Feedback control of arm movements using Neuro-Muscular Electrical Stimulation (NMES) combined with a lockable, passive exoskeleton for gravity compensation

Within the European project MUNDUS, an assistive framework was developed for the support of arm and hand functions during daily life activities in severely impaired people. This contribution aims at designing a feedback control system for Neuro-Muscular Electrical Stimulation (NMES) to enable reaching functions in people with no residual voluntary control of the arm and shoulder due to high level spinal cord injury. NMES is applied to the deltoids and the biceps muscles and integrated with a three degrees of freedom (DoFs) passive exoskeleton, which partially compensates gravitational forces and allows to lock each DOF. The user is able to choose the target hand position and to trigger actions using an eyetracker system. The target position is selected by using the eyetracker and determined by a marker-based tracking system using Microsoft Kinect. A central controller, i.e., a finite state machine, issues a sequence of basic movement commands to the real-time arm controller. The NMES control algorithm sequentially controls each joint angle while locking the other DoFs. Daily activities, such as drinking, brushing hair, pushing an alarm button, etc., can be supported by the system. The robust and easily tunable control approach was evaluated with five healthy subjects during a drinking task. Subjects were asked to remain passive and to allow NMES to induce the movements. In all of them, the controller was able to perform the task, and a mean hand positioning error of less than five centimeters was achieved. The average total time duration for moving the hand from a rest position to a drinking cup, for moving the cup to the mouth and back, and for finally returning the arm to the rest position was 71 s.EC/FP7/248326/EU/MUltimodal Neuroprostesis for Daily Upper limb Support/MUNDU

Functional and usability assessment of a robotic exoskeleton arm to support activities of daily life

An assistive device for upper limb support was developed and evaluated in terms of usability, user satisfaction and motor performance on six end-users affected by neuro-motor disorders (three spinal cord injury; one multiple sclerosis; two Friedreich's ataxia). The system consisted of a lightweight 3-degrees-of-freedom robotic exoskeleton arm for weight relief, equipped with electromagnetic brakes. Users could autonomously control the brakes using a USB-button or residual electromyogram activations. The system functionally supported all of the potential users in performing reaching and drinking tasks. For three of them, time, smoothness, straightness and repeatability were also comparable to healthy subjects. An overall high level of usability (system usability score, median value of 90/100) and user satisfaction (Tele-healthcare Satisfaction Questionnaire - Wearable Technology, median value of 104/120) were obtained for all subject

MUNDUS project : MUltimodal neuroprosthesis for daily upper limb support

Background: MUNDUS is an assistive framework for recovering direct interaction capability of severely motor impaired people based on arm reaching and hand functions. It aims at achieving personalization, modularity and maximization of the user’s direct involvement in assistive systems. To this, MUNDUS exploits any residual control of the end-user and can be adapted to the level of severity or to the progression of the disease allowing the user to voluntarily interact with the environment. MUNDUS target pathologies are high-level spinal cord injury (SCI) and neurodegenerative and genetic neuromuscular diseases, such as amyotrophic lateral sclerosis, Friedreich ataxia, and multiple sclerosis (MS). The system can be alternatively driven by residual voluntary muscular activation, head/eye motion, and brain signals. MUNDUS modularly combines an antigravity lightweight and non-cumbersome exoskeleton, closed-loop controlled Neuromuscular Electrical Stimulation for arm and hand motion, and potentially a motorized hand orthosis, for grasping interactive objects. Methods: The definition of the requirements and of the interaction tasks were designed by a focus group with experts and a questionnaire with 36 potential end-users. Five end-users (3 SCI and 2 MS) tested the system in the configuration suitable to their specific level of impairment. They performed two exemplary tasks: reaching different points in the working volume and drinking. Three experts evaluated over a 3-level score (from 0, unsuccessful, to 2, completely functional) the execution of each assisted sub-action. Results: The functionality of all modules has been successfully demonstrated. User’s intention was detected with a 100% success. Averaging all subjects and tasks, the minimum evaluation score obtained was 1.13 ± 0.99 for the release of the handle during the drinking task, whilst all the other sub-actions achieved a mean value above 1.6. All users, but one, subjectively perceived the usefulness of the assistance and could easily control the system. Donning time ranged from 6 to 65 minutes, scaled on the configuration complexity. Conclusions: The MUNDUS platform provides functional assistance to daily life activities; the modules integration depends on the user’s need, the functionality of the system have been demonstrated for all the possible configurations, and preliminary assessment of usability and acceptance is promising

Test- und Trainingsfahrrad für Personen mit Querschnittlähmung zur Optimierung der Stimulationsparameter

Mit Hilfe von Funktioneller Elektrostimulation (FES) der Beinmuskulatur wird es Personen mit Querschnittlähmung möglich auf adaptierten Fahrrädern eine Tretbewegung durchzuführen und auch - mit Einschränkungen - selbstständig zu fahren. Dabei übernimmt ein Stimulator an Stelle des Zentralnervensystems die Aufgabe die einzelnen Muskeln und Muskelgruppen in den entsprechenden Winkelbereichen der Tretkurbel zu aktivieren. Die Aktivierung der Muskeln erfolgt über Oberflächenelektroden die mittels einer Klebefläche auf der Haut des Fahrers angebracht sind und über das von ihnen erzeugte elektrische Feld den Muskel zur Kontraktion anregen.Das Fahrradfahren mit eigener Muskelkraft kann als therapeutische Maßnahme im Rahmen der Rehabilitation von querschnittgelähmten Personen eingesetzt werden und hat neben den erwünschten psychologischen Effekten auch zahlreiche positive physiologische Auswirkungen. Ziel dieser Arbeit war es ein Fahrrad für Personen mit Rückenmarksverletzungen zu entwickeln, welches zum einen als Prüfstand dient und zum anderen als einsatzfähiges Trainingsfahrrad Verwendung findet. Auf Grund von Tretkurbeln mit integrierter Kraftmessung ermöglicht das Fahrrad in seiner Funktion als Prüfstand über vorbereitete Messroutinen eine einfache Ermittlung der für die einzelnen Fahrer effizienten Stimulationsparameter. Durch die Möglichkeit das Tretlager vertikal und horizontal zu verstellen und den Sitz und die Rückenlehne unabhängig von einander in einem großen Winkelbereich zu neigen ist es auch möglich die Sitzposition des jeweiligen Fahrers leistungsoptimal anzupassen. Mit diesen optimierten Parametern kann der Querschnittgelähmte nachfolgend auf dem Fahrrad trainieren und auf geeigneten Strecken im Freien Rad fahren.Ein in das Fahrrad integrierter Nabenmotor ermöglicht es eine konstante Umdrehungsgeschwindigkeit der Tretkurbeln für die Messroutinen vorzugeben und dient als Hilfsmotor, um dem Fahrer bei Steigungen und nach Ermüdung der Muskulatur zu unterstützen.Im Zuge des Projektes wurde auch ein Auswerteprogramm entwickelt, das eine schnelle Auswertung der Messergebnisse vor Ort im Rehabilitationszentrum bietet. Während dieser Messungen konnten erste viel versprechende Ergebnisse gewonnen werden und einigen querschnittgelähmten Probanden wurden so erste Eindrücke über das Radfahren mittels FES vermittelt.Functional electrical stimulation (FES) of the lower limbs enables persons with a spinal cord injury to perform cycling on modified tricycles. In this case the activation of the individual muscles and muscle groups in the corresponding crank angle areas is carried out by a stimulator instead of the central nerve system. Therefore surface electrodes are attached above the selected muscles which are stimulated to generate contractions due to the induced electrical field. Cycling with the power of their leg muscles can be an important supporting therapy for paraplegic persons during rehabilitation and has beside the psychological benefits also numerous positive physiological effects.The aim of this project was to develop a tricycle for persons with functional deficits of the lower limbs caused by injuries of the spinal cord. The vehicle should both work as a test bed to determine the optimal stimulation patterns for the individual rider, and should also find application as a tricycle for regular exercise. In its function as a test bed it is possible to choose between several prepared test routines and together with the integrated force measurement in the cranks the relation between stimulation and the power output can be recorded. Due to the possibility to vary the horizontal and vertical position of the crank shaft and to incline the seat and the backrest independently in a wide angle area an efficient sitting position for each driver can be adjusted. After running through the different test routines the person with paraplegia can use his/ her optimized settings to exercise on the tricycle or cycle on suitable routes outside the rehabilitation centre. There is a hub motor integrated in the tricycle, which can drive the cranks at a constant cadence for the measurements and supports the driver to get over steep inclinations or in the case of muscle fatigue. For a fast data processing a program was developed for the particular purpose to evaluate the measurements on site at the rehabilitation centre. During these measurements first promising results have been found and most of the paraplegic test persons were able to perform cycling by means of FES.10