Institutions

About Us

Help

Gaeilge
0
1000
Home
Browse
Advanced Search
Search History
Marked List
Statistics
A
A
A
Author(s)
Institution
Publication types
Funder
Year
Limited By:
Subject = optimal control;
11 items found
Sort by
Title
Author
Item type
Date
Institution
Peer review status
Language
Order
Ascending
Descending
25
50
100
per page
Bibtex
CSV
EndNote
RefWorks
RIS
XML
Displaying Results 1  11 of 11 on page 1 of 1
Marked
Mark
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/
Marked
Mark
Enhancement of the wave energy conversion characteristics of a hinge barge using pseudospectral control
(2016)
Paparella, Francesco; Ringwood, John
Enhancement of the wave energy conversion characteristics of a hinge barge using pseudospectral control
(2016)
Paparella, Francesco; Ringwood, John
Abstract:
This paper shows the benefits of using pseudospectral (PS) methods for the optimal control of a threebody hingebarge device. Two different control formulations are derived based on different representations of the dynamic model of the device: the differential and algebraic equations (DAE) formulation, and the ordinary differential equations (ODE) formulation. Wavetank tests are carried out in order to validate the DAE and ODE models against experimental data. For control design, PS methods show significant improvements in terms of absorbed power with respect to an optimal damping strategy.
http://mural.maynoothuniversity.ie/9412/
Marked
Mark
Input Disturbance Rejection in Channel SignaltoNoise Ratio Constrained Feedback Control
(2008)
Rojas, A.J.; Middleton, R.H.; Freudenberg, J.S.; Braslavsky, J.H.
Input Disturbance Rejection in Channel SignaltoNoise Ratio Constrained Feedback Control
(2008)
Rojas, A.J.; Middleton, R.H.; Freudenberg, J.S.; Braslavsky, J.H.
Abstract:
Communication channels impose a number of obstacles to feedback control. One recent line of work considers the problem of feedback stabilisation subject to a constraint on the channel signaltonoise ratio (SNR). It has been shown for continuoustime systems that the optimal control problem of achieving the infimal SNR can be formulated as a linear quadratic Gaussian (LQG) control problem with weights chosen as in the loop transfer recovery (LTR) technique. The present paper extends this formulation to: discretetime systems; communications over channels with memory; and input disturbance rejection. By using this formulation, we derive exact expressions for the linear time invariant (LTI) controller that achieves the infimal SNR under the effect of timedelay and additive coloured noise. We then quantify the infimal SNR required for both stabilisation and input disturbance rejection for a relative degree one, minimum phase plant and a memoryless Gaussian channel.
http://mural.maynoothuniversity.ie/2245/
Marked
Mark
Optimal control, MPC and MPClike algorithms for wave energy systems: An overview
(2017)
Faedo, Nicolás; Olaya, Sébastien; Ringwood, John
Optimal control, MPC and MPClike algorithms for wave energy systems: An overview
(2017)
Faedo, Nicolás; Olaya, Sébastien; Ringwood, John
Abstract:
Model predictive control (MPC) has achieved considerable success in the process industries, with its ability to deal with linear and nonlinear models, while observing system constraints and considering future behaviour. Given these characteristics, against the backdrop of the energy maximising control problem for Wave Energy Converters (WECs), with physical constraints on system variables and a noncausal optimal control solution it is, perhaps, natural to consider the application of MPC to the WEC problem. However, the WEC energy maximisation problem requires a significant modification of the traditional MPC objective function, resulting in a potentially nonconvex optimisation problem. A variety of MPC formulations for WECs have been proposed, with variations in the WEC model, discretisation method, objective function and optimisation algorithm employed. This paper attempts to provide a critical comparison of the various WEC MPC algorithms, while also presenting WEC MPC algorithms...
http://mural.maynoothuniversity.ie/12454/
Marked
Mark
Optimal metabolic regulation by temporal variation of enzyme activities: a control theoretic approach
(2007)
Oyarzun, Diego; Ingalls, Brian; Kalamatianos, Dimitrios
Optimal metabolic regulation by temporal variation of enzyme activities: a control theoretic approach
(2007)
Oyarzun, Diego; Ingalls, Brian; Kalamatianos, Dimitrios
Abstract:
In this paper we use an optimal control approach to analyze time dependent enzyme concentrations that minimize the transition time of a metabolic pathway while respecting the natural constraints imposed by a limited biosynthetical capacity. Our main result states that, under appropriate assumptions, at each time instant all the available enzyme production capacity is allocated to a single reaction, a finding reminiscent of bangbang control laws typical in classical timeoptimal control.
http://mural.maynoothuniversity.ie/2119/
Marked
Mark
Optimal Signal to Noise Ratio in Feedback over Communication Channels with Memory
(2006)
Rojas, A.J.; Freudenberg, J.S.; Braslavsky, J.H.; Middleton, R.H.
Optimal Signal to Noise Ratio in Feedback over Communication Channels with Memory
(2006)
Rojas, A.J.; Freudenberg, J.S.; Braslavsky, J.H.; Middleton, R.H.
Abstract:
Communication channels impose a number of obstacles to feedback control, such as delay, noise, and constraints in communication datarate. One alternate line of recent work considers the problem of feedback stabilization subject to a constraint in the signaltonoise ratio (SNR). It has been shown for continuoustime systems that the optimal control problem arising in achieving minimal SNR can be formulated as a linear quadratic Gaussian (LQG) control problem with weights chosen as in the loop transfer recovery (LTR) technique. The present paper extends such LQG/LTR formulation to discretetime systems with feedback over channels with memory. By using such formulation, we derive exact expressions for the LTI controller and loop sensitivity functions that achieve minimal SNR under the effect of timedelay, non minimum phase zeros and colored additive noise. For the minimumphase case with white noise and no time delay, we show that the optimal feedback loop obtained after applying LTR...
http://mural.maynoothuniversity.ie/1789/
Marked
Mark
Receding horizon pseudospectral optimal control for wave energy conversion
(2016)
Genest, Romain; Ringwood, John
Receding horizon pseudospectral optimal control for wave energy conversion
(2016)
Genest, Romain; Ringwood, John
Abstract:
The present study introduces a realtime control algorithm for applications involving energy maximisation and subject to technological limitations. Development of Wave energy converters constitutes an actual topic of research, in their designs and fluidinteractions, and particularly on their controllability. Immersed WECs are subject to fluidinteraction forces, generating unusual solicitations specific to hydrodynamic equation, such as radiation force or excitation forces. Various control strategies were recently developed and more advance control algorithms are currently applied on WECS, such as Model Predictive Control [1], or Pseudospectral optimal control [2]. Such control strategies, capable of maximizing the energy production while insuring the respect of path constraints, are more realistic and applicable in real conditions involving technological limitation aspects. This paper presents a receding horizon type control, based on pseudospectral approach in the control problem...
http://mural.maynoothuniversity.ie/9414/
Marked
Mark
RecedingHorizon Pseudospectral Control of Wave Energy Converters Using Periodic Basis Functions
(2018)
Auger, Clément; Mérigaud, Alexis; Ringwood, John
RecedingHorizon Pseudospectral Control of Wave Energy Converters Using Periodic Basis Functions
(2018)
Auger, Clément; Mérigaud, Alexis; Ringwood, John
Abstract:
Powermaximising control of wave energy converters (WECs) can be implemented within a recedinghorizon (RH) framework, whereby the reference force or velocity trajectory is updated in realtime by a feedforward control (FFC) algorithm. For the computation of optimal WEC trajectories and control forces, Fourier pseudospectral (PS) control, using periodic basis functions, is simple and computationally attractive, for both linear and nonlinear WEC dynamics. However, the finitelength wave excitation signal, as seen by the FFC, is in general nonperiodic. In this paper, it is shown that, despite the nonperiodicity of the input wave signal, a simple Fourier PS method can be successfully used as a FFC algorithm, by applying suitable windowing functions to the input signal when necessary. Furthermore, a simple wave forecasting algorithm is introduced, solely based on past values of the wave excitation, and the impact of wave forecast errors on the controller performance is investigated. ...
http://mural.maynoothuniversity.ie/12417/
Marked
Mark
State estimation for anaerobic digesters using the ADM1
(2012)
Gaida, Daniel; Wolf, Christian; Meyer, C.; Stuhlsatz, A.; Lippel, J.; Back, Thomas; Bon...
State estimation for anaerobic digesters using the ADM1
(2012)
Gaida, Daniel; Wolf, Christian; Meyer, C.; Stuhlsatz, A.; Lippel, J.; Back, Thomas; Bongards, Michael; McLoone, Sean F.
Abstract:
The optimization of fullscale biogas plant operation is of great importance to make biomass a competitive source of renewable energy. The implementation of innovative controi and optimization algorithms, such as Nonlinear Model Predictive Control, requires an online estimation of operating states of biogas plants. This state estimation allows for optimal control and operating decisions according to the actual state of a plant. In this paper such a state estimator is developed using a calibrated simulation model of a fullscale biogas plant, which is based on the Anaerobic Digestion Model N0.1. The use of advanced pattern recognition methods shows that model states can be predicted from basic online measurements such as biogas production, CH4 and CO2 content in the biogas, pH value and substrate feed volume of known substrates. The machine learning methods used are trained and evaluated using synthetic data created with the biogas plant model simulating over a wide range of possible...
http://mural.maynoothuniversity.ie/4152/
Marked
Mark
Suboptimal triangular controller design methodology for full MIMO stable systems
(2006)
Oyarzún, Diego A.; Salgado, Mario E.
Suboptimal triangular controller design methodology for full MIMO stable systems
(2006)
Oyarzún, Diego A.; Salgado, Mario E.
Abstract:
This paper proposes a design methodology of triangular controllers for full MIMO stable plants. The procedure is based on an optimal design for a triangular model of the plant. Stability and appropriate performance can be achieved by adjusting a set of design parameters involved in a weighting function. The resulting controller provides integration and can be computed analytically.
http://mural.maynoothuniversity.ie/1784/
Marked
Mark
Towards realistic nonlinear recedinghorizon spectral control of wave energy converters
(2018)
Mérigaud, Alexis; Ringwood, John
Towards realistic nonlinear recedinghorizon spectral control of wave energy converters
(2018)
Mérigaud, Alexis; Ringwood, John
Abstract:
Nonlinear, powermaximising control of wave energy converters (WECs) can be achieved within a recedinghorizon control framework, whereby an upper loop calculates a reference trajectory in realtime, ensuring maximal power absorption under operational constraints, while a tracking loop drives the device along the generated trajectory. This paper articulates the four fundamental components of such a control strategy: reference generation calculations, tracking loop, and wave excitation estimation and forecasting. The upperloop optimisation problem is efficiently solved through a Fourier spectral method, taking into account nonlinear dynamics and constraints. Tracking is achieved through a linear state feedback, combined with a nonlinear feedforward term. An extended Kalman filter is used for excitation force estimation, based on noisy WEC position and acceleration measurements. Finally, wave excitation forecasts are based on a linear predictor, whose coefficients are derived fro...
http://mural.maynoothuniversity.ie/12545/
Displaying Results 1  11 of 11 on page 1 of 1
Bibtex
CSV
EndNote
RefWorks
RIS
XML
Item Type
Book chapter (3)
Conference item (1)
Journal article (7)
Year
2018 (2)
2017 (2)
2016 (2)
2012 (1)
2008 (1)
2007 (1)
2006 (2)
built by Enovation Solutions