, performed on the same quantity of movements. Multi degrees of freedom robots, like the modern upper-limb exoskeletons, enables a distributed interaction on the whole assisted limb and can exploit a large amount of sensory feedback data, potentially providing new capabilities within standard rehabilitation sessions. Surprisingly, most publications in the field of exoskeletons focused only on mechatronic design of the devices while little details were given to the control aspects. On the contrary, we do believe a paramount aspect for robots potentiality lays on the control side. Therefore the aim of this paper is to provide a taxonomy of currently available control strategies for exoskeletons for neurorehabilitation, in order to formulate appropriate questions towards the development of innovative and improved control strategies.

    Phantom hand and wrist movements in upper limb amputees are slow but naturally controlled movements

    , , , , , , ,
    In Neuroscience , volume 312 , 2016.

    Abstract

    After limb amputation, patients often wake up with a vivid perception of the presence of the missing limb, called ''phantom limb''. Phantom limbs have mostly been studied with respect to pain sensation. But patients can experience many other phantom sensations, including voluntary movements. The goal of the present study was to quantify phantom movement kinematics and relate these to intact limb kinematics and to the time elapsed since amputation. Six upper arm and two forearm amputees with various delays since amputation (6months to 32years) performed phantom finger, hand and wrist movements at self-chosen comfortable velocities. The kinematics of the phantom movements was indirectly obtained via the intact limb that synchronously mimicked the phantom limb movements, using a Cyberglove for measuring finger movements and an inertial measurement unit for wrist movements. Results show that the execution of phantom movements is perceived as ''natural'' but effortful. The types of phantom movements that can be performed are variable between the patients but they could all perform thumb flexion/extension and global hand opening/closure. Finger extension movements appeared to be 24% faster than finger flexion movements. Neither the number of types of phantom movements that can be executed nor the kinematic characteristics were related to the elapsed time since amputation, highlighting the persistence of post-amputation neural adaptation. We hypothesize that the perceived slowness of phantom movements is related to altered proprioceptive feedback that cannot be recalibrated by lack of visual feedback during phantom movement execution.

2015

    Robotic prosthetics: beyond the technical performance. (A study of socio-anthropological and cultural phenomena influencing the appropriation of technical objects interacting with the body)

    , , ,
    In IEEE Technology and Society Magazine , volume 34 , 2015.

    Abstract

    While physical interaction with robots is becoming common in many domains, numerous devices are not appropriated by their users and remain unused in the cupboard. This phenomenon is particularly observed with robotic devices which interact closely with the body, especially if they are designed to compensate for a loss of sensory or motor capacity. This article uses the quite extreme example of prosthetics to highlight the socio-anthropological and cultural phenomena affecting the appropriation and use of technical objects which interact with the body as much as (or even more than) their technical performance. Considering these complementary points of views and theories in the design of such devices could be a way of improving their appropriation.

2014

    Robotic exoskeletons: a perspective for the rehabilitation of arm coordination in stroke patients

    , , , , , ,
    In Frontiers in Human Neuroscience , volume 8:947 , 2014.

    Abstract

    Upper-limb impairment after stroke is caused by weakness, loss of individual joint control, spasticity, and abnormal synergies. Upper-limb movement frequently involves abnormal, stereotyped, and fixed synergies, likely related to the increased use of sub-cortical networks following the stroke. The flexible coordination of the shoulder and elbow joints is also disrupted. New methods for motor learning, based on the stimulation of activity-dependent neural plasticity have been developed. These include robots that can adaptively assist active movements and generate many movement repetitions. However, most of these robots only control the movement of the hand in space. The aim of the present text is to analyze the potential of robotic exoskeletons to specifically rehabilitate joint motion and particularly inter-joint coordination. First, a review of studies on upper-limb coordination in stroke patients is presented and the potential for recovery of coordination is examined. Second, issues relating to the mechanical design of exoskeletons and the transmission of constraints between the robotic and human limbs are discussed. The third section considers the development of different methods to control exoskeletons: existing rehabilitation devices and approaches to the control and rehabilitation of joint coordinations are then reviewed, along with preliminary clinical results available. Finally, perspectives and future strategies for the design of control mechanisms for rehabilitation exoskeletons are discussed.

    Analysis of hand synergies in healthy subjects during bimanual manipulation of various objects

    , , , ,
    In Journal of NeuroEngineering and Rehabilitation , volume 11 , 2014.

    Abstract

    BACKGROUND: Hand synergies have been extensively studied over the last few decades. Objectives of such research are numerous. In neuroscience, the aim is to improve the understanding of motor control and its ability to reduce the control dimensionality. In applied research fields like robotics the aim is to build biomimetic hand structures, or in prosthetics to design more performant underactuated replacement hands. Nevertheless, most of the synergy schemes identified to this day have been obtained from grasping experiments performed with one single (generally dominant) hand to objects placed in a given position and orientation in space. Aiming at identifying more generic synergies, we conducted similar experiments on postural synergy identification during bimanual manipulation of various objects in order to avoid the factors due to the extrinsic spatial position of the objects. METHODS: Ten healthy naive subjects were asked to perform a selected "grasp-give-receive" task with both hands using 9 objects. Subjects were wearing Cyberglove Ⓒ on both hands, allowing a measurement of the joint posture (15 degrees of freedom) of each hand. Postural synergies were then evaluated through Principal Component Analysis (PCA). Matches between the identified Principal Components and the human hand joints were analyzed thanks to the correlation matrix. Finally, statistical analysis was performed on the data in order to evaluate the effect of some specific variables on the hand synergies: object shape, hand side (i.e., laterality) and role (giving or receiving hand). RESULTS: Results on PCs are consistent with previous literature showing that a few principal components might be sufficient to describe a large variety of different grasps. Nevertheless some simple and strong correlations between PCs and clearly identified sets of hand joints were obtained in this study. In addition, these groupings of DoF corresponds to well-defined anatomo-functional finger joints according to muscle groups. Moreover, despite our protocol encouraging symmetric grasping, some right-left side differences were observed. CONCLUSION: The set of identified synergies presented here should be more representative of hand synergies in general since they are based on both hands motion. Preliminary results, that should be deepened, also highlight the influence of hand dominance and side. Thanks to their strong correlation with anatomo-functional joints, these synergies could therefore be used to design underactuated robotics hands.

    Ergonomic Design of a Wrist Robot: the Influence of Hyperstaticity on Reaction connecting Forces and Motor Strategies

    , , , ,
    In International Journal of Intelligent Computing and Cybernetics , volume 7 , 2014.

    Abstract

    Purpose: The purpose of this paper is to propose a method to avoid hyperstaticity and eventually reduce the magnitude of undesired force/torques. The authors also study the influence of hyperstaticity on human motor control during a redundant task. Design/methodology/approach: Increasing the level of transparency of robotic interfaces is critical to haptic investigations and applications. This issue is particularly important to robotic structures that mimic the human counterpart's morphology and attach directly to the limb. Problems arise for complex joints such as the wrist, which cannot be accurately matched with a traditional mechanical joint. In such cases, mechanical differences between human and robotic joint cause hyperstaticity (i.e. over-constrained) which, coupled with kinematic misalignment, leads to uncontrolled force/torque at the joint. This paper focusses on the prono-supination (PS) degree of freedom of the forearm. The overall force and torque in the wrist PS rotation is quantified by means of a wrist robot. Findings: A practical solution to avoid hyperstaticity and reduce the level of undesired force/torque in the wrist is presented. This technique is shown to reduce 75 percent of the force and 68 percent of the torque. It is also shown an over-constrained mechanism could alter human motor strategies. Practical implications: The presented solution could be taken into account in the early phase of design of robots. It could also be applied to modify the fixation points of commercial robots in order to reduce the magnitude of reaction forces and avoid changes in motor strategy during the robotic therapy. Originality/value: In this paper for the first time the authors study the effect of hyperstaticity on both reaction forces and human motor strategies.

    Slaves no longer: review on role assignment for human-robot joint motor action

    , ,
    In Adaptive Behavior (SAGE) , 2014.

    Abstract

    This paper summarizes findings on the growing field of role assignment policies for human–robot motor interaction. This topic has been investigated by researchers in the psychological theory of joint action, in human intention detection, force control, human–human physical interaction, as well as roboticists interested in developing robots with capabilities for efficient motor interaction with humans. Our goal is to promote fruitful interaction between these distinct communities by: (i) examining the role assignment policies for human–robot joint motor action in experimental psychology and robotics studies; and (ii) informing researchers in human–human interaction on existing work in the robotic field. After an overview of roles assignment in current robotic assistants, this paper examines key results about shared control between a robot and a human performing interactive motor tasks. Research on motor interaction between two humans has inspired recent developments that may extend the use of robots to applications requiring continuous mechanical interaction with humans.

2013

    A Framework to Describe, Analyze and Generate Interactive Motor Behaviors

    , ,
    In PLoS ONE , volume 7 , 2013.

    Abstract

    While motor interaction between a robot and a human, or between humans, has important implications for society as well as promising applications, little research has been devoted to its investigation. In particular, it is important to understand the different ways two agents can interact and generate suitable interactive behaviors. Towards this end, this paper introduces a framework for the description and implementation of interactive behaviors of two agents performing a joint motor task. A taxonomy of interactive behaviors is introduced, which can classify tasks and cost functions that represent the way each agent interacts. The role of an agent interacting during a motor task can be directly explained from the cost function this agent is minimizing and the task constraints. The novel framework is used to interpret and classify previous works on human-robot motor interaction. Its implementation power is demonstrated by simulating representative interactions of two humans. It also enables us to interpret and explain the role distribution and switching between roles when performing joint motor tasks.

2012

    Connecting a Human Limb to an Exoskeleton.

    ,
    In IEEE Transactions on Robotics , volume 28 , 2012.

    Abstract

    When developing robotic exoskeletons, the design of physical connections between the device and the human limb to which it is connected is a crucial problem. Indeed, using an embedment at each connection point leads to uncontrollable forces at the interaction port, induced by hyperstaticity. In practice, these forces may be large because in general the human limb kinematics and the exoskeleton kinematics differ. To cope with hyperstaticity, the literature suggests the addition of passive mechanisms inside the mechanism loops. However, empirical solutions that are proposed so far lack proper analysis and generality. In this paper, we study the general problem of connecting two similar kinematic chains through multiple passive mechanisms. We derive a constructive method that allows the determination of all the possible distributions of freed degrees of freedom across different fixation mechanisms. It also provides formal proofs of global isostaticity. Practical usefulness is illustrated through two examples with conclusive experimental results: a preliminary study made on a manikin with an arm exoskeleton controlling the movement (passive mode) and a larger campaign on ten healthy subjects performing pointing tasks with a transparent robot (active mode).

2010

    A methodology to quantify alterations in human upper limb movement during co-manipulation with an exoskeleton

    , , , , , ,
    In IEEE in Transactions on Neural Systems and Rehabilitation Engineering , volume 18 , 2010.

    Abstract

    While a large number of robotic exoskeletons have been designed by research teams for rehabilitation, it remains rather difficult to analyse their ability to finely interact with a human limb: no performance indicators or general methodology to characterize this capacity really exist. This is particularly regretful at a time when robotics are becoming a recognized rehabilitation method and when complex problems such as 3-D movement rehabilitation and joint rotation coordination are being addressed. The aim of this paper is to propose a general methodology to evaluate, through a reduced set of simple indicators, the ability of an exoskeleton to interact finely and in a controlled way with a human. The method involves measurement and recording of positions and forces during 3-D point to point tasks. It is applied to a 4 degrees-of-freedom limb exoskeleton by way of example.

    Rehabilitation robots: a compliment to virtual reality.

    , ,
    Chapter in (P.U.C., ed.) Schedae , volume 1 , 2010.

    Abstract

    The aim of this paper is to discuss the use of robots for upper limb rehabilitation following strokes in adults. We describe the main robots currently being developed and the results of clinical studies that have been carried out. The association of virtual reality interfaces and the robotic rehabilitation programs providing therapy in the form of games with a view to helping therapists increase the duration of rehabilitation exercise.

2009

2007

    De l'utilisation des robots pour la rééducation: intérêt et perspectives

    , , ,
    In La Lettre de Médecine Physique et de Réadaptation , volume 23 , 2007.

    Abstract

    Le but de ce texte est de présenter et discuter l’apport de la robotique pour la rééducation du membre supérieur, en particulier chez les patients hémiparétiques à la suite d’un accident vasculaire cérébral. La première partie présente les principes généraux qui guident le développement de ces robots, en particulier pour l’interaction mécanique entre le robot et le contrôle moteur humain. La seconde partie présente les principaux robots effectivement utilisés en rééducation avec leurs évaluations cliniques. Les robots permettent de faciliter l’initiation des gestes, la répétition de gestes de qualité, et un meilleur contrôle de la récupération des synergies. Ils autorisent aussi une quantification des gestes et une évaluation objective. Il est donc probable que leur place sera de plus en plus grande lorsque l’on désire un entraînement intensif, bien que leur apport ne soit pas encore cliniquement prouvé. L’aspect qualitatif devrait certainement progresser à l’avenir avec les progrès de la recherche dans le domaine de la robotique et une meilleure compréhension des mécanismes de l’interaction sensorimotrice avec les robots et de l’apprentissage pendant la rééducation. La prise en charge précoce des patients que semblent pouvoir permettre les robots est aussi un point intéressant, même si très peu d’éléments cliniques sur cette question sont actuellement disponibles.


Peer-reviewed book chapters

2017

    Versatile Interaction Control and Haptic Identification in Humans and Robots

    , ,
    Chapter in Geometric and Numerical Foundations of Movements (Springer, ed.) , volume 117 , 2017.

    Abstract

    Traditional industrial robot controllers are typically dedicated to a specific task, while humans always interact with new objects yielding unknown interaction forces and instability. In this chapter, we examine the neuromechanics of such contact tasks. We develop a model of the necessary adaptation of force, mechanical impedance and planned trajectory for stable and efficient interaction with rigid or compliant surfaces of different structures. Simulations demonstrate that this model can be used as a novel adaptive robot controller yielding versatile control in representative interactive tasks such as cutting, drilling and haptic exploration, where the robot acquires a model of the geometry and structure of the surface along which it is moving.

    Prothèses robotiques : vers un nouveau dualisme?

    Chapter in L'humain et ses prothèses: Savoirs et pratiques du corps transformé (CNRS editions, ed.) , 2017. (978-2-271-11416-7)

2015

    La rééducation fonctionnelle, une question de techniques corporelles.

    , ,
    Chapter in L'apprentissage des techniques corporelles (PUF, ed.) Collection ''Apprendre'' Presses Universitaires de France , 2015.

    Abstract

    -

2010

    Rehabilitation robots: a compliment to virtual reality.

    , ,
    Chapter in (P.U.C., ed.) Schedae , volume 1 , 2010.

    Abstract

    The aim of this paper is to discuss the use of robots for upper limb rehabilitation following strokes in adults. We describe the main robots currently being developed and the results of clinical studies that have been carried out. The association of virtual reality interfaces and the robotic rehabilitation programs providing therapy in the form of games with a view to helping therapists increase the duration of rehabilitation exercise.


Peer-reviewed conference articles

2017

    Control of prosthetics through EMG patterns associated to phantom limb voluntary gestures is possible in transhumeral amputees without surgical reinnervation

    , , , , , ,
    In 16th World Congress of the International Society of Prosthetics and Orthotics (ISPO) , 2017.

    Grasping after trans-radial amputation: comparison of kinematics between amputated limb equipped with myo-electric prosthesis and healthy limb.

    , , , , , ,
    In 32th annual congress of the French Society of Physical Medicine and Reha bilitation (SOFMER) , 2017.

    Abstract

    After upper limb amputation, myoelectric prosthesis does not allow total functional recovery: grasping is executed with compensation motions. The objective of this study is to compare grasping's kinematics between prosthetic and healthy upper limb for myoelectric trans-radial prosthesis users.

    Using phantom limb voluntary gestures in transhumeral amputees to control prostheses

    , , , , , ,
    In 32th annual congress of the French Society of Physical Medicine and Reha bilitation (SOFMER) , 2017.

    Pre-clinical evaluation of a natural prosthetic elbow control strategy using residual limb motion and a model of healthy inter-joint coordinations

    , , , , ,
    In 32th annual congress of the French Society of Physical Medicine and Reha bilitation (SOFMER) , 2017.

    Abstract

    A gap has been growing between the mechanical features of newly commercialized prosthetic devices and the control strategies available to the users. The prosthetic joints are controlled sequentially via myoelectric control, and each actuation requires the user's attention. Because of a complex control scheme, transhumeral amputees are generally equipped with a 1-degree-of-freedom myoelectric hand, a myoelectric wrist rotator, and a manually locked elbow. The prosthetic forearm position, adjusted before the movement, is not involved in the overall upper limb movements, resulting in the development of compensatory strategies. A promising solution to improve prosthetic control utilizes the residual limb motions to control the elbow. Previous studies have shown that elbow motion could be predicted from measures of the residual limb movements and an inter-joint coordination model. This study is the first to report the utilization of an automatically driven prosthetic elbow by a transhumeral amputee.

    Reconsidering phantom limb: potential applications for prosthesis control after above-elbow amputation

    , , , , , , , ,
    In 32th annual congress of the French Society of Physical Medicine and Rehabilitation (SOFMER) , 2017.

    Phantom upper limb mobility: characteristics and evolution

    , , , , , ,
    In 32th annual congress of the French Society of Physical Medicine and Reha bilitation (SOFMER) , 2017.

    Pre-clinical assessment of an intuitive prosthetic elbow control strategy using residual limb motion with osseointegrated patients

    , , , , ,
    In Annals of Physical and Rehabilitation Medicine Elsevier , volume 60 , 2017.

    Abstract

    Most transhumeral amputees deplore that their prosthesis lacks functionality due to control-related limitations. Externally powered prosthetic devices are commonly controlled via myoelectric control whereby biceps and triceps contractions drive sequentially the prosthetic joints. Because of a complex control scheme, transhumeral amputees are generally equipped with a 1-degree-of-freedom myoelectric hand, a myoelectric wrist rotator, and a manually locked elbow, despite the commercialization of more advanced devices. This results in the development of compensatory strategies to overcome the prosthesis’ lack of mobility. An alternative control strategy relates the residual limb motions to the prosthetic elbow motion using the natural coordination between shoulder and elbow observed in healthy movements. However, conventional external sockets tend to prevent the residual limb mobility, limiting the potentiality of this novel control strategy. Osseo-integration enables a stable attachment of the prosthetic device and frees the residual limb. This study focuses on the performance of three osseo-integrated patients using an automatically driven prosthesis.

    Voluntary phantom hand and finger movements in transhumeral amputees could be used to naturally control polydigital prostheses

    , , , , , ,
    In Proceedings of the 2017 IEEE-RAS-EMBS International Conference on Rehabilitation Robotics (ICORR) , 2017.

    Abstract

    An arm amputation is extremely invalidating since many of our daily tasks require bi-manual and precise control of hand movements. Perfect hand prostheses should therefore offer a natural, intuitive and cognitively simple control over their numerous biomimetic active degrees of freedom. While efficient polydigital prostheses are commercially available, their control remains complex to master and offers limited possibilities, especially for high amputation levels. In this pilot study, we demonstrate the possibility for upper-arm amputees to intuitively control a polydigital hand prosthesis by using surface myoelectric activities of residual limb muscles (sEMG) associated with phantom limb movements, even if these residual arm muscles on which the phantom activity is measured were not naturally associated with hand movements before amputation. Using pattern recognition methods, three arm amputees were able, without training, to initiate 5-8 movements of a robotic hand (including individual finger movements) by simply mobilizing their phantom limb while the robotic hand was mimicking the action in real time. This innovative control approach could offer to numerous upper-limb amputees an access to recent biomimetic prostheses with multiple controllable joints, without requiring surgery or complex training; and might deeply change the way the phantom limb is apprehended by both patients and clinicians.

    Comparison of different error signals driving the adaptation in assist-as-needed controllers for neurorehabilitation with an upper-limb robotic exoskeleton

    , , ,
    In in proceedings of the IEEE International Conference on Robotics and Automation (ICRA) , 2017.

    Abstract

    Assist-as-needed control aims at maximizing stroke survivors involvement during robotic-led therapies of neurorehabilitation. Besides the specific characteristics of the designed adaptive control strategy, a fundamental property of this control architecture is the choice of the error signal which will drive the adaptation process. This driving source is a necessary control parameter to be chosen, although often sidelined in the control design, and several solutions already exist in the state-of-the-art. For this reason, we wanted to compare three different strategies to guide the adaptation, respectively based on the local joint performances, on the end-effector only behaviour, or on the performance of one specific joint in the kinematic chain of the robot. The resulting analysis evaluates the possibilities offered by simply changing from one source to another with respect to the specific stage of the motor recovery of the patients, potentially extending the capabilities of current exoskeleton controllers for neurorehabilitation.

2016

    Frequency analysis of repetitive finger tapping – extracting parameters for movement quantification

    , , , , , ,
    In Proceedings of 3rd International Conference on Electrical, Electronic and Computing Engineering, IcETRAN 2016 , 2016.

    Abstract

    In clinical practice, the finger tapping movement is often validated visually, thus resulting in a coarse diagnostic resolution. However, by using miniature inertial sensor mounted on fingertip of index finger, finger tapping performance can be quantified, allowing objective assessment of specific characteristics or changes in the finger tapping pattern over time. Various parameters such as cadence, tapping duration, speed, and tapping angle can be extracted for detailed analysis of patient’s motor performance. However, the listed parameters, although intuitive and simple to interpret, do not always carry all necessary information regarding subject’s motor performance. Here we present kinematic parameters extracted from spectral analysis that are significant for finger tapping assessment. With these parameters, tapping’s intravariability, movement smoothness and anomalies that occur within the tapping performance can be identified and observed, providing significant information for further diagnostics and monitoring progress of the disease of response to therapy.

    Intuitive control of a prosthetic elbow

    , , ,
    In Proceedings of the International Conference on Neurorehabilitation (ICNR) , 2016.

    Abstract

    Many transhumeral amputees deplore the lack of functionality of their prosthesis, mostly caused by a counter-intuitive control strategy. This work is the first implementation of an automatic prosthesis control approach based on natural coordinations between upper limb joints and IMU-based humeral orientation measurement. One healthy individual was able to use the prosthetic elbow, fitted with a prosthetic forearm and attached to the subject’s upper arm, to point at targets with an encouragingly small error.

    Intuitive prosthetic control using upper limb inter-joint coordinations and IMU-based shoulder angles measurement: a pilot study

    , , ,
    In Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems , 2016.

    Abstract

    Commercialized upper limb prostheses do not match the expectations of amputated people, especially transhumeral amputees. Most of them report a lack of functionality, mostly explained by a counter-intuitive control strategy. This paper presents the first implementation of an automatic prosthesis control approach based on natural coordinations between upper limb joints and IMU-based humeral orientation measurement. Two healthy individuals were able to use the prosthetic forearm attached to their upper arm to point at targets in a 3D workspace with a reasonable error. The results demonstrate the potential applications of automatizing the motion of some joints along the upper limb, in the same way as human upper limbs are controlled.

    Towards the implementation of natural prosthetic elbow motion using upper limb joint coordination

    , ,
    In Proceedings of the 6th IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob) , 2016.

    Abstract

    The control of an active prosthetic elbow is problematic for most transhumeral amputees and a functional solution providing intuitive control over active multi-joint prosthetic upper limbs is yet to be found. The method in this paper uses IMU-based upper arm kinematics to predict the elbow motion based on upper limb joint coordinations during pointing movements. A RBFN-based regression was performed to model the shoulder/elbow coordination. The prediction results indicate that such an approach is ready to be implemented on current transhumeral prostheses equipped with embedded motion sensors like IMUs. Different algorithm training methods to obtain better prediction performance are also investigated.

    Learning motor coordination under resistive viscous force fields at the joint level with an upper-limb robotic exoskeleton

    , ,
    In Converging Clinical and Engineering Research on Neurorehabilitation II , 2016.

    Abstract

    In the field of rehabilitation robotics, few researchers have been focusing on the problem of controlling motor coordination in post-stroke patients. Studies on coordination learning, when the robotic devices act at the joint level on multiple interaction points, as in the case of exoskeletons, are lacking. For this reason, we studied on 10 healthy subjects the possibility of learning a non-natural inter-joint coordination while performing a pointing task. This coordination was induced by a 4-DOF robotic exoskeleton, applying resistive force fields at the joint level. Preliminary results showed the capability of our controller to modify human healthy natural coordination after exposition to the fields and generalization of these effects to movements which were never exposed to these constraints.

2015

    La personne amputée dans les médias : quand l'ambiguité des images bouleverse la compréhension du handicap et des technologies de compensation/restauration.

    ,
    In 4ème Conférence annuelle ALTER (European Society for Disability Research) , 2015.

    Abstract

    This conference aims to highlight the equivocal and ambiguous way amputees wearing external prostheses are being staged in the media. Its purpose is to present a critical analysis of collective representations of prosthetic devices, especially through the paradigm of the cyborg which is becoming more and more present in the media imagination and imagery. How do these images permeate the public sphere and amputees themselves? Do they have a concrete impact on how amputees are perceived and perceive themselves? What are the main differences between what is shown and what is really experienced by patients?
This presentation will focus on the way the vision conveyed by recent media has gradually shaked contemporary conceptions and representations of disability and disabled body. From the prosthetic devices' point of view, it has steadily drifted into the image of "bionic" body or "enhanced" body, even going so far as to influence the research field and technical innovation process. More broadly, we will show how the figure of the amputee wearing prosthesis questions in an iconic way the contemporary relation to the body and the new technologies (a gradual depreciation of the former, and an increasing fascination towards the latter).
The authors work with patients as part of their research, so the data collection is partly done through interviews and ground observations. A critical analysis of the collective imagination and recent media trends will also be put into perspective, especially around the concept increasingly popular of "human enhancement" which is at the core of this representational twist and novel notion that is currently made of the prosthetic body and the concept of disability.

    Quantitative Assessment of Motor Deficit with an Intelligent Key Object: A Pilot Study

    , , , , , ,
    In Proceedings of the EEE/RAS-EMBS International Conference on Rehabilitation Robotics (ICORR 2015 , 2015.

    Abstract

    Conventional assessment of sensorimotor functions is carried out using standard clinical scales which are subjective and insufficiently sensitive to changes in motor performance. Alternatively, sensor based systems offer a quantitative approach to motor assessment. We have designed a set of low cost, easy to use instrumented objects to assess a subject's performance during skilled tasks. In this pilot study we discuss the design of one object, the intelligent key, and describe how it can be used to assess a subject's performance during fine manipulation tasks using the proposed metrics and techniques. Three subjects with motor disability and one healthy subject participated in this study. Subjects performed insertion and rotation tasks that mimic the skills used in day to day key manipulation. A threshold detector algorithm based on Teager Energy Operator was applied to the object acceleration signal to quantify time spent struggling with the task and Spectral Arc Length was used to assess the smoothness of pronation/supination. Overall, the results indicate that increased difficulty in task performance correlates with decreased smoothness in task performance.

    Adaptive control of a robotic exoskeleton for neurorehabilitation

    , , ,
    In 2015 7th International IEEE/EMBS Conference on Neural Engineering (NER) IEEE , volume 1 , 2015.

    Abstract

    Neurorehabilitation efficiency increases with therapy intensity and subject's involvement during physical exercises. Robotic exoskeletons could bring both features, if they could adapt the level of assistance to patient's motor capacities. To this aim, we developed an exoskeleton controller, based on adaptive techniques, that can actively modulate the stiffness of the robotic device in function of the subject's activity. We tested this control law on one healthy subject with an upper-limb exoskeleton. The experiment consisted in learning a trajectory imposed by the robot. The early results show the different features allowed by our controller with respect to controllers commonly used for neurorehabilitation with exoskeletons.

2014

    Neuromuscular reorganisation after arm amputation revealed by stump EMG evoked by different phantom movements.

    , , , ,
    In 19th European Congress of Physical and Rehabilitation Medicine - SOFMER , 2014. (invited conference)

    Abstract

    After amputation, the cortical regions of which the neuronal activity was related to the control of the missing limb will gradually be active in relation to another, generally adjacent, part of the body. This reorganization often goes together with a vivid perception of the presence of the missing limb, called “phantom limb”. A little known phenomenon, but experienced by many amputees, is that the phantom limb can be moved at will. The patients feel the movements to be made in correspondence with their will and they are able to copy with their intact limb the movement they “performed” with their phantom limb. Results of recent studies suggest that, despite the cortical reorganisation, M1 still can send motor commands to the missing limb. These motor commands, being unable to project on the missing limb muscles, project on the preserved muscles of the stump, resulting in specific muscle activation patterns. We will (1) show the large panel of phantom movements experienced by patients and (2) make a comparison between the EMG patterns evoked by phantom movements and those generated by the patients for the control of myoelectric prostheses.

    Étude épidémiologique des mouvements volontaires du membre fantome dans les suites d’une amputation majeure de membre supérieur

    , , , , , , ,
    In Congrès annuel de la Société francaise de chirurgie de la main , 2014.

    Exploration of phantom limb mobility in arm amputees

    , , , , ,
    In Actes du Congrès Handicap 2014 - Les technologies d’assistance: de la compensation à l’autonomie, IFRATH , volume ISBN 978-2-9536899-4-5 , 2014.

    Effect of visual, tactile and proprioceptive sensory perturbations on grasp to lift tasks in healthy subjects.

    , , ,
    In Neural Control of Movement NCM , 2014.

    Abstract

    The present study uses an innovative instrumented object in order to analyse the effect of sensorimotor perturbations on several grasping tasks in healthy subjects. Our perspective is to develop a method in order to characterize the impairment of grasping and the compensatory strategies in patients with a stroke induced brain injury.

    Instrumented objects for the study and quantitative evaluation of grasping and manipulation strategies.

    , ,
    In European Journal of physical and rehabilitation medicine. Vol 50, Supl 1-3, p 64. , 2014.

    Abstract

    Impairment of grasping ability is very frequent in stroke survivors. However, despite the importance of this question and the numerous rehabilitation techniques dedicated to grasping, there still lacks comprehensive studies on grasping function and manipulation after stroke. In addition, there is also a lack of pertinent methods for the assessment of grasping function in hemiparetic patients; along with devices to evaluate patients’ motor performances in a simple way. We therefore developed a set of instrumented objects that can be grasped and manipulated by patients while wirelessly recording accelerations, orientations and forces applied over their surfaces. We present here the results obtained with one of this object (an instrumented rectangular box). An experimental protocol based on grasping/lifting and manipulation tasks was developed and run on a population of healthy subjects. Analysis was conducted on the data recorded, thanks to suitable developed metrics (timings analysis, force levels and repartition over the object, smoothness etc.). Results indicates that such simple instrumented object could be suitable to characterize sensorimotor impairments, which may help the understanding of grasping and manipulation strategies in hemiparetic patients and complement assessment using standard clinical scales.

    Toward the use of augmented auditory feedback for the rehabilitation of arm movements in stroke patients.

    , , , , , , , ,
    In European Journal of physical and rehabilitation medicine. Vol 50, Supl 1-3, , 2014.

    Abstract

    Introduction.– Following stroke, patients frequently demonstrate loss of motor control and function and altered kinematics of reaching movements (decreased velocity, loss of smoothness and loss of inter-joint coordination). Recent clinical observations using rehabilitation technology suggest that active training may reduce impairment thanks to motor learning. One method to promote motor learning is movement sonification. In this framework, we are exploring the potential of augmented auditory feedback as a means to guide movement performance during training (Knowledge of Performance) and not, as is usually done, simply to signal the success of the trial (Knowledge of Results). Material and methods.– Sonification of arm movement can provide patients with auditory feedback relative to the ongoing direction of the movement, coordination between shoulder and elbow movement and/or motion smoothness. This implies the on line recording of the movement and quantifying of the related impairment in order to generate feedback which stimulates appropriate audio-motor coupling. Results.– We present a literature review of previous pilot studies of sonification for motor rehabilitation and our current exploration involving different types of sonification and musical metaphors usable in rehabilitation (including source-filters, concatenative/granular synthesis and physical model sound synthesis). Conclusion.– The perspective of sonification for rehabilitation will be discussed.

2013

    Rééducation robotisée : bases conceptuelles et neurophysiologiques.

    , , , , ,
    In Revue Neurologique Vol 169S , 2013.

    Abstract

    -

    Analysis of grasping strategies and function in hemiparetic patients using an instrumented object

    , , , , , ,
    In Proceedings of the 13th International Conference on Rehabilitation Robotics (ICORR) , 2013.

    Abstract

    This paper validates a novel instrumented object, the iBox, dedicated to the analysis of grasping and manipulation. This instrumented box can be grasped and manipulated, is fitted with an Inertial Measurement Unit (IMU) and can sense the force applied on each side and transmits measured force, acceleration and orientation data wirelessly in real time. The iBox also provides simple access to data for analysing human motor control features such as the coordination between grasping and lifting forces and complex manipulation patterns. A set of grasping and manipulation experiments was conducted with 6 hemiparetic patients and 5 healthy control subjects. Measures made of the forces, kinematics and dynamics are developed, which can be used to analyse grasping and contribute to assessment in patients. Quantitative measurements provided by the iBox reveal numerous characteristics of the grasping strategies and function in patients: variations in the completion time, changes in the force distribution on the object and grasping force levels, difficulties to adjust the level of applied forces to the task and to maintain it, along with movement smoothness decrease and pathological tremor.

    Hyperstaticity for Ergonomic Design of a Wrist Exoskeleton

    , , , ,
    In Proceedings of the 13th International Conference on Rehabilitation Robotics (ICORR) , 2013.

    Abstract

    Increasing the level of transparency in rehabilitation devices has been one of the main goals in robot-aided neurorehabilitation for the past two decades. This issue is particularly important to robotic structures that mimic the human counterpart's morphology and attach directly to the limb. Problems arise for complex joints such as the human wrist, which cannot be accurately matched with a traditional mechanical joint. In such cases, mechanical differences between human and robotic joint cause hyperstaticity (i.e. overconstraint) which, coupled with kinematic misalignments, leads to uncontrolled force/torque at the joint. This paper focuses on the prono-supination (PS) degree of freedom of the forearm. The overall force and torque in the wrist PS rotation is quantified by means of a wrist robot. A practical solution to avoid hyperstaticity and reduce the level of undesired force/torque in the wrist is presented, which is shown to reduce 75% of the force and 68% of the torque.

2012

    A method for measuring the upper limb motion and computing a compatible exoskeleton trajectory

    , ,
    In Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'12) , 2012.

    Abstract

    This paper deals with the problem of computing trajectories for an exoskeleton that match a motion recorded on a given subject. Literature suggests that this problem can be solved by reconstructing the subject's joint motion using one of the numerous models available, and then feeding the exoskeleton with the joint trajectories. This is founded on the assumption that the exoskeleton kinematics reproduces the human kinematics. In practice, though, mismatches are unavoidable and lead to inaccuracies. We thus developed a method that is primarily based on an appropriate mechanical design: passive mechanisms are used to connect the exoskeleton with splints wore by the subject, in such a way that, within the workspace, there always exists a posture of the exoskeleton compatible with a given position and orientation of the splints. The trajectory computing method, by itself, consists of recording the position and orientation of the splints thanks to a conventional 3D motion tracker and to exploit standard robotics tools in order to compute an exoskeleton posture compatible with the measured human posture. Conclusive experimental results involving an existing 4 DoF upper-limb exoskeleton are shown.

    A Versatile Biomimetic Controller for Contact Tooling and Tactile Exploration

    , , , ,
    In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA'12) , 2012.

    Abstract

    This article presents a versatile controller that enables various contact tooling tasks with minimal prior knowledge of the tooled surface. The controller is derived from results of neuroscience studies that investigated the neural mechanisms utilized by humans to control and learn complex interactions with the environment. We demonstrate here the versatility of this controller in simulations of cutting, drilling and surface exploration tasks, which would normally require different control paradigms. We also present results on the exploration of an unknown surface with a 7-DOF manipulator, where the robot builds a 3D surface map of the surface profile and texture while applying constant force during motion. Our controller provides a unified control framework encompassing behaviors expected from the different specialized control paradigms like position control, force control and impedance control.

2011

    Changing human upper-limb synergies with an exoskeleton using viscous fields

    , , , ,
    In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA'11) , 2011.

    Abstract

    Robotic exoskeletons can apply forces distributed on the limbs of the subject they are connected to. This offers a great potential in the field of neurorehabilitation, to address the impairment of interjoint coordination in hemiparetic stroke patients. In these patients, the normal flexible joint rotation synergies are replaced by pathological fixed patterns of rotation. In this paper, we investigate how the concept of synergy can be exploited in the control of an upper limb exoskeleton. The long term goal is to develop a device capable of changing the joint synchronization of a patient performing exercises during rehabilitation. The paper presents a controller able of generating joint viscous torques in such a way that constraints on joint velocities can be imposed to the subject without constraining the hand motion. On another hand, the same formalism is used to describe synergies observed on the arm joint motion of subjects realizing pointing tasks. This approach is experimented on a 4 Degrees Of Freedom (DoF) upper arm exoskeleton with subjects performing pointing 3-dimensional tasks. Results exhibit the basic properties of the controller and show its capacity to impose an arbitrary chosen synergy without affecting the hand motion.

2010

    On the kinematic design of exoskeletons and their fixations with a human member

    ,
    In Proceedings of Robotics: Science and Systems (RSS'10) , 2010.

    Abstract

    A crucial problem in developing robotic exoskeletons lies in the design of physical connexions between the device and the human limb it is connected to. Indeed, because in general the human limb kinematics and the exoskeleton kinematics differ, using an embedment at each connection point leads to hyperstaticity. Therefore, uncontrollable forces can appear at the interaction port. To cope with this problem, literature suggests to add passive mechanisms at the fixation points. However, empirical solutions proposed so far suffer from a lack of proper analysis and generality. In this paper, the general problem of connecting two similar kinematic chains through multiple passive mechanisms is studied. A constructive method that allows to determine all the possible repartitions of freed DoFs across the different fixation mechanisms is derived. It includes formal proofs of global isostaticity. Practical usefulness is illustrated through an example with conclusive experimental results.

    Formal Methodology for Avoiding Hyperstaticity When Connecting an Exoskeleton to a Human Member

    ,
    In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA'10) , 2010.

    Abstract

    The design of a robotic exoskeleton often focuses on replicating the kinematics of the human limb that it is connected to. However, human joint kinematics is so complex that in practice, the kinematics of artificial exoskeletons fails to reproduce it exactly. This discrepancy results in hyperstaticity. Namely, uncontrolled interaction forces appear.

2009

    A Methodology to Design Kinematics of Fixations between an Orthosis and a Human Member

    ,
    In IEEE/ASME International Conference on Advanced Intelligent Mechatronics , 2009.

    Abstract

    The design of robotic orthoses focuses strongly on replicating kinematics of human limb. However, often sophisticated mechanisms which attempt at reproducing complex kinematics of human joints fails in adapting to geometrical variations of subjects sizes and eccentricities. One major that arises from this mismatching is an occurrence of hyperstaticity induced by the uncontrolled interaction forces. In this paper, we take the point of view of statics to investigate the force transmission problem, which is required for a fine force control. The main result of this study focuses on designing fixations between the orthosis and the human limb that provide additional degrees of freedom. The method involves two steps. Firstly, a set of possible solutions with respect to the isostaticity criterion is derived. Then, among these possible solutions, a set of design rules considering physiological aspects of transmitting forces to human limbs is used to select a preferred configuration. As an example, the method is applied to an existing 4 active DOF arm orthosis.

    Experimental Evaluation of Several Strategies for Human Motion Based Transparency Control

    , , ,
    In Proceedings of the International Symposium on Experimental Robotics (ISER'09) , 2009.

    Abstract

    Human interactive robots continue to improve human quality of life with their diverse applications. Their field includes, but is not limited to, haptic devices, force feedback tele-manipulation, surgical co-manipulation, medical rehabilitation, and various multi-degree of freedom robotic devices where the human operator and robot are often required to simultaneously execute tasks and collaborate with a specific share of forces/energy. More than tuning mechanical design, the robot control enhancement with a force sensor, is the key for increasing transparency (i.e the capacity for a robot to follow human movements without any human-perceptible resistive forces). With an ideal robot control, the interaction between robot and human would be extremely natural and fluid that the comanipulation of tasks would seem to be achieved with a transparent aid from the robot. For such, the classical force feedback control in certain cases still seems insufficient as is often limited by various factors (noise, bandwidth limitation, stability, sensor cost..etc). Our experiments are focused on evaluating the performance increase in terms of transparency of controller by using human motion predictions. We evaluate several ways to use predictive informations in the control to overcome present transparency limitations during a simple comanipulation pointing task.

2008

    How can human motion prediction increase transparency?

    , , ,
    In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA'08) , 2008.

    Abstract

    A major issue in the field of human-robot interaction for assistance to manipulation is transparency. This basic feature qualifies the capacity for a robot to follow human movements without any human-perceptible resistive forces. In this paper we address the issue of human motion prediction in order to increase the transparency of a robotic manipulator. Our aim is not to predict the motion itself, but to study how this prediction can be used to improve the robot transparency. For this purpose, we have designed a setup for performing basic planar manipulation tasks involving movements that are demanded to the subject and thus easily predictable. Moreover, we have developed a general controller which takes a predicted trajectory (recorded from offline free motion experiments) as an input and feeds the robot motors with a weighted sum of three controllers: torque feedforward, variable stiffness control and force feedback control. Subjects were then asked to perform the same task but with or without the robot assistance (which was not visible to the subject), and with several sets of gains for the controller tuning. First results seems to indicate that when a predictive controller with open loop torque feedforward is used, in conjunction with force- feedback control, the interaction forces are minimized. Therefore, the transparency is increased.

    Design and acceptability assessment of a new reversible orthosis

    , , , , , , , ,
    In Intelligent Robots and Systems, 2008. IROS 2008. IEEE/RSJ International Conference on , 2008.

    Abstract

    We present a new device aimed at being used for upper limb rehabilitation. Our main focus was to design a robot capable of working in both the passive mode (i.e. the robot shall be strong enough to generate human-like movements while guiding the weak arm of a patient) and the active mode (i.e. the robot shall be able of following the arm without disturbing human natural motion). This greatly challenges the design, since the system shall be reversible and lightweight while providing human compatible strength, workspace and speed. The solution takes the form of an orthotic structure, which allows control of human arm redundancy contrarily to clinically available upper limb rehabilitation robots. It is equipped with an innovative transmission technology, which provides both high gear ratio and fine reversibility. In order to evaluate the device and its therapeutic efficacy, we compared several series of pointing movements in healthy subjects wearing and not wearing the orthotic device. In this way, we could assess any disturbing effect on normal movements. Results show that the main movement characteristics (direction, duration, bell shape profile) are preserved.

2007

    Innovative concept of unfoldable wheel with an active contact adaptation mechanism

    , ,
    In Proceedings of the 12th IFToMM World Congress in Mechanism and Machine Science , 2007.

    Abstract

    In this paper, an original expandable mechanism for unfolding wheels is proposed. This mechanism combines two elementary mechanisms. One allows the deployment of the rim while the other one ensures the contact shape adaptation. In the first section, we analyse the different deployment mechanisms already proposed in the literature. Then, the design of the rim expansion mechanism is described and two complementary versions are proposed. Last, based on terramechanics models, a contact surface adaptation mechanism is proposed. This system allows to adapt the wheel-ground interaction properties and make the wheel ables to improve its traction and steering performance on soft soil.

2006

    Design of an innovative unfoldable wheel with contact surface adaptation mechanism for planetary rovers

    , ,
    In Proceedings of ASTRA'06 : 9th ESA Workshop on Advanced Space Technologies for Robotics and Automation , 2006.

    Abstract

    In this paper, an original expandable mechanism for unfolding wheels is proposed. This mechanism combines two elementary mechanisms. One allows the deployment of the rim while the other one ensuring the contact shape adaptation. In a first section, we analyse the different deployment mechanisms already proposed in the literature. Then, the design of the rim expansion mechanism is described and two complementary version are proposed. Last, based on terramechanics model, a contact surface adaptation mechanism is proposed. This system allows to adapt the wheel-ground interaction properties and make the wheel ables to improve its traction and steering performance on soft soil.


Thesis

2010


Vulgarization articles

2017

    The Myth of Human Enhancement

    CNRS News , 2017.

2014

    Le mythe de l'humain augmenté

    Libération / Journal du CNRS , 2014.

    Abstract

    Face à certains transhumanistes qui prônent le dépassement de notre condition biologique, nous devons revenir aux réalités des personnes appareillées qui ne sont pas des hommes machines.

    Les exosquelettes robotisés : réalités et perspectives.

    , , ,
    In Académie de Chirurgie Magazine , volume 13 , 2014.