Dissertations / Theses on the topic 'Closed loops'
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Chintapalli, Sree Vamsee. "Closed loops in protein folding." Thesis, University of Essex, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494193.
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Artic, Katharina [Verfasser], Gerhard [Akademischer Betreuer] Hiß, and Alice C. [Akademischer Betreuer] Niemeyer. "On right conjugacy closed loops and right conjugacy closed loop folders / Katharina Artic ; Gerhard Hiß, Alice C. Niemeyer." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1130792870/34.
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Guay, Jamie Andrew. "Closed-loop insulin delivery." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60434.pdf.
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Jones, Melvin. "Closed loop performance monitoring." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-04122007-115205.
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Elfving, Maria. "Hydraulic closed loop control." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-234932.
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The purpose of the thesis work is to investigate methods for closedloop control of hydraulic pressure in transmissions to make them bemore precise. This is desirable since it decreases the fuel consumptionas well as emissions, and improves the driving performance.To be able to study the behaviour of the transmission, a Simulink modelis designed with the parts relevant to the problem, and from this a linearmodel is obtained. Three different controllers are designed andimplemented in the Simulink model, to compare and analyze differentsolutions. The controllers implemented are a PI controller, a PIDcontroller and a LQR controller.The results from the simulation with the different controllers showstep responses to be able to evaluate their individual performance. Theresults show that all of the controllers meet the requirements for a stepreponse under better conditions, but under worse ones the LQR controllerperforms best of the three. The LQR controller is therefore themost suitable of the three controllers for this particular problem.Syftet med det här examensarbete är att undersöka olika metoder för återkopplad reglering av hydrauliskt tryck i en transmission för att göra det mer exakt. Detta är önskvärt eftersom det minskar bränsleåt- gången och utsläpp, och gör även körupplevelsen bättre. För att kunna studera transmission tas en Simulink-modell fram in- nehållande de delar som är relevanta för problemet, och från detta kan en linjär modell erhållas. Tre olika regulatorer tas fram och im- plementeras i Simulink-modellen, för att kunna jämföra och analysera de olika lösningarna. De regulatorer som tas fram är PI-regulator, PID- regulator och LQR-regualator. Resultaten från simuleringen med de olika regulatorerna visar stegs- var under varierande förutsättningar för att kunna utvärdera hur de presterar. Resultaten visar att alla regulatorer uppfyller kraven på ett stegsvar under bättre förhållanden, men LQR-regulatorn presterar bäst under svårare förhållanden. LQR-regulatorn är därför den mest relevanta reglerstrategin för det här problemet av de tre
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Fernandes, Pereira Sonia, and Nejat Hamid. "Closed-Loop Orchestration Solution." Thesis, KTH, Hälsoinformatik och logistik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-253005.
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Computer networks are continuously evolving and growing in size and complexity. New technologies are being introduced which further increases the complexity. Net- work Service Orchestration is all about pushing configuration out into the network devices automatically without human intervention. There can be issues that causes the orchestration to fail. In many cases manual operations must be done to recover from the error which is very contradicting since the goal of orchestration is that it should be fully automated. There is some indication that the errors that are being solved manually could be de- tected and handled by a feedback mechanism. This thesis work aimed to build on current insight and if possible, verify that the feedback mechanism is a viable method. After consideration on different ways to solve the research question, the choice fell on creating a test environment where the approach was tested. The test environment was used to investigate if a network orchestration system could be integrated with a feedback mechanism. The result of this project presents a way to automatically de- tect a network failure and send feedback to a Network Service Orchestrator. The or- chestrator is then able to identify and correct the error.Datornätverk utvecklas kontinuerligt och växer i storlek och komplexitet. Nyteknik införs som ytterligare ökar komplexiteten. Nätverksservice orkestrering handlar om att skicka ut konfiguration automatiskt till enheter i nätverket utan mänsklig in- blandning. Det kan finnas problem som gör att orkestreringen misslyckas. I många fall måste manuella åtgärder utföras för att lösa problemet, vilket är mycket motsä- gelsefullt, eftersom målet med orkestrering är att det ska vara fullt automatiserat. Det finns indikationer på att fel kan detekteras och hanteras av en återkopplings- mekanismen. Detta examensarbete syftar till att bygga på aktuell insikt, och om möj- ligt, verifiera att återkopplingsmekanismen är en möjlig metod. Efter överväganden på vilka olika sätt som projektmålet kunde uppnås föll valet på att skapa en testmiljö där ansatsen kunde testas. Testmiljön användes för att utreda om ett nätverksorkestreringssystem kan integreras med en återkopplings mekanism. Resultat av projektet presenterar ett sätt att automatiskt upptäcka ett nätverksfel och skicka återkoppling till ett nätverksorkestreringssystem. Nätverksorkestreraren kan sedan detektera och åtgärda felet.
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Mantzaridis, Haralmbos. "Closed-loop control of anaesthesia." Thesis, University of Strathclyde, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338938.
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Boudon, Benjamin. "Méthodologie de modélisation des systèmes mécatroniques complexes à partir du multi-bond graph : application à la liaison BTP-fuselage d’un hélicoptère." Thesis, Paris, ENSAM, 2014. http://www.theses.fr/2014ENAM0064/document.
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De par le fonctionnement de son rotor, l'hélicoptère est le siège de vibrations mécaniques importantes impactant notamment la fatigue des pièces mécaniques et le confort des passagers. La liaison BTP-Fuselage équipé du système SARIB est un système anti-vibratoire qui permet d'atténuer mono-fréquentiellement les vibrations transmises au fuselage. Des solutions intelligentes semi-actives sont donc étudiées afin que la filtration soit réglable en fonction des vibrations excitatrices. Ce type d'études souffre, par contre, d'un manque d'outils et de méthodes indispensables, d'une part, à la modélisation de systèmes mécaniques complexes et d'autre part, à l'élaboration d'une liaison intelligente. Ces travaux proposent une démarche de modélisation à partir d'un outil de modélisation structurel tel que le multi-bond graph (MBG) permettant une vision global et modulaire pour l'étude de systèmes mécaniques complexes tels qu'on peut les trouver sur un hélicoptère. Dans un premier temps, une analyse des outils de modélisation conduisant au choix du MBG a été présentée. Dans un second temps, les développements ont porté sur la modélisation MBG de la liaison BTP/ Fuselage 3D d'un banc d'essai réel qui a été conçu et réalisé au sein du laboratoire. Cette liaison est un système mécanique cinématiquement bouclé. Les équations de la dynamique d'un tel système forment un système d'équations algébro-différentiel (DAE) nécessitant des techniques de résolution spécifiques. Le modèle MBG de la liaison BTP-fuselage entier a été simulé à l'aide du logiciel 20-sim. Les résultats obtenus ont été vérifiés à l'aide du logiciel multicorps LMS Virtual Lab. Une comparaison des résultats obtenus par les deux méthodes a donné, pour différents cas d'excitations de la BTP (pompage, roulis, tangage), une corrélation très satisfaisante. Dans un troisième temps, le modèle MBG a été exploité pour la mise en place d'un dispositif de contrôle semi-actif. Le modèle du dispositif SARIB développé également sous 20-sim permet de régler la position des masses mobiles en fonctionnement de manière à minimiser le niveau de vibratoire du fuselage. L'algorithme de contrôle (algorithme de gradient) permet de calculer les consignes de position des masses mobiles sur les batteurs SARIB. La position des masses mobiles actionnée par un moteur électrique à courant continu et un système vis-écrou est ensuite asservie aux consignes générées par l'algorithme de contrôle. Enfin, la commande a pu être mise en place sur un modèle bond graph non-linéaire qui n'a pas nécessité une linéarisation en vue d'une transformation en fonction de transfertDue to the operation of the rotor, the helicopter is subject to important vibrations affecting namely the fatigue of mechanical parts and the passengers comfort. The MGB-Fuselage joint equipped with the DAVI system is an anti-vibration system that helps to reduce, in a single frequency way, vibrations transmitted to the fuselage. Semi-active intelligent solutions are studied so that the filtering can be adjusted according to the vibration sources. Such studies suffer from a lack of tools and necessary methods, firstly, for the design of complex mechanical systems and secondly, for the development of an intelligent joint. This work proposes a modeling approach using a structural modeling tool : the multi-bond graph (MBG) which offers a global and modular view for the study of complex mechatronic systems such as helicopter. At first, an analysis of modeling tools leading to the selection of MBG is presented. Secondly, developments have focused on the MBG modeling of the 3D MGB-fuselage joint of an experimental setup which was designed and built in the laboratory. This joint is a mechanical system with kinematic loops. The equations of the dynamics of such system are a differential-algebraic system (DAE) requiring specific solving methods. The MBG model of the MGB-fuselage was simulated using the 20-sim software. The results were verified using the multibody software LMS Virtual Lab. A comparison of results obtained by the two methods led to a very good correlation to various cases of excitations of the MGB (pumping, roll, pitch). Thirdly, the MBG model was used for the establishment of semi-active control system. The model of the DAVI device also developed in 20-sim allows to adjust the position of the moving masses in operation so as to minimize the level of vibration of the fuselage. The control algorithm (gradient algorithm) enables to calculate the setpoint positions of the moving masses on the DAVI beaters. The position of the moving masses driven by an electric DC motor and a screw-nut system is then controlled to the setpoints generated by the control algorithm. Finally, the command could be implemented on a non-linear bond graph model which did not require a linearization to get a transfer function
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Reitze, Clemens. "Closed-Loop-Entwicklungsplattform für mechatronische Fahrdynamikregelsysteme." Karlsruhe : Univ.-Verl, 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973301791.
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Bakke, Morten. "Subspace Identification using Closed-Loop Data." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9951.
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The purpose of this thesis was to investigate how different subspace identification methods cope with closed loop data, and how the controller parameters affect the quality of the acquired models. Three different subspace methods were subject for investigation; the MOESP method, the N4SID method and the DSR_e method. It is shown through a simulation example that all three subspace methods will identify the correct open-loop model from closed-loop data if the data record is noise-free (deterministic identification with perfect data). This result is not a new one, but a confirmation of the results from other researchers. Among the three different subspace methods that were investigated, the DSR_e method developed by dr. David Di Ruscio gave the best overall results. This method is especially designed to cope with closed-loop data, different from the MOESP and N4SID methods. Controller gain is shown to have a significant effect on the quality of the identified model when there is noise present in the loop. It is shown by simulations that up to a point, higher controller gain during the identification experiment actually gives more accurate open-loop models than models identified with lower controller gain. One of the reasons for this is that high gain tuning provides a higher signal to noise ratio through amplification of the reference signal, rendering the noise in the data used for identification less significant. Another reason may be that frequencies in the input signals will be more concentrated around the achievable bandwidth of the controller, which produces system outputs with more information of the frequency response around this bandwidth frequency. This is turn will reveal frequency information from the system that is important for control purposes.
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Lebreton, Baptiste. "Strategic closed-loop supply chain management." Palo Alto, Calif. : Ebrary, 2007. http://site.ebrary.com/id/10152065.
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Bernier, M. A. "Investigation of a closed-loop thermosyphon." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70171.
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Complementary analytical, numerical, and experimental investigations of fluid flow and heat transfer in closed-loop thermosyphons with vertical heated and cooled sections are presented in this thesis.A new model is proposed to couple the local results of numerical simulations performed in the heated and cooled section of a thermosyphon with a one-dimensional analytical model. The numerical simulations are based on a finite-volume numerical method which was formulated for the solution of laminar mixed-convection flows in vertical pipes with (or without) conjugate conduction in the pipe wall. Experimentally, a closed-loop thermosyphon was specially designed and constructed for this study. In the closed-loop, the power input is supplied by a semi-transparent gold-film which provides a uniform wall heat flux while enabling flow visualization.
The proposed model was successfully validated against experimental data obtained in this study. Results obtained with the proposed model also indicate that traditional one-dimensional models can significantly overpredict the average velocity in thermosyphons when strong mixed-convection effects are present in the heated and cooled sections. It is also shown that conduction in the pipe wall can significantly affect the velocity and temperature fields in mixed-convection flows. Photographs of flow visualization experiments in mixed-convection flows are also presented.
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Wang, Meihong. "Closed-loop identification using quantized data." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397912.
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A model of a system is important for applications such as simulation, prediction and control. Closed-loop identification (CLIO) is a means of identifying a process model while the process is still under feedback control. The motivation of this project is to find a way to do closed-loop identification while causing minimum disruption to the controlled process. There are two main categories of closed loop identification. One is closed-loop identification with external excitation (Ljung 1987, System Identification: theory for the user, Englewood Cliffs, NJ: Prentice-Hall). Another is relay identification (A strom and Hagglund I984a, Automatic Tuning of Simple Regulators with Specifications on Phase and Amplitude Margins, Alltomatim, Vo1.20, No.5. pp645-651 ). The first achievement of this thesis is the establishment of a connection between previously unrelated facts by comparing the two main categories of closed loop identification methods. Their advantages and disadvantages were highlighted through case studies. The second. and the main achievement of this thesis is to propose a new closed-loop identification scheme for a single-input-single-output (5IS0) control loop. It is based on a quantizer insel1ed into the feedback path. The novel contribution of this thesis is to bring the closed-loop identitication with external excitatiun method and the relay identification method into a unified framework for the first time. It gives recommendations about the appropriate method to use for a given quantizer interval. When the quantization interval is small, the quantization error is persistently exciting, equivalent to an external excitation. The two-stage (step) method can be applied. When the quantization interval is large. the relay method can be applied instead. Nonlinearity caused by the quantizer is analyzed. which indicates that nonlinearity increases with the quantization interval. Simulations and experiments showed that the proposed closed-loop idclItification schemc based on quantization is successful. The third achievement of this thesis is the implementation. testing and extension of a quantized regression (QR) algorithm that retrieves the underlying information from quantized signals such as those from the analogue to digital converter of a plant instrument. The algorithm is a combination of the 'Gaussian Fit' schcme with expectation-maximization (EM) algorithm. The new QR algorithm can optimally estimate the model parametcrs and recover the underlying signal at the same time for an arbitrary number of quantizer levels.
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Norfleet, Walton A. (Walton Arthur) 1973. "Algorithms for closed loop shape control." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8559.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (p. 147-149).
The stretch forming process is used to make structural sheet metal parts in the aerospace industry. The development of stretch forming tools has long been plagued by significant challenges. First, the low production volumes within the aerospace industry and the large numbers of stretch formed parts make the process capital intensive. Second, the development of stretch forming tooling has long been more of an art than a science. This results in poorly designed tools, poor quality parts, and lengthy tooling development cycles. A stretch forming tool capable of rapid reconfiguration was previously designed to address these issues. This tool is used in conjunction with a self-tuning shape control algorithm, which guides the die to the correct shape. There have been many simulations, and lab scale successes with these algorithms, but production scale implementations have experienced difficulties. These problems are related to the method of system identification and process variation. To better understand these issues, analysis and simulation are performed on the various forms of the algorithm. These investigations led to a greater understanding of the algorithms and the synthesis of an improved algorithm. In conclusion, a greater understanding of previously developed algorithms is presented. The system identification is mapped as a Point Spread Function applied through a cyclic convolution. This view provides insight into how the system identification is applied and allows system coupling to be quantified. Furthermore, through improved understanding a new algorithm is synthesized. This new algorithm offers an implementable solution that is optimized for performance, robustness to variation, and ease of use.
by Walton A. Norfleet.
S.M.
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Eyring, Andrew Stuart. "Analysis of Closed-Loop Digital Twin." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9242.
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Given recent advancements in technology and recognizing the evolution of smart manufacturing, the implementation of digital twins for factories and processes is becoming more common and more useful. Additionally, expansion in connectivity, growth in data storage, and the implementation of the Industrial Internet of Things (IIoT) allow for greater opportunities not only with digital twins but closed loop analytics. Discrete Event Simulation (DES) has been used to create digital twins and in some instances fitted with live connections to closely monitor factory operations. However, the benefits of a connected digital twin are not easily quantified. Therefore, a test bed demonstration factory was used, which implements smart technologies, to evaluate the effectiveness of a closed-loop digital twin in identifying and reacting to trends in production. This involves a digital twin of a factory process using DES. Although traditional DES is typically modeled using historical data, a DES system was developed which made use of live data with embedded machine learning to improve predictions. This model had live data updated directly to the DES model without user interaction, creating an adaptive and dynamic model. It was found that this DES with machine learning capabilities typically provided more accurate predictions of future performance and unforeseen near future problems when compared to the predictions of a traditional DES using only historic data
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Nalla, Ajit R. "Closed-loop flow control approaches for VARTM." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.86 Mb., 89 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1430781.
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Sung, Joon Hyun. "Transmitter Strategies for Closed-Loop MIMO-OFDM." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5029.
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This thesis concerns communication across channels with multiple inputs and multiple outputs. Specifically, we consider the closed-loop scenario in which knowledge of the state of the multiple-input multiple-output (MIMO) channel is available at the transmitter. We show how this knowledge can be exploited to optimize performance, as measured by the zero-outage capacity, which is the capacity corresponding to zero outage probability. On at-fading channels, a closed-loop transmitter allocates different powers and rates to the multiple channel inputs so as to maximize zero-outage capacity. Frequency-selective fading channels call for a combination of orthogonal-frequency-division multiplexing (OFDM) and MIMO known as MIMO-OFDM. This exacerbates the allocation problem because it multiplies the number of allocation dimensions by the number of OFDM tones. Fortunately, this thesis demonstrates that simple allocations are sufficient to approach the zero-outage capacity. These simple strategies exploit the tendency for random MIMO channels to behave deterministically as the number of inputs becomes large.
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Laspas, Theodoros. "Closed Force Loop Evaluation of Machining Systems." Licentiate thesis, KTH, Maskin- och processteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-227664.
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Machine tools accuracy has been a cornerstone in defining machining system capability and directly affecting dimensional and geometrical tolerance of machined parts. The effort for achieving higher precision and accuracy can be distinguished in two general ideas. One is to improve performance of machine tools by designing better, stiffer and more accurate machine tools. The other is to develop tools and methods for evaluating and measuring their behaviour and gain knowledge of their performance. In order to properly control the machine tool characteristics that can affect and improve their accuracy such as static stiffness and static accuracy.This thesis is aiming at establishing and further advancing the idea of loaded testing of machining systems and the concept of Elastically Linked Systems as a framework for measuring, identifying and characterising quasi-static stiffness of machine tools under loaded conditions. This will allow the creation of an improved capability profile of machining system accuracy. The focus is on the implementation of Elastically Linked Systems concept (ELS) through the Loaded Double Bar system, a measurement method that can partly simulate the process-machine interaction by reproducing forces exerted on the machine tool structure for the evaluation of system characteristics under loaded condition. This allows the qualitative and quantitative evaluation and comparison of machine tools for the purpose of accuracy enhancement, identification of weak directions with potential utilization in process planning, machine procurement and maintenance.Through two case studies, the capability to identify the effect of machine components and structure behaviour is shown.QC 20180514
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Corke, Peter Ian. "High-Performance Visual Closed-Loop Robot Control." Connect to thesis, 1994. http://repository.unimelb.edu.au/10187/1392.
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This thesis addresses the use of monocular eye-in-hand machine vision to control the position of a robot manipulator for dynamically challenging tasks. Such tasks are defined as those where the robot motion required approaches or exceeds the performance limits stated by the manufacturer.Computer vision systems have been used for robot control for over two decades now, but have rarely been used for high-performance visual closed-loop control. This has largely been due to technological limitations in image processing, but since the mid 1980sadvances have made it feasible to apply computer vision techniques at a sufficiently high rate to guide a robot or close a feedback control loop. Visual servoing is the use of computer vision for closed-loop control of a robot manipulator, and has the potential to solve a number of problems that currently limit the potential of robots in industry and advanced applications.
This thesis introduces a distinction between visual kinematic and visual dynamic control. The former is well addressed in the literature and is concerned with how the manipulator should move in response to perceived visual features. The latter is concerned with dynamic effects due to the manipulator and machine vision sensor which limit performance and must be explicitly addressed in order to achieve high-performance control. This is the principle focus of the thesis.
In order to achieve high-performance it is necessary to have accurate models of the system to be controlled (the robot) and the sensor (the camera and vision system).Despite the long history of research in these areas individually, and combined in visual servoing, it is apparent that many issues have not been addressed in sufficient depth, and that much of the relevant information is spread through a very diverse literature. Another contribution of this thesis is to draw together this disparate information and present it in a systematic and consistent manner. This thesis also has a strong theme of experimentation. Experiments are used to develop realistic models which are used for controller synthesis, and these controllers are then verified experimentally.
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Jiang, Xunqing. "Closed-loop system identification with operator intervention." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/MQ28821.pdf.
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Bao, Lei. "Source-channel coding for closed-loop control." Licentiate thesis, Stockholm, Communication Theory Lab, School of Electrical Engineering, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3980.
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Kwalik, Kristina Mary. "Bifurcation characteristics in closed-loop polymerization reactors." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/11711.
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Gross, Bryan Eric. "Psychrometric application to closed loop vapor degreasing." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16993.
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Kraft, Michael. "Closed loop digital accelerometer employing oversampling conversion." Thesis, Coventry University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361662.
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Reaves, Joel C. "Closed loop pole placement and cost analysis." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26914.
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Dong, Chao. "Closed-loop controlled total intra venous anaesthesia." Thesis, University of Plymouth, 2003. http://hdl.handle.net/10026.1/2253.
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Anaesthesia is important for both surgery and intensive care and intravenous anaesthetics are widely used to provide rapid onset, stable maintenance, and rapid recovery compared with inhaled anaesthetics. The aim of the project on which this thesis is based was to investigate a reliable and safe methodology for delivering total intravenous anaesthesia using closed-loop control technology and bispectral analysis of human electroencephalogram (EEG) waveform. In comparison with Target Controlled Infusion (TCI), drug effect is measured during drug infusion in closed loop anaesthesia (CLAN). This may provide superior safety, better patient care, and better quality of anaesthesia whilst relieving the clinician of the need to make recurrent and minor alterations to drug administration. However, the development of a CLAN system has been hindered by the Jack of a 'gold standard' for anaesthetic states and difficulties with patient variability in pharmacokinetic and pharmacodynamic modelling, and a new and generic mathematical model of a closed-loop anaesthesia system was developed for this investigation. By using this CLAN model, investigations on pharmacokinetic and pharmacodynamic variability existing in patients were carried out. A new control strategy that combines a Proportional, Integral, Derivative (PID) controller, bispectral analysis of EEG waveform and pharmacokinetic/ pharmacodynamic models was investigated. Based on the mathematical model, a prototype CLAN system, the first CLAN system capable of delivering both hypnotics and analgesics simultaneously for total intravenous anaesthesia, was developed. A Bispectral Index (BIS), derived from power spectral and bispectral analysis on EEG waveform, is used to measure depth of anaesthesia. A supervision system with built-in digital signal processing techniques was developed to compensate the non-linear characteristics inherent in the system while providing a comprehensive protection mechanism for patient safety. The CLAN system was tested in 78125 virtual patients modelled using published data. Investigations on intravenous anaesthesia induction and maintenance with the CLAN system were carried out in various clinical settings on 21 healthy volunteers and 15 patients undergoing surgery. Anaesthesia targets were achieved quickly and well maintained in all volunteers/patients except for 2 patients with clinically satisfactory anaesthesia quality.
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Saxena, Shreya 1988. "Moving fast : neural constraints in closed loop." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/114006.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 125-133).
The generation of fast movements during sensorimotor control is fundamentally limited by the biophysics of neural activity and the physiological dynamics of the muscles involved. Yet, the limiting factors and the corresponding tradeoffs have not been rigorously quantified. We use feedback control principles to identify limitations in the ability of the sensorimotor control system to track intended fast periodic movements. We show that (i) a linear model for movement generation fails to predict known undesirable phenomena encountered in the regime of fast movements, and (ii) the theory of pulsatile control of movement generation allows us to correctly characterize fundamental limitations in this regime. This thesis identifies the fastest periodic movement possible for given musculoskeletal and neuronal dynamics, which has far-reaching implications in sensorimotor control. The use of neuronal decoders in the Brain Machine Interface setting is discussed; we introduce a real-time decoder of neuronal activity, and derive conditions for its stability in the presence of feedback. The framework developed in this thesis allows us to characterize the effect of compromised neural and physiological activity on movement, and guide the design of corresponding therapeutic measures.
by Shreya Saxena.
Ph. D.
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Daniels, Richard, Jiasheng Su, Falei Zhang, and Zhuangdou Zhang. "Closed-Loop Liming and Tanning Systems - 57." Verein für Gerberei-Chemie und -Technik e. V, 2019. https://slub.qucosa.de/id/qucosa%3A34409.
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To reduce the environmental impact of tanneries at source for all types of leather, a series of investigations started at laboratory, then large pilot scale, to rationalise liming and tanning processes. This included the elimination of washes at the end of these processes, with retention of residual processing floats at maximum concentration as a chemical resource for reuse in subsequent processing.
Adopted by four tanneries manufacturing more than 70,000 hides per week to the chromium tanned state, analysis detailing the equalisation of ions and solubles within these closed-loops was possible, and the subsequent release mechanisms.
Large scale wet blue units specifically built to match the technology are now in the final stages of construction. From foundation level these differ from normal design, also uses of equipment, management of discharges, and plant operation. Low-impact chemical processing is locked into the fabric of these new tanneries.
The technology has also spread to large scale nappa sheepskin production. And at cottage scale, thirty small tanneries in a tanning cluster processing sheep, goat, and bovine leathers to the wet blue are already changed their processing to meet a policy of no chromium discharges from their tanning areas by June 2019.
The aims of low-impact manufacture, where the use of active chemicals is complete, quality fully maintained, and waste minimised are being met. This new approach to leather making offers considerable benefits at both large and small scale for wet blue manufacture.
Take-Away:
Closed loop systems for liming and tanning are highly effective in leather manufacture.
Hight quality leathers can result fron this technology.
There are considerable savings in chemical use and minimisation of waste water treatment.
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Wenzel, Brian Jeffrey. "CLOSED-LOOP ELECTRICAL CONTROL OF URINARY CONTINENCE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1120932206.
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Shaw, Feng-Rong. "Repetitive control of closed loop material testing /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487757723996636.
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Allmendinger, Richard. "Tuning evolutionary search for closed-loop optimization." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/tuning-evolutionary-search-for-closedloop-optimization(d54e63e2-7927-42aa-b974-c41e717298cb).html.
Full textAbstract:
Closed-loop optimization deals with problems in which candidate solutions are evaluated by conducting experiments, e.g. physical or biochemical experiments. Although this form of optimization is becoming more popular across the sciences, it may be subject to rather unexplored resourcing issues, as any experiment may require resources in order to be conducted. In this thesis we are concerned with understanding how evolutionary search is affected by three particular resourcing issues -- ephemeral resource constraints (ERCs), changes of variables, and lethal environments -- and the development of search strategies to combat these issues. The thesis makes three broad contributions. First, we motivate and formally define the resourcing issues considered. Here, concrete examples in a range of applications are given. Secondly, we theoretically and empirically investigate the effect of the resourcing issues considered on evolutionary search. This investigation reveals that resourcing issues affect optimization in general, and that clear patterns emerge relating specific properties of the different resourcing issues to performance effects. Thirdly, we develop and analyze various search strategies augmented on an evolutionary algorithm (EA) for coping with resourcing issues. To cope specifically with ERCs, we develop several static constraint-handling strategies, and investigate the application of reinforcement learning techniques to learn when to switch between these static strategies during an optimization process. We also develop several online resource-purchasing strategies to cope with ERCs that leave the arrangement of resources to the hands of the optimizer. For problems subject to changes of variables relating to the resources, we find that knowing which variables are changed provides an optimizer with valuable information, which we exploit using a novel dynamic strategy. Finally, for lethal environments, where visiting parts of the search space can cause the permanent loss of resources, we observe that a standard EA's population may be reduced in size rapidly, complicating the search for innovative solutions. To cope with such scenarios, we consider some non-standard EA setups that are able to innovate genetically whilst simultaneously mitigating risks to the evolving population.
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Whiting, Ian Martin. "Closed loop digital control of electrohydraulic systems." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375516.
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Jalkh, Pierre E. (Pierre Edovard). "Open loop and closed loop cup forming of aluminum sheet metals." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35953.
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Ambike, Ajit Dilip. "Closed-loop real-time control on distributed networks." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1079.
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This thesis is an effort to develop closed-loop control strategies on computer networks and study their stability in the presence of network delays and packet losses. An algorithm using predictors was designed to ensure the system stability in presence of network delays and packet losses. A single actuator magnetic ball levitation system was used as a test bed to validate the proposed algorithm. A brief study of real-time requirements of the networked control system is presented and a client-server architecture is developed using real-time operating environment to implement the proposed algorithm. Real-time performance of the communication on Ethernet based on user datagram protocol (UDP) was explored and UDP is presented as a suitable protocol for networked control systems. Predictors were designed based on parametric estimation models. Autoregressive (AR) and autoregressive moving average (ARMA) models of various orders were designed using MATLAB and an eighth order AR model was adopted based on the best-fit criterion. The system output was predicted several steps ahead using these predictors and control output was calculated using the predictions. This control output output was used in the events of excessive network delays to maintain system stability. Experiments employing simulations of consecutive packet losses and network delays were performed to validate the satisfactory performance of the predictor based algorithm. The current system compensates for up to 20 percent data losses in the network without loosing stability.
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Myklebust, Andreas. "Closed Loop System Identification of a Torsion System." Thesis, Linköping University, Department of Electrical Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17531.
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A model is developed for the Quanser torsion system available at Control Systems Research Laboratory at Chulalongkorn University. The torsion system is a laboratory equipment that is designed for the study of position control. It consists of a DC motor that drives three inertial loads that are coupled in series with the motor, and where all components are coupled to each other through torsional springs.
Several nonlinearities are observed and the most significant one is an offset in the input signal, which is compensated for. Experiments are carried out under feedback as the system is marginally stable. Different input signals are tested and used for system identification. Linear black-box state-space models are then identified using PEM, N4SID and a subspace method made for closed-loop identification, where the last two are the most successful ones. PEM is used in a second step and successfully enhances the parameter estimates from the other algorithms.
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Pothier, Raymond Peter. "Closed-loop temperature control of friction stir welding." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/10362.
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This study develops and presents a friction stir weld (FSW) quality assurance tool based on control of weld zone temperature. Apart from correct tool geometry, tool tilt angle, traverse speed and forge force during welding, one important requirement is that the weld material be sufficiently plasticised (softened). The level of plasticisation is related to weld zone temperature which is primarily dependent on spindle speed, traverse speed and forge force. When all other conditions are correct, sufficiently plasticised material flows around and consolidates behind the tool without the production of voids in the weld. Typically, weld temperature varies along the weld length which may result in variations in weld quality. Weld zone temperature control makes constant weld zone temperature possible. In this study, thermocouple sensors were embedded in the FSW tool and a weld zone temperature control algorithm was developed. Spindle speed was the actuating mechanism for controlling weld temperature. The system was modelled and controllers were designed using Matlab tools. The system was simulated and the performance was compared to the system performance during welding. The control system ensures that the weld zone temperature can be maintained irrespective of the presence of thermal disturbances. Tensile testing was conducted which confirmed a range of temperature in which the welds resulted in consistent strength.
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Braudrick, Michael Wayne. "Closed-loop preaching : enhancing preaching using lay feedback." Thesis, Middlesex University, 2004. http://eprints.mdx.ac.uk/2658/.
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This study has been conducted under the direction of Middlesex University and through the good favor of the Frisco (Texas) Christian Alliance. The concern of this research has been whether the existence of a standing lay pulpit team increases measurably the preacher’s openness to feedback. This process of developing sensitivity to useful feedback is known as “closing the feedback loop.” Multiple case studies, triangulated with many other data collection instruments, have been the primary means of examining the hypothesis that a standing lay evaluation team closes the feedback loop. Further, existing studies and literature have been used to not only support this hypothesis but to convincingly establish that openness to feedback leads inevitably to improved teaching. The results clearly demonstrate the efficacy of a lay pulpit team in opening a preacher to feedback and thus increasing effectiveness. Thus, the theory herein tested, supported by this research and further validated by other work, may provide a simple means to achieve an end long sought in the preaching profession.
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Yang, Xiaobo. "A closed-loop driver/vehicle directional dynamics predictor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq43568.pdf.
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Tran, Mai. "Mobile WiMAX Open and Closed Loop MIMO Evaluation." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520187.
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Zhang, Zhenyu. "Closed-Loop Flow Control for Boundary Layer Instabilities." Thesis, Queen Mary, University of London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504556.
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Since O. Reynolds' experiment revealed the transition from laminar state to turbulence in pipe flow (1883), numerous efforts had been exerted in order to understand the mechanism. Linear hydrodynamic stability theory was established in the first half ofthe twentieth century. This theory predicts the growth of small disturbances during the initial stage of transition. As an important achievement, the Tollmien-Schlichting (T-S) instability, which represents the initial evolution of disturbances in two dimensional shear flows, has been described and verified in boundary layer experiments. Once the enonnous benefits from the delay of flow transition (and then turbulence) were acknowledged, diversities of flow control techniques have been motivated. In fact, some relevant techniques have already been demonstrated, such as the drag reduction oflarge aeroplane through laminar flow control. At the same time, the development of control theory makes it possible to implement deliberately designed systems to control transitional flows. After decades of advances with passive control, the concept of active control became widely accepted in fluid mechanics in the early 1980s. . The study in this thesis attempts to find an efficient closed-loop active control scheme to cancel the unstable Tollmien-Schlichting waves in a transitional boundary layer flow. The T-S instabilities was simulated by numerical solutions of the linearised Navier-Stokes equation system. Controllers were designed according to the frequency characteristics ofthe disturbed flowfield and implemented on the basis of the classical control theory in frequency domain. The perfonnance of controllers in the disturbed boundary layer flow along a flat plate were evaluated through numerical simulations and then validated by experiments.
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Werner, Loren M. (Loren Michael) 1977. "Analysis and design of closed loop manufacturing systems." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/82688.
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Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2001.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 89-90).
by Loren M. Werner.
S.M.
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Cirmirakis, D. "Novel telemetry system for closed loop vestibular prosthesis." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1389947/.
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Disorders of the vestibular system result in loss of body balance and a steady vision in humans and animals. The most common consequences include vertigo, oscillopsia, postural instability and blurred vision. Currently, conventional medicine cannot cure the damage or restore the function of the vestibular system. Vestibular prosthesis may assist in restoring its function using electrical stimulation, which involves delivering current pulses into the nerves innervating the semi-circular canals in the inner ear. A vestibular prosthesis contains external electronics and an implantable medical device . The system delivers modulated electrical pulses and stimulates vestibular nerves with these pulses to inform the brain about the motion. Power transfer to, and communication with the implanted device, is provided by telemetry. In biomedical implanted devices the telemetry is usually implemented by radio-frequency induction using weakly coupled coils. Using a single set of coils for simultaneous power transfer and communication creates the challenge of contradicting requirements. For high data rates the inductive link must have a wide bandwidth but power transfer requires a low bandwidth. Moreover by modulating a carrier the power transfer is degraded. This thesis describes the design, implementation and experimental evaluation of a novel telemetry system for a three-dimensional vestibular prosthesis with neural recording. The developed telemetry system uses a single pair of inductively-coupled coils to power-up the implant and maintain bi-directional communication to control its operation. It also relays raw electroneurogram (ENG) data out of the body at high speed. For inductive power control two methods are combined: a geometrical approach and a feedback loop to maintain a constant level of delivered power. The communication to the implant (downlink) is obtained by amplitude modulation while the communication from the implant to the external transmitter (uplink) uses passive phase shift modulation. On-chip humidity sensing capabilities are facilitated in the implant microelectronics to monitor hermeticity of the package. The uplink achieves the highest data speed demonstrated in the literature of available methods using a single set of coils with combined power and communication links. The developed technique can be applied to other applications including RFID.
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Palliyaguru, Lalinda Niroshana. "Investigation of Closed-Loop Control of Polyatomic Molecules." Diss., Temple University Libraries, 2008. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/16646.
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ChemistryPh.D.
ABSTRACT Investigation of Closed-Loop Control of Polyatomic Molecules Lalinda N. Palliyaguru Doctor of Philosophy Temple University, 2009 Doctoral Advisory Committee Chair: Prof. Robert J. Levis Experimental results that are based on mass spectral data, in this thesis includes ionization/fragmentation of DMMP and CH2BrI in strong femtosecond laser fields, coherent control using closed-loop optimization method for bond dissociation in both DMMP and CH2BrI, as well as application of closed-loop control as a detection method for air borne organophosphates such as DMMP. Investigation of mass spectral data as a function of laser field intensity, wavelength, and polarization provided details of ionization/fragmentation of DMMP and CH2BrI. Furthermore, quantum mechanical calculations carried out with Gaussian 03 Computational package were used to analyze the mass spectral data. The analysis of the peak splitting pattern of the molecular fragments reveals that Coulomb explosion as well as the photodissociation of CH2BrI produces the TOF mass spectral product distribution. We observed a considerable enhancement of photodissociation of CH2BrI in strong elliptically polarized femtosecond laser fields. The enhanced photodissociation of CH2BrI in circularly polarized fields could be due to the interaction with both parallel and perpendicular electronic transitions that cause the efficient dissociation of C-I and C-Br bonds. We also demonstrate the selective dissociation of C-I and C-Br bonds using closed-loop optimal control method. The fragmentation processes of polyatomic molecules induced by an intense laser field exhibit sensitive dependence on the laser characteristics such as intensity, pulse duration, wavelength, and shape of the temporal pulse envelope. Adaptive laser pulse shaping can control the fragmentation of methyl/methoxy groups in dimethyl methylphosphonate (DMMP), a simulant for nerve agent Sarin. The exploitation of the sensitivity of molecular fragmentation to laser pulse shapes represents a new way to discriminate molecular identity. Here we have shown manipulation of the branching M-(OCH3)+/M-(CH3)+, M-2(CH3)+/M-(CH3)+ and M-(OCH3)+/M-2(CH3)+ fragment ion ratios for DMMP in the presence of complex background in the extraction region of TOF spectrometer using tailored femtosecond laser pulses. We also investigated the TOF mass spectra of DMMP as a function of laser field parameters, such as intensity, wavelength, polarization, and linear chirp. We positively identified that non-sequential ionization plays a role in the fragmentation process of DMMP.
Temple University--Theses
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Khandekar, Sameer. "Thermo-hydrodynamics of closed loop pulsating heat pipes." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11312755.
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Guidi, Hernan. "Open and closed-loop model identification and validation." Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-07032009-170311/.
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Reitze, Clemens [Verfasser]. "Closed-Loop-Entwicklungsplattform für mechatronische Fahrdynamikregelsysteme / Clemens Reitze." Karlsruhe : Univ.-Verl. Karlsruhe, 2004. http://d-nb.info/973301791/34.
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Ho, Du. "Some results on closed-loop identification of quadcopters." Licentiate thesis, Linköpings universitet, Reglerteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-152701.
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In recent years, the quadcopter has become a popular platform both in research activities and in industrial development. Its success is due to its increased performance and capabilities, where modeling and control synthesis play essential roles. These techniques have been used for stabilizing the quadcopter in different flight conditions such as hovering and climbing. The performance of the control system depends on parameters of the quadcopter which are often unknown and need to be estimated. The common approach to determine such parameters is to rely on accurate measurements from external sources, i.e., a motion capture system. In this work, only measurements from low-cost onboard sensors are used. This approach and the fact that the measurements are collected in closed-loop present additional challenges. First, a general overview of the quadcopter is given and a detailed dynamic model is presented, taking into account intricate aerodynamic phenomena. By projecting this model onto the vertical axis, a nonlinear vertical submodel of the quadcopter is obtained. The Instrumental Variable (IV) method is used to estimate the parameters of the submodel using real data. The result shows that adding an extra term in the thrust equation is essential. In a second contribution, a sensor-to-sensor estimation problem is studied, where only measurements from an onboard Inertial Measurement Unit (IMU) are used. The roll submodel is derived by linearizing the general model of the quadcopter along its main frame. A comparison is carried out based on simulated and experimental data. It shows that the IV method provides accurate estimates of the parameters of the roll submodel whereas some other common approaches are not able to do this. In a sensor-to-sensor modeling approach, it is sometimes not obvious which signals to select as input and output. In this case, several common methods give different results when estimating the forward and inverse models. However, it is shown that the IV method will give identical results when estimating the forward and inverse models of a single-input single-output (SISO) system using finite data. Furthermore, this result is illustrated experimentally when the goal is to determine the center of gravity of a quadcopter.This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 642153.
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Lee, Chanjoo. "Analysis of decision-making in closed-loop supply chains." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44925.
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Closed-loop supply chains (CLSCs) that integrate the activities for reclaiming residual values in postconsumer products with the traditional forward supply chain activities are important from financial and environmental perspectives. This thesis develops models and analyses on three topics novel to the field of CLSC research with a goal of advancing knowledge about effective decision-makings in CLSCs.
In the first part of the thesis, we study joint control of stochastic forward and stochastic reverse material flows in CLSCs. With an application to a CLSC where postconsumer products are collected for warranty service purposes, we demonstrate that the benefit of coordinating two production activities could be significant. We develop a model that can be used to obtain an effective inventory control policy for coordinating forward and reverse material flows. Through Monte Carlo simulation and global sensitivity analysis, we identify major influential factors that affect system's warranty cost savings performance. The results indicate that joint control of forward and reverse material flows greatly improves warranty cost savings performance as well as system's robustness to uncertainties.
The second part of the thesis develops a differential game model for characterizing decentralized time-varying competitive decision-making in a CLSC.
The differential game model is particularly useful for studying time-varying interactive decision-making in CLSCs that involve many stakeholders who pursue different objectives in forward and reverse production activities. We identify optimal prices and production strategies that evolve over time under fluctuating market demand. Also, the model provides a quantitative scheme that can be used to obtain an efficient apportionment of product recovery processes.
The third part of the thesis describes the relationship among consumers' risk-aversion, product cannibalization of new products by remanufactured products, and growth of CLSCs through price optimization models. Whereas price is one of the most effective variables for managing market demand, previous CLSC research has mainly focused on operational problems without paying much attention on the interface between CLSCs and markets. We develop models that jointly determine optimal prices in forward and reverse channels considering consumers' willingness-to-pay (WTP) for remanufactured products, consumers' willingness-to-accept (WTA) for a buyback price, and consumers' risk aversion to uncertain quality perceptions. The results show that consumers' active participation in CLSC is an important factor for the viability and growth of a CLSC. Also, we show that companies can benefit from product remanufacturing although it may be accompanied by production cannibalization.
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Afshar, Saman. "Investigating product acquisition strategies in closed-loop supply chains." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33496/.
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Remanufacturing is one of the main recovery operations in Closed-Loop Supply Chains (CLSCs) that not only can contribute to a more sustainable environment, but also has significant economic and social benefits. A key factor for having an efficient remanufacturing operation is to control the heterogeneous characteristics of product returns in terms of quantity, quality and timing. Product Acquisition Management is an essential process in CLSCs, which aims to deal with these characteristics of product returns. The present study extends knowledge in Product Acquisition Management, by developing quantitative models that generate meaningful insights into the economics of proactive product acquisitioning. In addition, case studies inform the present study with the current status of product acquisition management in practice and the relevant challenges. The economic-oriented decision about operating a proactive or passive strategy is explored under quantity and quality-based incentive approaches. Closed-form solutions and quality thresholds are derived for the optimal return rate and optimal quality rate that minimises the total cost of the proactive strategy. The analysis of the infinite planning horizon models show that, the optimal acquisition strategy depends on a trade-off between the relevant remanufacturing cost advantage and the acquisition cost structure. A diseconomy of scale in the acquisition of returns leads to a decrease of the remanufacturing amount. Sensitivity analysis further highlights the differences between the quantity and the quality-based incentive approaches. This study extends its investigation on the economic viability of the proactive acquisition strategy under the finite planning horizon. Using the product life cycle as a basis for matching demand and supply, the analysis shows that delays in the processing of returns will reduce the cost advantages of a proactive acquisition strategy and that applying a dynamic acquisition policy will increase the cost improvement of the proactive strategy. Finally, the study investigates a dynamic manufacturing-remanufacturing system with a responsive buy-back policy by considering multiple quality levels and decay rates. The model is formulated using optimal control theory, and shows that the optimal acquisition strategy depends on the manufacturing-remanufacturing cost difference and price sensitivity of the return response function for high and low quality used products. The sensitivity analysis indicates that in general it is beneficial to obtain a higher rate of high quality returns in the beginning of the planning horizon, and a higher rate of low quality returns towards the end. The fluctuation in demand is mainly absorbed by manufacturing new products and much less by remanufacturing returns. Within the optimal buy-back policy, the result has indicated that it is the acquisition of high quality of returns that mirror the fluctuation in the demand, while the acquisition of low quality of returns show a relatively stable trend.
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Hodge, Steven Eric. "Discrete-time closed-loop control of a hinged wavemaker." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26704.
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The waves produced by a flap-type wavemaker, hinged in the middle, are modelled using first-order linear wavemaker theory. A simplified closed-loop, discrete-time system is proposed. This includes a proportional
plus integral plus derivative (PID) controller, and the wavemaker in order to compare the actual wave spectral density with the desired wave spectral density at a single frequency. Conventional discrete-time control theory is used with the major difference being the use of a relatively long timestep duration between changes in waveboard motion.
The system response is calculated for many controller gain combinations
by the computer simulation program CBGANES. System stability is analyzed for the gain combinations by using two different methods. One method is an extension of the Routh criterion to discrete-time and the other is a state-space eigenvalue approach. The computer simulation and the stability analysis provide a means for selecting possible controller gains for use at a specific frequency in an actual wave tank experiment.
The computer simulation performance response and the two stability analyses predict the same results for varying controller gains. It is evident that integral control is essential in order to achieve a desired response for this long duration timestep application. The variation in discrete timestep duration and in desired spectral density (an indirect indication of frequency variation) provide variation in the constraints on controller gain selection. The controller gain combinations yielding the fastest stable response at a single frequency are for large proportional gain and small integral and derivative gains.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate