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Author = Ringwood, John;
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Displaying Results 1  25 of 313 on page 1 of 13
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24h electrical load data — a sequential or partitioned time series?
(2003)
Fay, Damien; Ringwood, John; Condon, Marissa; Kelly, Michael
24h electrical load data — a sequential or partitioned time series?
(2003)
Fay, Damien; Ringwood, John; Condon, Marissa; Kelly, Michael
Abstract:
Variations in electrical load are, among other things, hour of the day dependent, introducing a dilemma for the forecaster: whether to partition the data and use a separate model for each hour of the day (the parallel approach), or use a single model (the sequential approach). This paper examines which approach is appropriate for forecasting hourly electrical load in Ireland. It is found that, with the exception of some hours of the day, the sequential approach is superior. The final solution however, uses a combination of linear sequential and parallel neural models in a multitime scale formulation.
http://mural.maynoothuniversity.ie/9504/
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24Hour Electrical Load Data  A Time Series or a Set of Independent Points?
(2001)
Fay, Damien; Ringwood, John; Condon, Marissa; Kelly, Michael
24Hour Electrical Load Data  A Time Series or a Set of Independent Points?
(2001)
Fay, Damien; Ringwood, John; Condon, Marissa; Kelly, Michael
Abstract:
The paper investigates whether a time series or a set of independent points is a more appropriate description of 24hour Irish electrical load data. A set of independent points means that the load at each hour of the day is independent from the load at any other hour. The data is first split into 24 series, one for each hour of the day i.e. a 1am 2am 3am series etc. These are called parallel series. The linear crosscorrelation's of the parallel series are used to indicate independence. While the loads at 9am and 6pm to 8pm appear independent the remaining loads are highly intercorrelated. This suggests that 24hour electrical load data has a dual nature. Two techniques are used to test this hypothesis. The first technique models each parallel series using neural networks. This technique is found to be computationally expensive. The second technique uses a hybrid technique called the Multi Time Scale (MTS) technique. This models 24hour electrical load data as a time series th...
http://mural.maynoothuniversity.ie/1967/
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3winding flyback transformer model extraction using time domain system identification
(2012)
Trong Vu, T.; Ringwood, John
3winding flyback transformer model extraction using time domain system identification
(2012)
Trong Vu, T.; Ringwood, John
Abstract:
For low frequency applications, transformer model extraction has been widely investigated using both time and frequency domain data. However, the studies for high frequency transformers have been carried out in the frequency domain only. The reason is due to the complications in acquiring time domain data for high frequency transformer model estimation. This paper presents a methodology to deal with the numerical difficulties associated with time domain data collection, and to obtain a frequencydependent model of a 3winding flyback transformer using time domain system identification techniques. The obtained transformer model is experimentally verified.
http://mural.maynoothuniversity.ie/6862/
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A 5component mathematical model for saltinduced hypertension in DahlS and DahlR rats
(2011)
McLoone, Violeta I.; Ringwood, John; Van Vliet, Bruce
A 5component mathematical model for saltinduced hypertension in DahlS and DahlR rats
(2011)
McLoone, Violeta I.; Ringwood, John; Van Vliet, Bruce
Abstract:
Saltinduced hypertension has been demonstrated in a variety of species including rats, monkeys, chimpanzees and humans. Until recently, the multiple phases of this blood pressure increase due to high salt intake had not been closely studied. This work builds upon a recent study, which developed a greyboxmulticomponent model of saltinduced hypertension in the DahlS rat. The previous 3component model has been extended here to include additional model dynamics to improve the model fit and add new important elements to the model response. The model was optimised using numerical techniques with experimental data from 4 different protocols with DahlS, DahlR and FF2 hybrid rats. Results show a marked improvement over the previous model and confirm the merit of the 5component model structure. A comparison between the model dynamics for different rat strains has also been included
http://mural.maynoothuniversity.ie/3862/
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A 5component model for saltinduced hypertension
(2009)
McLoone, Violeta I.; Ringwood, John; Van Vliet, Bruce
A 5component model for saltinduced hypertension
(2009)
McLoone, Violeta I.; Ringwood, John; Van Vliet, Bruce
Abstract:
Saltinduced hypertension has been widely studied in rats, monkeys, chimpanzees and humans. Until recently, the multiple phases of this blood pressure increase to high salt intake had not been closely studied. This work builds upon a recent study, which developed a greybox multicomponent model of saltinduced hypertension in the DahlS rat. The previous 3component model has been extended here to include additional model dynamics to improve the model fit and add new important elements to the model response. The model was optimised using numerical techniques with experimental data from 4 different protocols with DahlS and hybrid rats. Results show a marked improvement over the previous model and confirm the merit of the 5component model structure.
http://mural.maynoothuniversity.ie/2128/
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A 5component model for saltinduced hypertension in DahlS and DahlR rats
(2011)
McLoone, Violeta I.; Ringwood, John; Van Vliet, Bruce
A 5component model for saltinduced hypertension in DahlS and DahlR rats
(2011)
McLoone, Violeta I.; Ringwood, John; Van Vliet, Bruce
Abstract:
Saltinduced hypertension has been demonstrated in a variety of species including rats, monkeys, chimpanzees and humans. Until recently, the multiple phases of this blood pressure increase due to high salt intake had not been closely studied. This work builds upon a recent study, which developed a greybox multicomponent model of saltinduced hypertension in the DahlS rat. The previous 3component model has been extended here to include additional model dynamics to improve the model fit and add new important elements to the model response. The model was optimised using numerical techniques with experimental data from 4 different protocols with DahlS, DahlR and FF2 hybrid rats. Results show a marked improvement over the previous model and confirm the merit of the 5component model structure. A comparison between the model dynamics for different rat strains has also been included.
http://mural.maynoothuniversity.ie/9474/
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A class of globally stabilising controllers for the control of wave energy devices for potable water production
(2012)
Lekka, Angeliki; Turner, Mathew C.; Ringwood, John
A class of globally stabilising controllers for the control of wave energy devices for potable water production
(2012)
Lekka, Angeliki; Turner, Mathew C.; Ringwood, John
Abstract:
This paper provides a stability analysis for a system that captures wave energy in order to produce potable water. The system, introduced in [1], is a Wave Energy Converter (WEC) of the pointabsorber type coupled to a hydraulic Power TakeOff (PTO) that converts wave energy into pressure. Previous work has used a partial statefeedback controller with integral action and feedforward to provide good nominal control behaviour. Although openloop stability was proven in [1], no guarantees of closedloop stability were given; in this paper we provide such guarantees for a class of controllers, of which the controller proposed in [1] is a special case.
http://mural.maynoothuniversity.ie/4412/
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A classification of techniques for the compensation of time delayed processes. Part 2. Structurally optimised controllers
(1999)
O'Dwyer, Aidan; Ringwood, John
A classification of techniques for the compensation of time delayed processes. Part 2. Structurally optimised controllers
(1999)
O'Dwyer, Aidan; Ringwood, John
Abstract:
Structurally optimised controllers are those in which the controller structure and parameters are adapted optimally to the structure and parameters of the process model [1, 2]. A classification of such controllers for time delay processes is provided.
http://mural.maynoothuniversity.ie/9516/
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A classification of techniques for the compensation of time delayed processes. Part 1: Parameter optimised controllers
(1999)
O'Dwyer, Aidan; Ringwood, John
A classification of techniques for the compensation of time delayed processes. Part 1: Parameter optimised controllers
(1999)
O'Dwyer, Aidan; Ringwood, John
Abstract:
An extensive literature exists on the compensation of time delayed processes. It is possible to identify themes that are common to many of the available techniques. The intention of the two parts of this paper is to provide a framework against which the literature may be viewed; Part 1 of the paper considers the use of parameter optimised controllers for the compensation problem, with Part 2 of the paper considering the use of structurally optimised compensators. Conclusions are drawn at the end of Part 2.
https://arrow.dit.ie/engscheleart/56
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A classification of techniques for the compensation of time delayed processes. Part 1. Parameter optimised controllers
(1999)
O'Dwyer, Aidan; Ringwood, John
A classification of techniques for the compensation of time delayed processes. Part 1. Parameter optimised controllers
(1999)
O'Dwyer, Aidan; Ringwood, John
Abstract:
Modern Applied Mathematical Techniques in Circuits, Systems An extensive literature exists on the compensation of time delayed processes. It is possible to identify themes that are common to many of the available techniques. The intention of the two parts of this paper is to provide a framework against which the literature may be viewed; Part 1 of the paper considers the use of parameter optimised controllers for the compensation problem, with Part 2 of the paper considering the use of structurally optimised compensators. Conclusions are drawn at the end of Part 2.
http://mural.maynoothuniversity.ie/9514/
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A classification of techniques for the compensation of time delayed processes. Part 2: Structurally optimised controllers
(1999)
O'Dwyer, Aidan; Ringwood, John
A classification of techniques for the compensation of time delayed processes. Part 2: Structurally optimised controllers
(1999)
O'Dwyer, Aidan; Ringwood, John
Abstract:
Following on from Part 1, Part 2 of the paper considers the use of structurally optimised controllers to compensate time delayed processes.
https://arrow.dit.ie/engscheleart/62
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A Compact 6DoF Nonlinear Wave Energy Device Model for Power Assessment and Control Investigations
(2019)
Giorgi, Giuseppe; Ringwood, John
A Compact 6DoF Nonlinear Wave Energy Device Model for Power Assessment and Control Investigations
(2019)
Giorgi, Giuseppe; Ringwood, John
Abstract:
High accuracy at a low computational time is likely to be a fundamental trait for mathematical models for wave energy converters, in order to be effective tools for reliable motion prediction and power production assessment, device and controller design, and loads estimation. Wave energy converters are particularly prone to exhibit complex and nonlinear behaviours, which are difficult to be modelled efficiently. Highlynonlinear effects, related to nonlinear FroudeKrylov forces, are nonlinear coupling, instability, and parametric resonance, which may damage or improve the power production. It is therefore fundamental to be able to describe such nonlinearities, in order to assess their repercussion on the performance of the device, and eventually design the system in order to exploit them. This paper provides a computationally efficient, compact, and flexible modelling approach for describing nonlinear Froude Krylov forces for axisymmetric wave energy devices, in 6 degrees of freedo...
http://mural.maynoothuniversity.ie/12443/
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A comparative study of delta and zbased output feedback pole placement adaptive controllers
(1995)
Flynn, M.; Ringwood, John
A comparative study of delta and zbased output feedback pole placement adaptive controllers
(1995)
Flynn, M.; Ringwood, John
Abstract:
This paper selects a popular zdomain adaptive controller based on output feedback pole placement, utilising recursive least squares for system identification. The adaptive algorithm is recast in the deltadomain with a corresponding reformulation of the identification algorithm. Simulation results, incorporating finite wordlength effects, are convincingly used to demonstrate the improvement in the delta formulation, when smaller wordlengths are used. Small word lengths are a feature of most popular industrial controllers. In addition, a pilotscale rig is used as an application example to demonstrate the effectiveness of the delta controller in reallife implementation. The paper concludes by comparing and contrasting the z and deltacontrollers not only in performance terms but also in terms of design complexity, intuitive appeal and cost benefits.
http://mural.maynoothuniversity.ie/9532/
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A comparison of linear and neural parallel time series models for shortterm load forecasting in the Republic of Ireland
(2000)
Fay, Damien; Ringwood, John; Condon, Marissa; Kelly, Michael
A comparison of linear and neural parallel time series models for shortterm load forecasting in the Republic of Ireland
(2000)
Fay, Damien; Ringwood, John; Condon, Marissa; Kelly, Michael
Abstract:
This paper presents a comparison between parallel linear and parallel neural network models. Parallel models consist of 24 separate models, one for each hour of the day. Each parallel model decomposes the load into a linear Auto Regressive (AR) part and a residual. Exogenous linear and neural network model performance is compared in predicting this residual. Three days or 72 hours of current and delayed weather variables are available as exogenous inputs for the residual models. Input selection comprises of testing the bootstrapped performance of a linear model. The inputs are ordered using 4 methods derived from a mix of the Tratio of the linear coefficients and Principal Component Analysis (PCA). The neural network models are found to give superior results due to the nonlinear AR nature of the residual
http://mural.maynoothuniversity.ie/1913/
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A competition for WEC control systems
(2017)
Ringwood, John; Ferri, Francesco; Ruehl, Kelley M.; Yu, YiHsiang; Coe, Ryan G.; Bacell...
A competition for WEC control systems
(2017)
Ringwood, John; Ferri, Francesco; Ruehl, Kelley M.; Yu, YiHsiang; Coe, Ryan G.; Bacelli, Giorgio; Weber, Jochem; Kramer, Morten
Abstract:
This paper outlines a proposed open competition which will compare energymaximising controllers for wave energy converters (WECs), both in simulation, and in real time,using a scale device in a tank test situation. To date, a wide variety of WEC control algorithms have been proposed, but have been difficult to compare due to differences in the simulation/scale models they are evaluated on, the range of incident sea states employed, and the reliance to a greater or lesser extent on wave or excitation force forecasts. In addition, most WEC control algorithms have been evaluated only in simulation, which masks the realtime computational capability, as well as the degree to which the modelbased controllers are robust to WEC modelling errors, since the controllers are predominantly evaluated with a WEC simulation model identical to that upon which the controller is based.This paper describes the format of a proposed WEC control com...
http://mural.maynoothuniversity.ie/12455/
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A computational tool for evaluating the economics of solar and wind microgeneration of electricity
(2009)
Kelleher, J.; Ringwood, John
A computational tool for evaluating the economics of solar and wind microgeneration of electricity
(2009)
Kelleher, J.; Ringwood, John
Abstract:
This paper presents a method, implemented as a freely available computer programme, which is used to estimate the economics of renewable microgeneration of electricity from wind and solar energy sources. A variety of commercial small wind turbines and photovoltaic (PV) panels are considered and combined with raw energy data gathered from a variety of locations. Both residential and holiday home user profiles are available and options are selectable concerning feedin tariffs (if available), government incentive schemes and the cost of capital borrowing. The configuration of the generation setup, which can consist of wind, PV and combination of wind/PV, is fully selectable by the user, with a range of appropriate default data provided. A numerical example, based on Irish data, is presented, which suggests that payback periods for solar and wind microgeneration systems can vary greatly (2.5–500 years), depending on the location, installation and economic variables.
http://mural.maynoothuniversity.ie/2766/
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A control system for a selfreacting point absorber wave energy converter subject to constraints
(2011)
Bacelli, Giorgio; Ringwood, John; Gilloteaux, JeanChristophe
A control system for a selfreacting point absorber wave energy converter subject to constraints
(2011)
Bacelli, Giorgio; Ringwood, John; Gilloteaux, JeanChristophe
Abstract:
The problem of the maximization of the energy produced by a self reacting point absorber subject to motion restriction is addressed. The main objective is to design a control system suitable for realtime implementation. The method presented for the solution of the optimization problem is based on the approximation of the motion of the device and of the force exerted by the power take off unit by means of a linear combination of basis functions. The result is that the optimal control problem is reformulated as a non linear program where the properties of the cost function and of the constraint are affected by the choice of the basis functions. An example is described where the motion and the force are approximated using Fourier series; an optimization algorithm for the solution of the non linear program is also presented. The control system is implemented and simulated using a real sea profile measured by a waverider buoy.
http://mural.maynoothuniversity.ie/3555/
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A Critical Comparison of AR and ARMA Models for Shortterm Wave Forecasting
(2017)
PeñaSanchez, Yerai; Ringwood, John
A Critical Comparison of AR and ARMA Models for Shortterm Wave Forecasting
(2017)
PeñaSanchez, Yerai; Ringwood, John
Abstract:
In order to extract as much energy as possible from ocean waves, an optimal control must be implemented in a wave energy converter (WEC), which requires the knowledge of the future incident waves (η). One of the most used methods to predict the future η, is to use a linear combination of past η values. Several models can be found in the literature, but only two of these models are compared in this paper, the autoregressive (AR) and autoregressive moving average (ARMA) models. Real wave data from different locations is used to determine which model is the best and in which scenario. This comparison addresses the discrepancies between [1], where the ARMA model is discarded for showing no improvement against the AR, and [2], which states that the ARMA model does improve the AR. The present paper shows that the two models achieve a similar performance for all the different conditions analysed. Thus, due to the simplicity and the lower computational requirement, the AR model is chosen as...
http://mural.maynoothuniversity.ie/12461/
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A critical comparison of modelpredictive and pseudospectral control for wave energy devices
(2016)
Genest, Romain; Ringwood, John
A critical comparison of modelpredictive and pseudospectral control for wave energy devices
(2016)
Genest, Romain; Ringwood, John
Abstract:
Model predictive control (MPC) and pseudospectral optimal control (PSC) have been proposed over the past decade to maximise energy capture for wave energy devices. Both philosophies share a similar cost function and both can deal with constraints on system (displacement, velocity)and control (force) variables. Recently, a receding horizon version of the PSC method (RHPSC) has been developed, permitting a direct comparison between MPC and RHPSC formulations. This paper demonstrates that while the control objectives are very similar, the numerical properties of both algorithms are quite different, having implications for practical use, both in terms of performance and implementation issues.
http://mural.maynoothuniversity.ie/12471/
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A demonstration rig for control systems based on the ballandbeam with vision feedback
(1994)
Whelan, J.; Ringwood, John
A demonstration rig for control systems based on the ballandbeam with vision feedback
(1994)
Whelan, J.; Ringwood, John
Abstract:
This paper describes a rig based on the ballandbeam apparatus which has been used to effectively demonstrate the power of electronic control systems. Though the controller employs some complex electronic systems, its operation closely mimics that of a human performing the same action, and is therefore easily understood. This is achieves through measurement of the ball position and velocity states using a machine vision system.
http://mural.maynoothuniversity.ie/9540/
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A feasibility study into prognostics for the main bearing of a wind turbine
(2012)
Butler, S.; O'Connor, F.; Farran, D.; Ringwood, John
A feasibility study into prognostics for the main bearing of a wind turbine
(2012)
Butler, S.; O'Connor, F.; Farran, D.; Ringwood, John
Abstract:
Maintenance for wind turbines, particularly offshore turbines, presents a significant cost component to wind farm operators. The main bearing, which supports the lowspeed shaft, is one of the major wind turbine system components. Since maintenance is confined to suitable weather windows, which are unpredictable, there is a need for decision support tools to ensure that maintenance is carried out in a timely way, but also at minimum cost and with minimum turbine downtime. This paper presents a methodology for the estimation of the remaining useful life (RUL) of the main bearing for a commercial wind turbine. A residual model is used to highlight potentially faulty behaviour, which is then post processed to provide a suitable signal for extrapolation using particle filters. The RUL is then effectively specified as a probability distribution which narrows as the failure point is approached, providing an estimate of RUL and a confidence measure. Our results suggest that RULs beyond 30 d...
http://mural.maynoothuniversity.ie/6870/
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A feasibility study into the robust control of a variablefrequency wide operating range flyback converter
(2014)
Trong Vu, T.; O'Driscoll, S.; Ringwood, John
A feasibility study into the robust control of a variablefrequency wide operating range flyback converter
(2014)
Trong Vu, T.; O'Driscoll, S.; Ringwood, John
Abstract:
Modelling and design of a robust controller for fixedfrequency PWM DC toDC power converters are wellknown problems and have been intensively investigated in the literature. However, none of the existing studies considers the variablefrequency applications recently employed to improve efficiency. This paper focuses on synthesizing a robust compensator for a variablefrequency, wide operating range, flyback converter using the H1 framework. The simulation results show that it is possible to design a single controller that can preserve stability over the whole working range of the converter, but robust performance may be compromised.
http://mural.maynoothuniversity.ie/6777/
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A final year undergraduate digital control laboratory assignment
(1994)
Ringwood, John; McCorkell, C.; Whelan, J.
A final year undergraduate digital control laboratory assignment
(1994)
Ringwood, John; McCorkell, C.; Whelan, J.
Abstract:
This paper describes a positive experience with a digital control assignment used in the BEng in Electronic Engineering course at Dublin City University (DCU). The objective of the assignment is to give the student considerable freedom in tackling a 'realworld' problem, involving modelling, control system design and implementation. Support is provided through documentation, a standard hardware/software platform, control system CAD tools and tutorials. The rig used is a fully instrumented coupled tanks apparatus. Completion of the assignment gives students a sense of confidence in tackling other practical, unknown problems, and gives them the sense of being true 'realworld' engineers.
http://mural.maynoothuniversity.ie/9541/
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A flexible electronic controller for a manipulatortype robot
(1991)
Gibbs, Patrick J.; Jones, F.; Ringwood, John
A flexible electronic controller for a manipulatortype robot
(1991)
Gibbs, Patrick J.; Jones, F.; Ringwood, John
Abstract:
Manipulator arm construction has changed little over the decades and is unlikely to change radically in the near future. The mechanical design necessary to achieve dexterity results in a system with complex dynamic properties. However, many manipulator manufacturers choose to ignore this complexity, concentrating on the mechanical design aspects rather than the design of the dynamic controller. In most cases, simple fixedparameter singleloop PID compensators are utilised. In spite of the fact that the compensators are implemented on programmable devices, there is simply not enough processing power available to implement an improved dynamic control strategy. A multiprocessor controller has been developed which allows all the hierarchical levels of a manipulator controller to be implemented. The major advantage of the new controller is its ability to handle complex and time consuming dynamic algorithms for positioning of the robot end effector. This has been accomplished by adopting...
http://mural.maynoothuniversity.ie/9562/
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A frequency domain based selftuning PID controller
(1994)
Ringwood, John; O'Dwyer, Aidan
A frequency domain based selftuning PID controller
(1994)
Ringwood, John; O'Dwyer, Aidan
Abstract:
Traditionally, both explicit and implicit selftuning controllers have employed time domain techniques for the identification and tracking of plant and controller parameters. The use of the frequency domain provides concise information on the dynamics of the process which has led to its wide acceptance as a domain for controller design. This paper demonstrates a method employing recursive, online measurement of the process frequency response, with a straightforward calculation of PID controller parameters. The computational effort involved is comparable with that of a time domain technique.
https://arrow.dit.ie/engscheleart/52
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