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G.E. Stewart

G.E. Stewart
Honeywell · Automation and Control Solutions Division

PhD

About

64
Publications
4,013
Reads
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1,028
Citations
Introduction
G.E. Stewart currently works at Honeywell as a Senior Fellow doing research and development with data analytics and control engineering.

Publications

Publications (64)
Article
Finite-time optimal control problems with quadratic performance index for linear systems with linear constraints can be transformed into Quadratic Programs (QPs). Model Predictive Control requires the online solution of such QPs. This can be obtained by using a QP solver or evaluating the associated explicit solution. Objective of this note is to s...
Patent
Full-text available
A method includes generating a model associated with cross-directional fiber orientation of a web, which includes identifying spatial frequency characteristics of a fiber orientation (FO) process. The method also includes providing the model for control of the FO process. Generating the model could include performing a spatial impulse test of the F...
Patent
Full-text available
An inferential sensor module is incorporated into an engine simulation model. One or more parameters for the inferential sensor module are calibrated using one or more of engine measurement data and the engine simulation model. The calibration is performed such that a difference between an inferred signal predicted by the inferential sensor module...
Article
This paper presents the application of model predictive control (MPC) to DOC temperature control during DPF regeneration. The model predictive control approach is selected for its advantage - using a model to optimize control moves over horizon while handling constraints. Due to the slow thermal dynamics of the DOC and DPF, computational bandwidth...
Patent
Full-text available
A method and system for configuring a model of a process. A model of a process is provided, which follows a particular sequence. Such a model includes a plurality of component sub-models, wherein each component sub-model among the component sub-models includes one or more input variables and one or more output variables. Such a method and system al...
Patent
Full-text available
A method and system of predictive model control of a controlled system with one or more physical components using a model predictive control (MPC) model, determining an iterative, finite horizon optimization of a system model of the controlled system, in order to generate a manipulated value trajectory as part of a control process. At time t sampli...
Patent
Full-text available
A method includes receiving at least one measurement of a dissolved carbon dioxide concentration of a mixture of fluid containing an autotrophic organism. The method also includes determining an adjustment to one or more manipulated variables using the at least one measurement. The method further includes generating one or more signals to modify th...
Patent
Methods and systems for the design and implementation of optimal multivariable MPC controllers for fast-sampling constrained dynamic systems utilizing a primal-dual feasibility approach and/or a graph approach. The primal-dual feasibility approach can compute and store matrices defining constraints of quadratic programming problems in an off-line p...
Article
This article presents the authors' perspectives on the transfer of research results in control to industrial practice. The distinction between the immediate recipient of a technology development and the end user or beneficiary is drawn and the notion of customer value chains for control applications explained. We argue that successful technology tr...
Article
This paper deals with switching between several linear time-invariant controllers to be used in feedback with a MIMO linear time-invariant (not necessarily stable) plant to be controlled. We explore the fact that, aside from selecting the controllers' transfer functions and deciding which controller to use in the feedback loop at each time instant,...
Conference Paper
An input-output approach to gain scheduling is proposed using a structure that is motivated by the Youla-Kucera parameterization of stabilizing controllers. We present the design in terms of a tradeoff between model uncertainty and aggressiveness of the controller. This approach enables a constructive technique that allows practitioners to design g...
Article
The use of mathematical models is widespread in the design process of modern internal combustion engines. A driving factor for this trend is the rising complexity of engine systems due to tightening emission limits and increasing demands on fuel efficiency. This chapter focuses on control oriented models for turbocharged diesel engines which were s...
Article
The well-known method of exact diagonalization on finite lattices to estimate the properties of quantum spin systems on the square lattice was greatly enhanced recently by the introduction of additional finite lattices based on nonsquare parallelogram tiles. In this paper an analogous approach is taken for quantum spin systems on the simple cubic l...
Chapter
The efficient development of high performance control is becoming more important and more challenging with ever tightening emissions legislation and increasingly complex engines. Many traditional industrial control design techniques have difficulty in addressing multivariable interactions among subsystems and are becoming a bottleneck in terms of d...
Conference Paper
This paper deals with switching between several linear time-invariant controllers to be used in feedback with a MIMO linear time-invariant (not necessarily stable) plant to be controlled. We explore the fact that, aside from selecting the controllers' transfer functions and deciding which controller to use in the feedback loop at each time instant,...
Conference Paper
Finite-time optimal control problems with quadratic performance index for linear systems with linear constraints can be transformed into Quadratic Programs (QPs). Model Predictive Control requires the on-line solution of such QPs. This can be obtained by using a QP solver or evaluating the associated explicit solution. The objective of this note is...
Article
It is well known that use of scanning sensors in the presence of high frequency machine direction process variations gives rise to aliasing effects that cannot be avoided when designing algorithms that seek to separate cross machine (CD) variations from those in machine direction (MD). These effects are particularly troublesome when machine directi...
Article
We present a methodology for designing reference tracking controllers for constrained, discrete-time piecewise affine systems. The approach follows the idea of reference governor techniques where the desired set-point is filtered by a system called the “reference governor”. Based on the system current state, set-point, and prescribed constraints, t...
Conference Paper
Full-text available
This article describes the development and implementation of a practical explicit model predictive control (MPC) approach that allows subcontrollers to receive and accommodate time-varying setpoints and constraints from higher levels in standard industrial automotive controller hierarchies. The MPC approach requires a small computational footprint...
Article
In this paper we present a novel approach to the design of reference tracking controllers for constrained, discrete-time piecewise affine systems and apply it to a vehicle yaw control problem. The paper is divided in two parts. In the first part, we present a methodology for designing reference tracking controllers for constrained, discrete-time pi...
Article
Cross-directional control and monitoring of paper machines require a knowledge of cross directional profile of the quality variables. However, sensors used in paper machines follow a zig-zag trajectory providing only data that is a combination of cross and machine direction variations. In this paper, we propose a new model-based approach to estimat...
Conference Paper
An important class of switched systems consists of those systems built as the feedback interconnection of a plant to be controlled, together with a multicontroller whose dynamics switch. When designing this type of switching controllers, one is faced with the questions of how to select controller realizations and how to initialize the state of the...
Article
Among the wide class of the switched systems, a particularly significant one is provided by those systems built as the feedback interconnection of a plant to be controlled, together with a multicontroller whose dynamics switch among different controllers, all stabilizing the given plant. Indeed, by suitably orchestrating the switch among the contro...
Conference Paper
We present a technique that allows switching between alternative controllers based on the online and predicted performance of each sub-controller. The overall switched control system is guaranteed to be exponentially stable under arbitrary switching and the transients induced by the switching are included in the performance index. The proposed tech...
Conference Paper
This paper presents an automated tuning method of a large-scale multivariable model predictive controller for multiple array paper machine cross-directional (CD) processes. Paper machine CD processes are large-scale spatially-distributed dynamical systems. Due to these systems' (almost) spatially invariant nature, the closed-loop transfer functions...
Article
Full-text available
Sensor-based bleaching control systems have been in use for over twenty years. Today, most modern bleach plants are operated with the help of systems that control brightness based on a variety of sensors. However, the economic performance of these plants still depends heavily on the setpoints chosen by the operators. This paper proposes a novel Set...
Conference Paper
Full-text available
A decentralized control scheme is proposed to address a spatially distributed paper machine control problem under industrial investigation. The methodology is based on constrained optimal control and tackles the complexity of the problem by solving local problems of small size, which are coupled through their performance objectives and constraints....
Article
Control performance close to the sheet edges is often unsatisfactory because of the inadequate knowledge of edge response model. The design of paper machine cross directional control systems is normally based on actuator response models obtained in the centre rather than the machine edges. Various assumptions are made regarding edge responses but t...
Article
When tuning the parameters of a constrained model predictive controller (MPC), one usually will use closed-loop simulations in order to predict closed-loop performance. Closed-loop simulation can be very time-consuming and inconvenient for large-scale constrained MPC, such as paper machine cross-directional (CD) predictive control. Paper machine CD...
Conference Paper
Full-text available
This paper presents a fundamental spatial performance limitation analysis method for multiple array paper machine cross-directional (CD) processes based on a two-dimensional (temporal and spatial) frequency decomposition method. Paper machine CD processes are spatially-distributed dynamical systems. Due to their (almost) spatially invariant charact...
Conference Paper
Full-text available
Motivated by three applications which are under investiga- tion at the Honeywell Research Laboratory in Minneapolis, we introduce a class of large scale control problems. In particular we show that a for- mation flight problem, a paper machine control problem and the coordi- nation of cameras in a monitoring network can be cast into this class. In...
Article
Full-text available
Paper machine data taken from scanning sensors, used to assess the quality of the two-dimensional sheet, normally includes significant noise components as well as aliasing effects resulting from the irregular sampling pattern of the scanning sensor. The separation of the cross machine (CD) variations from those in the machine direction (MD) is impo...
Article
This paper presents consistent criteria for evaluating the selection of tuning parameters for an industrial model predictive control of large-scale cross-directional (CD) processes using a two-dimensional (temporal and spatial) frequency analysis technique. The concept of rectangular circulant matrices (RCMs) and their properties are presented. It...
Article
The features of IntelliMap, a software tool which is designed to ease the burden of cross-direction (CD) controller tuning to improve the quality of the paper sheet, are discussed. IntelliMap includes logic for automatically designing values for the CD controller tuning parameters. It gives a flashing warning when the tuning is judged to be either...
Conference Paper
Full-text available
This paper describes the application of a technique for the two-dimensional frequency domain analysis of the closed-loop performance of a cross-directional papermaking process under industrial model predictive control (MPC). For such spatially-distributed systems, the process model and the linear portion of the controller are approximated as linear...
Article
It is well known that use of scanning sensors in the presence of high frequency machine direction process variations gives rise to aliasing effects that cannot be avoided when designing algorithms that seek to separate cross machine (CD) variations from those in machine direction(MD). These effects are particularly troublesome when machine directio...
Article
This article describes the application of a novel technique for the modification of a standard cross-directional (CD) control strategy to accommodate the differences in the papermaking process encountered at the edges of the produced paper sheet. The proposed design technique isolates the sheet edges in terms of perturbations on the closed-loop sys...
Conference Paper
Full-text available
This paper proposes modifications to an industrial paper machine cross-directional (CD) controller, initially designed assuming process spatial invariance, near the sheet edges where the assumption of spatial invariance is clearly violated. The resulting design problem is equivalent to a block-decentralized static output feedback problem. The propo...
Article
This brief paper presents a perturbation technique with which a controller stabilizing one plant may be modified so that it stabilizes a second, related plant. The proposed technique produces an internally stable loop for a broad class of linear systems without requiring any further calculations on the part of the designer. Four seemingly different...
Article
Full-text available
This paper reports on the development and implementation of an algorithm for the design of spatially distributed feedback controllers for the wide variety of physical processes that are included in cross-directional (CD) control of industrial paper machines. The spatial and temporal structure of this class of process models is exploited in the use...
Article
This article considers the design of practical feedback controllers for a class of spatially distributed processes where the state of a uniform physical substrate is influenced by an array of evenly distributed, identically constructed actuators and measured by an array of evenly distributed, identical sensors. A constructive procedure is introduce...
Conference Paper
The optimal controller design for spatially distributed dynamical systems is greatly simplified when spatially invariant models are used. However, the true spatial boundary conditions of many practical systems, including paper machine cross-directional processes, disrupt the spatial invariance and potentially destabilize the control system if not t...
Article
When tuning a feedback loop for a dynamical system, there exist many rules of thumb to aid the control engineer. However, there are no such convenient guidelines available when approaching a cross-directional control problem. In recent years there have been many significant advances made by researchers in CD control. While the understanding of thes...
Article
The performance limitations imposed by model uncertainty for multivariable feedback control systems are well known. The goal of this work is to examine these limitations in terms of cross-directional (CD) control. In CD control, the model uncertainty places limitations on the spatial and dynamical closed-loop bandwidths of a CD control system, whic...
Conference Paper
The performance limitations imposed by model uncertainty for multivariable feedback control systems are well known. The goal of this work is to examine these limitations in terms of cross-directional (CD) control, In CD control, the model uncertainty places limitations on the spatial and dynamical closed-loop bandwidths of a CD control system, whic...
Article
Multivariable processes are controlled by model predictive controller (MPC). The controller coordinates all actuator beams and minimizes sheet variation. The advantages of cross directional (CD)-MPC are discussed. The CD-MPC was implemented on two board liner machine. The process model has a dynamic component and a spatial component. Disturbances w...
Article
The implemented CD (cross-directional) control scheme presented in this paper uses hard-constrained MPC (model predictive control) with quadratic programming. The implemented scheme is applied to the challenging problem of coordinated regulation of CD weight and CD moisture variation using the top headbox on a linerboard machine, where the objectiv...
Article
When tuning a feedback loop for a dynamical system, there exist many rules of thumb to aid the control engineer. However, there are no such convenient guidelines available when approaching a cross-directional control problem. In recent years there have been many significant advances made by researchers in CD control. While the understanding of thes...
Conference Paper
This paper considers &Hscr;<sub>∞</sub> robustification of an industrial paper machine cross-directional (CD) control system. The existing industrial controller is reinterpreted as a precompensator weight for shaping the open-loop response. The robustification is then achieved by performing a robust stabilization of the nominal plant model and indu...
Conference Paper
This work considers recent theoretical results for dynamical systems distributed in one spatial dimension. An application is presented for an industrial papermaking control system that had been experiencing frequent closed-loop instability problems. Two-dimensional frequency domain analysis uncovered a very small robust stability margin in the regi...
Conference Paper
In this paper, recent developments in control of spatially-invariant processes are applied to an industrial problem of cross-directional profile control in web manufacturing. Approximating such processes in terms of a spatial frequency decomposition allows the extension of traditional concepts of loopshaping to the two-dimensional dynamical and spa...
Conference Paper
Developments in control of spatially-invariant processes are applied to an industrial problem of cross-directional profile control in web manufacturing. Approximating such processes in terms of a spatial frequency decomposition allows the extension of traditional concepts of loopshaping to the two-dimensional dynamical and spatial frequency domain....
Conference Paper
In this paper, recent developments in control of spatially-invariant processes are applied to an industrial problem of cross-directional profile control in papermaking. The process is approximated in terms of a spatial frequency decomposition which allows the extension of traditional techniques of loopshaping to the two-dimensional dynamical and sp...
Conference Paper
Considers design of feedback controllers for spatially distributed processes. A constructive design approach is developed based on two-dimensional loopshaping concepts. The closed-loop response of the system is modified through the design of an H<sub>2</sub> optimization problem in terms of spatial and dynamical frequencies. The conflicting objecti...
Article
Here we generate finite bipartite body-centred cubic lattices up to 32 vertices. We have studied the spin one half Heisenberg antiferromagnet by diagonalizing its Hamiltonian on each of the finite lattices and hence computing its ground state properties. By extrapolation of these data we obtain estimates of the T = 0 properties on the infinite bcc...
Conference Paper
Considers the cross directional (CD) control of web manufacturing processes, such as in paper machines. In particular, it proposes a practical method for regularizing control of poorly controllable modes of the CD profile, while preserving the attenuation of the disturbances for the well controllable modes. A multivariable generalized minimum varia...
Conference Paper
This work considers the control of sampled distributed parameter systems. These large-scale systems have a specific structure which allows for simplification of robust controller design compared to the general MIMO system case. This paper introduces and analyzes a controller structure which has been developed specifically for these systems. The con...
Article
First we introduce the upper triangular lattice form method that permits one to derive easily the complete set of finite lattices of any given number, N, of vertices for any regular infinite lattice in any number of dimensions, and we use it to obtain all finite fcc lattices of N < 28. We compute the ground state energy, magnetization and spin-spin...
Article
The well-known finite-lattice method for the calculation of the properties of quantum spin systems on a two-dimensional lattice at zero temperature was introduced in 1978. The method has now been greatly improved for the square lattice by including finite lattices based on parallelogram tiles as well as the familiar finite lattices based on square...
Article
This paper deals with switching between several linear time-invariant controllers to be used in feedback with a MIMO linear time-invariant (not necessarily stable) plant to be controlled. We explore the fact that, aside from selecting the controllers' transfer functions and deciding which controller to use in the feedback loop at each time instant,...

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