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AN EXPERT SYSTEMS-APPROACH TO CONTROLLER-DESIGN

IEE PROCEEDINGS-D CONTROL THEORY AND APPLICATIONS 1990年第6期137卷 367-373页

作者： TEBBUTT, CD Department of Electrical and Electronic Engineering University of Cape Town Cape Town South Africa

An expert system has been used to build an intelligent interface to a recently developed CACSD technique for the design of linear controllers. This combination allows the design to be specified in terms of time and frequency domain constraints on the closed-loop transfer functions, and provides the designer with assistance in formulating a reasonable specification and in dealing with constraint conflicts.

关键词： Expert systems and other AI software and techniques Control engineering computing frequency domain constraints frequency-domain synthesis linear systems control system CAD linear controllers expert systems time-domain synthesis closed-loop transfer functions Control system analysis and synthesis methods time domain synthesis

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Robust disturbance rejection controller for systems with uncertain parameters

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IET CONTROL THEORY AND APPLICATIONS 2019年第13期13卷 1995-2007页

作者： Zachi, Alessandro R. L. Correia, Carlos Alberto M. Filho, Jair Luiz A. Gouvea, Josiel A. Fed Ctr Technol Educ Rio De Janeiro Grad Program Elect Engn Rio De Janeiro Brazil Fed Ctr Technol Educ Rio De Janeiro Dept Control & Automat Engn Nova Iguacu Brazil

This work proposes a mathematical solution for plants with full set of uncertain parameters which is based on the active disturbance rejection control method. This method has been studied for three decades and its main characteristic is the use of an extended state observer to estimate the non-measurable signals of the plant. However, the application of the basic methodology requires the exact knowledge of the system control gain, which is difficult to measure in the case of parametric uncertainties. Recently, some advances have been discussed in the literature. Some results have revealed the capability of them of rejecting the unknown input disturbance and of ensuring the stability of closed-loop transfer functions, even in the case of unknown order and/or relative degrees. However, such proposals have not been effective for large level of parametric uncertainties. The idea of the present work is to relax the requirement of exact knowledge of plant parameters by proposing modifications in the control structure. Mathematical analysis show that the proposed modification does not affect the original purpose of output tracking. The performance of the proposed strategy is compared with other schemes by using numerical simulations. In addition, experimental results on a real cart-pendulum system are presented.

关键词： closed loop systems mathematical analysis stability nonlinear control systems pendulums transfer functions observers uncertain systems active disturbance rejection control extended state observer nonmeasurable signals exact knowledge control gain uncertain parameters unknown input disturbance closed-loop transfer functions plant parameters structural modification control structure classical control theory cart-pendulum system robust disturbance rejection controller active disturbance rejection control method parametric uncertainties mathematical analysis numerical simulations

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Stable operating area of photovoltaic cells feeding DC-DC converter in output voltage regulation mode

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IET Renewable Power Generation 2015年第8期9卷 970-981页

作者： Qin, Ling Xie, Shaojun Hu, Mao Yang, Chen Nanjing Univ Aeronaut & Astronaut Coll Automat Engn Nanjing 210016 Jiangsu Peoples R China Nantong Univ Sch Elect Engn Nantong 226019 Peoples R China

From the perspective of output voltage control stability, this study investigates the stable operating area of photovoltaic (PV) cells feeding the DC-DC converter in output voltage regulation (OVR) mode. In this study, the boost interface converter is taken as an example, and its control system arrangements, small-signal model including the dynamic equivalent circuit of PV cells and the closed-loop transfer functions with different control loop formation are deduced at first. After that, according to the Hurwitz criterion, the essential condition for output voltage control stability is analysed and the relations between control loop formation of the interface converter in OVR mode and the stable operating area are obtained. The validity of the theoretical analysis has been verified by the experiment and simulation results of a 150 W prototype. The investigation shows that: (i) no matter what kind of control loop formation is adopted, the PV cells cannot output the maximum power when the PV interface converter operates in OVR mode;(ii) when the interface converter operates in OVR mode, PV cells can only operate stably in voltage area or current area. Moreover, the type of operating area entirely depends on the converter's output voltage control loop formation.

关键词： DC-DC power convertors solar cells voltage control photovoltaic power systems transfer functions closed loop systems equivalent circuits stable operating area photovoltaic cells DC-DC converter output voltage regulation mode output voltage control stability PV cells OVR mode boost interface converter small-signal model dynamic equivalent circuit closed-loop transfer functions Hurwitz criterion PV interface converter converter output voltage control loop formation power 150 W

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A polynomial perspective on the stability of multivariable predictive controllers

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COMPUTERS & CHEMICAL ENGINEERING 2003年第8-9期27卷 1097-1111页

作者： Nunes, GC Kincal, S Crisalle, OD Univ Florida Dept Chem Engn Gainesville FL 32611 USA

A rigorous method for analyzing the stability of unconstrained multivariable predictive controllers is developed using polynomial operators and coprime matrix factorizations. The technique permits deriving explicit expressions for the closed-loop transfer functions that describe the relevant system dynamics. It is shown that the closed-loop poles can be determined by finding the roots of two characteristic polynomial equations, hence allowing a complete characterization of the asymptotic stability of the system. The controllers require the specification of a large number of tuning parameters, including prediction and control horizons for every input and output signal as well as the elements of input and output weighting matrices. The stability analysis tools proposed tend significant support to the tuning task because sets of parameters that produce unstable poles can be identified and rejected. Further-more, since the location of the poles influences the speed of the closed-loop response, it is also possible to compare the relative merits of alternative sets of stabilizing tuning parameters. Finally, it is shown that the multivariable predictive-control law can be written in standard shift-operator form, facilitating the implementation in a digital control computer using only shift registers, scalar multiplications, and scalar additions. The approach is illustrated in an example involving the control of a multistage gas-liquid absorption column. (C) 2003 Elsevier Science Ltd. All rights reserved.

关键词： multivariable predictive controllers polynomial operators closed-loop transfer functions stability of predictive control

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Generalized Lyapunov Demodulator for Amplitude and Phase Estimation by the Internal Model Principle 8

Generalized Lyapunov Demodulator for Amplitude and Phase Est...

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8th International-Federation-of-Automatic-Control (IFAC) Symposium on Mechatronic Systems (MECHATRONICS) / 11th International-Federation-of-Automatic-Control (IFAC) Symposium on Nonlinear Control Systems (NOLCOS)

作者： Ragazzon, Michael R. P. Messineo, Saverio Gravdahl, Jan Tommy Harcombe, David M. Ruppert, Michael G. Norwegian Univ Sci & Technol NTNU Dept Engn Cybernet Trondheim Norway NTNU Dept ICT & Nat Sci Trondheim Norway Univ Newcastle Sch Elect Engn & Comp Callaghan NSW Australia

Effective demodulation of amplitude and phase is a requirement in a wide array of applications. Recent efforts have increased the demodulation performance, in particular, the Lyapunov demodulator allows bandwidths up to the carrier frequency of the signal. However, being inherently restricted to a single order filtering of the input signal, signal components outside its passband are not sufficiently attenuated for all applications, such as in multifrequency atomic force microscopy. In this article, the structure of the Lyapunov demodulator is transformed to an equivalent form, taking advantage of the internal model representation of the sinusoid to be tracked. A generalization of this formulation allows the application of standard filtering techniques in order to shape the characteristics of the demodulator, while retaining the perfect tracking condition provided by the internal model. Guidelines for the filter design are provided in order to achieve the desired characteristics, such as filtering order, tracking bandwidth, and transient performance. The resulting generalized Lyapunov demodulator structure is highly flexible, allows for direct employment of any standard filter type, is computationally simple, and easy to implement requiring only a bandpass filter, a single integrator, and two nonlinear transformations. Numerical results demonstrate the effectiveness of the approach, and provide a comparison of the various filters considered. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

关键词： demodulators estimation internal model principle atomic force microscopy bandpass filters closed-loop transfer functions

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A polynomial perspective on the stability of multivariable predictive controllers

A polynomial perspective on the stability of multivariable p...

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2nd Pan American Workshop on Process Systems Engineering

作者： Nunes, GC Kincal, S Crisalle, OD Univ Florida Dept Chem Engn Gainesville FL 32611 USA

关键词： multivariable predictive controllers polynomial operators closed-loop transfer functions stability of predictive control

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Frequency-domain analysis of aperiodic control loops with identically distributed delays

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AUTOMATICA 2023年第1期151卷

作者： Antunes, Duarte J. Eindhoven Univ Technol Control Syst Technol POB 513 NL-5600 MB Eindhoven Netherlands

Extending classical frequency domain analysis to systems with time-varying delays remains a challenge in the systems and control field. These systems are receiving a renewed interest due to emergent control applications in which the use of shared communication and computation resources induce severe time-varying delays in the loop. Here, an extension of frequency domain analysis is proposed for aperiodic control loops with time-varying delays, assumed to be independent and identically distributed and to follow an exponential distribution. In aperiodic control loops, the actuation is updated immediately after a delayed sensor measurement arrives at the controller. In the present framework, the amplitudes of expected values and variances of output responses to sinusoidal inputs are plotted as a function of the input frequency. This plot allows for inferring the behavior of the response to general input signals. The usefulness of the results is illustrated in the control of a double integrator with delayed measurements.(c) 2022 Published by Elsevier Ltd.

关键词： Frequency-response methods Delay analysis Stochastic analysis Communication networks Frequency domains Analysis of variance closed-loop transfer functions Computer controlled systems

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Generalized Lyapunov Demodulator for Amplitude and Phase Estimation by the Internal Model Principle

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IFAC-PapersOnLine 2019年第15期52卷 247-252页

作者： Michael R.P. Ragazzon Saverio Messineo Jan Tommy Gravdahl David M. Harcombe Michael G. Ruppert Department of Engineering Cybernetics Norwegian University of Science and Technology (NTNU) Norway Department of ICT and Natural Sciences NTNU School of Electrical Engineering and Computing University of Newcastle Australia

关键词： demodulators estimation internal model principle atomic force microscopy bandpass filters closed-loop transfer functions

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Dynamic modelling of grid-connected permanent magnet synchronous generator wind turbine: rectifier dynamics and control design

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JOURNAL OF ENGINEERING-JOE 2019年第18期2019卷 5202-5207页

作者： Ahmed, Muhammad Ammar Messo, Tuomas Rasilo, Paavo Rekola, Jenni Tampere Univ Technol Lab Elect Energy Engn POB 692 FI-33101 Tampere Finland

Wind energy technology is developing more and more from recent decades in many countries. Therefore, addressing the latest wind turbine research issues, this study develops a dynamic model of a permanent magnet synchronous generator and an active rectifier-as part of a unified dynamic model of a wind turbine generator in MATLAB/Simulink. In addition, a novel technique for the verification of the open-loop and the closed-loop transfer functions in the frequency domain is presented. The technique develops by analysing the frequency responses of the transfer function at various frequencies. Furthermore, the cascaded control loops of the developed model are designed and the stability of the designed controllers is tested in response to step changes in reference values.

关键词： permanent magnet generators wind turbines transfer functions cascade control closed loop systems wind power synchronous generators dynamic modelling grid-connected permanent magnet synchronous generator wind turbine rectifier dynamics control design wind energy technology latest wind turbine research issues active rectifier—as part unified dynamic model wind turbine generator closed-loop transfer functions cascaded control loops designed controllers

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