This paper investigates robust stability of linear time-invariant (LTI) uncertain sampled-data control systems with generalized sampled-data hold functions (GSHFs). A new sufficient condition for robust stability of s...
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This paper investigates robust stability of linear time-invariant (LTI) uncertain sampled-data control systems with generalized sampled-data hold functions (GSHFs). A new sufficient condition for robust stability of such systems is developed. Unlike that of most of the previous works, it directly uses the data of the continuous-time plant and therefore it is less conservative. The condition is expressed in terms of the spectral radius of a certain matrix and is shown to be a unimodal function of a free parameter. This property enabled LIS to use standard one-dimensional optimization algorithm to perfom the proposed test. Copyright (C) 2006 John Wiley & Soils, Ltd.
This paper investigates the decentralized control of LTI continuous-time plants using generalized sampled-data hold functions (GSHF). GSHFs can be used to modify the structure of the digraph of the resultant discrete ...
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This paper investigates the decentralized control of LTI continuous-time plants using generalized sampled-data hold functions (GSHF). GSHFs can be used to modify the structure of the digraph of the resultant discrete plant, by removing certain interconnections in the discrete-time equivalent model to form a hierarchical system model of the plant. This is a new application of discretization and has, as its motivation, the design of decentralized controllers using centralized methods. (c) 2006 Elsevier Ltd. All rights reserved.
This paper investigates the decentralized control of LTI continuous-time plants using generalized sampled-data hold functions (GSHF). GSHFs can be used to modify the structure of the digraph of the resultant discrete ...
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This paper investigates the decentralized control of LTI continuous-time plants using generalized sampled-data hold functions (GSHF). GSHFs can be used to modify the structure of the digraph of the resultant discrete plant, by removing certain interconnections in the equivalent discrete-time model to form a hierarchical system model of the plant. This is a new application of discretization, and has as its motivation, the design of decentralized controllers using centralized methods.
This paper studies the application of generalized sampled-data hold functions in minimizing the strength of the interconnections between the subsystems of large-scale interconnected systems. To this end, it proposes a...
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This paper studies the application of generalized sampled-data hold functions in minimizing the strength of the interconnections between the subsystems of large-scale interconnected systems. To this end, it proposes a quadratic programming approach to the minimization of the magnitude of specific elements of the transfer function matrix of a discrete-time equivalent system. A quantitative measure for the degree of hierarchicalness of the discrete-time equivalent model is also given.
This paper considers the robust control of a finite-dimensional linear time-invariant (FDLTI) continuous-time plant by a static generalizedsampled-datahold function (GSHF) controller. It is shown that it is possible...
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This paper considers the robust control of a finite-dimensional linear time-invariant (FDLTI) continuous-time plant by a static generalizedsampled-datahold function (GSHF) controller. It is shown that it is possible to design a static GSHF controller to provide a gain margin as large as desired, and a phase margin of up to 90 degrees. The design is straight-forward, and we illustrate it with an example. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
The use of generalized sampled-data hold functions for adaptive pole placement control of linear systems with unknown parameters, is investigated. The particular control structure used relies on a periodic controller,...
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The use of generalized sampled-data hold functions for adaptive pole placement control of linear systems with unknown parameters, is investigated. The particular control structure used relies on a periodic controller, which suitably modulates the sampled plant output by a multirate periodically time-varying function. Such a control strategy, allows us to assign the eigenvalues of the closed-loop monodromy matrix to the desired prespecified values and does not make assumptions on the plant other than controllability, observability and known order. The proposed indirect adaptive scheme estimates the unknown plant parameters on-line, from sequential data of the inputs and the outputs of the plant, which are recursively updated within the time limit imposed by a fundamental sampling period. On the basis of the proposed algorithm, the adaptive pole placement problem is reduced to a controller determination based on the well-known Ackermanns' formula. Known adaptive control schemes usually resort to the computation of dynamic controllers through the solution of polynomial Diophantine equations, thus introducing high-order exogenous dynamics in the control loop. Moreover, in many cases, this solution might yield an unstable controller, and the overall adaptive scheme is then unstable with unstable compensators because their outputs are unbounded. The proposed control strategy avoids these problems, since here gain controllers essentially need to be designed. Moreover, persistency of excitation and, therefore, parameter convergence, of the continuous-time plant is provided without making any assumption either on the existence of specific convex sets in which the estimated parameters belong or on the coprimeness of the polynomials describing the ARMA model, or finally on the richness of the reference signals, as compared to known adaptive pole placement schemes. (C) 1999 The Franklin Institute. Published by Elsevier Science Ltd.
In this note, the intersample performance of linear systems, which are controlled on the basis of generalized sampled-data hold functions, in order to achieve exact model matching at the sampling instants, is analyzed...
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In this note, the intersample performance of linear systems, which are controlled on the basis of generalized sampled-data hold functions, in order to achieve exact model matching at the sampling instants, is analyzed. The proposed technique relies on an appropriate error system and of the expansion of its output signal in suitable basis functions, which are selected such that some finite rank linear nonself-adjoint operators are represented exactly. As it is shown, it is plausible to localize the intersample ripples, which may cause a degradation of the control performance, by appropriately selecting the arbitrary elements of the general forms of the modulating holdfunctions. This guarantees that the performance of the closed-loop system is the desired one, not only at the sampling instants, but even between them. (C) 1998, Elsevier Science Ltd. All rights reserved.
In this paper we study robustness and sensitivity properties of a sampled-data feedback system with a generalizedsampled-datahold function (GSHF), We argue that shifting nonminimum phase zeros using GSHF control can...
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In this paper we study robustness and sensitivity properties of a sampled-data feedback system with a generalizedsampled-datahold function (GSHF), We argue that shifting nonminimum phase zeros using GSHF control can lead to difficulties unless the zero is outside the closed-loop bandwidth.
Alternatives to the Zero Order hold known as generalized sampled-data hold functions have been proposed by several authors. More recently, it has been noticed that these new holds incur intersample behavior penalties ...
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ISBN:
(纸本)0780326857
Alternatives to the Zero Order hold known as generalized sampled-data hold functions have been proposed by several authors. More recently, it has been noticed that these new holds incur intersample behavior penalties in many cases. In studying such behavior, one of the issues of relevance is the 'frequency response' of the hold;e.g., it is known that 'non-minimum phase' zeros of the hold impose design tradeoffs in the continuous-time response to disturbances of the sampled-data system. This paper goes deeper into the analysis of the frequency response of these devices, and provides some preliminary results on zero location and integral constraints satisfied by the hold. We give a number of circumstances in which non-minimum phase zeros may occur and, furthermore, we show that holds with zeros off the jω-axis will tend to have poor frequency responses properties.
Loop transfer recovery (LTR) techniques are kown to enhance the input or output robustness properties of linear quadratic gaussian (LQG) designs. One restriction of the existing discrete-time LQG/LTR methods is that t...
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Loop transfer recovery (LTR) techniques are kown to enhance the input or output robustness properties of linear quadratic gaussian (LQG) designs. One restriction of the existing discrete-time LQG/LTR methods is that they can obtain arbitrarily good recovery only for minimum-phase plants. A number of researchers have attempted to devise new techniques to cope with non-minimum-phase plants and have achieved some degrees of success.6-9 Nevertheless, their methods only work for a restricted class of non-minimum-phase systems. Here, we explore the zero placement capability of generalized sampled-data hold functions (GSHF) developed in Reference 14 and show that using the arbitrary zero placement capability of GSHF, the discretized plant can always be made minimum-phase. As a consequence, we are able to achieve discrete-time perfect recovery using a GSHF-based compensator irrespective of whether the underlying continuous-time plant is minimum-phase or not.
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