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Articles 31 - 60 of 85
Full-Text Articles in Controls and Control Theory
Comparative Study Of Two Techniques For Determining Critical Frequency Response Characteristics, Niall O'Connor, Aidan O'Dwyer
Comparative Study Of Two Techniques For Determining Critical Frequency Response Characteristics, Niall O'Connor, Aidan O'Dwyer
Conference papers
The paper presents a review of a comparative study of two separate techniques for obtaining important frequency and time domain characteristics of a system consisting of a process in series with a PI/PID controller in closed loop. The first technique involves the use of a Pseudo Random Binary Sequence (PRBS) to obtain the closed loop frequency response of the system. This closed loop frequency information may then be manipulated to obtain both open loop frequency response information and process model parameters. A further mathematical simulation using Matlab may then be performed independent of the actual process in order to obtain …
Pid Control: The Early Years, Aidan O'Dwyer
Pid Control: The Early Years, Aidan O'Dwyer
Conference papers
This contribution outlines controller developments 1788 – c.1900; 1900-1950: The role of instrument companies; early theoretical description of the PID controller; early tuning of the PID controller; some further developments since 1950; some conclusions.
Using Information Technology To Enhance Control Engineering Education: Some Experiences, Aidan O'Dwyer
Using Information Technology To Enhance Control Engineering Education: Some Experiences, Aidan O'Dwyer
Conference papers
In the past decade, the use of computer based design and analysis tools, such as MATLAB/SIMULINK, has revolutionised practice in Control Engineering. Concepts that were previously only understandable after sustained mathematical analysis or experimental work may now be readily simulated on the computer. Over the past four years, the author has experimented with the use of MATLAB/SIMULINK, in the lecture and laboratory environment, with degree and taught masters students in control engineering at Dublin Institute of Technology (DIT). It has been found that the tool helps to increase student understanding of challenging topics, to act as motivation to further exploration …
Enhancing Process Performance Through Automatic Control, Aidan O'Dwyer
Enhancing Process Performance Through Automatic Control, Aidan O'Dwyer
Conference papers
The proportional integral derivative (PID) controller is the most dominant form of automatic controller in industrial use today. With this technique, it is necessary to adjust the controller parameters according to the nature of the process. Thus, for effective control of a pasteurisation process, for example, specific values need to be chosen for the P, I and D parameters, which will be different for the values required to control, for example, a distillation column. This tailoring of controller to process is known as controller tuning.
State Feedback Integral Control By Velocity-Based Multiple Model Networks, Ruiyao Gao, Aidan O'Dwyer
State Feedback Integral Control By Velocity-Based Multiple Model Networks, Ruiyao Gao, Aidan O'Dwyer
Conference papers
Velocity-based (VB) multiple model networks have the advantage of allowing the capture of the dynamics of non-linear systems when compared to conventional multiple model networks, for they build a direct relationship between the non-linear system and the VB linearisation. To have the best use of modelled dynamic information for the controller design, this paper proposes a novel controller design approach, which associates an integral action with state feedback in local controller design. It overcomes the difficulty in the implementation of the velocity-based approach, which normally involves deducing the differential signal. It holds continuity with linear control theory in the analysis …
Implementation Of New Modified Smith Predictor Designs, Pauline Sourdille, Aidan O'Dwyer
Implementation Of New Modified Smith Predictor Designs, Pauline Sourdille, Aidan O'Dwyer
Conference papers
This paper outlines two modified Smith predictors developed previously by the authors and then presents the implementation results of these structures for the control of a pilot scale heating and ventilation system, the PT 326 process trainer from Feedback Instruments Ltd. These results are compared to the results obtained with a Smith predictor structure.
Determination Of The Phase Of A Transfer Function: Theory Versus Practice, Pauline Sourdille, Aidan O'Dwyer
Determination Of The Phase Of A Transfer Function: Theory Versus Practice, Pauline Sourdille, Aidan O'Dwyer
Conference papers
In control systems, a way to evaluate the stability of a system is to determine the magnitude and phase of the open loop system transfer function in the frequency domain. But due to the nature of the phase expression, practice and theory are not aligned. Some problems arise when the phase is determined, caused by the properties of the arctan function. This paper analyses these phase problems for a third order lag system and a third order lag with time delay system. It also presents modifications to obtain the analytically correct phase values from the computed values.
Control Loop Performance Assessment: A Classification Of Methods, Niall O'Connor, Aidan O'Dwyer
Control Loop Performance Assessment: A Classification Of Methods, Niall O'Connor, Aidan O'Dwyer
Conference papers
This paper presents an overview of a number of controller performance assessment techniques. The techniques discussed are divided into five categories, namely, time domain assessment, frequency domain assessment, minimum variance control (MVC) as a benchmark, statistical analysis, and other more ‘problem specific’ assessment techniques. Recent work, by various authors, in each of the five categories is outlined.
Tuning Rules For Pi And Pid Control Of Time Delayed Processes: Some Recent Developments, Aidan O'Dwyer
Tuning Rules For Pi And Pid Control Of Time Delayed Processes: Some Recent Developments, Aidan O'Dwyer
Conference papers
The ability of PI and PID controllers to compensate many practical processes has led to their wide acceptance in industrial applications. The requirement to choose two or three controller parameters is most easily done using tuning rules. Starting with a general discussion of industrial practice, the paper will discuss, in particular, recent work in tuning rule development for processes with time delay.
Comparison Between Theoretical And Practical Phase Computation, Pauline Sourdille, Aidan O'Dwyer
Comparison Between Theoretical And Practical Phase Computation, Pauline Sourdille, Aidan O'Dwyer
Conference papers
Transfer functions which are a composite of delay terms cause problems for computer packages, such as MATLAB, in calculating the frequency response open loop transfer function, as the form of the open loop transfer function is irrational. So, the delay terms have to be approximated. There are several ways to evaluate a delay term. A calculator such as MATHEMATICA uses the exact representation of the delay called the Euler form. A computer package such as MATLAB uses a rational approximation for the delay. Using the MATLAB built-in function pade(n,tau), the open loop transfer function of a system with delay can …
System Identification Using The Delta Operator, Aidan O'Dwyer
System Identification Using The Delta Operator, Aidan O'Dwyer
Conference papers
The aim of this contribution is to communicate, to a wide audience in signal processing and telecommunications, work that has been carried out, primarily in control engineering, on the use of alternative discrete time operators to the z-domain operator. The advantages of the delta domain operator will be communicated using examples, primarily with the aid of plotted results, to give a creative and easily understood impact. Some original work carried out by the author on identification issues will also be communicated.
Comparison Of Process Identification Techniqies In The Time- And Frequency-Domains, Tony Kealy, Aidan O'Dwyer
Comparison Of Process Identification Techniqies In The Time- And Frequency-Domains, Tony Kealy, Aidan O'Dwyer
Conference papers
This paper describes ten methods to identify a mathematical model for a real process with a time delay. The process is the Process Trainer, PT326 from Feedback Instruments Limited. Six of the methods use step response data and one of the methods uses impulse response data for identification. Two of the methods use frequency response data and the final method uses information from relay-based experiments. The best results are obtained using a combined analytical and gradient method [6] in the frequency-domain and, in the time-domain, using the two-point algorithm [1] and a method proposed by Suganda et al. [5].
Analytical Ise Calculation And Optimum Control System Design, Tony Kealy, Aidan O'Dwyer
Analytical Ise Calculation And Optimum Control System Design, Tony Kealy, Aidan O'Dwyer
Conference papers
Abstract – In control system theory, a performance index is a quantitative measure of the performance of a system and is chosen so that emphasis is given to the important system parameters. In this paper, the authors demonstrate two methods to determine analytically the Integral of the Square of the Error (ISE) performance index value for a first-order-plus-dead-time (FOPDT) process model under PI control. The ability of proportional/integral (PI) and proportional/integral/derivative (PID) controllers to compensate most practical industrial processes has led to their wide acceptance in industrial applications. The most direct way to set up PI/PID controller parameters is the …
Pid Compensation Of Time Delayed Processes 1998-2002: A Survey, Aidan O'Dwyer
Pid Compensation Of Time Delayed Processes 1998-2002: A Survey, Aidan O'Dwyer
Conference papers
A time delay may be defined as the time interval between the start of an event at one point in a system and its resulting action at another point in the system. Delays are also known as transport lags or dead times; they arise in physical, chemical, biological and economic systems, as well as in the process of measurement and computation. Methods for the compensation of time delayed processes may be broadly divided into proportional integral derivative (PID) based controllers, in which the controller parameters are adapted to the controller structure, and structurally optimised controllers, in which the controller structure …
A New Modified Smith Predictor Design, Pauline Sourdille, Aidan O'Dwyer
A New Modified Smith Predictor Design, Pauline Sourdille, Aidan O'Dwyer
Conference papers
A new modified Smith predictor structure is presented with its associated tuning rules.
An Outline And Further Development Of Smith Predictor Based Methods For The Compensation Of Processes With Time Delay, Pauline Sourdille, Aidan O'Dwyer
An Outline And Further Development Of Smith Predictor Based Methods For The Compensation Of Processes With Time Delay, Pauline Sourdille, Aidan O'Dwyer
Conference papers
An extensive literature review is presented and a new modified Smith predictor is subsequently presented.
On Stability Of Affine Blending Systems, Ruiyao Gao, Aidan O'Dwyer, Seamus Mcloone, Eugene Dermot Coyle Professor
On Stability Of Affine Blending Systems, Ruiyao Gao, Aidan O'Dwyer, Seamus Mcloone, Eugene Dermot Coyle Professor
Conference papers
This paper presents a novel approach to stability analysis of affine blending systems. The analysis is based on Quadratic Lyapunov functions. The approach considers the nonlinear offset term in affine blending systems as non-vanishing perturbations added to the corresponding nominal linear blending systems. The affine blending systems will be bounded if the corresponding linear blending system is exponentially stable. The bound is determined by an ultimate limit, which is proportional to the maximum of the offset terms of each affine system.
New Modified Smith Predictor Designs, Pauline Sourdille, Aidan O'Dwyer
New Modified Smith Predictor Designs, Pauline Sourdille, Aidan O'Dwyer
Conference papers
By combining several existing modified Smith predictor structures, presented in a literature review, a generalised form of the Smith predictor is proposed. From this structure, excellent servo and regulator responses can be obtained by specifying three controller dynamic elements. Two new modified Smith predictor structures are presented with their associated tuning rules. The results of the simulations indicate that the two new designs give better overall responses than the original Smith predictor.
Comparison Of Process Identification Techniques In The Time And Frequency Domains, Tony Kealy, Aidan O'Dwyer
Comparison Of Process Identification Techniques In The Time And Frequency Domains, Tony Kealy, Aidan O'Dwyer
Conference papers
This paper describes ten methods to identify a mathematical model for a real process with a time delay. The process is the Process Trainer, PT326 from Feedback Instruments Limited. Six of the methods use step response data and one of the methods uses impulse response data for identification. Two of the methods use frequency response data and the final method uses information from relay-based experiments. The best results are obtained using a combined analytical and gradient method [6] in the frequency-domain and, in the time-domain, using the two-point algorithm [1] and a method proposed by Suganda et al. [5].
Analytical Ise Calculation And Optimum Control System Design, Tony Kealy, Aidan O'Dwyer
Analytical Ise Calculation And Optimum Control System Design, Tony Kealy, Aidan O'Dwyer
Conference papers
In control system theory, a performance index is a quantitative measure of the performance of a system and is chosen so that emphasis is given to the important system parameters. In this paper, the authors demonstrate two methods to determine analytically the ISE performance index value for a FOPDT process model under PI control. The ability of proportional/integral (PI) and proportional/integral/derivative (PID) controllers to compensate most practical industrial processes has led to their wide acceptance in industrial applications. The most direct way to set up PI/PID controller parameters is the use of tuning rules. The second part of this paper …
System Identification Using Higher Order Spectra, Aidan O'Dwyer
System Identification Using Higher Order Spectra, Aidan O'Dwyer
Conference papers
This communication will explore the use of particular types of frequency domain concepts, labelled higher order spectra, to help determine the frequency response of a process. This will allow the identification of the parameters of a single input, single output (SISO) model for a process (which includes a time delay), in both open loop and closed loop environments.
Comparison Of Open- And Closed-Loop Process Identification Techniques In The Time-Domain, Tony Kealy, Aidan O'Dwyer
Comparison Of Open- And Closed-Loop Process Identification Techniques In The Time-Domain, Tony Kealy, Aidan O'Dwyer
Conference papers
Abstract: This paper describes seven methods to identify a mathematical model for a real process with a time delay. The process is the Process Trainer, PT326 from Feedback Instruments Limited. Six of the methods use the step response data and one of the methods uses the impulse response data for identification.
Closed Loop Identification Of A First Order Plus Dead Time Process Model Under Pi Control, Tony Kealy, Aidan O'Dwyer
Closed Loop Identification Of A First Order Plus Dead Time Process Model Under Pi Control, Tony Kealy, Aidan O'Dwyer
Conference papers
Abstract -- This paper discusses the estimation of the parameters of a first order plus dead-time process model using the closed-loop step response data of the process under proportional plus integral (PI) control. The proportional gain and the integral time, in the PI controller, are chosen such that the closed-loop step response exhibits an under-damped response. From this response data, five characteristic points are used to determine a second order plus dead-time model and subsequently, the frequency response of the closed-loop system. Knowing the dynamics of the closed-loop system and the dynamics of the controller, the open-loop dynamics of the …
Multiple Model Networks In Non-Linear System Modelling For Control – A Review, Ruiyao Gao, Aidan O'Dwyer
Multiple Model Networks In Non-Linear System Modelling For Control – A Review, Ruiyao Gao, Aidan O'Dwyer
Conference papers
Non-linear processes, by their nature, are non-uniform and invariably require custom designed control schemes to deal with individual characteristics. No general theory deals comprehensively with the wide range of non-linear systems encountered. In an attempt to accurately model non-linear dynamical systems, a wide variety of techniques have been developed such as non-linear auto-regressive moving average with exogeneous inputs (NARMAX) models (Chen and Billings, 1989), Weiner models (Schetzen, 1981), Hammerstein models (Billings and Fakhouri, 1982) and Multiple Layer Perceptron (MLP) neural networks (Narendra and Kannan, 1990). While the accuracy of such models offers a potentially significant improvement over linear models, the …
Model Predictive Control Of Cstr Based On Local Model Networks, Ruiyao Gao, Aidan O'Dwyer, Eugene Dermot Coyle Professor
Model Predictive Control Of Cstr Based On Local Model Networks, Ruiyao Gao, Aidan O'Dwyer, Eugene Dermot Coyle Professor
Conference papers
A non-linear predictive controller is presented. It judiciously combines predictive controllers with a local model network utilizing a neural-network-like gating system. It avoids the time consuming quadratic optimization calculation, which is normally necessary in non-linear predictive control. A controller simulation on a Continuous Stirred Tank Reactor (CSTR) case study was shown to be satisfactory both in terms of set point tracking and regulation performance over the entire operating range. Moreover, the inherent integration action in the local predictive controller provides zero static offsets.
Closed Loop Identification Of A First Order Plus Dead-Time Process Model Under Pi Control, Tony Kealy, Aidan O'Dwyer
Closed Loop Identification Of A First Order Plus Dead-Time Process Model Under Pi Control, Tony Kealy, Aidan O'Dwyer
Conference papers
This paper discusses the estimation of the parameters of a first order plus dead-time process model using the closed-loop step response data of the process under proportional plus integral (PI) control. The proportional gain and the integral time, in the PI controller, are chosen such that the closed-loop step response exhibits an under-damped response. From this response data, five characteristic points are used to determine a second order plus dead-time model and subsequently, the frequency response of the closed-loop system. Knowing the dynamics of the closed-loop system and the dynamics of the controller, the open-loop dynamics of the process can …
Comparison Of Open And Closed Loop Process Identification Techniques In The Time Domain, Tony Kealy, Aidan O'Dwyer
Comparison Of Open And Closed Loop Process Identification Techniques In The Time Domain, Tony Kealy, Aidan O'Dwyer
Conference papers
This paper describes seven methods to identify a mathematical model for a real process with a time delay. The process is the Process Trainer, PT326 from Feedback Instruments Limited. Six of the methods use the step response data and one of the methods uses the impulse response data for identification.
Discrete-Time Velocity-Based Multiple Model Networks, Ruiyao Gao, Seamus Mcloone, Eugene Dermot Coyle Professor
Discrete-Time Velocity-Based Multiple Model Networks, Ruiyao Gao, Seamus Mcloone, Eugene Dermot Coyle Professor
Conference papers
The velocity-based local model (LM) network is a novel modelling approach that overcomes the lack of interpretability associated with the conventional LM network technique. The global dynamics of the nonlinear network are directly related to the underlying sub-model dynamics. Thus, the velocity-based network is ideally suited to the development of local controller (LC) networks. Furthermore, the local models are continuous-time, velocity-based and linear, providing continuity with established linear theory. To date, research has focused on the continuous-time version of the velocity-based network. The application of digital computer is widely popular in the field of control and, therefore, this paper develops …
A Non-Linear Pid Controller For Cstr Using Local Model Networks, Ruiyao Gao, Aidan O'Dwyer, Eugene Dermot Coyle Professor
A Non-Linear Pid Controller For Cstr Using Local Model Networks, Ruiyao Gao, Aidan O'Dwyer, Eugene Dermot Coyle Professor
Conference papers
The basic PID controllers have difficulty in dealing with problems that appear in complex non-linear processes. This paper presents a practical non-linear PID controller that deals with these non-linear difficulties. It utilises a local model (LM) network, which combines a set of local models within an artificial neural network structure, to adaptively characterise the process non-linearity. Then a local controller network is formulated through a gating system deduced from the LMN to handle the non-linearity. A continuous stirred tank reaction (CSTR) case study illustrates the practicality of this method in the modelling and control of non-linear processes. PID controllers are …
Time Delay Estimation In Signal Processing Applications: An Overview, Aidan O'Dwyer
Time Delay Estimation In Signal Processing Applications: An Overview, Aidan O'Dwyer
Conference papers
An extensive though scattered literature exists on the estimation of time delays in signal processing applications. However, it is possible to identify themes that are common to many of the available techniques. The intention of this paper is to provide a framework against which the literature may be viewed. In addition, original work on gradient based time delay estimation is described.