161,653 research outputs found
Norm optimal iterative learning control based on a multiple model switched adaptive framework
No full textIn this paper a prominent class of iterative learning control (ILC) algorithm is reformulated in the framework of estimation-based multiple model switched adaptive control (EMMSAC). The resulting control scheme uses a bank of Kalman filters to assess the performance of a set of candidate plant models, and the ILC update at the end of each trial is constructed using the plant model with smallest residual. Through exploitation of the powerful underlying EMMSAC framework, rigorous bounds are available to guarantee robust ILC performance without placing constraints on the form of uncertainty or control action.This paper hence addresses current limitations in ILC approaches for uncertain systems which are typically highly restrictive in the form or magnitude of the uncertainty, employ prescribed controller forms, or, alternatively are heuristically motivated with no theoretical stability/performance guarantees. Experimental results from a highly relevant application of ILC in stroke rehabilitation are given to confirm the efficacy and scope of the framework
Implementation and experimental evaluation of multiple model switched adaptive control for FES-based rehabilitation
No full textFunctional electrical stimulation (FES) is a well-established approach that is employed as a therapeutic tool for the restoration of motor control in individuals experiencing muscle impairment. Although its use as a rehabilitation tool is validated by clinical results, current control approaches limit the full exploitation of its potential due to the lack of accuracy with which the FES is applied. Research has thus focused on the use of advanced, closed-loop control algorithms to provide more accurate FES that is both task-oriented, and matches the rehabilitation needs of the patient. Experimental results have been reported for a variety of control schemes. However, the majority of approaches have failed to transfer to clinical practice due to the difficulties associated with identifying a model of electrically stimulated muscle that adapts as the true plant varies with time.Estimation-based multiple model switched adaptive control (EMMSAC) is a robust control approach that has the potential to overcome the problems associated with the uncertain, time-varying properties of electrically stimulated muscle. EMMSAC utilises optimal disturbance estimation to assess the respective performances of a set of candidate plant models. Then the controller associated with the model that has best performance is switched into closed-loop operation. This thesis details the algorithmic modifications that allow disturbance estimation to be performed in the time-varying setting for nonlinear Hammerstein structures. Then it is shown experimentally that a general plant model set can be identified that represents the time-varying, FES-induced muscle activation dynamics for the population of younger healthy adults. This finding is exploited to design an EMMSAC controller that achieves accurate trajectory tracking for multiple participants with minimal prior model identification. Results indicate that the use of EMMSAC reduces RMS tracking error when compared with a fixed controller; similar results are also reported for older healthy participants. Furthermore, initial results for a small sample of stroke-participants are shown, which confirms the potential for the proposed control approach to be applied in a clinical setting for FES-based rehabilitation
Adaptive control of functional electrical stimulation for upper limb stroke rehabilitation
No full textIn this paper a multiple model adaptive control scheme is designed and evaluated for the electrically stimulated isometric human arm. Experimental data are first used to identify models that represent various stages of muscular fatigue. The control scheme is then implemented on four unimpaired participants supplying zero voluntary effort. Results illustrate the ability of the scheme to track the time-variance of the true plant and provide improved torque tracking compared with a fixed controller. An advantage of the proposed method is the ability to achieve similar levels of performance across multiple participants without the need to perform identification tests
Application of multiple model adaptive control to upper limb stroke rehabilitation
No full textImpaired arm function has a significant impact on the quality of life of stroke sufferers. Research has shown that the application of functional electrical stimulation (FES) to assist their movement over repeated attempts at a task is effective in restoring function. However, current FES control systems lack robustness to changes in plant dynamics caused by fatigue and spasticity. This paper details the application of a multiple model adaptive control algorithm that has the potential to overcome this problem. It is shown in an experimental setting that an adaptive estimation mechanism is able to detect changes in the true plant through optimal disturbance estimation. Finally, the performance of the algorithm is compared with that of fixed optimal controllers. These initial results suggest that the application of estimation-based multiple model switched adaptive control (EMMSAC) can increase the potential of FES based rehabilitation through improved controller accuracy
Multiple model adaptive control of functional electrical stimulation
No full textThis paper establishes the feasibility of multiple-model switched adaptive control to regulate functional electrical stimulation for upper limb stroke rehabilitation. An estimation-based multiple-model switched adaptive control (EMMSAC) framework for nonlinear time-invariant systems is described, and extensions are presented to enable application to time-varying Hammerstein structures that can accurately represent the stimulated arm. A principled design procedure is then developed to construct both a suitable set of candidate models from experimental data and a corresponding set of tracking controllers. The procedure is applied to a sample of able-bodied young participants to produce a general EMMSAC controller. This is then applied to a different sample of the population during an isometric nonvoluntary trajectory tracking task. The results show that it is possible to eliminate model identification while employing closed-loop controllers that maintain high performance in the presence of rapidly changing system dynamics. This paper hence addresses critical limitations to effective stroke rehabilitation in a clinical setting
OLIY TA'LIMDA BREND KAPITALI BOSHQARUVINING O'ZIGA XOS XUSUSIYATLARI
No full textMaqolada Oliy ta'limda brend kapitali boshqaruvining o'ziga xos xususiyatlari ochib berilgan. Muallif tomonidan brendlar qiymatini baholash usullariga cheklovlar o`rganilib, Interbrand kompaniyasining usuli bo'yicha hisoblash metodologiyasi tahlil qilinga
Nacionalni brend Srbije kao faktor unapređenja konkurentnosti zemlje
No full textNacionalni brend predstavlja jedinstven, privlačan i zanimljiv paket nacionalnih vrednosti, dok se proces izgradnje jakog nacionalnog brenda zasniva na pronalaženju, izgradnji i prezentovanju skupa vrednosti koje jedna država želi da promoviše kao sopstveni nacionalni brend. Kao takav, može predstavljati značajan faktor konkurentnosti pri ostvarenju ekonomskih ciljeva (povećanja izvoza, veći priliv stranih direktnih investicija, povećanje obima turističkog promet). Uz to, jak nacionalni brend doprinosi kreiranju pozitivne percepcije sveta o datoj državi te unapređenju ekonomske i političke pozicije zemlje, a posledično i unapređuje nacionalnu konkurentnost. Otuda je i cilj ovog rada da afirmiše značaj procesa nacionalnog brendiranja i analizira poziciju Srbije kao nacionalnog brenda u svetskim razmerama. Akcenat u radu biće stavljen na nekoliko krucijalnih područja kao što su: koncept nacionalnog brendiranja, nacionalni identitet kao temelj nacionalnog brenda, pozicioniranost Srbije na svetskoj mapi nacionalnih brendova; preporuke i instrumenti za unapredjenje nacionalnog brenda Srbije
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Larry O. Spencer, Conference Author Presentation
No full textGen. Larry O. Spencer, USAF (Ret.), author of Dark Horse: A Journey from the Horseshoe to the Pentago
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