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- Seoane Martinez, Fernando, 1976
(författare)
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Electrical Bioimpedance Cerebral Monitoring: Fundamental Steps towards Clinical Application
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Neurologically related injuries cause a similar number of deaths as cancer, and brain damage is the second commonest cause of death in the world and probably the leading cause of permanent disability. The devastating effects of most cases of brain damage could be avoided if it were detected and medical treatment initiated in time. The passive electrical properties of biological tissue have been investigated for almost a century and electrical bioimpedance studies in neurology have been performed for more than 50 years. Even considering the extensive efforts dedicated to investigating potential applications of electrical bioimpedance for brain monitoring, especially in the last 20 years, and the specifically acute need for such non-invasive and efficient diagnosis support tools, Electrical Bioimpedance technology has not made the expected breakthrough into clinical application yet. In order to reach this stage in the age of evidence-based medicine, the first essential step is to demonstrate the biophysical basis of the method under study. The present research work confirms that the cell swelling accompanying the hypoxic/ischemic injury mechanism modifies the electrical properties of brain tissue, and shows that by measuring the complex electrical bioimpedance it is possible to detect the changes resulting from brain damage. For the development of a successful monitoring method, after the vital biophysical validation it is critical to have available the proper electrical bioimpedance technology and to implement an efficient protocol of use. Electronic instrumentation is needed for broadband spectroscopy measurements of complex electrical bioimpedance; the selection of the electrode setup is crucial to obtain clinically relevant measurements, and the proper biosignal analysis and processing is the core of the diagnosis support system. This work has focused on all these aspects since they are fundamental for providing the solid medico-technological background necessary to enable the clinical usage of Electrical Bioimpedance for cerebral monitoring.
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| 2. |
- Ortiz Catalan, Max Jair, 1982
(författare)
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Towards Natural Control of Artificial Limbs
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of implantable electrodes has been long thought as the solution for a more natural control of artificial limbs, as these offer access to long-term stable and physiologically appropriate sources of control, as well as the possibility to elicit appropriate sensory feedback via neurostimulation. Although these ideas have been explored since the 1960’s, the lack of a long-term stable human-machine interface has prevented the utilization of even the simplest implanted electrodes in clinically viable limb prostheses.In this thesis, a novel human-machine interface for bidirectional communication between implanted electrodes and the artificial limb was developed and clinically implemented. The long-term stability was achieved via osseointegration, which has been shown to provide stable skeletal attachment. By enhancing this technology as a communication gateway, the longest clinical implementation of prosthetic control sourced by implanted electrodes has been achieved, as well as the first in modern times. The first recipient has used it uninterruptedly in daily and professional activities for over one year. Prosthetic control was found to improve in resolution while requiring less muscular effort, as well as to be resilient to motion artifacts, limb position, and environmental conditions.In order to support this work, the literature was reviewed in search of reliable and safe neuromuscular electrodes that could be immediately used in humans. Additional work was conducted to improve the signal-to-noise ratio and increase the amount of information retrievable from extraneural recordings. Different signal processing and pattern recognition algorithms were investigated and further developed towards real-time and simultaneous prediction of limb movements. These algorithms were used to demonstrate that higher functionality could be restored by intuitive control of distal joints, and that such control remains viable over time when using epimysial electrodes. Lastly, the long-term viability of direct nerve stimulation to produce intuitive sensory feedback was also demonstrated.The possibility to permanently and reliably access implanted electrodes, thus making them viable for prosthetic control, is potentially the main contribution of this work. Furthermore, the opportunity to chronically record and stimulate the neuromuscular system offers new venues for the prediction of complex limb motions and increased understanding of somatosensory perception. Therefore, the technology developed here, combining stable attachment with permanent and reliable human-machine communication, is considered by the author as a critical step towards more functional artificial limbs.
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| 3. |
- Mastinu, Enzo, 1987
(författare)
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Embedded Controller for Artificial Limbs
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Promising developments are currently ongoing worldwide in the field of neuroprosthetics and artificial limb control. It is now possible to chronically connect a robotic limb to bone, nerves and muscles of a human being, and use the signals sourced from these connections to enable movements in the artificial limb. It is also possible to surgically redirect a nerve, deprived from its original target muscle due to amputation, to a new target in order to restore the original motor functionality. Intelligent signal processing algorithms can now utilize the bioelectric signals gathered from remaining muscles on the stump to decode the motor intention of the amputee, providing an intuitive control interface. Unfortunately for patients, clinical implementations still lag behind the advancements of research, and the conventional solutions for amputees remained basically unchanged since decades. More efforts are therefore needed from researchers to close the gap between scientific publications and hospital practices.The ultimate focus of this thesis is set on the intuitive control of a prosthetic upper limb. It was developed an embedded system capable of prosthetic control via the processing of bioelectric signals and pattern recognition algorithms. It includes a neurostimulator to provide direct neural feedback modulated by sensory information from artificial sensors. The system was designed towards clinical implementation and its functionality was proven by amputee subjects in daily life. It also constitutes a research platform to monitor prosthesis usage and training, machine learning based control algorithms, and neural stimulation paradigms.
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| 4. |
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| 5. |
- Mastinu, Enzo, 1987, et al.
(författare)
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An Alternative Myoelectric Pattern Recognition Approach for the Control of Hand Prostheses : A Case Study of Use in Daily Life by a Dysmelia Subject
- 2018
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Ingår i: IEEE Journal of Translational Engineering in Health and Medicine. - : Institute of Electrical and Electronics Engineers (IEEE). - 2168-2372. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The functionality of upper limb prostheses can be improved by intuitive control strategies that use bioelectric signals measured at the stump level. One such strategy is the decoding of motor volition via myoelectric pattern recognition (MPR), which has shown promising results in controlled environments and more recently in clinical practice. Moreover, not much has been reported about daily life implementation and real-time accuracy of these decoding algorithms. This paper introduces an alternative approach in which MPR allows intuitive control of four different grips and open/close in a multifunctional prosthetic hand. We conducted a clinical proof-of-concept in activities of daily life by constructing a self-contained, MPR-controlled, transradial prosthetic system provided with a novel user interface meant to log errors during real-time operation. The system was used for five days by a unilateral dysmelia subject whose hand had never developed, and who nevertheless learned to generate patterns of myoelectric activity, reported as intuitive, for multi-functional prosthetic control. The subject was instructed to manually log errors when they occurred via the user interface mounted on the prosthesis. This allowed the collection of information about prosthesis usage and real-time classification accuracy. The assessment of capacity for myoelectric control test was used to compare the proposed approach to the conventional prosthetic control approach, direct control. Regarding the MPR approach, the subject reported a more intuitive control when selecting the different grips, but also a higher uncertainty during proportional continuous movements. This paper represents an alternative to the conventional use of MPR, and this alternative may be particularly suitable for a certain type of amputee patients. Moreover, it represents a further validation of MPR with dysmelia cases.
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| 6. |
- Buendia, Ruben, 1982, et al.
(författare)
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A Novel Approach for Removing the Hook Effect Artefact from Electrical Bioimpedance Spectroscopy Measurements
- 2009
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Ingår i: Journal of Physics: Conference Series. - : Institute of Physics Publishing Ltd.. - 1742-6596.
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Konferensbidrag (refereegranskat)abstract
- Very often in Electrical Bioimpedance (EBI) spectroscopy measurements the presence of stray capacitances creates a measurement artefact commonly known as Hook Effect. Such an artefact creates a hook-alike deviation of the EBI data noticeable when representing the measurement on the impedance plane. Such Hook Effect is noticeable at high frequencies but it also causes a data deviation at lower measurement frequencies. In order to perform any accurate analysis of the EBI spectroscopy data, the influence of the Hook Effect must be removed. An established method to compensate the hook effect is the well known Td compensation, which consist on multiplying the obtained spectrum, Zmeas() by a complex exponential in the form of exp[jTd]. Such a method cannot correct entirely the Hook Effect since the hook-alike deviation occurs a broad frequency range in both magnitude and phase of the measured impedance, and by using a real value for Td. First, a real value only modifies the phase of the measured impedance and second, it can only correct the Hook Effect at a single frequency. In addition, the process to select a value for Td by an iterative process with the aim to obtain the best Cole fitting lacks solid scientific grounds. In this work the Td compensation method is revisited and a modified approach for correcting the Hook Effect that includes a novel method for selecting the correcting values is proposed. The initial validation results confirm that the proposed method entirely corrects the Hook Effect at all frequencies.
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| 7. |
- Buendia, Ruben, 1983-, et al.
(författare)
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Cole Parameter Estimation from the Modulus of the Electrical Bioimpeadance for Assessment of Body Composition : A Full Spectroscopy Approach
- 2011
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Ingår i: Journal of Electrical Bioimpedance. - Oslo : University of Oslo. - 1891-5469. ; 2, s. 72-78
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Tidskriftsartikel (refereegranskat)abstract
- Activities around applications of Electrical Bioimpedance Spectroscopy (EBIS) have proliferated in the past decade significantly. Most of these activities have been focused in the analysis of the EBIS measurements, which eventually might enable novel applications. In Body Composition Assessment (BCA) the most common analysis approach currently used in EBIS is based on the Cole function, which most often requires curve fitting. One of the most implemented approaches for obtaining the Cole parameters is performed in the impedance plane through the geometrical properties that the Cole function exhibit in such domain as depressed semi-circle. To fit the measured impedance data to a semi-circle in the impedance plane, obtaining the Cole parameters in an indirect and sequential manner has several drawbacks. Applying a Non-Linear Least Square (NLLS) iterative fitting on the spectroscopy measurement, obtains the Cole parameters considering the frequency information contained in the measurement. In this work, from experimental total right side EBIS measurements, the BCA parameters have been obtained to assess the amount and distribution of whole body fluids. The values for the BCA parameters have been obtained using values for the Cole parameters estimated with both approaches: circular fitting on the impedance plane and NLLS impedance-only fitting. The comparison of the values obtained for the BCA parameters with both methods confirms that the NLLS impedance-only is an effective alternative as Cole parameter estimation method in BCA from EBIS measurements. Using the modulus of the Cole function as the model for the fitting would eliminate the need for performing a phase detection in the acquisition process, simplifying the hardware specifications of the measurement instrumentation when implementing a bioimpedance spectrometer.
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| 8. |
- Li, Yan, et al.
(författare)
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Osseointegrated amputation prostheses and implanted electrodes
- 2021
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Ingår i: Bionic Limb Reconstruction. - Cham : Springer International Publishing. ; , s. 45-55
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The load transfer from the external prosthesis to the residual limb via the socket can cause significant stress on the soft tissues, leading to irritation and skin ulcers. Osseointegrated bone-anchored prostheses systems create a direct structural and functional connection between the prosthesis and residual skeleton. Up to date, standardized implant systems, surgical techniques, and postoperative rehabilitation protocols have been developed for osseointegrated prostheses for the rehabilitation of amputees (OPRA), which has resulted in better functionality, fewer complications, and a better quality of life for implant recipients. The OPRA implant systems can now incorporate neuromuscular electrodes to facilitate myoelectric control and sensory feedback, which is especially important for upper extremity amputees. The latest development, called the osseointegrated human-machine gateway, allows for permanent implantation of neuromuscular electrodes, which provide long-term stable signals for myoelectric control, independent of limb position or environmental conditions, as well as artificial sensory feedback. In addition, the modular design of this system allows any part to be upgraded or replaced with minimal disturbance to the other components. The osseointegrated implants and the human-machine gateway represent frontiers in amputee rehabilitation.
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| 9. |
- Ouyang, Quan, et al.
(författare)
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Cell Balancing Control for Lithium-Ion Battery Packs: A Hierarchical Optimal Approach
- 2020
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Ingår i: IEEE Transactions on Industrial Informatics. - 1941-0050 .- 1551-3203. ; 16:8, s. 5065-5075
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Tidskriftsartikel (refereegranskat)abstract
- Effective cell equalization is of extreme importance to extract the maximum capacity of a battery pack. In this article, two cell balancing objectives, including balancing time reduction and cells' temperature rise suppression, are taken into consideration simultaneously. Furthermore, hard constraints are imposed on the cells' state-of-charge levels, currents, and equalizing currents. Based on a developed module-based cell-to-cell balancing system model, a multiobjective constrained optimization problem is formulated, which aims at the coordinated control of all equalizers rather than individually controlling the equalizer for its two adjacent cells' equalization. Next, a hierarchical cell equalizing control approach is proposed, where the module-level controlled equalizing currents are first designed at the top layer, and then, the cell-level equalizers are controlled for each battery module in parallel at the bottom layer. The designed hierarchical structure significantly reduces the computational burden, making the cell equalizing algorithm more implementable in real time. Following the Lyapunov stability analysis, the convergence of the designed cell equalizing control algorithm is proved. Illustrative results demonstrate that the balancing time can be reduced by up to 29.8 % compared with the decentralized equalizing control.
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| 10. |
- WINGES, JOHAN, 1987
(författare)
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Inverse and optimization problems in electromagnetics -- a finite-element method perspective
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, a selection of inverse and optimization problems are studied where the finite element method (FEM) serves as a comprehensive tool to solve electromagnetic field problems that lack an analytic solution. The inverse problems are typically formulated in terms of an optimization problem where the misfit between a measurement and the corresponding result of a computational model is minimized. The optimization problems are solved by a combination of techniques that involve gradient-based methods, stochastic methods and parameter studies.The first contribution of the thesis is a new higher-order hybrid FEM for Maxwell's equations that combines (i) brick-shaped elements for large homogeneous regions with (ii) tetrahedrons for regions where local refinement is necessary. The tangential continuity of the electric field at the interface between the different element types is enforced in the weak sense using Nitsche's method. This yields a flexible and efficient computational method that is free of spurious solutions and features a low dispersion error. We employ a stable implicit-explicit time-stepping scheme using an implicitness parameter associated with the tetrahedrons and the hybrid interface. No late-time instabilities are observed in the solution for computations with up to 300 000 time steps.The second contribution of this thesis deals with four inverse scattering problems: (i) gradient-based estimation of the dielectric properties of moist micro-crystalline cellulose in terms of a Debye model; (ii) detection and positioning of multiple scatterers inside a metal vessel using compressed sensing; (iii) monitoring of the material perturbations in a pharmaceutical process vessel using a linearized model around an operation point that varies with the process state; and (iv) a subspace-based classification method for the detection of intracranial bleedings in a simulated data set. The third contribution of the thesis explores stochastic optimization for an inductive power transfer (IPT) system consisting of four magnetically coupled resonance circuits, which is intended for power transfer distances on the order of the coils' radius. A genetic algorithm is employed to compute the Pareto front that contrast the maximum efficiency and power transfer. Results are presented for both linear and non-linear circuits: (i) a time-harmonic model for magnetically coupled resonance circuits with a resistive load; and (ii) a transient model for an IPT system with square-wave excitation, rectifier, smoothing filter and battery.
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