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Ultrasonic Sensing and Life Prediction for the DARPA Structural Integrity Prognosis System

AIP Conference Proceedings 2007年第1期894卷 1453-1460页

作者： Jennifer E. Michaels Thomas E. Michaels Adam C. Cobb Gregory J. Kacprzynski 1School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332‐0250 2Impact Technologies LLC Rochester NY 14627

The overall objective of the DARPA Structural Integrity Prognosis System (SIPS) program is to develop technologies to advance material damage state condition assessment with limited or no dedicated maintenance action. As a part of the sensors thrust area, an in situ ultrasonic sensing method was developed and demonstrated to detect cracks initiating from fastener holes and provide an estimate of total crack area. Crack area estimates were combined with load history data, projected future loads, and life prediction models to determine a probability density function for time‐to‐failure. The ultrasonic method utilizes two shear wave angle beam transducers operating in through transmission mode which are mounted on either side of the hole. The transmitted wave travels through the area of expected cracking, and the presence of cracks around the fastener holes decreases the amount of acoustic energy that is received. Furthermore, as cracks open and close during the fatigue process, the received energy is modulated, i.e., decreased when the cracks are open versus closed, and this non‐linear behavior is the basis of algorithms developed to detect and size fastener holes cracks. The ultrasonic method was demonstrated as part of an integrated SIPS demonstration whereby aircraft‐grade aluminum subcomponents were fatigued to failure. Results are presented from both the ultrasonic measurements and the integrated life prediction software.

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Microcavity effect on the electron-hole relative motion in semiconductor quantum wells

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Physical Review B 2003年第20期68卷 205325-205325页

作者： D. S. Citrin J. B. Khurgin 1School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta Georgia 30332-0250 USA Department of Electrical and Computer Engineering The Johns Hopkins University Baltimore Maryland 21218 USA

We rigorously find that for a quantum well embedded within a semiconductor microcavity near resonance with the 1s-exciton transition, the upper (lower) polariton is associated with an electron-hole relative-motion probability-density distribution larger (smaller) than the two-dimisional exciton Bohr radius if half the normal-mode splitting exceeds the 1s-exciton binding energy. In this case, the exciton continuum comprises an essential part of the description of the upper mode, leading to a strong asymmetry of the microcavity lines observed in transmission.

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Experimentally verified 2D systems theory based robust iterative learning control

Experimentally verified 2D systems theory based robust itera...

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作者： Hladowski, Lukasz Galkowski, Krzysztof Cai, Zhonglun Rogers, Eric Freeman, Chris T. Lewin, Paul L. Institute of Control and Computation Engineering University of Zielona Gora Poland School of Electronics and Computer Science University of Southampton Southampton SO17 1BJ United Kingdom

ISBN: (纸本)9781424474264

This paper uses 2D control systems theory to develop robust iterative learning control laws for linear plants with experimental validation on a gantry robot used for 'pick and place' operations commonly found in industries such as food processing. In particular, the stability theory for linear repetitive processes provides the setting for analysis and this allows design to take account of trial-to-trial error convergence, transient response along the trials and robustness. The mechanism for this is the use of a strong form of stability for repetitive processes/2D linear systems known as stability along the pass (or trial) with the added requirement for maintaining this property in the presence of model uncertainty. The resulting design computations are in terms of Linear Matrix Inequalities (LMIs) and the control laws can be implemented without the need to estimate state vector entries. © 2010 AACC.

关键词： Uncertainty analysis

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Delay-dependent robust stabilization of uncertain discrete-time state-delayed systems 15th

Delay-dependent robust stabilization of uncertain discrete-t...

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15th World Congress of the International Federation of Automatic control, 2002

作者： Lee, Young Sam Kwon, Wook Hyun Engineering Research Center for Advanced Control and Instrumentation School of Electrical Engineering and Computer Science Seoul National Univ. San 56-1 Shillim-dong Kwanak-ku Seoul151-742 Korea Republic of

ISBN: (纸本)9783902661746

This paper concerns a problem of robust stabilization of a class of discrete-time systems with norm-bounded parameter uncertainty and unknown constant delay. A new delay-dependent stabilization condition using a memoryless controller is formulated in terms of matrix inequalities. An algorithm involving convex optimization is proposed to design a controller guaranteeing a suboptimal maximal delay such that the system can be stabilized for all admissible uncertainties. Numerical examples are given to illustrate the proposed results. Copyright © 2002 IFAC.

关键词： Stabilization

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Robust stability and H-infinity control for uncertain discrete-time Markovian jump singular systems

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控制理论与应用（英文版） 2008年第2期6卷 133-140页

作者： Shuping MA Chenghui ZHANG Xinzhi LIU School of Mathematics and System Science Shandong University Jinan Shandong 250100 China School of Computer Science and Technology Shandong University Jinan Shandong 250061 China School of Control and Engineering Shandong University Jinan Shandong 250061 China Department of Applied Mathematics University of Waterloo Waterloo Ontario N2L 3G1 Canada

The robust stability and stabilization, and H-infinity control problems for discrete-time Markovian jump singular systems with parameter uncertainties are discussed. Based on the restricted system equivalent （r.s.e.） transformation and by introducing new state vectors, the singular system is transformed into a discrete-time Markovian jump standard linear system, and the linear matrix inequality （LMI） conditions for the discrete-time Markovian jump singular systems to be regular, causal, stochastically stable, and stochastically stable with 7- disturbance attenuation are obtained, respectively. With these conditions, the robust state feedback stochastic stabilization problem and H-infinity control problem are solved, and the LMI conditions are obtained. A numerical example illustrates the effectiveness of the method given in the oaoer.

关键词： Discrete-time singular system Markovian jump system Robust stability and stabilization H-infinitycontrol Linear matrix inequality（LMI）

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Selection of Decentralised control Structures: Structural Methodologies and Diagnostics

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IFAC-PapersOnLine 2016年第9期49卷 80-85页

作者： Karcanias, N. Leventides, J. Milonidis, E. Meintanis, I. Systems and Control Research Centre School of Mathematics Computer Science and Engineering City University London Northampton Square LondonEC1V 0HB United Kingdom University of Athens Department of Economics Section of Mathematics and Informatics Pezmazoglou 8 Athens Greece

The paper aims at formulating an integrated approach for the selection of decentralized control structures using a number of structural criteria aiming at facilitating the design of decentralised control schemes. This requires the selection of decentralisation structure that will allow the generic solvability of a variety of decentralised control problems, such as pole assignment by decentralised output feedback. The approach is based on the use of necessary and sufficient conditions for generic solvability and exact solvability of decentralised control problems. The generic solvability conditions lead to characterisations of inputs and outputs channel partitions. The exact solvability conditions use criteria on avoiding the presence of fixed modes, as well as necessary conditions for pole assignment, expressed in terms of properties of Plcker invariants and Markov type matrices. The structural approach provides a classification of desirable input and output partitions based on structural criteria and it is embedded in an overall framework that may involve aspects related to large scale design. © 2015

关键词： Decentralized control Algebra control theory Feedback Multivariable systems Poles Algebraic method Decentralised control Geometric method Linear multivariable systems Output feedback controls Structural methods

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Self‐Calibrating Ultrasonic Methods for In‐Situ Monitoring of Fatigue Crack Progression

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AIP Conference Proceedings 2005年第1期760卷 1765-1772页

作者： J. E. Michaels T. E. Michaels B. Mi A. C. Cobb D. M. Stobbe 1School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332‐0250 2G.W.Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta GA 30332‐0405

Ultrasonic sensors permanently affixed to aluminum coupons are used to monitor progression of damage during fatigue testing with the long term goal of structural health monitoring for diagnostics and prognostics. Necessary for success are proper design of the ultrasonic testing methods, robust transducer mounting techniques, and real‐time signal processing for determining the state of the structure. It is also highly desirable for the overall system to be self‐calibrating with built‐in diagnostics in order to detect and compensate for sensor degradation or failure. Self‐calibrating ultrasonic techniques are applied for monitoring of cracks initiating and propagating from the inaccessible inner diameters of rivet holes where the transducers are mounted on the accessible specimen surface. Angle beam ultrasonic methods are utilized that are suitable for detecting small defects in critical local regions of high stress. Results are presented for aluminum coupons subjected to low cycle fatigue and demonstrate ultrasonic tracking of crack growth.

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System Degeneracy and the Output Feedback Problem: Parametrisation of the Family of Degenerate Compensators

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IFAC-PapersOnLine 2016年第9期49卷 68-73页

作者： Karcanias, N. Meintanis, I. Leventides, J. Systems and Control Research Centre School of Mathematics Computer Science and Engineering City University London Northampton Square LondonEC1V 0HB United Kingdom University of Athens Department of Economics Section of Mathematics and Informatics Pezmazoglou 8 Athens Greece

The paper provides a new characterisation of constant and dynamic degenerate compensators for proper multivariable systems. The motivation stems from the very important property that degenerate feedback gains may be used for the linearisation of the pole assignment map and enable frequency assignment. The objective is the characterisation and parametrisation of all feedback gains that may allow the asymptotic linearisation of the pole placement map. Such a parametrisation introduces new degrees of freedom for the linearisation of the related frequency assignment map and plays an important role to the solvability of the output feedback pole assignment problem. The paper reviews the Global Asymptotic Linearisation method associated with the core versions of determinantal pole assignment problems and defines the conditions which characterises degenerate solutions of different types. Using the theory of ordered minimal bases, we provide a parametrisation of special families of degenerate compensators according to their degree. Finally, the special properties of degenerate solutions that allow frequency assignment are considered. © 2015

关键词： Feedback Algebra Combinatorial optimization control theory Degrees of freedom (mechanics) Multivariable systems Poles Algebraic method Geometric method Linear multivariable systems Output feedback controls Pole assignment

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Selection of Decentralised Schemes and Parametrisation of the Decentralised Degenerate Compensators

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IFAC-PapersOnLine 2016年第9期49卷 74-79页

The design of decentralised control schemes has two major aspects. The selection of the decentralised structure and then the design of the decentralised controller that has a given structure and addresses certain design requirements. This paper deals with the parametrisation and selection of the decentralized structure such that problems such as the decentralised pole assignment may have solutions. We use the approach of global linearisation for the asymptotic linearisation of the pole assignment map around a degenerate compensator. Thus, we examine in depth the case of degenerate compensators and investigate the conditions under which certain degenerate structures exist. This leads to a parametrisation of decentralised structures based on the structural properties of the system. © 2015

关键词： Decentralized control Algebra control theory Multivariable systems Poles Algebraic method Decentralised control Geometric method Linear multivariable systems Output feedback controls Pole assignment

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Zero Assignment Problem in RLC Networks

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IFAC-PapersOnLine 2016年第9期49卷 92-98页

作者： Leventides, John Livada, Maria Karcanias, Nicos University of Athens Department of Economics Section of Mathematics and Informatics Pezmazoglou 8 Athens Greece City University London Systems and Control Research Centre School of Mathematics Computer Science & Engineering Northampton Square LondonEC1V 0HB United Kingdom

The paper deals with the problem of zero assignment in RLC networks by selection of appropriate values for the non- dynamical elements, the resistors. For a certain family of network redesign problems by the additive perturbations may be described as diagonal perturbations and such modifications are considered here. This problem belongs to the family of DAP problems (Determinantal Assignment Problem) and has common features with the pole assignment problem by decentralized output feedback and the zero assignment problem via structured additive perturbations. We demonstrate that the sufficient condition for generic zero assignment by selecting the resistors holds true. This condition is related to the rank of the differential of the related map and holds true generically when the degrees of freedom of the matrix of resistors exceeds the number of frequencies to be assigned (n > p + q). Using this result, we show through a generic example that the sufficient condition for the general zero assignment problems in RLC networks is satisfied and thus, zero assignment can be achieved via resistor determination. © 2015

关键词： Resonant circuits Algebra Circuit theory Combinatorial optimization Degrees of freedom (mechanics) Resistors System theory Algebraic geometry Assignment problems Common features Diagonal perturbation Output feedback Pole assignment problem Show through Zero assignment

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