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Control Systems Technology, IEEE Transactions on

Issue 5 • Date Sept. 2003

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Displaying Results 1 - 16 of 16
  • IEEE Transactions on control systems technology special issue on control of industrial spatially distributed processes

    Publication Year: 2003 , Page(s): 609 - 611
    Cited by:  Papers (3)
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    Freely Available from IEEE
  • Control of temperature profile for a spray deposition process

    Publication Year: 2003 , Page(s): 656 - 667
    Cited by:  Papers (11)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2653 KB) |  | HTML iconHTML  

    Spray forming is a novel method of rapidly manufacturing tools and dies for stamping and injection operations. The process sprays molten tool steel from a set of arc spray guns onto a ceramic former to build up a thick steel shell. The volumetric contraction that occurs as the steel cools is offset by a volumetric expansion taking place within the sprayed steel, which allows the dimensional accurate tools to be produced. To ensure that the required phase transformation takes place, the temperature of the steel is regulated during spraying. The sprayed metal acts both as a source of mass and a source of heat and by adjusting the rate at which metal is sprayed, the surface temperature profile over the surface of the steel shell can be controlled. The temperature profile is measured using a thermal imaging camera and regulated by adjusting the rate at which the guns spray the steel. Because the temperature is regulated by adjusting the feed rate to an actuator that is moving over the surface, this is an example of mobile control, which is a class of distributed parameter control. The paper describes the design of a time-varying H2 controller for the process and presents results from the implementation of the controller on the spray forming process. View full abstract»

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  • Reduced order cross-directional controller design for sheet forming processes

    Publication Year: 2003 , Page(s): 746 - 756
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2127 KB) |  | HTML iconHTML  

    This paper presents a novel control strategy that efficiently addresses the issue of the large number of cross machine direction actuators with which sheet-forming processes are equipped. The approach relies on using the Karhunen-Loeve expansion (KLE) to model the disturbances affecting the properties of interest together with vector autoregressive processes to design a low-order representation of the disturbances. Subsequently, the control space is also reduced by appropriate transformations that rely on the use of KLE. Model predictive control is then implemented on the reduced order model and an optimal solution is obtained in that space, satisfying various types of actuator constraints defined on the full-order system and minimizing the cross-directional variability. The solution from the reduced order model is then projected back to the original space for implementation on the real plant. Simulation examples are included to illustrate the method. View full abstract»

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  • Worst-case and distributional robustness analysis of finite-time control trajectories for nonlinear distributed parameter systems

    Publication Year: 2003 , Page(s): 694 - 704
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (762 KB) |  | HTML iconHTML  

    A novel approach is proposed that quantifies the influence of parameter and control implementation uncertainties upon the states and outputs of finite-time control trajectories for nonlinear lumped and distributed parameter systems. The worst-case values of the states and outputs due to model parameter uncertainties are computed as a function of time along the control trajectories. The algorithm can also compute the part of the optimal control trajectory for which implementation inaccuracies are of increased importance. An analytical expression is derived that provides an estimate of the distribution of the states and outputs as a function of time, based on simulation results. The approaches require a relatively low computational burden to perform the analysis, compared to Monte Carlo approaches for robustness analysis. The technique is applied to the crystallization of an inorganic chemical with uncertainties in the nucleation and growth parameters and in the implementation of the control trajectory. View full abstract»

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  • Modeling and control of cement grinding processes

    Publication Year: 2003 , Page(s): 715 - 725
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (510 KB) |  | HTML iconHTML  

    In this study, a nonlinear dynamic model of a cement grinding process, including a ball mill and an air separator in closed loop, is developed. This gray-box model consists of a set of algebraic and partial differential equations containing a set of unknown parameters. The selection of a model parametrization, the design of experiments, the estimation of unknown parameters from experimental data, and the model validation are discussed. Based on the resulting model, a dynamic simulator can be developed, which appears as a useful tool to analyze the process behavior and to understand the origin of instabilities observed in real-life operations. As a result, a cascaded control structure for regulating the mill flow rate, and a proportional integral controller for regulating the cement fineness are designed. Experimental data demonstrate the effectiveness of this control scheme. Alternatively, if on line measurements of the recirculated flow rate are available, a feedforward control of the feed flow rate is described, which ensures a better decoupling of mass flow rate and fineness regulation. View full abstract»

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  • Scanning actuator guidance scheme in a 1-D thermal manufacturing process

    Publication Year: 2003 , Page(s): 757 - 764
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (694 KB) |  | HTML iconHTML  

    In this paper, a theoretical scheme for the actuator guidance in thermal materials processing is proposed and verified experimentally. The problem under consideration involves heat distribution on a metallic strip with a moving heat source. The control objective is to optimally move the heat source in order to maintain the uniform-in-space temperature field, which is directly connected to specific material properties. The optimal position and signal intensity (control signal) of the heat source at successive time periods is determined by minimization with-respect-to-location of quadratic performance indexes corresponding to preselected actuator locations. For the experimental verification of the theoretical scheme the optimal closed-loop control algorithm is implemented on a plasma-arc welding station using real-time feedback. Experimental and simulations results are presented and analyzed. View full abstract»

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  • Control of lateral motion in moving webs

    Publication Year: 2003 , Page(s): 684 - 693
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (562 KB) |  | HTML iconHTML  

    A partial differential equation for the lateral motion of a web conveyance system is derived by modeling the web as a viscoelastic beam under axial tension. This model treats the web position between rollers as a function of both time and space, assumes that there is no slip between the web material and the rollers, and incorporates the web material's viscoelastic damping property. A finite-difference approximation of the model is used to simulate a typical two-span web system. The finite-difference approximation is validated by comparing its frequency responses with those of an analytical frequency domain model. The analytical frequency domain model is used to design feedback compensation strategies that make the two-span web system less sensitive to upstream disturbances. The results show that, using a transverse vibration model incorporating viscoelasticity to design even simple classical controllers, it is possible to make the web system less sensitive to upstream disturbances at the sensor location. View full abstract»

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  • Augmented Kalman filtering for a superheated steam header system

    Publication Year: 2003 , Page(s): 773 - 781
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (603 KB) |  | HTML iconHTML  

    This paper examines the distributed parameter model of a main steam header system and simplifies it to retain only the significant dynamics of the pipe wall temperature and quasisteady-state behavior of the steam in the headers. An augmented linear optimal filter is developed for estimating the steam and pipe wall temperatures along the interconnected main steam headers, between the superheater outlet and the turbine. The filter algorithm is illustrated using data from a power plant. View full abstract»

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  • Identification tool for cross-directional processes

    Publication Year: 2003 , Page(s): 629 - 640
    Cited by:  Papers (16)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1119 KB)  

    This paper considers an industrial identification tool for cross-directional (CD) process of continuous web manufacturing such as papermaking. A special focus is on identification of the mapping between CD actuators and measured profiles of the web properties from input-output process data. The developed algorithms are based on nonlinear parametric models of the CD response shape and mapping and minimize a model fit error for a two-dimensional array of data. The algorithms are deployed as a part of an automated process control support tool and have been successfully used over a period of time on many paper mills with various types of the CD actuators. The paper is illustrated by identification results from a real-life paper mill. View full abstract»

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  • Optimal actuator/sensor placement for nonlinear control of the Kuramoto-Sivashinsky equation

    Publication Year: 2003 , Page(s): 737 - 745
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB) |  | HTML iconHTML  

    In this paper, we use a methodology that was recently proposed by Antoniades and Christofides (2001) to compute the optimal actuator/sensor locations for the stabilization, via nonlinear static output feedback control, of the zero solution of the Kuramoto-Sivashinsky equation (KSE) for values of the instability parameter for which this solution is unstable. The theoretical results are illustrated through computer simulations of the closed-loop system using a high-order discretization of the KSE. View full abstract»

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  • Feedback controller design for a spatially distributed system: the paper machine problem

    Publication Year: 2003 , Page(s): 612 - 628
    Cited by:  Papers (23)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1054 KB) |  | HTML iconHTML  

    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 of the 2D frequency domain for analysis and 2D loop shaping design of feedback controllers. This algorithm forms the basis of a software tool that has recently been implemented in a commercial product and its use is illustrated for tuning CD controllers on two different industrial paper machines. The first example describes the use of the tool in stabilizing an unstable closed-loop system by retuning the distributed controller. The second paper machine example exposes an underperforming controller. Subsequent retuning of the controller resulted in a dramatic performance improvement. View full abstract»

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  • Model predictive control of a catalytic reverse flow reactor

    Publication Year: 2003 , Page(s): 705 - 714
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (634 KB) |  | HTML iconHTML  

    This paper deals with the control of a catalytic reverse flow reactor. The aim of this process is to reduce, by catalytic reaction, the amount of volatile organic compounds (VOCs) released into the atmosphere. The peculiarity of this process is that the gas flow inside the reactor is periodically reversed in order to trap the heat released during the reaction. This allows use of the reactor in a heat saving mode. The goal of this work is to provide a model predictive control (MPC) framework to significantly enhance the poor overall performance currently obtained through the actual control strategy. It is directly addressed for the nonlinear parabolic partial differential equations (PDEs) that describe the catalytic reverse flow reactor. In the context of the application of MPC to this particular distributed parameter system, we propose a method that aims to reduce the online computation time needed by the control algorithm. The nonlinear model is linearized around a given operating trajectory to obtain the model to be solved on-line in the approach. MPC strategy combined with internal model control (IMC) structure allows using less accurate and less time-consuming control algorithm. Method efficiency is illustrated in simulation for this single-input-single-output system. View full abstract»

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  • Spatial system identification of a simply supported beam and a trapezoidal cantilever plate

    Publication Year: 2003 , Page(s): 726 - 736
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2343 KB) |  | HTML iconHTML  

    Dynamic models of structural and acoustic systems are usually obtained by means of either modal analysis or finite element modeling. Detrimentally, both techniques rely on a comprehensive knowledge of the system's physical properties. As a consequence, experimental data and a nonlinear optimization are required to refine the model. For the purpose of control, system identification is often employed to estimate the dynamics from disturbance and command inputs to set of outputs. Such discretization of a spatially distributed system places unknown weightings on the control objective, in many cases, contradicting the original goal of optimal control. This paper introduces a frequency domain system identification technique aimed at obtaining spatially continuous models for a class of distributed parameter systems. The technique is demonstrated by identifying a simply supported beam and a trapezoidal cantilever plate, both with bonded piezoelectric transducers. The plate's dimensions are based on the scaled side elevation of a McDonnell Douglas FA-18 vertical stabilizer. View full abstract»

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  • Modeling and control of distributed thermal systems

    Publication Year: 2003 , Page(s): 668 - 683
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1333 KB) |  | HTML iconHTML  

    This paper investigates the application of model-based control design techniques to distributed temperature control systems. Multivariable controllers are an essential part of modern-day rapid thermal processing (RTP) systems. We consider all aspects of the control problem beginning with a physics-based model and concluding with implementation of a real-time embedded controller. The thermal system used as an example throughout is an RTP chamber widely used in semiconductor wafer processing. With its exceptionally stringent performance requirements (low nonuniformity of wafer temperature, high temperature ramp rates), RTP temperature control is a challenging distributed temperature control problem. Additionally, it is important in the semiconductor industry because of the progressively smaller "thermal budget" resulting from ever decreasing integrated circuit dimensions. Despite our emphasis on faster cold wall single-wafer processing RTP chambers, the approach described here for solving distributed temperature control problems is equally applicable to slower distributed thermal systems, such as hot-wall batch-processing furnaces. For the physical model, finite volume techniques are used to develop high-fidelity heat transfer models that may be used for both control design and optimal chamber design. Model-order reduction techniques are employed to reduce these models to lower orders for control system design. In particular, principal orthogonal decomposition techniques have been used to derive low order models. Techniques such as linear quadratic Gaussian H2/H methods are employed for feedback control design. While the methods are illustrated here using a generic RTP system, they have been successfully implemented on commercial RTP chambers. View full abstract»

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  • Variable sampling adaptive control of a distributed collector solar field

    Publication Year: 2003 , Page(s): 765 - 772
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB) |  | HTML iconHTML  

    Distributed collector solar fields are spatially distributed engineering systems, which aim at collecting and storing energy from solar radiation. They are formed by mirrors which concentrate direct incident sun light in a pipe where a fluid, able to accumulate thermic energy, flows. From the control point of view, the objective considered here consists of making the outlet oil temperature to track a reference signal by manipulating the oil flow, in the possible presence of fast disturbances caused by passing clouds. Although this plant may be successfully controlled by methods assuming it to be modeled as a "black box" lumped parameter system, the point of view advocated in this paper is that explicit consideration of its distributed character leads to an increased control performance. In this respect, the contributions of this paper are twofold: First, a controller relying on variable sampling is developed. This is derived from the partial differential equation describing the oil temperature evolution in time and space on the field and has the effect of linearizing the plant model. Second, the resulting performance is illustrated by means of experiments performed in an actual solar field. The experiments reported show that it is possible to make fast temperature setpoint changes, with reduced overshoot. The ideas presented are applicable to other types of industrial processes, involving transport phenomena. View full abstract»

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  • Force allocation in a large-scale distributed active surface

    Publication Year: 2003 , Page(s): 641 - 655
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1328 KB) |  | HTML iconHTML  

    This paper investigates the problem of closed-loop control of a small number of parameters by allocating actuation in a system with many binary degrees of freedom, using an actual large-scale air-jet table as an example. In this system, the desired force and torque are produced by a large number of spatially distributed binary air jets directing individual forces on an object. Various algorithms for solving the force allocation problem-determining the appropriate valve states in this hyper-redundant system-are investigated. The algorithms range from discrete optimal search to continuous constrained optimization to a hybrid hierarchical approach that can be distributed. The latter consists of using the continuous optimal solutions to recursively break the large optimization problems into smaller problems that can be solved using optimal search methods or precomputed lookup tables. A tradeoff between computation time and allocation error was found. The optimal algorithms yield low errors but the time is exponential in the number of actuators, while the continuous solutions execute quickly but yield larger errors. The hybrid hierarchical optimal algorithms give the best compromise between these conflicting goals, and their applicability spans the full range of degrees of freedom from a few to many thousands. These hierarchical algorithms are useful in many such highly redundant systems. View full abstract»

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