Structural Synthesis of Multivariable Controllers

Controller Synthesis for Maximizing Disturbance Bounds in Linear Uncertain Systems

Input-output decoupling and disturbance rejection problems in structural analysis

In this paper, we investigate the structure of the transfer function set which includes all the transfer functions deduced from the plant available information. It is shown that when an upper bound of the plant transfer function's H/sup /spl infin//-norm has been supplied, and the noise contaminating the time domain identification experiment data is not too significant, such a transfer function set can be parameterized by a linear fractional transformation of two transfer function matrices. One of them is a fixed transfer function matrix which is completely determined by the plant available information and the noise magnitude. The other is a norm bounded, structure fixed, free transfer function matrix. Moreover, it is shown that the problem of analytically obtaining the fixed complexity nominal model that best approximates this transfer function set is as difficult as the /spl mu/-synthesis problem. >

Volume visualization based on the intensity and SUSAN transfer function spaces

On closed-loop system identification using polyspectral analysis given noisy input–output time-domain data

This paper concerns the disturbance rejection problem arising in the coordination control of a group of autonomous agents subject to external disturbances. The agent network is said to possess a desired level of disturbance rejection, if the H∞ norm of its transfer function matrix from the disturbance to the controlled output is satisfactorily small. Undirected graph is used to represent the information flow topology among agents. It is shown that the disturbance rejection problem of an agent network can be solved by analyzing the H∞ control problem of a set of independent systems whose dimensions are equal to that of a single node. An interesting result is that the disturbance rejection ability of the whole agent network coupled via feedback of merely relative measurements between agents will never be better than that of an isolated agent. To improve this, local feedback injections are applied to a small fraction of the agents in the network. Some criteria for possible performance improvement are derived in terms of linear matrix inequalities. Finally, extensions to the case when communication time delays exist are also discussed.

In this paper, an intelligent method for image contrast enhancement in real time digital video applications is proposed. This new technique is based on the generation of adaptive transfer functions by using Neural Network. The method is designed in order to be implemented in digital television systems, based on Thin Film Transistor Liquid Cristal Displays (TFT-LCD), that has become the dominant technology in consumer electronics. The method provides the required amount of contrast enhancement for every image according to real time analysis of brightness and contrast in the video frame information, then a different contrast enhancement transfer curve for each image is generated. The statistical information is extracted by histogram analysis from current or previous image frames. Technological factors are considered where it is applied, as well as aspects of the visual perception within a non-controlled environment, which is the case of the consumer environment. The method is based on the design of a general transfer function model that compensates the decrement in gray scale dynamic range in images representation which is a consequence of the TFT-LCD technology limits; in particular the light leakage from the panel backlight sources of the Cold Cathode Fluorescent Light (CCFL) or the LED type, as well as an unsuitable dynamic control of backlight intensity. Using subjective methods for image quality, the contrast is enhanced in a set of representative images for different degrees of brightness and contrast, a unique transfer function is obtained for each representative image. This set of transfer functions, as well as the statistic of the pixel values distribution from each image frame are used as an input - output pattern during the training of a neural network. On the basis of the experimentation, an evaluation and comparative analysis takes place between the functions of transformation obtained by subjective method of image quality and the curves obtained through the trained neural network.

This paper is concerned with the problem of disturbance rejection in an adaptive controller design. A new adaptive control algorithm is derived to obtain the complete measurable disturbance rejection both in dynamic and static states for a class of non-minimum phase MIMO systems by reassigning the system zeros to the stable region

For the linear multivariable system <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\dot{x} = Ax + Bu + Er, z_{i} = D_{i}x(i \in k), x \in X</tex> , with disturbance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Gamma(\cdot)</tex> , it is shown that the decoupling problem and disturbance rejection problem are simultaneously solvable, so as to yield a stable closed-loop system, if and only if <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Im(E)\subset V_{g}^{*}</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_{i}^{*} + \ker D_{i} = X, i \in k</tex> . Here <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_{g}^{*}</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_{i}^{*}</tex> are subspaces uniquely defined by and constructible from the data <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A, B, D_{i} i\in k</tex> .

A biologically inspired controller for sound and vibration applications

SUMMARY This paper investigates the problem of global disturbance rejection for switched nonlinear systems in strict-feedback form with unknown exosystem where the solvability of the disturbance rejection problem for subsystems is not assumed. First, a sufficient condition for the solvability of the global disturbance rejection problem is given. As an extension of the classic concept of internal model for non-switched systems, a new concept of switched internal model is proposed. Second, in order to solve the problem in question, a constructive adaptive control methodology is established on the basis of the multiple Lyapunov functions method, backstepping, and the changing supply functions technique. Finally, an example is provided to demonstrate the effectiveness of the proposed approach. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper the robust asymptotic tracking and disturbance rejection problem is studied for linear periodic discrete-time systems, and for general classes of disturbance functions and reference signals, consisting in free responses of periodic processes. The necessary and sufficient conditions for the existence of a solution, which involve the periodic notion of invariant zero, are found. A constructive design procedure of the periodic compensator is given; it is based on the internal model principle.

Circular correlation based identification of switching power converter with uncertainty analysis using fuzzy density approach

The human being, because of his complex audition system, has the ability to identify the spatial position of any sound from the surrounding environment. The objective of this work is to develop a measurement system that enables to mathematically model the hearing system by using a set of transfer functions. These equations, called head related transfer function (HRTF), synthesize mathematically the binaural transformation that the listener produces (principally from the torso, the head, and the pinna) in the audition process. To find the HRTF, the measurement system uses an acoustic dummy called head and torso simulator. With two microphones located in their ears, this dummy captures the sound with the same binaural properties as a real listener. The mathematical process to obtain these transfer functions is based on the LTI systems theory, using as excitation signal the sine sweep. Matlab was chosen for the processing environment, taking advantage of its flexibility on the digital sign process and their powerful computational tools.

The design and theoretical basis of a new database tool that quickly generates vibroacoustic response estimates using a library of transfer functions (TFs) is discussed. During the early stages of a launch vehicle development program, these response estimates can be used to provide vibration environment specification to hardware vendors. The tool accesses TFs from a database, combines the TFs, and multiplies these by input excitations to estimate vibration responses. The database is populated with two sets of uncoupled TFs; the first set representing vibration response of a bare panel, designated as H(sup s), and the second set representing the response of the free-free component equipment by itself, designated as H(sup c). For a particular configuration undergoing analysis, the appropriate H(sup s) and H(sup c) are selected and coupled to generate an integrated TF, designated as H(sup s +c). This integrated TF is then used with the appropriate input excitations to estimate vibration responses. This simple yet powerful tool enables a user to estimate vibration responses without directly using finite element models, so long as suitable H(sup s) and H(sup c) sets are defined in the database libraries. The paper discusses the preparation of the database tool and provides the assumptions and methodologies necessary to combine H(sup s) and H(sup c) sets into an integrated H(sup s + c). An experimental validation of the approach is also presented.