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Control Systems, IEEE

Issue 4 • Date Aug. 1995

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Displaying Results 1 - 10 of 10
  • Robust PID control for an industrial distillation column

    Page(s): 46 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (818 KB)  

    State-space controllers are difficult to implement in a distributed control system. Therefore a control design based on the common PID control structures is desirable. This article presents the μ-optimal tuning of advanced PID control structures as well as a simple feedforward control design for an industrial binary high purity distillation column. The design is based on an optimization approach. The resulting controllers ensure stability and a high performance for the entire operating range of the distillation column. A summary of the practical experiences complements the theoretical results. View full abstract»

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  • Qualitative model-based fault detection in air-handling units

    Page(s): 11 - 22
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    The feasibility of a qualitative approach for detecting faults in an air-conditioning system is considered. The system considered is a multi-zone variable air volume air-handling unit, and the faults investigated include types which result in deterioration of operation, as distinct from actual failure. The operating modes of the sequential controller for the central air-handling plant can be matched to a corresponding qualitative classification of steady-state temperatures. Observed mismatches indicate the presence of faults. Trials of the method in an air-conditioning test laboratory are reported View full abstract»

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  • Modeling and control of variable-speed wind-turbine drive-system dynamics

    Page(s): 28 - 38
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    When designing control for variable-speed wind turbines, one deals with highly resonant, nonlinear dynamic systems subject to random excitation, i.e., wind turbulence. This requires good knowledge of the dynamics to be controlled, particularly when combined with the increasingly common “soft” concept of lightweight, flexible constructional components; it creates cost advantages compared to more material-consuming rigid constructions, but also results in low frequency structural eigenfrequencies, some of which may appear in the bandwidth of closed-loop operation. For this article, system-identification experiments have been performed on an existing 400 kW, variable-speed, horizontal-axis wind turbine using various identification schemes. The identification results have then provided numerical values of the parameters in a physical model of the drive system. The acquired model has been used for design and evaluation of a number of linear and nonlinear control schemes for wind-turbine speed regulation View full abstract»

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  • Increased roles of linear algebra in control education

    Page(s): 76 - 90
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    In the past, control theory developed along different lines that required different mathematical tools. Time-varying systems required one set of tools, time-invariant another. Single-input, single-output problems lend themselves easily to one approach, but this approach is awkward for multivariable systems, etc. The purpose of this article is to point to the desirability of a unified approach to elementary control education using only tools of linear algebra as the enabling unifier. The following is a description and motivation for the proposed new control course (approach). There is only one main theorem from linear algebra, and at least 17 different control problems all reduce to solving a single linear algebra problem View full abstract»

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  • Application of enhanced LQG/LTR for distillation control

    Page(s): 56 - 63
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    O'Dell and Misawa (1995) proposed a modification to the traditional LQG/LTR design procedure which provides uniform singular values across all frequencies for the target loop. The modification is easy to implement and significantly improves the performance of the LQG/LTR compensator. This article explores applicability of the technique for distillation column control, the most common multivariable control problem in the process industries. When applied to the Wood/Berry column (1973), performance of the enhanced LQG/LTR compensator is found to be comparable to a MAC model predictive controller and significantly better than traditional SISO PI control. Despite the lack of guaranteed performance and robust stability for nonlinear, nonminimum phase plants, the results suggest further consideration of enhanced LQG/LTR for application in the process industries View full abstract»

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  • Optimal indoor temperature control using a predictor

    Page(s): 4 - 10
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    This article deals with optimal control of the indoor temperature in a building. The control system attempts to find an economic optimum to supply heat to the building with the use of a predictor for the indoor temperature, while maintaining a comfortable temperature in the building. A general control structure is described that uses a linear objective function, which is minimized by linear programming. This general control structure is applied to a specific test facility called passive climate system, whose main feature is that it uses natural ventilation by means of adjustable windows for cooling purposes. This article also describes some field tests with the optimal predictive control system applied to the passive climate system View full abstract»

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  • Material mix control in cement plant automation

    Page(s): 23 - 27
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    The objective of this article is the development of a novel raw material mix proportion control algorithm for a cement plant raw mill, so as to maintain preset target mix proportion at the raw mill outlet. This algorithm utilizes one of the most basic and important tools of numerical linear algebra, the singular value decomposition (SVD), for calculation of raw mix proportion. The strength of this algorithm has been verified by comparing the results of this method with that of the results of the QCX-software developed by F.L. Smidth of Denmark, a pioneer in cement plant automation, on a 2500 tons-per-day (tpd) dry process cement plant situated at Jayanthipuram, Andhra Pradesh, India View full abstract»

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  • Sensor, actuator, and loop validation

    Page(s): 39 - 45
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    Economic pressures are dispersing machine intelligence away from centralized computers toward distributed Fieldbus devices. Simultaneously, the control concept is being extended to include other operational factors such as quality assurance, process data management, just-in-time maintenance, and plant safety and availability. As credible sensing and actuation are essential prerequisites for advanced control, validation of the sensor and actuator interface is necessary. As such subsystems are linked to a range of different overall plant systems. We must consider generic validation and its reporting to the “next level up”. This article discusses validation features which are best embedded in local devices View full abstract»

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  • Engineers, psychologists, and administrators: control systems research in wartime, 1940-45

    Page(s): 91 - 99
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    Describes the organisation and work of 2 US wartime scientific agencies, the National Defense Research Committee (NDRC) and its successor and umbrella organization, the Office of Scientific Research and Development (OSRD) View full abstract»

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  • Control design and implementation in continuous steel casting

    Page(s): 64 - 71
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    Accurate control of the mold level in continuous casting is believed to be a key factor in improving the quality of the cast product. This paper describes an application of advanced control to this problem leading to a complete recommissioning of the mold level control system. Careful physical modeling identified smooth as well as nonsmooth nonlinearities in the process. Three different control strategies were implemented and evaluated. The article also describes some of the steps necessary to bring advanced control to practical reality, including safety, rapid prototyping, online tuning, and economic evaluation View full abstract»

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IEEE Control Systems Magazine is the largest circulation technical periodical worldwide devoted to all aspects of control systems.

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Richard D. Braatz
braatz@mit.edu