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Search Results: 1 - 10 of 14490 matches for " Do?en Strahinja "
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Design of optimal profiles of electrical stimulation for restoring of the walking
Doen Strahinja,Milovanovi? Ivana
Journal of Automatic Control , 2009, DOI: 10.2298/jac0901013d
Abstract: We present a method for the synthesis of electrical stimulation profiles for assisting of the walking in hemiplegic individuals. The stimulation profiles are synthesized by combining the joint torques estimated from the simulation that optimizes the tracking errors with a constraint of the minimal coactivation of antagonist muscles and the recruitment of the muscles for the potential user. The predicted electrical stimulation profiles were compared with the EMG recordings of the prime movers of the leg joints. The conclusion is that synthesis of controls should rely on muscle activation profiles determined through simulation, in which the level of coactivation of antagonist muscles are preset to ensure stability of the joints and smooth movements. The example presented uses data from a healthy individual (model parameters), but the methodology is directly implantable for hemiplegic individual just by replacing the model parameters, the EMG and the trajectory of the nonparetic leg.
Control of prehension for the transradial prosthesis: Natural-like image recognition system
Klisi? ?or?e,Kosti? Milo?,Doen Strahinja,Popovi? Dejan B.
Journal of Automatic Control , 2009, DOI: 10.2298/jac0901027k
Abstract: We describe the hardware and software for the control of prehension for a dexterous transradial prosthesis. The prehension process comprises hand orientation (three degrees of freedom) and the opening of the hand in a manner that is appropriate for the shape and size of the object. The hardware consists of a standard web camera, accelerometer, ultrasound distance sensor, laser pointer and an LED illumination system. Software operating in real time estimates the shape and size of the object as well as the relative orientation of the hand with respect to the object. Based on this data, the controller generates signals that are sent to the three-dimensional (3D) wrist rotator, and drives which control fingers and thumb of the transradial prosthesis, thereby preparing the hand for palmar, lateral, or precision (2-digit or 3-digit) grasps. The choice of the grasp follows heuristics captured from healthy humans when grasping and expressed in the form of IF-THEN rules.
Neural prostheses for walking restoration
Popovi? Dejan B.,Popovi? Mirjana B.,Doen Strahinja
Journal of Automatic Control , 2008, DOI: 10.2298/jac0802063p
Abstract: We review the state of the art of multi-channel electrical stimulation (ES) systems with surface electrodes for assistance in the standing and walking of paraplegics and hemiplegics. For the group of complete paraplegics, walking achieved with available ES systems is below their expectations, especially since these systems cannot compete with mobility provided to them by a wheelchair. However, standing and walking with ES systems are beneficial because they contribute to the improvement of physiological functions. For individuals who can stand with some arm support (e.g., paraplegics with incomplete injury and hemiplegics), the current ES systems are an effective augmentation of walking. We suggest that an ES system for walking of incomplete paraplegics and hemiplegics will be better accepted if the stimulation is regulated by a rule-based control, that is, a preprogrammed, sensor-triggered activation of several muscles resulting in normal walking. We present a method to obtain muscle activity profiles from simulation of a customized model of the patient that can be used for the synthesis of rules for control.
Learning Arm/Hand Coordination with an Altered Visual Input
Simona Denisia Iftime Nielsen,Strahinja Doen,Mirjana B. Popovi?,Dejan B. Popovi?
Computational Intelligence and Neuroscience , 2010, DOI: 10.1155/2010/520781
Abstract: The focus of this study was to test a novel tool for the analysis of motor coordination with an altered visual input. The altered visual input was created using special glasses that presented the view as recorded by a video camera placed at various positions around the subject. The camera was positioned at a frontal (F), lateral (L), or top (T) position with respect to the subject. We studied the differences between the arm-end (wrist) trajectories while grasping an object between altered vision (F, L, and T conditions) and normal vision (N) in ten subjects. The outcome measures from the analysis were the trajectory errors, the movement parameters, and the time of execution. We found substantial trajectory errors and an increased execution time at the baseline of the study. We also found that trajectory errors decreased in all conditions after three days of practice with the altered vision in the F condition only for 20 minutes per day, suggesting that recalibration of the visual systems occurred relatively quickly. These results indicate that this recalibration occurs via movement training in an altered condition. The results also suggest that recalibration is more difficult to achieve for altered vision in the F and L conditions compared to the T condition. This study has direct implications on the design of new rehabilitation systems. 1. Introduction Visual information plays an important role in both planning and executing goal-directed movements. When planning the reaching aspect of the “reach to grasp movement,” vision provides information about the object’s properties (shape, size, and position in space) as described in detail many years ago by Jeannerod [1]. During the execution of the action, the proprioceptive system (muscle spindles, Golgi tendon organs, and joint receptors) sends information to the central nervous system, which is then used for estimation of the accuracy of the execution. In parallel, vision provides feedback, which allows corrections if they are required [2]. The performance depends on the level of mastery in executing the movement that follows the learning. The role of vision during reaching to grasp was studied in detail by either preventing the subject from viewing either only the hand or both the object and the hand during movement (this is often referred to as visual open loop; e.g., [3–5]). The results of previous studies agree that preventing vision during the reaching movement affects movement parameters (i.e., hand-target distance at the initiation of aperture closure, grip aperture amplitude, wrist velocity, and
Cognitive vision system for control of dexterous prosthetic hands: Experimental evaluation
Strahinja Doen, Christian Cipriani, Milo? Kosti?, Marco Controzzi, Maria C Carrozza, Dejan B Popovi?
Journal of NeuroEngineering and Rehabilitation , 2010, DOI: 10.1186/1743-0003-7-42
Abstract: The central component of the proposed method is an autonomous controller comprising a vision system with rule-based reasoning mounted on a dexterous hand (CyberHand). The controller, termed cognitive vision system (CVS), mimics biological control and generates commands for prehension. The CVS was integrated into a hierarchical control structure: 1) the user triggers the system and controls the orientation of the hand; 2) a high-level controller automatically selects the grasp type and size; and 3) an embedded hand controller implements the selected grasp using closed-loop position/force control. The operation of the control system was tested in 13 healthy subjects who used Cyberhand, attached to the forearm, to grasp and transport 18 objects placed at two different distances.The system correctly estimated grasp type and size (nine commands in total) in about 84% of the trials. In an additional 6% of the trials, the grasp type and/or size were different from the optimal ones, but they were still good enough for the grasp to be successful. If the control task was simplified by decreasing the number of possible commands, the classification accuracy increased (e.g., 93% for guessing the grasp type only).The original outcome of this research is a novel controller empowered by vision and reasoning and capable of high-level analysis (i.e., determining object properties) and autonomous decision making (i.e., selecting the grasp type and size). The automatic control eases the burden from the user and, as a result, the user can concentrate on what he/she does, not on how he/she should do it. The tests showed that the performance of the controller was satisfactory and that the users were able to operate the system with minimal prior training.Most commercially available hand prostheses are simple one degree-of-freedom grippers [1,2] in which one motor drives the index and middle fingers synchronously with the thumb. The remaining fingers serve aesthetic purposes and move passiv
Correction of beam-beam effects in luminosity measurement in the forward region at CLIC
Strahinja Lukic
Physics , 2013, DOI: 10.1088/1748-0221/8/05/P05008
Abstract: Procedures for correcting the beam-beam effects in luminosity measurements at CLIC at 3 TeV center-of-mass energy are described and tested using Monte Carlo simulations. The angular counting loss due to the combined Beamstrahlung and initial-state radiation effects is corrected based on the reconstructed velocity of the collision frame of the Bhabha scattering. The distortion of the luminosity spectrum due to the initial-state radiation is corrected by deconvolution. At the end, the counting bias due to the finite calorimeter energy resolution is numerically corrected. To test the procedures, BHLUMI Bhabha event generator, and Guinea-Pig beam-beam simulation were used to generate the outgoing momenta of Bhabha particles in the bunch collisions at CLIC. The systematic effects of the beam-beam interaction on the luminosity measurement are corrected with precision of 1.4 permille in the upper 5% of the energy, and 2.7 permille in the range between 80 and 90% of the nominal center-of-mass energy.
Novus Atlas in the Collection of Printing and Book Binding in the Museum of Arts and Crafts in Zagreb - the Problem of Attribution and Dating of Geographical Maps
An?elka Gali?,Antonia Doen
Geoadria , 2012,
Abstract: A collection of 99 engraved maps inserted in two volumes featuring a luxurious book binding equipment from the Collection of printing and book binding in the Museum of Arts and Crafts in Zagreb were believed to be Johannes Janssonius’s (1588 – 1664) edition of the Novus Atlas, approximately dated in the 17th century. Even though the volumes had identical covers and numerous Janssonius’s labels, their content, which included maps of different provenance, was an incentive to re-investigate their attribution. This article brings forth the results of a detailed investigation by the use of the comparison and correlation method, which brought about the new attribution and date of creation for the Novus Atlas. Within the two volumes, alongside the lesser known names, there are the names of publishers, cartographers and map engravers such as Abraham Ortelius (1527 – 1598), Henricus Hondius (1597 – 1651), Pierre Duval (1619 – 1683), Frederick de Wit (1629 – 1706), Pierre Mortier (1661 – 1711) and others, which shifted not only the set attribution but also the dates of the maps’ creation to the period from the late 16th to the first half of the 18th century.
Editorial Preface
?ur?ana Ozreti? Doen
Tr?i?te/Market , 2012,
Abstract:
Editorial Preface
?ur?ana Ozreti? Doen
Tr?i?te/Market , 2009,
Abstract:
Editorial Preface
?ur?ana Ozreti? Doen
Tr?i?te/Market , 2008,
Abstract:
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