Browsing by Author "Keller, Thierry"
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Item Absolute position calculation for a desktop mobile rehabilitation robot based on three optical mouse sensors(2011) Zabaleta, Haritz; Valencia, David; Perry, Joel; Veneman, Jan; Keller, Thierry; Tecnalia Research & InnovationArmAssist is a wireless robot for after stroke upper limb rehabilitation. In this paper, we describe a method based on artificial landmark navigation system. The navigation system is only based in three optical mouse sensors. This enables to build a cheap but reliable position sensor. Two of the sensors are the data source for odometry calculations, and the third optical mouse sensor takes very low resolution pictures of a custom designed mat. These pictures are processed by an optical symbol recognition algorithm which will estimate the orientation of the robot and recognize the landmarks placed on the mat. The data fusion strategy is described to detect the misclassifications of the landmarks in order to fuse only the reliable information. The orientation given by the OSR algorithm is used to improve significantly the odometry and the recognition of the landmarks is used to reference the odometry to a absolute coordinate systemItem Analysis of the movements generated by a multi-field functional electrical stimulation device for upper extremity rehabilitation(2022-10) Martín-Odriozola, Aitor; Rodríguez-de-Pablo, Cristina; Caceres-Salegi, Ane; García-Calleja, Andrea; Marín-Ojea, Juan Ignacio; Hernández, Erik; Imatz-Ojanguren, Eukene; Keller, Thierry; Zabaleta-Rekondo, Haritz; Martín‐Odriozola, Aitor; Rodríguez‐de‐Pablo, Cristina; Caceres‐Salegi, Ane; García‐Calleja, Andrea; Marín‐Ojea, Juan Ignacio; Imatz‐Ojanguren, Eukene; Zabaleta‐Rekondo, Haritz; Medical Technologies; Tecnalia Research & InnovationBackground: The most common chronic sequela after stroke is the loss of arm function, and functional electrical stimulation (FES) applied to the forearm muscles is one of the options to treat it. Surface multi-field electrodes have emerged, showing a great potential to improve the selectivity of the stimulation, delay muscle fatigue, and provide easier donning and doffing. The muscular selectivity takes on special relevance in the rehabilitation of the upper extremity as hand dexterity requires a wide diversity of specific muscle actions. Methods: This pilot study analyses the movements generated in the wrist and fingers using a commercial multi-field technology-based FES device (Fesia Grasp). The study included five patients with hemiplegic subacute stroke, in which scanning of all cathodes of the electrode was carried out daily for 5 days, in two different forearm positions, with the resulting movements being labeled by experienced therapists. Results: The aim of this pilot study was to determine if there were differences between subjects and between forearm positions in terms of produced movements. Movements of the wrist (two movements) and the fingers (six movements) could be achieved in two different forearm positions. Conclusions: The multi-field electrode of Fesia Grasp enables to generate a wide range of movements of the hand in different positions. This fact could allow to produce more physiological movement patterns during the rehabilitation process with FES, which could have a beneficial effect on the recovery of patients with neurological diseases.Item ArmAssist Robotic System versus Matched Conventional Therapy for Poststroke Upper Limb Rehabilitation: A Randomized Clinical Trial: A randomized clinical trial(2017) Tomić, Tijana J. Dimkić; Savić, Andrej M.; Vidaković, Aleksandra S.; Rodić, Sindi Z.; Isaković, Milica S.; Rodríguez-de-Pablo, Cristina; Keller, Thierry; Konstantinović, Ljubica M.; Tecnalia Research & InnovationThe ArmAssist is a simple low-cost robotic system for upper limb motor training that combines known benefits of repetitive task-oriented training, greater intensity of practice, and less dependence on therapist assistance. The aim of this preliminary study was to compare the efficacy of ArmAssist (AA) robotic training against matched conventional arm training in subacute stroke subjects with moderate-to-severe upper limb impairment. Twenty-six subjects were enrolled within 3 months of stroke and randomly assigned to the AA group or Control group (n = 13 each). Both groups were trained 5 days per week for 3 weeks. The primary outcome measure was Fugl-Meyer Assessment-Upper Extremity (FMA-UE) motor score, and the secondary outcomes were Wolf Motor Function Test-Functional Ability Scale (WMFT-FAS) and Barthel index (BI). The AA group, in comparison to the Control group, showed significantly greater increases in FMA-UE score (18.0 +/- 9.4 versus 7.5 +/- 5.5, p = 0.002) and WMFT-FAS score (14.1 +/- 7.9 versus 6.7 +/- 7.8, p = 0.025) after 3 weeks of treatment, whereas the increase in BI was not significant (21.2 +/- 24.8 versus 13.1 +/- 10.7, p = 0.292). There were no adverse events. We conclude that arm training using the AA robotic device is safe and able to reduce motor deficits more effectively than matched conventional arm training in subacute phase of stroke.Item Consensus-Based Core Set of Outcome Measures for Clinical Motor Rehabilitation After Stroke—A Delphi Study(2020-09-02) Pohl, Johannes; Held, Jeremia Philipp Oskar; Verheyden, Geert; Alt Murphy, Margit; Engelter, Stefan; Flöel, Agnes; Keller, Thierry; Kwakkel, Gert; Nef, Tobias; Ward, Nick; Luft, Andreas Rüdiger; Veerbeek, Janne Marieke; Tecnalia Research & InnovationIntroduction: Outcome measures are key to tailor rehabilitation goals to the stroke patient’s individual needs and to monitor poststroke recovery. The large number of available outcome measures leads to high variability in clinical use. Currently, an internationally agreed core set of motor outcome measures for clinical application is lacking. Therefore, the goal was to develop such a set to serve as a quality standard in clinical motor rehabilitation poststroke. Methods: Outcome measures for the upper and lower extremities, and activities of daily living (ADL)/stroke-specific outcomes were identified and presented to stroke rehabilitation experts in an electronic Delphi study. In round 1, clinical feasibility and relevance of the outcome measures were rated on a 7-point Likert scale. In round 2, those rated at least as “relevant” and “feasible” were ranked within the body functions, activities, and participation domains of the International Classification of Functioning, Disability, and Health (ICF). Furthermore, measurement time points poststroke were indicated. In round 3, answers were reviewed in reference to overall results to reach final consensus.Item Consistent arm rehabilitation from clinical to home environment - Integrating the universal haptic drive into the TeleReha software platform(Springer International Publishing, 2013) Veneman, Jan F.; Jung, Je Hyung; Perry, Joel C.; Keller, Thierry; Tecnalia Research & Innovation; Medical TechnologiesThis paper describes the current work on integrating a haptic force feedback device, named the Universal Haptic Drive (UHD), for upper limb training into a software platform for telerehabilitation which has been developed for at-home rehabilitation after stroke. The aim of the integration is to provide a consistent training and assessment platform during the entire rehabilitation period, from clinical facilities to home, while also allowing less specialized supervision to rehabilitate a stroke patient.Item A decision support system for electrode shaping in multi-pad FES foot drop correction(2017-07-03) Malešević, Jovana; Dedijer Dujović, Suzana; Savić, Andrej M.; Konstantinović, Ljubica; Vidaković, Aleksandra; Bijelić, Goran; Malešević, Nebojša; Keller, Thierry; Tecnalia Research & Innovation; SG; MercadoBackground: Functional electrical stimulation (FES) can be applied as an assistive and therapeutic aid in the rehabilitation of foot drop. Transcutaneous multi-pad electrodes can increase the selectivity of stimulation; however, shaping the stimulation electrode becomes increasingly complex with an increasing number of possible stimulation sites. We described and tested a novel decision support system (DSS) to facilitate the process of multi-pad stimulation electrode shaping. The DSS is part of a system for drop foot treatment that comprises a customdesigned multi-pad electrode, an electrical stimulator, and an inertial measurement unit. Methods: The system was tested in ten stroke survivors (3-96 months post stroke) with foot drop over 20 daily sessions. The DSS output suggested stimulation pads and parameters based on muscle twitch responses to short stimulus trains. The DSS ranked combinations of pads and current amplitudes based on a novel measurement of the quality of the induced movement and classified them based on the movement direction (dorsiflexion, plantar flexion, eversion and inversion) of the paretic foot. The efficacy of the DSS in providing satisfactory pad-current amplitude choices for shaping the stimulation electrode was evaluated by trained clinicians. The range of paretic foot motion was used as a quality indicator for the chosen patterns. Results: The results suggest that the DSS output was highly effective in creating optimized FES patterns. The position and number of pads included showed pronounced inter-patient and inter-session variability; however, zones for inducing dorsiflexion and plantar flexion within the multi-pad electrode were clearly separated. The range of motion achieved with FES was significantly greater than the corresponding active range of motion (p < 0.05) during the first three weeks of therapy. Conclusions: The proposed DSS in combination with a custom multi-pad electrode design covering the branches of peroneal and tibial nerves proved to be an effective tool for producing both the dorsiflexion and plantar flexion of a paretic foot. The results support the use of multi-pad electrode technology in combination with automatic electrode shaping algorithms for the rehabilitation of foot drop.Item Design and Development of OECT Logic Circuits for Electrical Stimulation Applications(2022-04-14) Kostić, Miloš; Kojić, Vladimir; Ičagić, Savo; Andersson Ersman, Peter; Mulla, Mohammad Yusuf; Strandberg, Jan; Herlogsson, Lars; Keller, Thierry; Štrbac, Matija; Tecnalia Research & Innovation; SGThis paper presents the first successful implementation of fully printed electronics for flexible and wearable smart multi-pad stimulation electrodes intended for use in medical, sports and lifestyle applications. The smart multi-pad electrodes with the electronic circuits based on organic electrochemical transistor (OECT)-based electronic circuits comprising the 3–8 decoder for active pad selection and high current throughput transistors for switching were produced by multi-layer screen printing. Devices with different architectures of switching transistors were tested in relevant conditions for electrical stimulation applications. An automated testbed with a configurable stimulation source and an adjustable human model equivalent circuit was developed for this purpose. Three of the proposed architectures successfully routed electrical currents of up to 15 mA at an output voltage of 30 V, while one was reliably performing even at 40 V. The presented results demonstrate feasibility of the concept in a range of conditions relevant to several applications of electrical stimulation.Item Design of multi-pad electrotactile system envisioned as a feedback channel for supernumerary robotic limbs(2022-10) Boljanić, Tanja; Isaković, Milica; Malešević, Jovana; Formica, Domenico; Di Pino, Giovanni; Keller, Thierry; Štrbac, Matija; SG; Tecnalia Research & InnovationBackground: Providing real-time haptic feedback is an important, but still not sufficiently explored aspect of the use of supernumerary robotic limbs (SRLs). We present a multi-pad electrode for conveying multi-modal proprioceptive and sensory information from SRL to the user's thigh and propose a method for stimuli calibration. Methods: Within two pilot tests, we investigated return electrode configuration and active electrode discrimination in three healthy subjects to select the appropriate electrode pad topology. Based on the obtained results and anthropometric data from the literature, the electrode was designed to have three branches of 10 pads and two additional pads that can be displaced over/under the electrode branches. The electrode was designed to be connected to the stimulator that allows full multiplexing so that specific branches can serve as a common return electrode. To define the procedure for application of this system, the sensation, localization, and discomfort thresholds applicable for the novel electrode were determined and analyzed in 10 subjects. Results: The results showed no overlaps between the three thresholds for individual pads, with significantly different average values, suggesting that the selected electrode positioning and design provide a good active range of useful current amplitude. The results of the subsequent analysis suggested that the stimuli intensity level of 200% of the sensation threshold is the most probable value of the localization threshold. Furthermore, this level ensures a low chance (i.e., 0.7%) of reaching the discomfort. Conclusions: We believe that envisioned electrotactile system could serve as a high bandwidth feedback channel that can be easily set up to provide proprioceptive and sensory feedback from supernumerary limbs.Item Development of computer games for assessment and training in post-stroke arm telerehabilitation(2012) Rodriguez-De-Pablo, Cristina; Perry, Joel C.; Cavallaro, Francesca I.; Zabaleta, Haritz; Keller, Thierry; Tecnalia Research & InnovationStroke is the leading cause of long term disability among adults in industrialized nations. The majority of these disabilities include deficiencies in arm function, which can make independent living very difficult. Research shows that better results in rehabilitation are obtained when patients receive more intensive therapy. However this intensive therapy is currently too expensive to be provided by the public health system, and at home few patients perform the repetitive exercises recommended by their therapists. Computer games can provide an affordable, enjoyable, and effective way to intensify treatment, while keeping the patient as well as their therapists informed about their progress. This paper presents the study, design, implementation and user-testing of a set of computer games for at-home assessment and training of upper-limb motor impairment after stroke.Item European evidence-based recommendations for clinical assessment of upper limb in neurorehabilitation (CAULIN): data synthesis from systematic reviews, clinical practice guidelines and expert consensus: data synthesis from systematic reviews, clinical practice guidelines and expert consensus(2021-12) Prange-Lasonder, Gerdienke B.; Alt Murphy, Margit; Lamers, Ilse; Hughes, Ann-Marie; Buurke, Jaap H.; Feys, Peter; Keller, Thierry; Klamroth-Marganska, Verena; Tarkka, Ina M.; Timmermans, Annick; Burridge, Jane H.; Tecnalia Research & InnovationBackground: Technology-supported rehabilitation can help alleviate the increasing need for cost-effective rehabilitation of neurological conditions, but use in clinical practice remains limited. Agreement on a core set of reliable, valid and accessible outcome measures to assess rehabilitation outcomes is needed to generate strong evidence about effectiveness of rehabilitation approaches, including technologies. This paper collates and synthesizes a core set from multiple sources; combining existing evidence, clinical practice guidelines and expert consensus into European recommendations for Clinical Assessment of Upper Limb In Neurorehabilitation (CAULIN). Methods: Data from systematic reviews, clinical practice guidelines and expert consensus (Delphi methodology) were systematically extracted and synthesized using strength of evidence rating criteria, in addition to recommendations on assessment procedures. Three sets were defined: a core set: strong evidence for validity, reliability, responsiveness and clinical utility AND recommended by at least two sources; an extended set: strong evidence OR recommended by at least two sources and a supplementary set: some evidence OR recommended by at least one of the sources. Results: In total, 12 measures (with primary focus on stroke) were included, encompassing body function and activity level of the International Classification of Functioning and Health. The core set recommended for clinical practice and research: Fugl-Meyer Assessment of Upper Extremity (FMA-UE) and Action Research Arm Test (ARAT); the extended set recommended for clinical practice and/or clinical research: kinematic measures, Box and Block Test (BBT), Chedoke Arm Hand Activity Inventory (CAHAI), Wolf Motor Function Test (WMFT), Nine Hole Peg Test (NHPT) and ABILHAND; the supplementary set recommended for research or specific occasions: Motricity Index (MI); Chedoke-McMaster Stroke Assessment (CMSA), Stroke Rehabilitation Assessment Movement (STREAM), Frenchay Arm Test (FAT), Motor Assessment Scale (MAS) and body-worn movement sensors. Assessments should be conducted at pre-defined regular intervals by trained personnel. Global measures should be applied within 24 h of hospital admission and upper limb specific measures within 1 week. Conclusions: The CAULIN recommendations for outcome measures and assessment procedures provide a clear, simple, evidence-based three-level structure for upper limb assessment in neurological rehabilitation. Widespread adoption and sustained use will improve quality of clinical practice and facilitate meta-analysis, critical for the advancement of technology-supported neurorehabilitation.Item Evoked sensations with transcutaneous electrical stimulation with different frequencies, waveforms, and electrode configurations(2023-01) Imatz-Ojanguren, Eukene; Keller, Thierry; Imatz‐Ojanguren, Eukene; Medical Technologies; Tecnalia Research & InnovationBackground: Current Perception Threshold (CPT) is a technique used for diagnostic purposes that applies sinusoidal currents transcutaneously at 5 Hz, 250 Hz, and 2KHz to preferentially excite C, Aδ, and Aβ afferent nerve fibers correspondingly. This fact may be interesting for evoking different electrotactile sensations for a wide variety of applications. Methods: Sensations evoked by 5 Hz, 250 Hz, and 2KHz frequencies; sinusoidal, square, and 250 μs-pulsed waveforms; and conventional and concentric electrode configurations were analyzed in 19 healthy volunteers. Stimuli were applied in the dorsum of the hand in a double-blind manner and CPTs were defined based on participants' verbal feedback. After each stimulus participants filled in a form with sensation modality, irradiation, intensity, and emotion descriptors. Results: The frequency showed a significant effect on the four domains of evoked sensations and the waveform showed a significant effect on the modality domain. For most waveform and electrode configuration combinations, 5 Hz evoked mostly a low-intensity prickling sensation; 250 Hz mostly evoked an uncomfortable medium-intensity tingling sensation; and 2KHz mostly evoked a low-intensity tingling sensation. No thermal or noxious sensations were evoked. A significant interaction effect was only found between the frequency and the waveform factors. The electrode configuration did not show either a significant effect on the evoked sensations or an interaction effect with the frequency or waveform type. Conclusions: Transcutaneous electrical stimulation may evoke different sensations at different frequencies due to the preferential activation of different fiber types. The results of these analysis could be used to enhance human-machine/computer-interaction systems based on electrotactile feedback.Item Feasibility of Using Neuro-Fuzzy Subject-Specific Models for Functional Electrical Stimulation Induced Hand Movements(2015-09-01) Imatz-Ojanguren, Eukene; Irigoyen, Eloy; Valencia, David; Keller, Thierry; Tecnalia Research & Innovation; Medical TechnologiesFunctional Electrical Stimulation (FES) is a technique that artificially elicits muscle contractions and it is used to restore motor/sensory functions in both assistive and therapeutic applications. The use of multi-field surface electrodes is a novel popular approach in transcutaneous FES applications. Lately, hybrid systems that combine artificial neural networks and fuzzy logic have also been proposed for many applications in different areas. This paper presents the possibility of combining both approaches for obtaining subject-specific models of FES induced hand movements for grasping applications. Data of the hand and finger motion from two subjects affected by acquired brain injury were used to train two different approaches: coactive neuro-fuzzy inference system and recurrent fuzzy neural network. Preliminary results show that these approaches can be considered in modelling applications for their ability to learn and predict main characteristics of the system, as well as providing useful information from the original system that could be interpreted as subject-specific knowledge.Item A foot drop compensation device based on surface multi-field functional electrical stimulation—Usability study in a clinical environment(2019) Imatz-Ojanguren, Eukene; Sánchez-Márquez, Gema; Asiain-Aristu, Jose Ramón; Cueto-Mendo, Joxean; Jaunarena-Goicoechea, Edurne; Zabaleta, Haritz; Keller, Thierry; Tecnalia Research & InnovationFunctional electrical stimulation applies electrical pulses to the peripheral nerves to artificially achieve a sensory/motor function. When applied for the compensation of foot drop it provides both assistive and therapeutic effects. Multi-field electrodes have shown great potential but may increase the complexity of these systems. Usability aspects should be checked to ensure their success in clinical environments. We developed the Fesia Walk device, based on a surface multi-field electrode and an automatic calibration algorithm, and carried out a usability study to check the feasibility of integrating this device in therapeutic programs in clinical environments. The study included 4 therapists and 10 acquired brain injury subjects (8 stroke and 2 traumatic brain injury).Item HoMEcare aRm rehabiLItatioN (MERLIN): telerehabilitation using an unactuated device based on serious games improves the upper limb function in chronic stroke: telerehabilitation using an unactuated device based on serious games improves the upper limb function in chronic stroke(2021-03) Rozevink, Samantha G.; van der Sluis, Corry K.; Garzo, Ainara; Keller, Thierry; Hijmans, Juha M.; Tecnalia Research & Innovation; Medical TechnologiesHoMEcare aRm rehabiLItatioN (MERLIN) is an unactuated version of the robotic device ArmAssist combined with a telecare platform. Stroke patients are able to train the upper limb function using serious games at home. The aim of this study is to investigate the effect of MERLIN training on the upper limb function of patients with unilateral upper limb paresis in the chronic phase of stroke (> 6 months post stroke). Patients trained task specific serious games for three hours per week during six weeks using an unactuated version of a robotic device. Progress was monitored and game settings were tailored through telerehabilitation. Measurements were performed six weeks pre-intervention (T0), at the start (T1), end (T2) and six weeks post-intervention (T3). Primary outcome was the Wolf Motor Function Test (WMFT). Secondary outcomes were other arm function tests, quality of life, user satisfaction and motivation.Item MERLIN: Upper-Limb Rehabilitation Robot System for Home Environment(Springer Science and Business Media Deutschland GmbH, 2022) Garzo, Ainara; Arcas-Ruiz-Ruano, Javier; Dorronsoro, Iñigo; Gaminde, Gabriel; Jung, Je Hyung; Téllez, Javier; Keller, Thierry; Medical Technologies; Tecnalia Research & InnovationArmAssist is a cost-effective robotic system for post-stroke upper-limb rehabilitation. The system incorporates the ArmAssist Assessment platform based on serious games that enables fast, quantitative and automatic evaluation of the arm functions. The aim of the MERLIN European project is to bring this system to the patients’ homes to personalize the therapy with reduced supervision while increasing the number of movement repetitions to improve the effectiveness. To this end, the ArmAssist system developed by TECNALIA, has been integrated with GMV’s Antari Home Care platform, to customize and supervise the training remotely. Additionally, several technical improvements have been done to enhance the usability and functionality of the system according to the patients and therapists’ feedback. In this paper, the technical progress of the MERLIN system is presented.Item Modelling the Component-based Architecture and Safety Contracts of ArmAssist in Papyrus for Robotics(Institute of Electrical and Electronics Engineers Inc., 2021-06) Martinez, Jabier; Ruiz, Alejandra; Garzo, Ainara; Keller, Thierry; Radermacher, Ansgar; Tonetta, Stefano; Tecnalia Research & Innovation; SWT; Quantum; Medical TechnologiesHealthcare robots are increasingly being used and the way they are engineered they still have several challenges regarding reference models and validation. In this experience report we focus on the ArmAssist robotic system and how it can be modelled including safety considerations for validation in early design phases. ArmAssist is an upper-limb robotic system for stroke rehabilitation based on serious games. The open-source tool Papyrus for Robotics was used for modelling the robotic system in close collaboration with neurorehabilitation domain experts. Papyrus for Robotics includes new functionalities that we contributed for contract-based design at component and system level, allowing to make explicit and validate the safety considerations using formal languages. In our case, the assertions are expressed in OCL and Othello. We present the resulting model and a discussion from domain experts.Item Neuro-fuzzy models for hand movements induced by functional electrical stimulation in able-bodied and hemiplegic subjects(2016-11-01) Imatz-Ojanguren, Eukene; Irigoyen, Eloy; Valencia-Blanco, David; Keller, Thierry; Tecnalia Research & Innovation; Medical TechnologiesFunctional Electrical Stimulation (FES) may be effective as a therapeutic treatment for improving functional reaching and grasping. Upper-limb FES models for predicting joint torques/angles from stimulation parameters can be useful to support the iterative design and development of neuroprostheses. Most such models focused on shoulder or elbow joints and were defined for fixed electrode configurations. This work proposes the use of a Recurrent Fuzzy Neural Network (RFNN) for modeling FES induced wrist, thumb, and finger movements based on surface multi-field electrodes and kinematic data from able-bodied and neurologically impaired subjects. Different combinations of structure parameters comprising fuzzy term numbers and feedback approaches were tested and analyzed in order to see their effect on the model performance for six subjects. The results showed mean success rates in the range from 60% to 99% and best success rates in the range from 78% to 100% on test data for all subjects. No common trend was found across subjects regarding structure parameters. The model showed the ability to successfully reproduce the response to FES for both able-bodied and hemiplegic subjects at least with one of the tested combinations.Item Optimization of Semiautomated Calibration Algorithm of Multichannel Electrotactile Feedback for Myoelectric Hand Prosthesis(2019) Isaković, Milica; Malešević, Jovana; Keller, Thierry; Kostić, Miloš; Štrbac, Matija; Isakovic, Milica; Tecnalia Research & Innovation; SGThe main drawback of the commercially available myoelectric hand prostheses is the absence of somatosensory feedback. We recently developed a feedback interface for multiple degrees of freedom myoelectric prosthesis that allows proprioceptive and sensory information (i.e., grasping force) to be transmitted to the wearer instantaneously. High information bandwidth is achieved through intelligent control of spatiotemporal distribution of electrical pulses over a custom-designed electrode array. As electrotactile sensations are location-dependent and the developed interface requires that electrical stimuli are perceived to be of the same intensity on all locations, a calibration procedure is of high importance. The aim of this study was to gain more insight into the calibration procedure and optimize this process by leveraging a priori knowledge. For this purpose, we conducted a study with 9 able-bodied subjects performing 10 sessions of the array electrode calibration. Based on the collected data, we optimized and simplified the calibration procedure by adapting the initial (baseline) amplitude values in the calibration algorithm. The results suggest there is an individual pattern of stimulation amplitudes across 16 electrode pads for each subject, which is not affected by the initial amplitudes. Moreover, the number of user actions performed and the time needed for the calibration procedure are significantly reduced by the proposed methodology.Item Reinforcement Learning for Hand Grasp with Surface Multi-field Neuroprostheses(Springer International Publishing, 2017) Imatz-Ojanguren, Eukene; Irigoyen, Eloy; Keller, Thierry; Lopez-Guede, Jose Manuel; Herrero, Alvaro; Quintian, Hector; Grana, Manuel; Etxaniz, Oier; Corchado, Emilio; Tecnalia Research & InnovationHand grasp is a complex system that plays an important role in the activities of daily living. Upper-limb neuroprostheses aim at restor- ing lost reaching and grasping functions on people su ering from neural disorders. However, the dimensionality and complexity of the upper-limb makes the neuroprostheses modeling and control challenging. In this work we present preliminary results for checking the feasibility of using a re- inforcement learning (RL) approach for achieving grasp functions with a surface multi- eld neuroprosthesis for grasping. Grasps from 20 healthy subjects were recorded to build a reference for the RL system and then two di erent award strategies were tested on simulations based on neuro- fuzzy models of hemiplegic patients. These rst results suggest that RL might be a possible solution for obtaining grasp function by means of multi- eld neuroprostheses in the near future.Item Stimulation Discomfort Comparison of Asynchronous and Synchronous Methods with Multi-Field Surface Electrodes(2013-06) Imatz-Ojanguren, Eukene; Hoffmann, Ulrich; Veneman, Jan; Malešević, Nebojša; Keller, Thierry; Tecnalia Research & InnovationFunctional Electrical Stimulation (FES) is a technique that artificially stimulates motor nerves in order to restore motor/sensory functions for assistive and therapeutic applications. Recently, multi-field surface electrodes for transcutaneous electrical stimulation have been suggested to overcome problems of single channel surface stimulation. This study compares sensation perceived by 15 healthy subjects on upper limb when two different stimulation methods are applied by means of multi-field electrodes. Asynchronous and synchronous stimulation methods are compared for four different cases: activation of two neighbor fields, three neighbor fields, two distant fields and three distant fields. Two descriptors rated from 1 to 5 are used to describe discomfort: superficial discomfort and deep discomfort. Results expressed no differences in superficial discomfort for any case, but showed significant differences in deep discomfort for distant field activations. In these cases, synchronous stimulation resulted in higher perceived deep discomfort than asynchronous stimulation and affected its efficacy.