Showing papers on "MIMO published in 1992"

Equalizers for multiple input/multiple output channels and PAM systems with cyclostationary input sequences

Abstract: The author studies minimum mean square error (MMSE) linear and decision feedback (DF) equalisers for multiple input/multiple output (MIMO) communication systems with intersymbol interference (ISI) and wide-sense stationary (WSS) inputs. To derive these equalizers, one works in the D-transform domain and uses prediction theory results. Partial-response MMSE equalizers are also found. As an application, the author considers a pulse amplitude modulation (PAM) communication system with ISI and cyclostationary inputs. The MMSE linear and DF equalizers are determined by studying an equivalent MIMO system. The resulting filters are expressed in compact matrix notation and are time-invariant, whereas the corresponding single input/single output filters are periodically time-invariant. The author also considers MMSE equalizers for a wide-sense stationary process by introducing a 'random phase'. To aid in the performance evaluation of various equalizers, the author derives their mean square errors. >

Discontinuous output feedback stabilizing an uncertain MIMO plant

Abstract: The problem of output stabilization for uncertain MIMO systems is considered. Using structural transformations, an uncertain system is changed to a "form convenient for output feedback design. Synthesis of observer-based variable structure control for asymptotical stabilization and uniform ultimate boundedness of the closed-loop system is provided. Examples are considered and simulation results are given.

Adaptive cross-directional decoupling control systems

Abstract: A method and apparatus for controlling a multiple-input, multiple-output (MIMO) system, such as a sheetmaking system, including identifying a decoupling gain matrix by comparing an actuator control vector against a measured output vector and processing an error vector to update the decoupling gain matrix. The dynamic components of one dynamic mode in the system are separated from that of other dynamic modes such that the input-output characteristic of the process may be treated as independent channels.

Frequency response characteristics of MIMO GPC

Abstract: This paper is concerned with the frequency response properties of MIMO generalized predictive control. A number of frequency response indicators (characteristic loci, principal gains and Gershgorin bands) are used to evaluate stability and the performance of the closed-loop. This is done via three realistic examples which demonstrate the effect of the predictive controller tuning parameters on the measures of robust stability and performance in the frequency domain. A series of heuristic tuning rules is compiled for methodical tuning of this type of controller in multivariable environments

Development of an Analog MIMO Quantitative Feedback Theory (QFT) CAD Package

Abstract: : This thesis describes the development of an analog MIMO Quantitative Feedback Theory (QFT) CAD package for the automation of the multivariable control design process. The CAD package is capable of carrying a design from problem setup through the design process to a frequency domain analysis of the compensated MIMO system. The package automates the selection of the weighting matrix, formation of the square effective plants, the polynomial matrix inverse required to form the equivalent plants, generation of stability, tracking, disturbance, gamma, and composite bounds, loop shaping, design of the prefilter elements, and the frequency domain analysis of the completed design. Disturbance allocation is automatically performed while generating tracking bounds. The package allows gain scheduling to be used in the weighting matrix. The improved method may be applied for the case of 2x2 effective plant. The package is implemented using Mathematica for use on the Sun Workstations. QFT, Quantitative Feedback Theory, CAD, Computer Aided Design, Multivariable Control, MIMO Control System Design.

Time moment and Padé approximation methods applied to the order reduction of MIMO linear systems

Abstract: The combined use of the time moment and Pade approximation methods (in time space and frequency domain description), coupled with three powerful dominant pole selection criteria, is introduced for the purpose of application to high-order MIMO linear time-invariant state-space original system models, in order to obtain corresponding adequate reduced order model(s). The proposed approach has been applied successfully to a 10 th-order two-input two-output time-invariant linear model of a practical power system.

The MIMO Discrete-Time Convergent Approximation of the Optimal Recursive Parameter Estimator

Abstract: A new discrete-time recursive parameter estimation algorithm is derived for a general multiple-input, multiple-output (MIMO) stochastic system that is bilinear in state and parameters. In contrast to the extended Kalman filter (EKF) for this system, the new algorithm can identify noise covariances and can be proven globally convergent. However, the new algorithm must also update approximations to third order moments, and so is more complicated than the EKF.

Optimal Hankel-norm approximation approach to model reduction of large-scale Markov chains

Abstract: A model reduction problem of certain large-scale Markov chains under an optimal criterion for Hankel-norm approximation is discussed. The multi-dimensional Markov chain under investigation is assumed to have a finite-dimensional stationary state-transition matrix, which is first reformulated as a multi-input/multi-output (MIMO) linear time-invariant (LT1) stochastic system. Consequently, the resulting large-scale MIMO LTI stochastic system has a closed-form best approximant in the Hankel-norm from a specified class of stable lower-dimensional MIMO LTI systems.

General MIMO H, Control Design Framework

Abstract: A general framework is presented for solving the multiple-input multiple-output (MIMO) H, control design problem. Algorithms are available which solve the problem, once the control design configuration including process model and weighting functions has been rewritten into the standard H, problem. In this paper a general framework is defined to close the gap between all the different control configurations, the standard H, problem and the final closed-loop system evaluation. Because no solution is known for translating design specifications such as desired behaviour, robustness, performance etc. directly into weighting functions in the frequency domain, the necessarily iterative design procedure becomes much easier. A floating platform laboratory process is used to illustrate the main steps of the framework and to show the results of the optimized H, controller design.

Applying variations of the quantitative feedback technique (QFT) to unstable, non-minimum phase aircraft dynamics models

Abstract: Variations of the quantitative feedback technique (QFT) are applied to a multi-input-multi-output (MIMO) flight control problem with unstable, nonminimum phase plants. The authors present specialized techniques that enable the designer to achieve acceptable results for effective plants which are both unstable and non-minimum phase. The weighting matrix function is discussed, and a method of developing frequency dependent compensation is presented. The longitudinal control system, defined as a single-input-single-output (SISO) system, is designed using the loop transmission function. The limitations imposed by right-half-plane poles and zeros are discussed as the design is presented. A straightforward approach to designing a prefilter is also presented. Singular-G and optimal blending methods are used to improve the achievable stability characteristics of the lateral-directional (MIMO) effective plant. A brief discussion of the design of prefilters for a MIMO system is included. >

Control-canonical-form method applied to generating systems to improve dynamic stability characteristics

Abstract: The control-canonical-form (CCF) method is introduced for the purpose of applying it to high-order state-space single-input single or multiple-output (SISO or SIMO) and multiple-input multiple-output (MIMO) linear time-invariant system models to determine closed-loop systems (i.e. design robust controllers) from which enchanced dynamic stability characteristics and overall performance of these systems is achieved. The method has been applied successfully to a SISO 6th-order linearized state-space open-loop model (representing a simplified hydro power system), and to a MIMO 8th-order linearized state-space open-loop model (representing an 87.5 kVA synchronous machine with conventional exciter supplying power to an electric utility system through an interconnection network)

Experimental Comparison of Control Structures

Abstract: In process control applications multiloop single-input-single-output (SISO) control is the most common approach to solve multi-input-multi-output (MIMO) control problems. These so-called decentralized control systems are usually easier to design and tune than a full MIMO control system. Also tolerance against failure of individual sensors or actuators is generally easier to achieve with properly designed decentralized control systems.

Optimal Model Matching Control for Mimo Continuous-Time Systems

Abstract: In this paper, we consider the optimal model matching control problem in the MIMO continuous-time systems with persistent bounded input signals. The objective is to design an optimal controller for a given MIMO plant, so that the possible maximum difference between the output of the controlled system and the outputs of an assigned model in response to a class of arbitrary persistent bounded signals is minimized. It is shown that the optimal controller design problem is equivalent to a constrained L1-norm minimization problem. Based on the solution to the LL-norm minimization problem, an optimal controller design algorithm is presented.

On minimal order stabilization of multivariable plants

Abstract: A technique is derived for a MIMO (multiple-input multiple-output) plant which uses the SISO (single-input single-output) results to yield an upper bound for the MIMO minimal-order stabilizing compensator. First, the MIMO problem is set up. Some theorems which provide an upper bound for the minimal-order compensator are then presented. Finally, some examples show how this method can be used and where it fails. >

The capacity region for the multiple access Gaussian channel with stochastic fading

Abstract: The problem of finding the capacity region of a multiple access channel occupies one of the cornerstones of information theory In this type of communications system several users transmit simultaneously to a common receiver The main multiplexing strategies that fall in that category include frequency division multiple access (FDMA), time division multiple access (TDMA) and code division multiple access (CDMA) The indoor wireless channel can be analysed through the use of an information theoretic approach, whose main objective is to find the set of information rates at which the simultaneous reliable communication of the messages of each user is possible This article presents an analysis of the capacity region for the multiaccess Gaussian channel, when subject to random fading >

The capacity region for the Gaussian channel with random multipath

Abstract: In order to provide the decoder with essential information on the channel state, and improve the effectiveness of the communication, a probabilistic analysis of the communication channel is needed Such modeling must include fading and multipath, as well as interference An insight into the behavior of the channel can be gained by attempting an information theoretical approach for the multipath model of the wireless indoor channel The main objective of the information theoretic approach of the multipath Gaussian channel is to find its capacity region, ie the set of information rates at which the simultaneous reliable communication of the messages of each user is possible >

Nearly decoupled robust MIMO control systems design

Abstract: The paper deals with the robust design of an MIMO feedback control system It is divided into two parts The first part presents a necessary and sufficient condition for the robustness of a unit feedback system The uncertainty model considered in this analysis is nontrivial, and the present approach is applicable to nearly decoupled systems as well as nondecoupled systems The second part of the paper presents an effective technique for the design of a robust, nearly decoupled MIMO system using the result of Part I The design technique to be presented in Part II can be applied to a nonminimum phase plant

Direct shaping of reference input response for mimo systems via output feedback

Abstract: A new method for designing linear MIMO control systems using constant and dynamic output feedback is presented. The direct algebraic controller design is based on a new representation of linear systems using generalized Fourier series expansions for the state, input and output signals. This procedure leads to a very simple approximation rule for transfer functions, which fixes points on the real axis of the complex s-plane, where two different transfer functions have to coincide to have similar input-output behaviour. This important statement will then be used to derive a simple controller formula in a closed form. The design objective is to shape the reference input response and to provide approximate non – interaction. In order to illustrate the simplicity and efficiency of the proposed method, the design for an unstable chemical reactor and a non-minimum-phase rear-axle- gear test stand are considered, using output feedback loops with either constant or PI characteristics.

An Object-Oriented Computer Aided Design Program for Modern Control Systems Analysis

Abstract: : This investigation is a continuation of the ICECAP-PC research project conducted under Prof. Gary B. Lamont at the Air Force Institute of Technology. It is an ongoing development of a public domain Computer Aided Design (CAD) package for Control Engineering students and faculty.with a special emphasis on education. This investigation focuses on three areas. First, an object-oriented environment is specified, designed and implemented. The functional structure of ICECAP-PC is then converted into an object-oriented structure because object-orientation provides an advanced logic and implementation structure and effectively addresses common software engineering issues. Additionally, a new interface featuring pull-down menus, mouse support, and single stroke access provides optimal user friendliness. Second, the numerical methods used for modern control capabilities are updated providing state of the art numerical capabilities. Third, using a program extension known as a toolbox, a basic MIMO (Multiple Input Multiple Output) faculty is created to augment the MISO capabilities. The MIMO QFT toolbox allows the entry and manipulation of up to a 3x3 MIMO plant matrix of transfer functions for the QFT solution to MIMO control systems problems.

Variable Structure Control Strategies: Application to a MIMO Nonlinear Steam Generating Unit

Abstract: A robust second order sliding mode technique is used to control a stream generating unit represented by a nonlinear MIMO model. A set of inequalities is developed to test and verify robustness. Simulation results are presented.

Optimal tracking and rejection of persistent bounded signals for MIMO continuous systems

Abstract: This paper introduces a design methodology for an optimal stabilizing compensator that not only minimizes the maximum tracking error but also minimizes the maximum amplitude of the undesired part of the output of a multivariable (MIMO) continuous-time system due to any persistent bounded disturbances. For this purpose a two-parameter compensator scheme is adopted in the design of the feedback system. This paper emphasizes that the optimal compensator design problem is equivalent to a constrained L1-norm minimization problem and its solution can be obtained by standard non-linear programming routines.

Bounds on Bandwidth for MIMO Systems

Abstract: This paper deals with the analysis in frequency domain of linear feedback MIMO systems. In particular it is shown, transforming a MIMO system to n SISO systems, that exists a frequency response amplitude relationship between non-diagonal systems and systems in which the cross-coupling terms are neglected. Moreover this relationship between amplitudes is used to demonstrate that the channels bandwidth with cross-coupling between loops is bounded by the channel dynamic in which the loops interaction effect is neglected.

An adaptive controller for abruptly changing MIMO systems with nonlinear model uncertainties

Abstract: A novel adaptive control algorithm for deterministic unknown abruptly changing MIMO (multi-input multiple output) systems subject to nonlinear model uncertainties is presented. A fast parameter tracking algorithm and pole-assignment calculation are included in the proposed controller. It is shown that all the variables in the closed-loop system are uniformly bounded if the linear bound of the nonlinear model uncertainties is comparatively small. >