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  • Conference paper
    Sharifzadeh M, Thornhill NF, 2011,

    Optimal controlled variable selection using a nonlinear simulation-optimization framework

    , 21st European Symposium on Computer Aided Process Engineering

    In feedback control, controlled variables are those process variables which are measuredand fed back to controllers. Then in the presence of disturbances, controllers by themeans of manipulating the inputs aim to maintain the controlled variables at theirsetpoints. The objectives for the selection of controlled variables can be conflicting andcompeting. These objectives include minimization of (1) economic losses, (2) inputmanipulations, (3) output variations and (4) changes in process states. This researchaims to present a systematic framework for optimal selection of controlled variables.Each of the above-mentioned objectives is defined within a multi-objective function. Inaddition, the reasoning behind the selection of nonlinear steady state model is explained.The proposed methodology is benchmarked on an industrial distillation train.Optimization programming is presented and the paper discusses how the size of theoptimization problem can be reduced by means of engineering insights and addressingthe concerns regarding feasibility of the developed control structure. The methodologyis scalable to large industrial problems, while maintaining its rigour. The results confirmthat a very good trade-off is established between different objectives.

  • Journal article
    Thambirajah J, Thornhill NF, Pal BC, Thambirajah J, Thornhill NF, Pal BCet al., 2011,

    A Multi­variate Approach Towards Inter-Area Oscillation Damping Estimation Under Ambient Conditions Via Independent Component Analysis And Random Decrement

    , IEEE Transactions on Power Systems, Vol: 26, Pages: 315-322, ISSN: 0885-8950

    This paper presents a novel approach to the monitoring of interarea oscillation frequency and damping using multivariate analysis techniques. A two-step method is presented 1) independent component analysis for the detection of interarea modes and estimation of their frequencies and 2) random decrement for the estimation of mode damping. The method is applied to real measurements taken in Finland within the Nordic Power System to estimate the critical interarea mode frequency and damping in the system.

  • Conference paper
    Stonier A, Pain D, Westlake A, Hutchinson N, Thornhill NF, Farid SSet al., 2011,

    Integration of stochastic simulation with advanced multivariate and visualisation analyses for rapid prediction of facility fit issues in biopharmaceutical processes

    , 21st European Symposium on Computer Aided Process Engineering (ESCAPE-21), Publisher: ELSEVIER SCIENCE BV, Pages: 1356-1360, ISSN: 1570-7946
  • Conference paper
    Di Geronimo Gil GJ, Alabi DB, Iyun OE, Thornhill NFet al., 2011,

    Merging process models and plant topology

    , International Symposium on Advanced Control of Industrial Processes, ADCONIP 2011, Pages: 15-21

    The paper discusses the merging of first principles process models with plant topology derived in an automated way from a process drawing. The resulting structural models should make it easier for a range of methods from the literature to be applied to industrial-scale problems in process operation and design. © 2011 Zhejiang University.

  • Report
    Craig I, Aldrich C, Braatz R, Cuzzola F, Domlan E, Engell S, Hahn J, Havlena V, Horch A, Huang B, Khanbaghi M, Konstantellos A, Marquardt W, McAvoy T, Parisini T, Pistikopoulos E, Samad T, Skogestad S, Thornhill N, Yu Jet al., 2011,

    Control in the process industries

    , Control in the process industries, in The Impact of Control Technology, Overview, Success Stories, and Research Challenges, T. Samad and A. Annaswamy (Eds), Publisher: IEEE
  • Journal article
    Jukka T, Thambirajah J, Larsson M, Pal BC, Thornhill NF, Haarla LC, Hung W, Carter A, Rauhala Tet al., 2011,

    Comparison of Three Electromechanical Oscillation Damping Estimation Methods

    , IEEE Transactions on Power Systems, Vol: 26, Pages: 2398-2407, ISSN: 0885-8950

    This paper describes three data driven methods to monitor electromechanical oscillations in interconnected power system operation. The objective is to compare and contrast the performance of the methods. The accuracy of damping ratio and frequency of oscillations are the measures of the performance of the algorithms. The advantages and disadvantages of various techniques and their limitations to measurement noise have been considered while assessing performance. The target frequency and damping are computed using the Nordic power system simulation model.

  • Journal article
    Sharifzadeh M, Rashtchian D, Pishvaie M, Thornhill NFet al., 2010,

    Energy Induced Separation Network Synthesis of an Olefin Compression Section: A Case Study

    , Industrial & Engineering Chemistry Research, Vol: 50, Pages: 1610-1623

    When latent heat is transferred in a heat exchanger network, the formation of the second phase creates an opportunity for separation. This network is known as a Heat Induced Separation Network (HISEN). HISENs have been extended to include pressure adjusting devices for improving the thermodynamic feasibility of the network. This extended network is termed an Energy Induced Separation Network (EISEN). Most examples of EISENs in the literature are environmental pollution treatment case studies which do not require liquid phase mass integration or shaft power integration. They assume a predetermined extent of separation and mostly are based on conceptual methods of design. This paper explains how the optimization framework must be developed in order to systematically address the general characteristics of EISENs. The framework is illustrated using a case study of the synthesis problem of an olefin compression section.

  • Conference paper
    Ikram W, Thornhill NF, 2010,

    Wireless communication in process automation: A survey of opportunities, requirements, concerns and challenges

    , Pages: 471-476

    The advancements in wireless networking technology, specifically in the short-range wireless networking technology, offer an enormous opportunity for wireless connectivity of field devices both in oil and gas and other chemical processing plants. The prerequisite of a field network includes real-time support for mixed traffic, availability, security, reliability and scalability in a harsh industrial environment. These conditions have to be fulfilled by any wireless network in order to operate. This paper presents a brief overview of the requirements for wireless in process automation, relative standings of existing short-range wireless network technologies based on the outlined criteria, and associated shortcomings. Furthermore, an examination of emerging industrial wireless standards which are designed to address the unique and stringent requirements of the process industry, is presented.

  • Journal article
    Thambirajah J, Barocio E, Thornhill NF, 2010,

    Comparative review of methods for stability monitoring in electrical power systems and vibrating structures

    , IET GENERATION TRANSMISSION & DISTRIBUTION, Vol: 4, Pages: 1086-1103, ISSN: 1751-8687
  • Conference paper
    Ikram W, Stoianov I, Thornhill NF, 2010,

    Towards a Radio-Controlled Time Synchronized Wireless Sensor Network

    , IEEE Emerging Technologies and Factory Automation (ETFA 2010), ISSN: 1946-0740

    Wireless sensor networks are deployed to monitor real-world phenomena, and are seeing growing demand in commerce and industry. These networks can benefit from time synchronized clocks on distributed nodes. The precision of time synchronization depends on error elimination or reliable estimation of errors associated with synchronization message delays. This paper examines an approach to time synchronize motes using onboard radio-controlled clocks. The advantage will be the minimisation of non-deterministic sources of errors in time synchronization amongst receivers. This approach of synchronization using out-of-band and dedicated time source is aimed to achieve network-wide, scalable, topology-independent, fast-convergent and less application-dependent solutions.

  • Journal article
    Apelt TA, Thornhill NF, 2009,

    Inferential measurement of sag mill parameters IV: Inferential model validation

    , MINERALS ENGINEERING, Vol: 22, Pages: 1032-1044, ISSN: 0892-6875
  • Journal article
    Apelt TA, Thornhill NF, 2009,

    Inferential measurement of SAG mill parameters V: MPC simulation

    , MINERALS ENGINEERING, Vol: 22, Pages: 1045-1052, ISSN: 0892-6875
  • Journal article
    Thambirajah J, Benabbas L, Bauer M, Thornhill NFet al., 2009,

    Cause-and-effect analysis in chemical processes utilizing XML, plant connectivity and quantitative process history

    , COMPUTERS & CHEMICAL ENGINEERING, Vol: 33, Pages: 503-512, ISSN: 0098-1354
  • Conference paper
    Beez S, Fay A, Thornhill NF, 2008,

    Automatic generation of Bond Graph models of process plants

    , IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2008, Publisher: IEEE, Pages: 1294-1301

    This paper presents an application for the automatic generation of Bond Graph models. The basis for this automated creation is a modified plant model in the XML-format according to the IEC PAS 62424 (CAEX). The application developed in the programming language C, extracts and converts the information which is, then, stored in a model file meeting the requirements and structure of the modelling/simulation-language Dymola. Bond Graphs are used as the modelling technique since they do not distinguish between different energy domains and, therefore, combine several advantages against other modelling techniques. The developed application can be used for multiple purposes such as simulations, visualizations and other specific tasks that might emerge during the planning and operation process of plants and other engineering systems. © 2008 IEEE.

  • Journal article
    Bauer M, Thornhill NF, 2008,

    A practical method for identifying the propagation path of plant-wide disturbances

    , JOURNAL OF PROCESS CONTROL, Vol: 18, Pages: 707-719, ISSN: 0959-1524
  • Journal article
    Thornhill NF, Patwardhan SC, Shah SL, 2008,

    A continuous stirred tank heater simulation model with applications

    , JOURNAL OF PROCESS CONTROL, Vol: 18, Pages: 347-360, ISSN: 0959-1524
  • Journal article
    Edwards-Parton S, Thornhill NF, Bracewell DG, Liddell JM, Titchener-Hooker NJet al., 2008,

    Principal component score modeling for the rapid description of chromatographic separations

    , BIOTECHNOLOGY PROGRESS, Vol: 24, Pages: 202-208, ISSN: 8756-7938
  • Software
    Thornhill NF, 2008,

    The CSTH Simulation model

    This code is a first principles simulation of a continuous stirred tank heater (CSTH) pilot plant at the University of Alberta. The model has heat and mass balance, and a very realistic feature is that instrument, actuator and process non-linearities have been carefully measured. Models in Simulink, supporting Matlab files are available together with experimental noise and disturbance sequences.A full description is given in:Thornhill, N.F., Patwardhan, S.C., and Shah, S.L., 2008, A continuous stirred tank heater simulation model with applications, Journal of Process Control, 18, 347-360.

  • Journal article
    Bauer M, Cox JW, Caveness MH, Downs JJ, Thornhill NFet al., 2007,

    Nearest neighbors methods for root cause analysis of plantwide disturbances

    , INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 46, Pages: 5977-5984, ISSN: 0888-5885
  • Journal article
    Choudhury MAAS, Kariwala V, Thornhill NF, Douke H, Shah SL, Takada H, Forbes JFet al., 2007,

    Detection and diagnosis of plant-wide oscillations

    , CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Vol: 85, Pages: 208-219, ISSN: 0008-4034

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