57 research outputs found
A system for electrotactile feedback using electronic skin and flexible matrix electrodes: Experimental evaluation
No full textMyoelectric prostheses are successfully controlled using muscle electrical activity, thereby restoring lost motor functions. However, the somatosensory feedback from the prosthesis to the user is still missing. The sensory substitution methods described in the literature comprise mostly simple position and force sensors combined with discrete stimulation units. The present study describes a novel system for sophisticated electrotactile feedback integrating advanced distributed sensing (electronic skin) and stimulation (matrix electrodes). The system was tested in eight healthy subjects who were asked to recognize the shape, trajectory, and direction of a set of dynamic movement patterns (single lines, geometrical objects, letters) presented on the electronic skin. The experiments demonstrated that the system successfully translated the mechanical interaction into the moving electrotactile profiles, which the subjects could recognize with a good performance (shape recognition: 86±8% lines, 73±13% geometries, 72±12% letters). In particular, the subjects could identify the movement direction with a high confidence. These results are in accordance with previous studies investigating the recognition of moving stimuli in human subjects. This is an important development towards closed-loop prostheses providing comprehensive and sophisticated tactile feedback to the user, facilitating the control and the embodiment of the artificial device into the user body scheme
Short- and Long-Term Learning of Feedforward Control of a Myoelectric Prosthesis with Sensory Feedback by Amputees
No full textPublisher Copyright: © 2017 IEEE.Human motor control relies on a combination of feedback and feedforward strategies. The aim of this study was to longitudinally investigate artificial somatosensory feedback and feedforward control in the context of grasping with myoelectric prosthesis. Nine amputee subjects performed routine grasping trials, with the aim to produce four levels of force during four blocks of 60 trials across five days. The electrotactile force feedback was provided in the second and third block usingmultipad electrode and spatial coding. The first baseline and last validation block (open-loop control) evaluated the effects of long-(across sessions) and short-term (within session) learning, respectively.The outcomemeasureswere the absolute error between the generated and target force, and the number of force saturations. The results demonstrated that the electrotactile feedback improved the performance both within and across sessions. In the validation block, the performance did not significantly decrease and the quality of openloop control (baseline) improved across days, converging to the performance characterizing closed-loop control. This paper provides important insights into the feedback and feedforwardprocessesin prosthesiscontrol, contributing to the better understanding of the role and design of feedback in prosthetic systems.Manuscript received October 19, 2016; revised April 2, 2017; accepted May 17, 2017. Date of publication June 6, 2017; date of current version November 6, 2017. This work was supported in part by Tec-nalia Research & Innovation, Spain, in part by FIK, Spain, in part by the European Commission under the MYOSENS project (FP7-PEOPLE-2011-IAPP-286208), and in part by the Ministry of Education, Science and Technological Development of Serbia under Project 175016. (Corresponding author: Matija Štrbac.) M. Štrbac and M. Isaković are with Tecnalia Serbia Ltd., 11000 Belgrade, Serbia, and also with the School of Electrical Engineering, University of Belgrade, Belgrade 11000, Serbia (e-mail: [email protected]; [email protected]).Peer reviewe
Multichannel electrotactile feedback with spatial and mixed coding for closed-loop control of grasping force in hand prostheses
No full textPublisher Copyright: © 2016 IEEE.Providing somatosensory feedback to the user of a myoelectric prosthesis is an important goal since it can improve the utility as well as facilitate the embodiment of the assistive system. Most often, the grasping force was selected as the feedback variable and communicated through one or more individual single channel stimulation units (e.g., electrodes, vibration motors). In the present study, an integrated, compact, multichannel solution comprising an array electrode and a programmable stimulator was presented. Two coding schemes (15 levels), spatial and mixed (spatial and frequency) modulation, were tested in able-bodied subjects, psychometrically and in force control with routine grasping and force tracking using real and simulated prosthesis. The results demonstrated that mixed and spatial coding, although substantially different in psychometric tests, resulted in a similar performance during both force control tasks. Furthermore, the ideal, visual feedback was not better than the tactile feedback in routine grasping. To explain the observed results, a conceptual model was proposed emphasizing that the performance depends on multiple factors, including feedback uncertainty, nature of the task and the reliability of the feedforward control. The study outcomes, specific conclusions and the general model, are relevant for the design of closed-loop myoelectric prostheses utilizing tactile feedback.Thiswork was supported by the German Ministry for Education and Research (BMBF) via the Bernstein Focus Neurotechnology (BFNT) Gottingen under the Grants 01GQ0817 and Grant 01GQ0810, and the European Commission under the MYOSENS (FP7-PEOPLE-2011-IAPP-286208) projects.Peer reviewe
Artificial Skin and Electrotactile Stimulation for Advanced Tactile Feedback in Myoelectric Prostheses
No full textModern prosthetic arms and hands are sophisticated robotic devices that can
provide some of the motor functions lost due to an amputation. However,
none of the commonly used commercial systems restores somatosensory
feedback to its user. In principle, the latter can be achieved by recording data
from prosthesis sensors and conveying this information by stimulating the
sensory structures of the amputee using invasive and noninvasive interfaces.
Many such systems have been presented in the literature with promising
results; however, they all rely on using several stimulation points to transmit
information and hence suffer from a limited information bandwidth. In this
chapter, we propose a novel concept of a high-bandwidth feedback interface
that relies on advanced sensing and stimulation to convey a large amount
of information to the prosthesis user. The interface comprises an artificial
skin covering the prosthesis with a dense network of tactile sensors (taxels)
and a compact stimulation device delivering electrical current pulses through
a matrix electrode with many conductive pads. The state-of-the-art in the
two technologies that are required for the implementation of the proposed
concept are reviewed. This includes biomimetic e-skins that are suitable
for the application in a wearable scenario, stimulation systems integrating
a demultiplexing circuit to distribute electrical pulses, and flexible electrodes
that can be produced with arbitrary shape, size, and distribution of conductive
pads. Finally, the challenges in selecting feedback variables (raw signals
versus high-level features) and mapping of these variables into stimulation
parameters are addressed
Dual-parameter modulation improves stimulus localization in multichannel electrotactile stimulation
No full textAmong most challenging open issues in prosthetic research is the development of a robust bidirectional interface between a prosthesis and its user. Commercially available prosthetic systems are mechanically advanced, but they do not provide somatosensory feedback. Here, we present a novel non-invasive interface for multichannel electrotactile feedback, comprising a matrix of 24 pads, and we investigate the ability of able-bodied human subjects to localize the electrotactile stimulus delivered through the matrix. For this purpose, we tested conventional stimulation (same frequency for all pads) and a novel dual-parameter modulation scheme (interleaved frequency and intensity) designed to facilitate the spatial localization over the electrode. Electrotactile stimulation was also compared to mechanical stimulation of the same locations on the skin. Experimental results on eight able-bodied subjects demonstrated that the proposed interleaved coding substantially improved the spatial localization compared to same-frequency stimulation. The results also showed that same-frequency stimulation was equivalent to mechanical stimulation, whereas the performance with dual-parameter modulation was significantly better. These are encouraging outcomes for the application of a multichannel interface for the restoration of feedback in prosthetics. The high-resolution augmented interfaces might be used to explore novel scenarios for effective communication with the prosthesis user enabled by maximizing information transmission.</p
Software tool for the prosthetic foot modeling and stiffness optimization
No full textWe present the procedure for the optimization of the stiffness of the prosthetic foot. The procedure allows the selection of the elements of the foot and the materials used for the design. The procedure is based on the optimization where the cost function is the minimization of the difference between the knee joint torques of healthy walking and the walking with the transfemural prosthesis. We present a simulation environment that allows the user to interactively vary the foot geometry and track the changes in the knee torque that arise from these adjustments. The software allows the estimation of the optimal prosthetic foot elasticity and geometry. We show that altering model attributes such as the length of the elastic foot segment or its elasticity leads to significant changes in the estimated knee torque required for a given trajectory.Peer reviewe
Low-complexity decentralized algorithm for aggregate load control of thermostatic loads
No full textThermostatically controlled loads such as refrigerators are exceptionally suitable as a flexible demand resource. This article derives a decentralized load control algorithm for refrigerators. It is adapted from an existing continuous time control approach, with the aim to achieve low computational complexity and an ability to handle discrete time steps of variable length - desirable features for embedding in appliances and high-throughput simulations. Simulation results of large populations of heterogeneous appliances illustrate the accurate aggregate control of power consumption and high computational efficiency. Tracking accuracy is quantified as a function of population size and time step size, and correlations in the tracking error are investigated. The controller is shown to be robust to errors in model specification and to sudden perturbations in the form of random refrigerator door openings.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid
Stereovision system for estimation of the grasp type for electrotherapy
No full textThis paper presents hardware and software for scene analysis that are designed for the system used in treatment of post stroke hemiplegic patients using electrical stimulation. New hardware includes two cameras and a laser pointer, while new software is given as a Matlab program that performs real-time estimate of size and shape of targeted object. Based on heuristic contemplation the system makes a decision grasp type and necessary actions for the purpose of hand opening and closing. The system was tested on 13 objects and in 95% of cases it worked according to demands, i.e. corresponding to choices of healthy subjects when they wanted to grab that same object
Integrated and flexible multichannel interface for electrotactile stimulation
No full textPublisher Copyright: © 2016 IOP Publishing Ltd.Objective. The aim of the present work was to develop and test a flexible electrotactile stimulation system to provide real-time feedback to the prosthesis user. The system requirements were to accommodate the capabilities of advanced multi-DOF myoelectric hand prostheses and transmit the feedback variables (proprioception and force) using intuitive coding, with high resolution and after minimal training. Approach. We developed a fully-programmable and integrated electrotactile interface supporting time and space distributed stimulation over custom designed flexible array electrodes. The system implements low-level access to individual stimulation channels as well as a set of high-level mapping functions translating the state of a multi-DoF prosthesis (aperture, grasping force, wrist rotation) into a set of predefined dynamic stimulation profiles. The system was evaluated using discrimination tests employing spatial and frequency coding (10 able-bodied subjects) and dynamic patterns (10 able-bodied and 6 amputee subjects). The outcome measure was the success rate (SR) in discrimination. Main results. The more practical electrode with the common anode configuration performed similarly to the more usual concentric arrangement. The subjects could discriminate six spatial and four frequency levels with SR >90% after a few minutes of training, whereas the performance significantly deteriorated for more levels. The dynamic patterns were intuitive for the subjects, although amputees showed lower SR than able-bodied individuals (86% 10% versus 99% 3%). Significance. The tests demonstrated that the system was easy to setup and apply. The design and resolution of the multipad electrode was evaluated. Importantly, the novel dynamic patterns, which were successfully tested, can be superimposed to transmit multiple feedback variables intuitively and simultaneously. This is especially relevant for closing the loop in modern multifunction prostheses. Therefore, the proposed system is convenient for practical applications and can be used to implement sensory perception training and/or closed-loop control of myoelectric prostheses, providing grasping force and proprioceptive feedback.European Commission under the MYOSENS (FP7-PEOPLE-2011-IAPP-286208) projects, and by the Ministry of Education, Science and Technological Development of Serbia (Project no. 175016).Peer reviewe
Kinect in neurorehabilitation:computer vision system for real time hand and object detection and distance estimation
No full textThis paper presents image processing and scene analysis methods that can provide artificial vision that is of interest for automatic selection of hand trajectory and prehension. The new algorithm, which uses data from the Kinect sensor, allows real-time detection of the hand of the person grasping an object at working table in front of that person. The outputs are real world coordinates of the hand and the object. The image processing is done in Matlab over the depth image stream taken from the Microsoft Kinect as a sensory input. Results show that in the presented system setup our program is capable of tracking hand movements in the transverse plane and estimating hand and object position in real-time with tolerable estimation error for the selection of stimulation paradigm that could control hand trajectory.Peer reviewe
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