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Articles 31 - 60 of 94
Full-Text Articles in Controls and Control Theory
Performance Improvement Using Simple Pid Controller Tuning Formulae, Aidan O'Dwyer
Performance Improvement Using Simple Pid Controller Tuning Formulae, 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 HVDC system, 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, an induction motor drive. This tailoring of controller to process is known as controller tuning. Controller tuning is easily and effectively performed using tuning rules (i.e. formulae for controller …
Synthesising Life-Sciences And Control Engineering: An Outline Survey And A Practical Example, Aidan O'Dwyer
Synthesising Life-Sciences And Control Engineering: An Outline Survey And A Practical Example, Aidan O'Dwyer
Conference papers
There is an increasing interest in life science related areas in the electrical and control engineering community [1]. One manifestation of this interest is the development of interdisciplinary programmes, such as the B.Sc. in Medical Physics and Bioengineering, offered by the Dublin Institute of Technology from September 2005. A significant amount of research work in control engineering has focused on aspects of human physiological system, for example blood glucose regulation [2], cardiovascular modelling and control [3], and limb control [4]. There is an increasing emphasis on interdisciplinary research; in recognition of this, the Institute of Electrical Engineers (IEE) has starting …
Smith Predictor Structure Stability Analysis Using Mikhailov Stability Criterion, Pauline Sourdille, Aidan O'Dwyer, Eugene Dermot Coyle Professor
Smith Predictor Structure Stability Analysis Using Mikhailov Stability Criterion, Pauline Sourdille, Aidan O'Dwyer, Eugene Dermot Coyle Professor
Conference papers
As is well known, stability is an important requirement for control systems. Due to the nature of time-delay processes, common methods to evaluate stability may be difficult to use. In 1938, Mikhailov proved a frequency response criterion, which is sufficient and necessary for the stability of processes described by known n-th order constant coefficient linear differential equations. This paper presents the Mikhailov method and the application of this method to a Smith predictor structure controlled by a PI controller.
Pid Controller Tuning Of Networked Computer Based Control Systems, Aidan O'Dwyer
Pid Controller Tuning Of Networked Computer Based Control Systems, Aidan O'Dwyer
Conference papers
This contribution discusses the use of PID controller tuning rules to assist in the implementation of network computer based control systems. Such systems typically have a variable time delay associated with the transfer of information. PID controller tuning rules can be directly implemented with minimal capital investment.
Maintaining A Balance At Undergraduate Degree Level In The Teaching Of Automation And Classical Control Systems, Eugene Coyle, Aidan O'Dwyer
Maintaining A Balance At Undergraduate Degree Level In The Teaching Of Automation And Classical Control Systems, Eugene Coyle, Aidan O'Dwyer
Conference papers
Advances in the past decade in the development and application of Programmable Logic Controllers (PLCs) and Automation Systems in both high technology industrial plants and in the more mainstream manufacturing sectors, has heightened the importance of ensuring that undergraduate degree programme syllabi are designed to adequately cater for the teaching and training of students in automation. Prior to this growth in automation, delivered syllabi in Control Systems on most Electrical Engineering programmes had a theoretical rigour, reflecting the mathematical nature of the topic. A major challenge currently facing departmental lecturing staff and programme coordinators is that of the design of …
Modelling And Control Of A Suspension System For Vehicle Applications, Padraig Dowds, Aidan O'Dwyer
Modelling And Control Of A Suspension System For Vehicle Applications, Padraig Dowds, Aidan O'Dwyer
Conference papers
This paper discusses the modelling of passive and active suspension systems in a car, and the subsequent design of appropriate feedback controllers for the active suspension system. The models will be investigated using a quarter car model and a full car model approach.
A Reference Guide To Smith Predictor Based Methods For The Compensation Of Dead-Time Processes, Aidan O'Dwyer
A Reference Guide To Smith Predictor Based Methods For The Compensation Of Dead-Time Processes, Aidan O'Dwyer
Conference papers
An extensive literature exists on the compensation of time delayed processes. These compensation methods may be broadly divided into parameter optimised controllers, in which the controller parameters are adapted to the controller structure (the most common such controller is the proportional integral derivative, or PID, controller), and structurally optimised controllers, in which the controller structure and parameters are adapted optimally to the structure and parameters of the process model. Important structurally optimised compensator strategies are the Smith predictor and its variations. The purpose of this paper is to extract the essence of the developments in design, tuning and implementation of …
Estimation Of The Parameters Of A Delayed Process Using Open Loop Time Domain Techniques, Yue Zhang, Aidan O'Dwyer
Estimation Of The Parameters Of A Delayed Process Using Open Loop Time Domain Techniques, Yue Zhang, Aidan O'Dwyer
Conference papers
All process investigations should start by a determination of the process model. The modeling strategy used will influence the value of the model parameters, which will in turn affect the controller values determined from tuning rules. This paper will describe an analytical method to identify a model of the dynamic characteristics of a process with a delay by using a tangent and point method, as originally suggested by Murrill, 1967. The methodology has been applied to eight benchmark transfer functions suitable for testing PID controllers, as suggested by Åström and Hägglund, 2000. The main advantages of the modeling approach are …
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.
On The Empirical Balanced Truncation For Nonlinear Systems, Marissa Condon, Rossen Ivanov
On The Empirical Balanced Truncation For Nonlinear Systems, Marissa Condon, Rossen Ivanov
Articles
Novel constructions of empirical controllability and observability gramians for nonlinear systems for subsequent use in a balanced truncation style of model reduction are proposed. The new gramians are based on a generalisation of the fundamental solution for a Linear Time-Varying system. Relationships between the given gramians for nonlinear systems and the standard gramians for both Linear Time-Invariant and Linear Time-Varying systems are established as well as relationships to prior constructions proposed for empirical gramians. Application of the new gramians is illustrated through a sample test-system.
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.