6 research outputs found

    Robust fractional-order fast terminal sliding mode control with fixed-time reaching law for high-performance nanopositioning

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    Open Access via the Wiley Agreement ACKNOWLEDGEMENTS This work is supported by the China Scholarship Council under Grant No. 201908410107 and by the National Natural Science Foundation of China under Grant No. 51505133. The authors also thank the anonymous reviewers for their insightful and constructive comments.Peer reviewedPublisher PD

    Computationalcost Reduction of Robust Controllers Foractive Magnetic Bearing Systems

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    This work developed strategies for reducing the computational complexity of implementing robust controllers for active magnetic bearing (AMB) systems and investigated the use of a novel add-on controller for gyroscopic effect compensation to improve achievable performance with robust controllers. AMB systems are multi-input multi-output (MIMO) systems with many interacting mechanisms that needs to fulfill conflicting performance criteria. That is why robust control techniques are a perfect application for AMB systems as they provide systematic methods to address both robustness and performance objectives. However, robust control techniques generally result in high order controllers that require high-end control hardware for implementation. Such controllers are not desirable by industrial AMB vendors since their hardware is based on embedded systems with limited bandwidths. That is why the computational cost is a major obstacle towards industry adaptation of robust controllers. Two novel strategies are developed to reduce the computational complexity of singlerate robust controllers while preserving robust performance. The first strategy identifies a dual-rate configuration of the controller for implementation. The selection of the dualrate configuration uses the worst-case plant analysis and a novel approach that identifies the largest tolerable perturbations to the controller. The second strategy aims to redesign iv the controller by identifying and removing negligible channels in the context of robust performance via the largest tolerable perturbations to the controller. The developed methods are demonstrated both in simulation and experiment using three different AMB systems, where significant computational savings are achieved without degrading the performance. To improve the achievable performance with robust controllers, a novel add-on controller is developed to compensate the gyroscopic effects in flexible rotor-AMB systems via modal feedback control. The compensation allows for relaxing the robustness requirements in the control problem formulation, potentially enabling better performance. The effectiveness of the developed add-on controller is demonstrated experimentally on two AMB systems with different rotor configurations. The effects of the presence of the add-on controller on the performance controller design is investigated for one of the AMB systems. Slight performance improvements are observed at the cost of increased power consumption and increased computational complexity

    Semi-blind robust indentification and robust control approach to personalized anemia management.

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    The homeostatic blood hemoglobin (Hb) content of a healthy individual varies between the range of 14-18 g/dL for a male and 12-16 g/dL for a female. This quantity provides an estimate of red blood cell (RBC) count in circulation at any given moment. RBC is a protein carrying substance that transports oxygen from the lungs to other tissues in the body and is synthesized by the kidney through a process known as erythropoiesis where erythropoietin is secreted in response to hypoxia. In this regard, the kidneys act not only as a controller but also as a sensor in regulating RBC levels. Patients with chronic kidney diseases (CKD) have dysfunctional kidneys that compromise these fundamental kidney functions. Consequently, anemia is developed. Anemics of CKD have low levels of Hb that must be controlled and properly regulated to the appropriate therapeutic range. Until the discovery of recombinant human erythropoietin (EPO) over three decades ago, treatment procedure of anemia conditions primarily involved repeated blood transfusions–a process known to be associated with several other health related complications. This discovery resulted in a paradigm shift in anemia management from blood transfusions to dosage therapies. The main objective of anemia management with EPO is to increase patients’ hemoglobin level from low to a suitable therapeutic range as defined by the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative (NKF-KDOI) to be in the range of 10 - 12 g/dL while avoiding response values beyond 14 g/dL to prevent other complications associated with EPO medication. It is therefore imperative that clinicians balance dosage efficacy and toxicity in anemia management therapies. At most treatment facilities, protocols are developed to conform to NKF-KDOI recommendations. These protocols are generally based on EPO packet inserts and the expected Hb responses from the average patient. The inevitable variability within the patient group makes this “one-size-fits-all” dosing scheme non-optimal, at best, and potentially dangerous for certain group of patients that do not adhere to the notion of expected “average” response. A dosing strategy that is tailored to the individual patients’ response to EPO medication could provide a better alternative to the current treatment methods. An objective of this work is to develop EPO dosing strategies tailored to the individual patients using robust identification techniques and modern feedback control methods. First, a unique model is developed based on Hb responses and dosage EPO of the individual patients using semi-blind robust identification techniques. This provides a nominal model and a quantitative information on model uncertainty that accounts for other possible patient’s dynamics not considered in the modeling process. This is in the framework of generalized interpolation theory. Then, from the derived nominal model and the associated uncertainty information, robust controller is designed via the =H1-synthesis methods to provide a new dosing strategies for the individual patients. The H1 control theory has a feature of minimizing the influence of some unknown worst case gain disturbance on a system. Finally, a framework is provided to strategize dosing protocols for newly admitted patients

    Compensation of Nonlinearities in AC Motor Control Algorithms

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    V úvodu dizertační práce je provedena analýza vlivu mrtvého času a dalších nelinearit napěťového měniče. Na základě provedené analýzy byly navrženy tři kompenzační strategie pro vektorově řízený PMSM (Permanent Magnet Synchronous Motor). Pozorovatel napěťového rušení s váhovanými odchylkami proudů je založen na modelu PMSM, známých parametrech a snadno měřitelných veličinách. Druhý pozorovatel, který odhaduje proud v dq- souřadnicích a hodnotu napěťové chyby pomocí pouze jednoho parametru, je navržen na základě provedené harmonické analýzy a algoritmu Kalmanova filtru. Třetí metoda kombinuje adaptivní přístup se zpětnou vazbou s pozorovatelem rušivých napětí, který je založen na modelu PMSM. Dále byly navrženy dvě metody kompenzace pro vektorově řízený asynchronní motor. V prvním případě je standardní kompenzační strategie rozšířena o harmonický kompenzátor, který potlačuje přetrvávající 6. harmonickou složku v dq- souřadnicích. Poslední strategie provádí detekci polarity z odhadovaných fázových proudů, které jsou získány pomocí Kalmanova filtru. Všechny kompenzační strategie byly ověřeny pomocí simulací v prostředí MATLAB/Simulink a experimentů na reálných pohonech.Analysis of the dead-time effect and other nonlinearities of the voltage source inverter was carried out in the introduction of the doctoral thesis. Three compensation strategies for vector controlled PMSM were proposed based on the analysis. The voltage disturbance observer with cost function of current errors is based on the model of PMSM, known machine parameters and easily measurable quantities. The second observer which estimates the dq- axes currents and the value of the voltage error with one parameter only is designed based on the harmonic analysis and Kalman filter algorithm. The third method combines an adaptive approach with feedback and voltage disturbance observer that is based on the PMSM model. Furthermore, the two compensation methods for vector controlled induction motor were proposed. In the first case, the standard compensation strategy is extended by a harmonic compensator that suppresses the residual 6th harmonic component in dq- axes currents. The last strategy detects the polarity of the estimated phase currents that are obtained by the Kalman filter. All compensation strategies have been verified by MATLAB/Simulink simulations and by experiments on real drives.

    Summary of Research 1994

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    The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. Government.This report contains 359 summaries of research projects which were carried out under funding of the Naval Postgraduate School Research Program. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, and technical reports. The research was conducted in the areas of Aeronautics and Astronautics, Computer Science, Electrical and Computer Engineering, Mathematics, Mechanical Engineering, Meteorology, National Security Affairs, Oceanography, Operations Research, Physics, and Systems Management. This also includes research by the Command, Control and Communications (C3) Academic Group, Electronic Warfare Academic Group, Space Systems Academic Group, and the Undersea Warfare Academic Group
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