By Topic

Control Theory and Applications, IEE Proceedings D

Issue 2 • Date Mar 1988

Filter Results

Displaying Results 1 - 24 of 24
  • Linear system reduction using approximate moment matching

    Page(s): 73 - 78
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    A method for reduction of continuous-time linear systems is presented which employs a singular-wave decomposition approximation to Hankel matrices. The method is related both to balancing reduction and to moment-matching methods. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • New pole assignment algorithm with reduced norm feedback matrix

    Page(s): 111 - 118
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    A new algorithm is described for the assignment of closed loop poles in linear time invariant multivariable systems. The approach is similar to the well known dyadic pole placement methods, but does not usually result in a unity rank controller. The algorithm can be put into iterative form in the sense that open loop poles can be relocated or preserved so that by repeating the assignment process, all of the open loop poles can be reassigned. There are only very mild constraints on the destinations of the poles. The paper also shows how any unused degrees of freedom can be exploited to reduce the control effort needed to achieve the pole assignment. Results are given for both the state and the output feedback cases. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robustness analysis of discrete-time adaptive control systems using input-output stability theory: a tutorial

    Page(s): 133 - 141
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    Presents a summary and consolidation of stability and robustness results based on input-output theory for discrete adaptive control systems. The objective of this paper is to clarify the techniques involved in applying this suitability approach to the adaptive control problem. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of nonlinear system transformations to control design for a chemical reactor

    Page(s): 90 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The design of a nonlinear regulator for the control of a nonisothermal continuous stirred tank reactor (CSTR) is derived using the technique of nonlinear system transformation. It is shown that recent developments are in the area of nonlinear transformation theory have direct application to the problem of controlling nonisothermal CSTRs. It is established that the transformation method leads to the design of robust and stable nonlinear regulators for these systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modified algorithm for steady-state integrated system optimisation and parameter estimation

    Page(s): 119 - 126
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The paper proposes an alternative modified two-step algorithm for steady state optimisation and parameter estimation. The aim is to simplify the model optimisation computation in the presence of general inequality constraints. Another advantage is that the existence of a model based optimal solution is ensured during the course of iteration. Optimality properties and convergence conditions are investigated. A simulation study is presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Self-tuning control of hypotension during ENT surgery using a volatile anaesthetic

    Page(s): 95 - 105
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1216 KB)  

    The generalised minimum-variance self-tuning controller of Clarke and Gawthrop has been used to regulate induced hypotension (reduced blood pressure) in 34 patients undergoing ENT surgery, by automatic adjustment of the inhaled concentration of the volatile anaesthetic agent isoflurane. The purpose of the investigation was: to assess the use of self-tuning control (STC) as an aid to the anaesthetist in normal clinical situations; to obtain information in an acceptable manner to illuminate the clinical situation and any signal conditioning, sources of outliers, and other possible problems to be met therein; to see to what extent STC compares with manual adjustments by an anaesthetist (10 patients); to provide a basis for the design of a stand alone controller for use in anaesthesia which would enable comparison with other drugs in the same situations; and to provide controlled conditions for measurement of various physiological variables of interest to anaesthetists. In summarising investigations and experiences from an engineering standpoint the potential of STC methods in clinical applications is indicated, and some ways of improving the performance of the authors' implementation are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Leak detection and location in gas pipelines

    Page(s): 142 - 148
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Describes a new method for detecting and locating leaks in long pipelines, based on an extended Kalman filter for the nonlinear distributed parameter system representing gas flow in pipes. Artificial leak states at predefined positions along the pipeline are included in the filter model, and relationships to estimate the actual leak position are derived. Simulation results are presented to assess the method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Decoupling and data sensitivity in singular systems

    Page(s): 106 - 110
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    A problem of decoupling and data sensitivity in singular systems is studied and solved algebraically. The controller used for decoupling is of PD state feedback type. Necessary and sufficient conditions among the parameter variations, such as the decoupling properties of the system remain invariant, are established. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive model following control of electrohydraulic velocity control systems subjected to unknown disturbances

    Page(s): 149 - 156
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    Considers the velocity control problem of nonlinear hydraulic servo systems subjected to known and time-varying external load disturbances. Hydraulically operated processes are usually represented by a hydraulic actuator-load system whose dynamic characteristics are complex and highly nonlinear, owing either to the flow-pressure relationships of the hydraulic system or to a load system motion itself. Furthermore, these characteristics are sometimes unknown owing to the uncertainty in external load disturbances to the processes. Therefore, the conventional approach to the controller design of these systems may not assure satisfactory control performance. To obtain better performance an adaptive model following control (AMFC) scheme was derived based upon Lyapunov's direct method. In order to deal with the uncertainties that are associated with the plant dynamics and the unknown disturbances, this method uses a small ultimate bound of the state error as an adaption criterion. A series of simulation studies were performed to demonstrate the effectiveness of this controller. The results show that the proposed AMFC is fairly robust to unknown and time-varying external load disturbances, yielding improved performance characteristics when compared with a suboptimal PID controller with constant feedback gain. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stability and performance bounds for the linearisation-based analysis and design of multivariable nonlinear systems

    Page(s): 79 - 89
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1044 KB)  

    The paper is concerned with the derivation of useful results that complement the linearisation-based analysis and design of multivariable systems with measurement nonlinearity. The approach is based on the closed-loop linearised system descriptions and certain nonlinearity related parameters representing sector and/or incremental sector properties, and also enables the consideration of nonlinearities with discontinuities at the origin. Nonlinear-system stability and performance is assessed on the basis of the stability and performance of the corresponding linearised system and certain easily computable sufficient conditions representing BIBO and asymptotic stability conditions, as well as absolute and derivative performance bounds. The results depend on useful linearised system descriptions such as the Linfinity operator norm, thus offering the advantages of meaningful assessments and overall computational simplicity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Parameter-bounding identification algorithms for bounded-noise records

    Page(s): 127 - 132
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    In the identification of dynamical models from noisy observations, an adequate stochastic characterisation of the noise is often unavailable, either because there are relatively few observations and little prior information, or because the noise behaviour is complicated, e.g., nonstationary. An alternative approach to identification has been suggested, which uses bounds on the noise instead of a stochastic description. From the noise bounds in a specified model structure, each observation yields a pair of bounds in parameter space. A succession of observations thus identifies a feasible parameter region rather than a point estimate of the parameters. This paper suggests combined use of two standard algorithms for parameter-bounding identification, outer-bounding by linear programming, and ellipsoidal outer-bounding. The former is expensive in computation but may result in a more accurately defined feasible parameter region. The latter is cheap, but often unsatisfactory on its own because it gives only a loose approximation to the parameter region. Various combined uses of the two methods are described and tested. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Controller designs for model-plant parameter mismatch

    Page(s): 157 - 164
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    A strategy of design for the controller and for a dynamic filter which compensates for disturbances is presented. The proposed algorithm has the robustness criteria which allows the controller to perform well under model uncertainties. The stability and dynamic performance of the control system is studied in relation to model-plant parameter mismatch. The algorithm is specially suited for time-delay processes. Simulation and experimental evaluation of the method is included in the paper. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Linear system reduction using approximate moment matching

    Page(s): 73 - 78
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    A method for reduction of continuous-time linear systems is presented which employs a singular-value decomposition approximation to Hankel matrices. The method is related both to balancing reduction and to moment-matching methods. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stability and performance bounds for the linearisation-based analysis and design of multivariable nonlinear systems

    Page(s): 79 - 89
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1527 KB)  

    The paper is concerned with the derivation of useful results that complement the linearisation-based analysis and design of multivariable systems with measurement nonlinearity. The approach is based on the closed-loop linearised system descriptions and certain nonlinearity related parameters representing sector and/or incremental sector properties, and also enables the consideration of nonlinearities with discontinuities at the origin. Nonlinear-system stability and performance is assessed on the basis of the stability and performance of the corresponding linearised system and certain easily computable sufficient conditions representing BIBO and asymptotic stability conditions, as well as absolute and derivative performance bounds. The results depend on useful linearised system descriptions such as the L¿¿ operator norm, thus offering the advantages of meaningful assessments and overall computational simplicity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of nonlinear system transformations to control design for a chemical reactor

    Page(s): 90 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (454 KB)  

    The design of a nonlinear regulator for the control of a nonisothermal continuous stirred tank reactor (CSTR) is derived using the technique of nonlinear system transformation. It is shown that recent developments in the area of nonlinear transformation theory have direct application to the problem of controlling nonisothermal CSTRs. It is established that the transformation method leads to the design of robust and stable nonlinear regulators for these systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Self-tuning control of hypotension during ENT surgery using a volatile anaesthetic

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1797 KB)  

    The generalised minimum-variance self-tuning controller of Clarke and Gawthrop has been used to regulate induced hypotension (reduced blood pressure) in 34 patients undergoing ENT surgery, by automatic adjustment of the inhaled concentration of the volatile anaesthetic agent isoflurane. The purpose of the investigation was: to assess the use of self-tuning control (STC) as an aid to the anaesthetist in normal clinical situations; to obtain information in an acceptable manner to illuminate the clinical situation and any signal conditioning, sources of outliers, and other possible problems to be met therein; to see to what extent STC compares with manual adjustments by an anaesthetist (10 patients); to provide a basis for the design of a stand alone controller for use in anaesthesia which would enable comparison with other drugs in the same situations; and to provide controlled conditions for measurement of various physiological variables of interest to anaesthetists. In summarising our investigations and experiences from an engineering standpoint the potential of STC methods in clinical applications is indicated, and some ways of improving the performance of our implementation are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Decoupling and data sensitivity in singular systems

    Page(s): 106 - 110
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (563 KB)  

    A problem of decoupling and data sensitivity in singular systems is studied and solved algebraically. The controller used for decoupling is of PD state feedback type. Necessary and sufficient conditions among the parameter variations, such that the decoupling properties of the system remain invariant, are established. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • New pole assignment algorithm with reduced norm feedback matrix

    Page(s): 111 - 118
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (860 KB)  

    A new algorithm is described for the assignment of closed loop poles in linear time invariant multivariable systems. The approach is similar to the well known dyadic pole placement methods, but does not usually result in a unity rank controller. The algorithm can be put into iterative form in the sense that open loop poles can be relocated or preserved so that by repeating the assignment process, all of the open loop poles can be reassigned. There are only very mild constraints on the destinations of the poles. The paper also shows how any unused degrees of freedom can be exploited to reduce the control effort needed to achieve the pole assignment. Results are given for both the state and the output feedback cases. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modified algorithm for steady-state integrated system optimisation and parameter estimation

    Page(s): 119 - 126
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    The paper proposes an alternative modified two-step algorithm for steady state optimisation and parameter estimation. The aim is to simplify the model optimisation computation in the presence of general inequality constraints. Another advantage is that the existence of a model based optimal solution is ensured during the course of iteration. Optimality properties and convergence conditions are investigated. A simulation study is presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Parameter-bounding identification algorithms for bounded-noise records

    Page(s): 127 - 132
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (713 KB)  

    In the identification of dynamical models from noisy observations, an adequate stochastic characterisation of the noise is often unavailable, either because there are relatively few observations and little prior information, or because the noise behaviour is complicated, e.g. nonstationary. An alternative approach to identification has been suggested, which uses bounds on the noise instead of a stochastic description. From the noise bounds in a specified model structure, each observation yields a pair of bounds in parameter space. A succession of observations thus identifies a feasible parameter region rather than a point estimate of the parameters. This paper suggests combined use of two standard algorithms for parameter-bounding identification, outer-bounding by linear programming, and ellipsoidal outer-bounding. The former is expensive in computation but may result in a more accurately defined feasible parameter region. The latter is cheap, but often unsatisfactory on its own because it gives only a loose approximation to the parameter region. Various combined uses of the two methods are described and tested. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robustness analysis of discrete-time adaptive control systems using input-output stability theory: a tutorial

    Page(s): 133 - 141
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1088 KB)  

    This paper presents a summary and consolidation of stability and robustness results based on input-output theory for discrete adaptive control systems. The objective of this paper is to clarify the techniques involved in applying this stability approach to the adaptive control problem. It is intended that this tutorial may provide a basis for continuing work in this area. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Leak detection and location in gas pipelines

    Page(s): 142 - 148
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (677 KB)  

    The paper describes a new method for detecting and locating leaks in long pipelines, based on an extended Kalman filter for the nonlinear Distributed Parameter (DP) system representing gas flow in pipes. Artificial leak states at predefined positions along the pipeline are included in the filter model, and relationships to estimate the actual leak position are derived. Simulation results are presented to assess the method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive model following control of electrohydraulic velocity control systems subjected to unknown disturbances

    Page(s): 149 - 156
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (881 KB)  

    This paper considers the velocity control problem of nonlinear hydraulic servo systems subjected to unknown and time-varying external load disturbances. Hydraulically operated processes are usually represented by a hydraulic actuator-load system whose dynamic characteristics are complex and highly nonlinear, owing either to the flow-pressure relationships of the hydraulic system or to a load system motion itself. Furthermore, these characteristics are sometimes unknown owing to the uncertainty in external load disturbances to the processes. Therefore, the conventional approach to the controller design of these systems may not assure satisfactory control performance. To obtain better performance an adaptive model following control scheme was derived based upon Lyapunov's direct method [8]. In order to deal with the uncertainties that are associated with the plant dynamics and the unknown disturbances, this method uses a small ultimate bound of the state error as an adaptation criterion. A series of simulation studies were performed to demonstrate the effectiveness of this controller. The results show that the proposed AMFC is fairly robust to unknown and timevarying external load disturbances, yielding improved performance characteristics when compared with a suboptimal PID controller with constant feedback gain. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Controller designs for model-plant parameter mismatch

    Page(s): 157 - 164
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (845 KB)  

    A strategy of design for the controller and for a dynamic filter which compensates for disturbances is presented. The proposed algorithm has the robustness criteria which allows the controller to perform well under model uncertainties. The stability and dynamic performance of the control system is studied in relation to model-plant parameter mismatch. The algorithm is specially suited for time-delay processes. Simulation and experimental evaluation of the method is included in the paper. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.