Journal articles: 'Observer Unifiée'

1

Hou, M., and P. C. Muller. "Disturbance decoupled observer design: a unified viewpoint." IEEE Transactions on Automatic Control 39, no. 6 (June 1994): 1338–41. http://dx.doi.org/10.1109/9.293209.

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Lee, Dong-Gi, and Inha Hyun. "Optimal Observer of a Stochastic Decentralized Singularly Perturbed Unified System." Journal of Korean Institute of Information Technology 18, no. 7 (July 30, 2020): 29–41. http://dx.doi.org/10.14801/jkiit.2020.18.7.29.

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Xiang, Yan, Jing Yang, Hao Zhu, and Ding Xiang Dong. "The Observer Pattern Research Based on rCOS." Applied Mechanics and Materials 513-517 (February 2014): 936–40. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.936.

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Design patterns is a good method to solve software crisis and realize the software reuse. It is usually combined with the Unified Modeling Language (UML) to establish the system framework. And Observer pattern is high frequently used in actual modeling. So this paper presents formalization of the Observer pattern based on refinement Calculus of Object Systems (rCOS), this research describes formal semantics of the patterns UML class diagram and sequence diagram and guarantee the characteristics and properties of the pattern at the same time in order to use system model accurately which involved Observer pattern.

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Boulkroune, A., M. Tadjine, M. M’Saad, and M. Farza. "Design of a unified adaptive fuzzy observer for uncertain nonlinear systems." Information Sciences 265 (May 2014): 139–53. http://dx.doi.org/10.1016/j.ins.2013.12.026.

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Cimini, Gionata, Gianluca Ippoliti, Giuseppe Orlando, Sauro Longhi, and Rosario Miceli. "A unified observer for robust sensorless control of DC–DC converters." Control Engineering Practice 61 (April 2017): 21–27. http://dx.doi.org/10.1016/j.conengprac.2017.01.012.

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Bianchi, Stefano, Roberto Maiolino, and Guido Risaliti. "AGN Obscuration and the Unified Model." Advances in Astronomy 2012 (2012): 1–17. http://dx.doi.org/10.1155/2012/782030.

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Unification Models of Active Galactic Nuclei postulate that all the observed differences between type 1 and type 2 objects are due to orientation effects with respect to the line of sight to the observer. The key ingredient of these models is the obscuring medium, historically envisaged as a toroidal structure on a parsec scale. However, many results obtained in the last few years are clearly showing the need for a more complex geometrical distribution of the absorbing media. In this paper, we review the various pieces of evidence for obscuring media on different scales, from the vicinity of the black hole to the host galaxy, in order to picture an updated unification scenario explaining the complex observed phenomenology. We conclude by mentioning some of the open issues.

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Bao Tran, Gia Quoc, Thanh-Phong Pham, and Olivier Sename. "Multi-objective Unified qLPV Observer: Application to a Semi-active Suspension System." IFAC-PapersOnLine 54, no. 8 (2021): 136–41. http://dx.doi.org/10.1016/j.ifacol.2021.08.593.

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Gao, Nan, Mohamed Darouach, Holger Voos, and Marouane Alma. "New unified H∞ dynamic observer design for linear systems with unknown inputs." Automatica 65 (March 2016): 43–52. http://dx.doi.org/10.1016/j.automatica.2015.10.052.

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Peng, Haipeng, Yan Shao, Lixiang Li, and Yixian Yang. "Cryptanalysis of a Chaotic Communication Scheme Using Parameter Observer." Mathematical Problems in Engineering 2010 (2010): 1–18. http://dx.doi.org/10.1155/2010/361860.

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This paper addresses the cryptanalysis of a secure communication scheme proposed by Wu (2006), where the information signal is modulated into a system parameter of a unified chaotic system. It is demonstrated that a parameter observer can be designed to identify the parameter determined by the transmitted information and then the transmitted information can be obtained. Compared with the existing analysis using adaptive observer, the cryptanalysis based on parameter observer is much simpler and needs less structure information of the transmitter system. With numerical simulations, it is shown that the parameter observer has stronger practicality and robustness. Furthermore, it is still possible to obtain the transmitted information, even if the derivative of the transmitted signal is unknown.

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Wiethölter, Mats, Doruk Akgün, Fabian Plachel, Marvin Minkus, Daniel Karczewski, Karl Braun, Kathi Thiele, Luis Becker, Ulrich Stöckle, and Philipp Moroder. "Inter-Observer and Intra-Observer Reliability Assessment of the Established Classification Systems for Periprosthetic Shoulder Fractures." Journal of Clinical Medicine 12, no. 9 (April 28, 2023): 3168. http://dx.doi.org/10.3390/jcm12093168.

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This study evaluated the reliability and comprehensiveness of the Unified classification system (UCPF), Wright & Cofield, Worland and Kirchhoff classifications and related treatment recommendations for periprosthetic shoulder fractures (PPSFx). Two shoulder arthroplasty specialists (experts) and two orthopaedic residents (non-experts) assessed 20 humeral-sided and five scapula-sided cases of PPSFx. We used the unweighted Cohen’s Kappa (κ) for measuring the intra-observer reliability and Krippendorff’s alpha (α) for measuring the inter-observer reliability. The inter-rater reliabilities for the Wright & Cofield and Worland classifications were substantial for all groups. The expert and non-expert groups for UCPF also showed substantial inter-rater agreement. The all-rater group for the UCPF and the expert and non-expert group for the Kirchhoff classification revealed moderate inter-rater reliability. For the Kirchhoff classification, only fair inter-rater reliability was found for the non-expert group. Almost perfect intra-rater reliability was measured for all groups of the Wright & Cofield classification and the all-rater and expert groups of the UCPF. All groups of the Kirchhoff and Worland classifications and the group of non-experts for the UCPF had substantial intra-rater reliabilities. Regarding treatment recommendations, substantial inter-rater and moderate intra-rater reliabilities were found. Simple classification systems for PPSFx (Wright & Cofield, Worland) show the highest inter- and intra-observer reliability but lack comprehensiveness as they fail to describe scapula-sided fractures. The complex Kirchhoff classification shows limited reliability. The UCPF seems to offer an acceptable combination of comprehensiveness and reliability.

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11

Swensson, Richard G. "Unified measurement of observer performance in detecting and localizing target objects on images." Medical Physics 23, no. 10 (October 1996): 1709–25. http://dx.doi.org/10.1118/1.597758.

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12

WANG, XING-YUAN, and XIN-GUANG LI. "PROJECTIVE SYNCHRONIZATION OF A CLASS OF CHAOTIC SYSTEMS BASED ON OBSERVER." International Journal of Modern Physics B 25, no. 28 (November 10, 2011): 3765–71. http://dx.doi.org/10.1142/s0217979211059061.

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Based on techniques from the state observer design and the pole placement technique, we present a systematic design procedure to synchronize a class of chaotic systems by a scaling factor (projective synchronization). Compared with the method proposed by Wen and Xu, this method eliminates the nonlinear item from the output of the drive system. Furthermore, the scaling factor can be adjusted arbitrarily in due course of control without degrading the controllability. Finally, feasibility of the technique is illustrated for the unified chaotic system.

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WANG, XING-YUAN, and ZUN-WEN HU. "PROJECTIVE SYNCHRONIZATION OF FRACTIONAL ORDER CHAOTIC SYSTEMS BASED ON STATE OBSERVER." International Journal of Modern Physics B 26, no. 30 (October 7, 2012): 1250176. http://dx.doi.org/10.1142/s0217979212501767.

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Based on the stability theory of fractional order systems and the pole placement technique, this paper designs a synchronization scheme with the state observer method and achieves the projective synchronization of a class of fractional order chaotic systems. Taking an example for the fractional order unified system by using this observer controller, and numerical simulations of fractional order Lorenz-like system, fractional order Lü system and fractional order Chen system are provided to demonstrate the effectiveness of the proposed scheme.

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14

Li, Baibing. "State estimation with partially observed inputs: A unified Kalman filtering approach." Automatica 49, no. 3 (March 2013): 816–20. http://dx.doi.org/10.1016/j.automatica.2012.12.007.

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15

Ferjani, A., I. Zaidi, and M. Chaabane. "Robust Observer-Based H∞ Controller Design for Motorcycle Lateral Dynamics." Mathematical Problems in Engineering 2018 (June 10, 2018): 1–11. http://dx.doi.org/10.1155/2018/2158129.

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The present work deals with the design problem of a robust observer-based controller for a motorcycle system using LPV approach. The designed model is specifically uncertain and disturbed one, whose uncertainties are related to variations of both the cornering stiffness and the longitudinal velocity. The nonlinear motorcycle model is firstly transformed on an uncertain LPV model with two vertices; then an observer-based H∞ robust controller is designed. Both the controller and observer gain matrices are computed by solving a unified convex optimization problem under LMI constraints using YALMIP solver. Numerical simulation results are given to illustrate the effectiveness of the designed method.

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16

Chang, Wei-Der, Shun-Peng Shih, and Chih-Yung Chen. "Chaotic Secure Communication Systems with an Adaptive State Observer." Journal of Control Science and Engineering 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/471913.

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This paper develops a new digital communication scheme based on using a unified chaotic system and an adaptive state observer. The proposed communication system basically consists of five important elements: signal modulation, chaotic encryption, adaptive state observer, chaotic decryption, and signal demodulation. A sequence of digital signals will be delivered from the transmitter to the receiver through a public channel. It is rather reasonable that if the number of signals delivered on the public channel is fewer, then the security of such communication system is more guaranteed. Therefore, in order to achieve this purpose, a state observer will be designed and its function is to estimate full system states only by using the system output signals. In this way, the signals delivered on the public channel can be reduced mostly. According to these estimated state signals, the original digital sequences are then retrieved completely. Finally, experiment results are provided to verify the applicability of the proposed communication system.

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17

Frank, P. M., and B. Koppen. "Review of Optimal Solutions to the Robustness Problem in Observer-Based Fault Detection." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 207, no. 2 (May 1993): 105–12. http://dx.doi.org/10.1243/pime_proc_1993_207_324_02.

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The paper presents a unified approach and general solution of the robustness problem in fault detection and isolation concepts. The ultimate objective is the design of an unknown input fault-detection observer providing a perfect decoupling between unknown inputs and faults. If this is not possible because certain prerequisites are not fulfilled, two optimal compromises in the time domain and in the frequency domain are described. The basic definitions concerning robustness and unknown input fault detectability are given, and the design techniques for the proposed approaches are outlined. The cross-connections to other methods are discussed and a practical example is given.

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Duan, Guangren, and Yunli Wu. "Unified parametric approaches for high-order integral observer design for matrix second-order linear systems." Journal of Control Theory and Applications 4, no. 2 (May 2006): 133–39. http://dx.doi.org/10.1007/s11768-006-4060-4.

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19

Baraffe, I., E. Vorobyov, and G. Chabrier. "OBSERVED LUMINOSITY SPREAD IN YOUNG CLUSTERS AND FU Ori STARS: A UNIFIED PICTURE." Astrophysical Journal 756, no. 2 (August 21, 2012): 118. http://dx.doi.org/10.1088/0004-637x/756/2/118.

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20

Wen, Na, Zhengyu Liu, Qinyu Liu, and Claude Frankignoul. "Observed Atmospheric Responses to Global SST Variability Modes: A Unified Assessment Using GEFA*." Journal of Climate 23, no. 7 (April 1, 2010): 1739–59. http://dx.doi.org/10.1175/2009jcli3027.1.

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Abstract The authors present a comprehensive assessment of the observed atmospheric response to SST variability modes in a unified approach using the Generalized Equilibrium Feedback Analysis (GEFA). This study confirms a dominant atmospheric response to the tropical SST variability associated with ENSO. A further analysis shows that the classical response to ENSO consists of two parts, one responding to the tropical Pacific ENSO mode and the other to the tropical Indian Ocean monopole (IOM) mode. The Pacific ENSO generates a significant baroclinic Rossby wave response locally over the tropical Pacific as well as equivalent barotropic wave train responses remotely into the extratropics. The IOM mode forces a strongly zonally symmetric response throughout the tropics and the extratropics. Furthermore, modest atmospheric responses to other oceanic modes were identified. For example, the North Pacific SST variability mode appears to generate an equivalent barotropic warm SST-ridge response locally over the Aleutian low with significant downstream influence on the North Atlantic Oscillation (NAO), whereas the North Atlantic tripole SST mode tends to force a local response on NAO. Finally, this pilot study serves as a demonstration of the potential utility of GEFA in identifying multiple surface feedbacks to the atmosphere in the observation.

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21

Li, Zhuoshi, Ming Liu, Hamid Reza Karimi, and Xibin Cao. "Observer-Based Stabilization of Spacecraft Rendezvous with Variable Sampling and Sensor Nonlinearity." Mathematical Problems in Engineering 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/902452.

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This paper addresses the observer-based control problem of spacecraft rendezvous with nonuniform sampling period. The relative dynamic model is based on the classical Clohessy-Wiltshire equation, and sensor nonlinearity and sampling are considered together in a unified framework. The purpose of this paper is to perform an observer-based controller synthesis by using sampled and saturated output measurements, such that the resulting closed-loop system is exponentially stable. A time-dependent Lyapunov functional is developed which depends on time and the upper bound of the sampling period and also does not grow along the input update times. The controller design problem is solved in terms of the linear matrix inequality method, and the obtained results are less conservative than using the traditional Lyapunov functionals. Finally, a numerical simulation example is built to show the validity of the developed sampled-data control strategy.

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22

Pradeep, Kandukuri, and K. Vinay Kumar. "Observer-Based Quadrature Signal Generator for UPQC in a Single-Phase Distribution System." ITM Web of Conferences 50 (2022): 03002. http://dx.doi.org/10.1051/itmconf/20225003002.

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This paper presents a control algorithm for generation of reference voltage and current based on Observerbased QSG (Quadrature Signal Generator) for UPQC (Unified Power Quality Conditioner) in a Single-Phase Distribution System. The proposed UPQC is a combination of DSTATCOM and DVR used for load and source compensation such as voltage sag and swell, voltage and current harmonics etc. The proposed control algorithm is capable of generating reference signals from the distorted voltages and currents. In this paper, an improved OQSGbased PLL (Phase-Locked Loop) is utilized over OQSG to enable and operate with increased bandwidths that will improve the dynamic response, tracking accuracy and faster detection of reference signal under all varying load and grid conditions. The control algorithm is tested and evaluated using MATLAB / Simulink.

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23

Mishkov, R., and V. Petrov. "Adaptive Tuning Functions Tracking Control with Nonlinear Adaptive Observers." Information Technologies and Control 11, no. 2 (October 2, 2014): 14–21. http://dx.doi.org/10.2478/itc-2013-0008.

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Abstract The paper is dedicated to the derivation of a unified approach for nonlinear adaptive closed loop system design with nonlinear adaptive state and parameter observers combined with tuning functions-based nonlinear adaptive control for trajectory tracking. The proposed approach guarantees asymptotic stability of the closed loop nonlinear adaptive system with respect to the tracking and state estimation errors and Lyapunov stability of the parameter estimator. The advantages of the approach are the lack of over-parametrization, resulting in a minimal number of estimator equations and the preservation of the overdamped performance specifications of the closed loop nonlinear adaptive system in its whole range of operation. The application of the approach to a permanent magnet synchronous motor driven inverted pendulum concludes with simulation of the closed loop nonlinear adaptive system time responses.

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Shimozaki, S. S., W. A. Schoonveld, and M. P. Eckstein. "A unified Bayesian observer analysis for set size and cueing effects on perceptual decisions and saccades." Journal of Vision 12, no. 6 (June 22, 2012): 27. http://dx.doi.org/10.1167/12.6.27.

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Meyer, Luc, Dalil Ichalal, and Vincent Vigneron. "A new unbiased minimum variance observer for stochastic LTV systems with unknown inputs." IMA Journal of Mathematical Control and Information 37, no. 2 (March 20, 2019): 475–96. http://dx.doi.org/10.1093/imamci/dnz009.

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Abstract This paper is devoted to the state and input estimation of a linear time varying system in the presence of an unknown input (UI) in both state and measurement equations, and affected by Gaussian noises. The classical rank condition used in this kind of approach is relaxed in order to be able to be used in a wider range of systems. A state observer, that is an unbiased estimator with minimum error variance, is proposed. Then a UI observer is constructed, in order to be a best linear unbiased estimator, it follows a unique construction whether the direct feedthrough matrix is null or not. In a sense the proposed approach, generalizes and unifies the existing ones. Besides, a stability result is given for linear time invariant systems, which is a novelty for unbiased minimum variance observers relaxing the classical rank condition.

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Guoping Lu and D. W. C. Ho. "Full-order and reduced-order observers for Lipschitz descriptor systems: the unified LMI approach." IEEE Transactions on Circuits and Systems II: Express Briefs 53, no. 7 (July 2006): 563–67. http://dx.doi.org/10.1109/tcsii.2006.875332.

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27

Knecht, Sebastian. "Procedural reform at the Arctic Council: the amended 2015 Observer Manual." Polar Record 52, no. 5 (April 8, 2016): 601–5. http://dx.doi.org/10.1017/s0032247416000206.

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ABSTRACTThis note studies the addendum to the Arctic Council (AC)'s 2013 Observer Manual adopted at the Senior Arctic Officials’ (SAO) meeting in Anchorage, Alaska, in October 2015. The amendment means another essential step to systematise further and improve the council's working relations with currently 32 entities that hold observer status in the forum. Compared to the initial manual that sketched out the role observers should play in the council's subsidiary bodies, the latest revisions delineate a framework for enhancing observer participation and commitment in working group, task force and expert group meetings. After reviewing the content and practical implications of the addendum in the context of larger reform efforts to adapt the council to the age of a global(ising) Arctic, the article further discusses a number of signals the Anchorage decision sends to observers. These comprise the council's willingness and ability to quick, unified and purposeful action towards institutional adaptation and procedural reform as considered necessary to address organisational deficiencies, strengthened top-down steering of the reform processes by SAOs as related to the work conducted in subsidiary bodies and the overall functioning of the council, and higher expectations on observers to contribute to the AC system and deliver on the new provisions.

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Piao, Minnan, Zhihong Yang, Mingwei Sun, Jian Huang, and Zengqiang Chen. "A practical attitude control scheme for hypersonic vehicle based on disturbance observer." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 12 (February 11, 2019): 4523–40. http://dx.doi.org/10.1177/0954410019827391.

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This paper proposes a practical three-channel attitude control scheme for hypersonic vehicle based on the linear active disturbance rejection control. The control scheme considers the weak and strong coupling scenarios separately due to the dynamic characteristics. For the weak coupling case, three linear active disturbance rejection controllers are designed for the Euler angles of the three channels, respectively, to deal with the strong uncertainties. The expected stability margin and dynamic performance can be guaranteed through the stability margin tester tuning method. Moreover, the control scheme for the pitch, yaw, and roll angles can be applied to the control of the angle of attack, the sideslip angle and the bank angle directly according to the flight dynamics of the hypersonic vehicle, thus realizing a unified control framework for all the attitude angles. For the strong coupling scenario like the fast reversal maneuver, the inner-loop angular rate feedback is performed first in this paper to enhance the damping characteristics, and then linear active disturbance rejection control is designed for the augmented plant to eliminate the strong coupling effects. Simulation results demonstrate the satisfactory tracking and disturbance rejection ability of the proposed methods.

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Kwon, SangJoo, and Wan Kyun Chung. "A Robust Tracking Controller Design With Hierarchical Perturbation Compensation." Journal of Dynamic Systems, Measurement, and Control 124, no. 2 (May 10, 2002): 261–71. http://dx.doi.org/10.1115/1.1468996.

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A robust tracking controller for mechanical systems is proposed by combining the robust perturbation compensator which effectively attenuates the perturbation to the plant with the nominal tracking controller designed using the sliding surface. This approach enables a smooth sliding mode in tracking control loop without chattering problem. A unified view is given on a class of perturbation observers. Three kinds of equivalent expressions for the perturbation of a plant is described. In terms of the equivalents, we propose the feedforward perturbation observer (FFPO), the feedback perturbation observer (FBPO), and the sliding mode perturbation observer (SMPO). Successively, by hierarchically adopting these three observers to attenuate the residual perturbation, the hierarchical perturbation compensator (HPC) is constructed with stability analysis. The adaptive and integral property of the HPC greatly enhances the robust performance with minimal control effort. The actuator saturation issue is also considered. Experimental results demonstrate the effectiveness of the proposed controller.

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30

Zerrougui, Mohamed, Latifa Boutat-Baddas, and Mohamed Darouach. "H∞Observers Design for a Class of Continuous Time Nonlinear Singular Systems." Journal of Control Science and Engineering 2011 (2011): 1–8. http://dx.doi.org/10.1155/2011/967571.

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This paper considers the problem ofH∞observers design for a class of Lipschitz continuous nonlinear singular systems. The method is based on the parameterization of the solution of the generalized Sylvester equations obtained from the estimation errors. Sufficient conditions for the existence of the observers which guarantee stability and the worst case observers error energy over all bounded energy disturbances is minimized are given. The approach also unifies the full-order, the reduced-order, and the minimal-order observers design. The solutions are obtained through linear matrix inequalities (LMIs) formulation. A numerical example is given to illustrate our results.

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Zemouche, Ali, and Mohamed Boutayeb. "A unified adaptive observer synthesis method for a class of systems with both Lipschitz and monotone nonlinearities." Systems & Control Letters 58, no. 4 (April 2009): 282–88. http://dx.doi.org/10.1016/j.sysconle.2008.11.007.

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32

Zong, Qun, Xiuyun Zhang, Shikai Shao, Bailing Tian, and Wenjing Liu. "Disturbance observer-based fault-tolerant attitude tracking control for rigid spacecraft with finite-time convergence." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 2 (November 19, 2017): 616–28. http://dx.doi.org/10.1177/0954410017740918.

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In this paper, finite-time fault-tolerant attitude tracking control is investigated for rigid spacecraft system with external disturbances, inertia uncertainties and actuator faults. A novel finite-time disturbance observer combined with a nonsingular terminal sliding mode controller is developed. Using an equivalent output error injection approach, a finite-time disturbance observer with simple structure is firstly designed to estimate lumped uncertainty. Then, to remove the requirement of prior knowledge about lumped uncertainty and reduce chattering, an adaptive finite-time disturbance observer is further proposed, and the estimations converge to the neighborhood of the true values. Based on the designed observer, a unified finite-time attitude controller is obtained automatically. Finally, both additive and multiplicative faults are considered for simulations and the results illustrate the great fault-tolerant capability of the proposed scheme.

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Chiu, C.-S., and T.-S. Chiang. "Observer-based exponential stabilization of Takagi–Sugeno fuzzy systems with state and input delays." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 225, no. 7 (August 4, 2011): 993–1004. http://dx.doi.org/10.1177/0959651811394504.

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This paper proposes an exponential stabilization control method for uncertain Takagi–Sugeno fuzzy systems with state and input delays via output feedback. First, a unified memoryless fuzzy observer-based control method is introduced for stabilizing continuous and discrete uncertain time-delay fuzzy systems. Then, the exponential stability conditions are derived and converted to solving linear matrix inequality (LMI) problems. Based on the developed novel LMI algorithms, the controller and observer gains are able to be separately designed even in the presence of modelling uncertainty, state delay, and input delay. In comparison with existing techniques the proposed technique produces controlled states and state estimation errors that are guaranteed to exponentially converge to zero via output feedback. This is a major breakthrough for the control of uncertain systems with both state and input unavailable time-varying delays. Finally, two studies are carried out on continuous and discrete time-delay systems. Numerical simulation and comparison results demonstrate the quality of the obtained performance.

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Cobb, J. D. "A unified theory of full-order and low-order observers based on singular system theory." IEEE Transactions on Automatic Control 39, no. 12 (1994): 2497–502. http://dx.doi.org/10.1109/9.362838.

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Lawson, A. J., and M. J. L. Turner. "The X-ray Emission of Quasars as Observed by Ginga." Symposium - International Astronomical Union 159 (1994): 123–25. http://dx.doi.org/10.1017/s007418090017490x.

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We present preliminary results on a spectal analysis of quasars observed by the X-ray observatory Ginga. Simple power-law models with fixed Galactic absorbtion provide an adequate description of the spectra for most of the sources in the 2–18 keV band. A small number of sources show evidence for a feature at 6.4 keV (in the source rest frame) due to Fe line emission. Maximum likelihood and Spearman rank tests were used to investigate the relationship between radio loudness and X-ray spectral index in this class of object. These tests showed, respectively, that the mean X-ray spectral index of radio quiet quasars (RQQs) is significantly different from that of flat spectrum radio loud quasars (FRSQs) at the >99% level, and that the dominant relationship with spectral index is radio loudness (not X-ray luminosity or redshift) at >99% significance. This last result has not previously been demonstrated in this band, but agrees with findings in the lower energy Einstein band (0.5–3.5 keV). These results are discussed in the context of current unified models.

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Lou, Guannan, Wei Gu, Jianhui Wang, Jianhua Wang, and Binshi Gu. "A Unified Control Scheme Based on a Disturbance Observer for Seamless Transition Operation of Inverter-Interfaced Distributed Generation." IEEE Transactions on Smart Grid 9, no. 5 (September 2018): 5444–54. http://dx.doi.org/10.1109/tsg.2017.2769675.

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37

Mohammadpour Shotorbani, Amin, Mohammad Pourmahmood Aghababa, Saeed Gassem Zadeh, Behzad Mahboubi, and Ali Ajami. "Robust terminal sliding mode power flow controller using unified power flow controller with adaptive observer and local measurement." IET Generation, Transmission & Distribution 8, no. 10 (October 1, 2014): 1712–23. http://dx.doi.org/10.1049/iet-gtd.2013.0637.

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38

Kim, Wonhee, and Sangmin Suh. "Suboptimal Disturbance Observer Design Using All Stabilizing Q Filter for Precise Tracking Control." Mathematics 8, no. 9 (August 26, 2020): 1434. http://dx.doi.org/10.3390/math8091434.

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For several decades, disturbance observers (DOs) have been widely utilized to enhance tracking performance by reducing external disturbances in different industrial applications. However, although a DO is a verified control structure, a conventional DO does not guarantee stability. This paper proposes a stability-guaranteed design method, while maintaining the DO structure. The proposed design method uses a linear matrix inequality (LMI)-based H∞ control because the LMI-based control guarantees the stability of closed loop systems. However, applying the DO design to the LMI framework is not trivial because there are two control targets, whereas the standard LMI stabilizes a single control target. In this study, the problem is first resolved by building a single fictitious model because the two models are serial and can be considered as a single model from the Q-filter point of view. Using the proposed design framework, all-stabilizing Q filters are calculated. In addition, for the stability and robustness of the DO, two metrics are proposed to quantify the stability and robustness and combined into a single unified index to satisfy both metrics. Based on an application example, it is verified that the proposed method is effective, with a performance improvement of 10.8%.

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Teng, Yongxiao, Qiang Gao, Xuehan Chen, and Dianguo Xu. "Design of Lumped Disturbance Observer in Current Loop of IPMSM Based on Recursive Integral Sliding Mode Surface." Energies 17, no. 4 (February 9, 2024): 836. http://dx.doi.org/10.3390/en17040836.

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To overcome the problem of current control effect being reduced by unideal factors in a motor control system, such as motor parameter variation, inverter dead time, nonlinearity of the system, etc., a sliding mode disturbance observer for an interior permanent magnet synchronous motor is proposed in this paper. The model of an interior permanent magnet synchronous motor with unideal factors is designed, and the unideal factors are unified into lumped disturbances of motor stator voltage. Then, the observer for lumped disturbance is designed. A recursive integral sliding surface is used to replace the terminal sliding surface to avoid the noise sensitivity and singularity problem of the traditional terminal sliding mode observer. The observer can estimate the lumped disturbance of the current loop without relying on the accurate system model in finite time. Moreover, the structure of the current loop does not need to be adjusted while using the observer to observe and compensate for disturbances. Experiments are carried out to verify the effectiveness of the proposed observer.

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Tong, L. H., B. N. Wu, Z. X. Lei, and C. J. Xu. "Unified creeping model identifying the critical state of granular materials." Journal of Applied Physics 132, no. 5 (August 7, 2022): 055105. http://dx.doi.org/10.1063/5.0101022.

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The mechanical properties of granular materials at a low shear rate are frequently viewed as rate-independent, and a rate-independent constitutive relation is used to describe the mechanical behaviors of the granular material. However, time-dependent behaviors (or creeping behaviors) become significant in the long run. In this paper, we conduct triaxial experiments to observe the creep of granular materials under both dynamic and static loading conditions. Three typical creeping behaviors, aging, transitional, and fluidic, have been observed. To describe the time-dependent behaviors, an internal state variable characterizing the fluidity of the granular system is introduced to propose a rate-dependent constitutive relation which we call in this paper, a state evolution model. A characteristic strain is also introduced into the model to account for the influences of historic strain on the current state. The experiments are analyzed using the proposed model and it has been found that our model can well discern the observed three creeping behaviors. A criterion to identify the stability of a granular system is also given out based on the proposed model. Two key factors dominating the stability of the granular system are recognized – shear wave velocity and critical velocity. Our laboratory experiments in combination with the proposed criterion offer a physical explanation of the intrinsic triggering mechanism of system evolution from a stable to fluidic state: decrease in wave velocity or/and critical velocity.

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Bierkens, Joris, Frank van der Meulen, and Moritz Schauer. "Simulation of elliptic and hypo-elliptic conditional diffusions." Advances in Applied Probability 52, no. 1 (March 2020): 173–212. http://dx.doi.org/10.1017/apr.2019.54.

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AbstractSuppose X is a multidimensional diffusion process. Assume that at time zero the state of X is fully observed, but at time $T>0$ only linear combinations of its components are observed. That is, one only observes the vector $L X_T$ for a given matrix L. In this paper we show how samples from the conditioned process can be generated. The main contribution of this paper is to prove that guided proposals, introduced in [35], can be used in a unified way for both uniformly elliptic and hypo-elliptic diffusions, even when L is not the identity matrix. This is illustrated by excellent performance in two challenging cases: a partially observed twice-integrated diffusion with multiple wells and the partially observed FitzHugh–Nagumo model.

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Bueno-Contreras, Holman, Germán Andrés Ramos, and Ramon Costa-Castelló. "Power Quality Improvement through a UPQC and a Resonant Observer-Based MIMO Control Strategy." Energies 14, no. 21 (October 21, 2021): 6938. http://dx.doi.org/10.3390/en14216938.

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Performance degradation is, in general, regarded as a power quality problem. One solution to recover grid performance is through the application of a unified power quality conditioner (UPQC). Although these devices are multi-input/multi-output (MIMO) systems, the most common control strategies consist of two decoupled controllers, which neglect the coupling effects and add uncertainty to the system. For this reason, this paper proposes a multivariable resonant observer-based control strategy of a UPQC system. This method includes all significant coupling effects between this system and the grid. This strategy results in a stability-based compensator, which differs from recently proposed strategies that are based on signal calculation and cannot assure closed-loop stability. In addition, this paper introduces a simplified controller tuning strategy based on optimal conventional methods without losing closed-loop performance. It implies that the controller can be easily tuned, despite the complexity of the MIMO dynamic model. The UPQC with the resonant observer is verified on an experimental setup for a single-phase system, obtaining three relevant results for power quality improvement: (1) harmonics compensation tested with a total harmonic distortion limit of 5%; (2) sags and swells mitigation; and (3) power factor correction, achieving a unitary value on the grid side.

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HU, B. L., and ALPAN RAVAL. "THERMAL RADIANCE FROM BLACK HOLE AND COSMOLOGICAL SPACETIMES: A UNIFIED VIEW." Modern Physics Letters A 11, no. 32n33 (October 30, 1996): 2625–38. http://dx.doi.org/10.1142/s0217732396002629.

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We investigate the origin and nature of thermal radiation emitted in two classes of spacetimes: in cosmological spacetimes (in general without event horizon), and in spacetimes with event horizons, such as that of an accelerated observer, a moving mirror, an eternal black hole and the inflationary universe. We propose the viewpoint that the detection of thermal radiance in these systems is a local, kinematic effect arising from the vacuum being subjected to an exponential scale transformation. In contradistinction to viewing these as global, geometric effects as is usually perceived, this viewpoint emphasizes the kinematic effect of scaling on the vacuum in altering the relative weight of quantum versus thermal fluctuations. It can also treat conditions which the geometric viewpoint cannot such as systems which do not have an event horizon. We show that in such systems radiance is indeed observed, albeit not in a precise Planckian spectrum. The deviation therefrom is determined by a parameter which measures the departure from exponential scaling which underlies uniform acceleration, eternal black holes or exact exponential cosmological expansion.

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Pham, Thanh-Phong, Olivier Sename, and Luc Dugard. "Unified $\mathcal{H}_{\infty}$ Observer for a Class of Nonlinear Lipschitz Systems: Application to a Real ER Automotive Suspension." IEEE Control Systems Letters 3, no. 4 (October 2019): 817–22. http://dx.doi.org/10.1109/lcsys.2019.2919813.

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ITO, Akihiro, and Masatake SHIRAISHI. "A Unified Observer Design and Its Structure Condition Based on Frequency Domain (2nd Report, Design Method of Disturbance Estimation)." Transactions of the Japan Society of Mechanical Engineers Series C 69, no. 681 (2003): 1317–22. http://dx.doi.org/10.1299/kikaic.69.1317.

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Zhou, Yitong, Jing Chang, and Weisheng Chen. "A Disturbance-Observer-Based Prescribed Performance Control Approach for Low-Earth-Orbit Satellite Trajectory Tracking." Remote Sensing 17, no. 3 (January 31, 2025): 499. https://doi.org/10.3390/rs17030499.

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As the complexity of Low-Earth-Orbit (LEO) satellite tasks and their performance requirements increase, higher demands are placed on satellites’ ability to track mission trajectories, including their accuracy, speed, and capacity to resist external disturbances during operation. This paper proposes an anti-disturbance prescribed performance control scheme for LEO satellites. The scheme establishes a unified framework to accommodate the high-performance requirements of satellite observation, while also incorporating a disturbance observer within this framework to counteract unknown external disturbances. Unlike existing trajectory tracking control methods, the proposed control scheme allows for the flexible selection of performance functions to adapt to diverse satellite performance demands. By focusing on the distance between tracking errors and the performance function, this approach avoids the performance boundary issues faced by traditional prescribed performance control, thus preventing excessive energy consumption by the LEO satellite. Additionally, within the proposed control framework, a disturbance observer is implemented to provide real-time compensation for unknown disturbances while ensuring minimal control input usage for disturbance rejection. Our experimental results show that the proposed control scheme achieves consistent performance for the LEO satellite and successfully accomplishes mission trajectory tracking, even in the presence of unknown disturbances.

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Levine, Edwin A. "Development and Implementation of The Dispersant Observation Job Aid." International Oil Spill Conference Proceedings 1999, no. 1 (March 1, 1999): 1015–18. http://dx.doi.org/10.7901/2169-3358-1999-1-1015.

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ABSTRACT The Job Aid is a field guide for dispersant observers after formal training. Individuals are prepared to observe applications by different platforms and able to competently describe their observations back to a command structure for decision making. The observer is not a controller or spotter for the actual application operation. For field durability it is formatted as bound 5″×7″plastic-coated cards. This Job Aid focuses on supporting the “Observation of Aerial Applications of Dispersants” training. This training imparts the ability to identify oil, describe its characteristics, and make recommendations back to the Federal On-Scene Coordinator (FOSC) concerning future dispersant actions. The observer's recommendations to the Unified Command (UC) may range from “continue operations,” “modify operations,” or “cease operations.”, The training is based upon the supposition that the decision to use dispersants has already been made. The training does not attempt to cover the decision making process. It is incumbent on the individual to be familiar with the local and regional policies regarding use of dispersants and subsequent monitoring requirements. This job aid should be used in conjunction with the “Open Water Oil Identification Job Aid for Aerial Observation” to help describe the surface oil.

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Dharmarajan, Aravindh, Parivallal Arumugam, Sakthivel Ramalingam, and Kavikumar Ramasamy. "Equivalent-Input-Disturbance Based Robust Control Design for Fuzzy Semi-Markovian Jump Systems via the Proportional-Integral Observer Approach." Mathematics 11, no. 11 (June 1, 2023): 2543. http://dx.doi.org/10.3390/math11112543.

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This work focuses on the design of a unified control law, which enhances the accuracy of both the disturbance estimation and stabilization of nonlinear T-S fuzzy semi-Markovian jump systems. In detail, a proportional-integral observer based equivalent-input-disturbance (PIO-EID) approach is considered to model and develop the controller. The PIO approach includes a variable for relaxation in the system design along with an additional term for integration to improve the flexibility of the design and endurance of the system. The proposed stability criteria are formulated in the form of matrix inequalities using Lyapunov theory and depend on the sojourn time for robust control design. Final analyses are performed using MATLAB software with simulations to endorse the theoretical findings of this paper.

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Béthermin, Matthieu, Emanuele Daddi, Georgios Magdis, Mark T. Sargent, Yashar Hezaveh, David Elbaz, Damien Le Borgne, et al. "A UNIFIED EMPIRICAL MODEL FOR INFRARED GALAXY COUNTS BASED ON THE OBSERVED PHYSICAL EVOLUTION OF DISTANT GALAXIES." Astrophysical Journal 757, no. 2 (September 11, 2012): L23. http://dx.doi.org/10.1088/2041-8205/757/2/l23.

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Tsunetoe, Yuh, Shin Mineshige, Tomohisa Kawashima, Ken Ohsuga, Kazunori Akiyama, and Hiroyuki R. Takahashi. "Diverse Polarimetric Features of AGN Jets from Various Viewing Angles: Towards a Unified View." Galaxies 10, no. 5 (October 21, 2022): 103. http://dx.doi.org/10.3390/galaxies10050103.

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Here, we demonstrate that polarization properties show a wide diversity depending on viewing angles. To simulate images of a supermassive black hole and surrounding plasma, we performed a full-polarimetric general relativistic radiative transfer based on three-dimensional general relativistic magnetohydrodynamics models with moderate magnetic strengths. Under an assumption of a hot-jet and cold-disk in the electron temperature prescription, we confirmed a typical scenario where polarized synchrotron emissions from the funnel jet experience Faraday rotation and conversion in the equatorial disk. Further, we found that linear polarization vectors are inevitably depolarized for edge-on-like observers, whereas a portion of vectors survive and reach the observers in face-on-like cases. We also found that circular polarization components have persistent signs in the face-on cases, and changing signs in the edge-on cases. It is confirmed that these features are smoothly connected via intermediate viewing-angle cases. These results are due to Faraday rotation/conversion for different viewing angles, and suggest that a combination of linear and circular polarimetry can give a constraint on the inclination between the observer and black hole’s (and/or disk’s) rotating-axis and plasma properties in the jet–disk structure. These can also lead to a more statistical and unified interpretation for a diversity of emissions from active galactic nuclei.

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Journal articles on the topic 'Observer Unifiée'

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