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Author = Bacelli, Giorgio;
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Displaying Results 1  23 of 23 on page 1 of 1
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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 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 geometric tool for the analysis of position and force constraints in wave energy converters
(2013)
Bacelli, Giorgio; Ringwood, John
A geometric tool for the analysis of position and force constraints in wave energy converters
(2013)
Bacelli, Giorgio; Ringwood, John
Abstract:
Most wave energy devices are subject to finite constraints on both the power takeoff (PTO) stroke length and the maximum force that the PTO can tolerate. It is also often the case that greater stroke lengths can reduce the maximum force in the PTO and vice versa. Ultimately, some informed choice of PTO constraints must be made in order to ensure that PTO constraints are not violated and that the tradeoff between position and force constraints is made in such as way that maximum energy is captured by the converter. This paper presents a tool to allow device developers to check the satisfaction of constraints for a given hydrodynamic model and set of sea conditions and, where constraints are not satisfied, shows how to relax the constraints to maximize energy capture. The tool is algebraic, requiring no simulation and the results are presented through intuitive geometrical constructs. Sample application results are presented for single and twobody wave energy systems.
http://mural.maynoothuniversity.ie/6853/
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A Geometrical Interpretation of Force and Position Constraints in the Optimal Control of Wave Energy Devices
(2011)
Bacelli, Giorgio; Ringwood, John
A Geometrical Interpretation of Force and Position Constraints in the Optimal Control of Wave Energy Devices
(2011)
Bacelli, Giorgio; Ringwood, John
Abstract:
Physical constraints need to be considered in the design of control systems for an oscillating body Wave Energy Converter (WEC). In the case of a hydraulic Power Take Off (PTO) unit, such constraints include the length of the stroke of a hydraulic piston or the maximum pressure permitted in the hydraulic circuit. In the paper, two types of WEC are considered: A 1body point absorber oscillating in heave and a 2body point absorber also oscillating in heave. A procedure for the analysis of the constraints is presented. It provides sufficient conditions for the satisfaction of both constraints and/or the violation of at least one constraint. The procedure is based on the discretization of the equations of motion of the WECs by approximating the forces and the velocities with a linear combination of basis functions. A special case is presented in which truncated Fourier series are used for the approximation. It is shown that the constraints can be interpreted as a geometrical object in...
http://mural.maynoothuniversity.ie/3549/
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A nonlinear potential model to predict largeamplitudesmotions: application to a multibody wave energy converter.
(2008)
Gilloteaux, JeanChristophe; Bacelli, Giorgio; Ringwood, John
A nonlinear potential model to predict largeamplitudesmotions: application to a multibody wave energy converter.
(2008)
Gilloteaux, JeanChristophe; Bacelli, Giorgio; Ringwood, John
Abstract:
The paper is dedicated to the study of nonlinear waves acting on three dimensional surfacepiercing structures. A timedomain nonlinear potentialflow model has been developed to predict the largeamplitude motions of devices in a prescribed seaway. While earlier models have been developed for single wave energy devices, this paper addresses multibody devices, with particular application to the WAVEBOB wave energy device.
http://mural.maynoothuniversity.ie/4417/
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A predictive controller for a heaving buoy producing potable water
(2009)
Bacelli, Giorgio; Gilloteaux, JeanChristophe; Ringwood, John
A predictive controller for a heaving buoy producing potable water
(2009)
Bacelli, Giorgio; Gilloteaux, JeanChristophe; Ringwood, John
Abstract:
A model predictive controller for a wavepowered desalination unit is presented. The desalination unit is composed of a reverse osmosis membrane, and the water is pumped at high pressure through the membrane by a wave energy converter. The wave energy converter is a heaving buoy type connected to an hydraulic circuit that converts the oscillating motion of the buoy into a rectified seawater flow at high pressure. The controller acts on a throttle valve to regulate the pressure in the reverse osmosis unit in order to avoid damage to the membrane caused by excessive pressure and to improve both its longevity and the overall efficiency of the device. The control is constrained due to the rate and position limits of the throttle valve and the recovery ratio, which is the ratio between the total amount of pumped seawater and the potable water. The system is also switched and nonstationary because of the check valves used for the rectification of the seawater flow and the variat...
http://mural.maynoothuniversity.ie/2129/
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Constrained control of arrays of wave energy devices.
(2013)
Bacelli, Giorgio; Ringwood, John
Constrained control of arrays of wave energy devices.
(2013)
Bacelli, Giorgio; Ringwood, John
Abstract:
It is well known in the literature that the total absorbed energy of a farm of wave energy converter depends, within a wide range of variability, on the hydrodynamic interaction between the individual devices. Several studies have addressed the problem of controlling the wave energy converters so as to exploit the positive interaction between the devices in order to increase the total amount of absorbed energy. This paper studies two types of control systems for array of wave energy converters: the first is similar to the classical optimal control which uses the complete (linear) hydrodynamic model of the array and information about the status (velocity) of the other devices, while the second is a suboptimal control systems which calculates the optimal motion while neglecting completely the interaction between the devices. Most importantly the comparison is carried out considering the effects of constraints on the maximum allowed oscillation amplitude and PTO force
http://mural.maynoothuniversity.ie/6799/
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Control Strategies for Arrays of Wave Energy Devices
(2011)
Westphalen, J.; Bacelli, Giorgio; Balitsky, Philip; Ringwood, John
Control Strategies for Arrays of Wave Energy Devices
(2011)
Westphalen, J.; Bacelli, Giorgio; Balitsky, Philip; Ringwood, John
Abstract:
In this paper, we investigate the differences between two control strategies for a twodevice linear array of wave energy converters (WEC) for device spacings of 4 to 80 times the device diameter. The WECs operate in heave only and are controlled in real time. The control strategies, called the independent device and global array control, estimate the excitation forces and calculate the optimum vertical velocity trajectory and reactive power take off force to achieve the velocity for a given sea state. The independent device controller assumes that each device is in isolation and only computes the excitation forces based on the incident wave, whereas the global array controller does take the radiation and diffraction effects from the other devices into account. Whatever controller is used in the simulations, all hydrodynamic coupling effects are accounted for. For a cylindrically shaped singlebody device with diameter of 5 m and a draught of 25 m we simulate the device motions for ...
http://mural.maynoothuniversity.ie/3547/
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ControlInfluenced Layout Optimization of Arrays of Wave Energy Converters
(2014)
Balitsky, Philip; Bacelli, Giorgio; Ringwood, John
ControlInfluenced Layout Optimization of Arrays of Wave Energy Converters
(2014)
Balitsky, Philip; Bacelli, Giorgio; Ringwood, John
Abstract:
In this paper we compare the optimal configurations for an array of WECs given two control schemes, a realtime global control and a passive seastate based tuning scheme. In a particular wave climate and array orientation with its axis normal to the prevailing wave direction, closelyspaced symmetrical arrays of 2, 3, 4, 5, and 6 cylinders of different radiative properties are simulated for varying interdevice separation distances. For each device and control type, we focus on the factors that influence the optimal layout, including number of devices, separating distance and angular spreading. The average annual power output is calculated for each optimal configuration.
http://mural.maynoothuniversity.ie/9448/
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ControlInformed Geometric Optimization of Wave Energy Converters: The Impact of Device Motion and Force Constraints
(2015)
GarciaRosa, Paula B.; Bacelli, Giorgio; Ringwood, John
ControlInformed Geometric Optimization of Wave Energy Converters: The Impact of Device Motion and Force Constraints
(2015)
GarciaRosa, Paula B.; Bacelli, Giorgio; Ringwood, John
Abstract:
The energy cost for producing electricity via wave energy converters (WECs) is still not competitive with other renewable energy sources, especially wind energy. It is well known that energy maximising control plays an important role to improve the performance of WECs, allowing the energy conversion to be performed as economically as possible. The control strategies are usually subsequently employed on a device that was designed and optimized in the absence of control for the prevailing sea conditions in a particular location. If an optimal unconstrained control strategy, such as pseudospectral optimal control (PSOC), is adopted, an overall optimized system can be obtained no matter whether the control design is incorporated at the geometry optimization stage or not. Nonetheless, strategies, such as latching control (LC), must be incorporated at the optimization design stage of the WEC geometry if an overall optimized system is to be realised. In this paper, the impact of device mo...
http://mural.maynoothuniversity.ie/9390/
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ControlInformed Optimal Array Layout for Wave Farms
(2015)
GarciaRosa, Paula B.; Bacelli, Giorgio; Ringwood, John
ControlInformed Optimal Array Layout for Wave Farms
(2015)
GarciaRosa, Paula B.; Bacelli, Giorgio; Ringwood, John
Abstract:
Somewhat similar to wind farms, commercial wave energy will be realized using farms of devices. However, for wave farms, both constructive and destructive interference may occur between individual devices; whereas, for wind farms, only destructive interference occurs. In order to maximize constructive interference, the layout of the wave farm must be optimized. In addition, power absorption may be improved by applying a control system technology to the farm of devices. As with many applications, there is a tendency in wave energy to separate the design of the array layout from the design of an energy maximizing control system. In this paper, we show that integrating the activities of optimal array layout design and control design are crucial if the full potential of the wave farm is to be realized. In particular, we show that a layout optimized without knowledge of the control system to be used can be inferior to the extent of recovering 40% less energy than a farm layout optimized ...
http://mural.maynoothuniversity.ie/9436/
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Control, forecasting and optimisation for wave energy conversion
(2014)
Ringwood, John; Bacelli, Giorgio; Fusco, Francesco
Control, forecasting and optimisation for wave energy conversion
(2014)
Ringwood, John; Bacelli, Giorgio; Fusco, Francesco
Abstract:
This paper presents an overview of the motivation, background to and stateof theart in energy maximising control of wave energy devices. The underpinning mathematical modelling is described and the control fundamentals established. Two example control schemes are presented, along with some algorithms for wave forecasting, which can be a necessary requirement, due to the noncausal nature of some optimal control strategies. One of the control schemes is extended to show how cooperative control of devices in a wave farm can be beneficial. The paper also includes perspectives on the interaction between control and the broader objectives of optimal wave energy device geometry and full technoeconomic optimisation of wave energy converters.
http://mural.maynoothuniversity.ie/6780/
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Coordinated Control of Arrays of Wave Energy Devices—Benefits Over Independent Control
(2013)
Bacelli, Giorgio; Balitsky, Philip; Ringwood, John
Coordinated Control of Arrays of Wave Energy Devices—Benefits Over Independent Control
(2013)
Bacelli, Giorgio; Balitsky, Philip; Ringwood, John
Abstract:
It is well known that control systems, which can modulate the power takeoff force of a wave energy device, have the capability of extending the effective device bandwidth and thereby improve energy capture. For an array of wave energy devices, there is the additional complication that each device is subject to radiated waves from other devices, which are a function of the device motion and, hence, an indirect function of each of the device controllers. This gives the possibility of enhancing the energy harvesting properties of the wave farm as a whole, by giving each controller information about the motion of other devices and employing a global performance function which allows coordinated control for the overall benefit of the farm. This paper examines the possibilities of using such coordinated control and makes conclusions on the types of devices, and types of arrays, that might benefit from such coordinated control. In addition, the overall benefit of a global array control str...
http://mural.maynoothuniversity.ie/9449/
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Energy maximising control of wave energy converters
(2014)
Ringwood, John; Bacelli, Giorgio; Fusco, Francesco
Energy maximising control of wave energy converters
(2014)
Ringwood, John; Bacelli, Giorgio; Fusco, Francesco
Abstract:
With the recent sharp increases in the price of oil, issues of security of supply, and pressure to honor greenhouse gas emission limits (e.g., the Kyoto protocol), much attention has turned to renewable energy sources to fulfill future increasing energy needs. Wind energy, now a mature technology, has had considerable proliferation, with other sources, such as biomass, solar, and tidal, enjoying somewhat less deployment. Waves provide previously untapped energy potential, and wave energy has been shown to have some favorable variability properties (a perennial issue with many renewables, especially wind), especially when combined with wind energy
http://mural.maynoothuniversity.ie/6782/
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Estimation and Control in Semiconductor Etch: Practice and Possibilities
(2010)
Ringwood, John; Lynn, Shane; Bacelli, Giorgio; Ma, Beibei Ma; Ragnoli, Emanuele; McLoon...
Estimation and Control in Semiconductor Etch: Practice and Possibilities
(2010)
Ringwood, John; Lynn, Shane; Bacelli, Giorgio; Ma, Beibei Ma; Ragnoli, Emanuele; McLoone, Sean F.
Abstract:
Semiconductor wafer etching is, to a large extent, an openloop process with little direct feedback control. Most silicon chip manufacturers rely on the rigorous adherence to a “recipe” for the various etch processes, which have been built up based on considerable historical experience. However, residue buildup and difficulties in achieving consistent preventative maintenance operations lead to drifts and step changes in process characteristics. This paper examines the particular technical difficulties encountered in achieving consistency in the etching of semiconductor wafers and documents the range of estimation and control techniques currently available to address these difficulties. An important feature of such an assessment is the range of measurement options available if closedloop control is to be achieved.
http://mural.maynoothuniversity.ie/1988/
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Impedance matching controller for an inductively coupled plasma chamber: Ltype Matching Network Automatic Controller
(2007)
Bacelli, Giorgio; Ringwood, John; Iordanov, Petar
Impedance matching controller for an inductively coupled plasma chamber: Ltype Matching Network Automatic Controller
(2007)
Bacelli, Giorgio; Ringwood, John; Iordanov, Petar
Abstract:
Plasma processing is used in a variety of industrial systems, including semiconductor manufacture (deposition and etching) and accurate control of the impedance matching network is vital if repeatable quality is to be achieved at the manufacturing process output. Typically, impedance matching networks employ series (tune) and parallel (load) capacitors to drive the reflection coefficient on the load side of the network to zero. The reflection coefficient is normally represented by real and imaginary parts, giving two variables to be controlled using the load and tune capacitors. The resulting problem is therefore a nonlinear, multivariable control problem. Current industrial impedance matching units employ simple singleloop proportional controllers, which take no account of interaction between individual channels and, in many cases, may fail to tune altogether, if the starting point is far away from the matching point. A hierarchical feedback controller is developed which, at the u...
http://mural.maynoothuniversity.ie/1426/
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Multibody Modelling of Wave Energy Converters Using PseudoSpectral Methods With Application to a ThreeBody HingeBarge Device
(2016)
Paparella, Francesco; Bacelli, Giorgio; Paulmeno, Andrew; Mouring, Sarah E.; Ringwood, ...
Multibody Modelling of Wave Energy Converters Using PseudoSpectral Methods With Application to a ThreeBody HingeBarge Device
(2016)
Paparella, Francesco; Bacelli, Giorgio; Paulmeno, Andrew; Mouring, Sarah E.; Ringwood, John
Abstract:
Multibody wave energy converters are composed of several bodies interconnected by joints. Two different formulations are adopted to describe the dynamics of multibody systems: the differential and algebraic equations (DAEs) formulation, and the ordinary differential equations (ODEs) formulation. While the number of variables required for the description of the dynamics of a multibody system is greater in the DAE formulation than in the ODE formulation, the ODE formulation involves an extra computational effort in order to describe the dynamics of the system with a smaller number of variables. In this paper, pseudospectral (PS) methods are applied in order to solve the dynamics of multibody wave energy converters using both DAE and ODE formulations. Apart from providing a solution to the dynamics of multibody systems, pseudospectral methods provide an accurate and efficient formulation for the control of multibody wave energy converters. As an application example, this paper focuse...
http://mural.maynoothuniversity.ie/9392/
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Nonlinear control of flaptype wave energy converter with a nonideal power takeoff system
(2015)
Bacelli, Giorgio; Genest, Romain; Ringwood, John
Nonlinear control of flaptype wave energy converter with a nonideal power takeoff system
(2015)
Bacelli, Giorgio; Genest, Romain; Ringwood, John
Abstract:
Wave energy converters (WECs) require active control to maximise energy capture over a wide range of sea conditions, which is generally achieved by making the device resonate. The exaggerated device motion arising at resonance, however, may result in nonlinear effects that are ignored by the linear models that are typically employed. In particular, nonlinear viscous forces are significant for particular device types, such as hinged flaps, which we take as a case study in this paper. The paper develops a general nonlinear WEC control methodology based on pseudospectral methods. The continuous time energy maximisation problem is fully discretised (both state and control), and the optimal solution is obtained by solving the resulting finite dimensional optimisation problem. By way of example, the nonlinear viscous damping for a hinged flap WEC is incorporated into the control model which also considers nonideal power takeoff efficiency. It is shown that the ratio of energy captured t...
http://mural.maynoothuniversity.ie/9444/
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Nonlinear optimal wave energy converter control with application to a aptype device
(2014)
Bacelli, Giorgio; Ringwood, John
Nonlinear optimal wave energy converter control with application to a aptype device
(2014)
Bacelli, Giorgio; Ringwood, John
Abstract:
Wave energy converters (WECs) require active control to maximise energy capture over a wide range of sea conditions, which is generally achieved by making the device resonate. The exaggerated device motion arising at resonance, however, may result in nonlinear effects that are ignored by the linear models that are typically employed. In particular, nonlinear viscous forces are significant for particular device types, such as hinged aps, which we take as a case study in this paper. The paper develops a general nonlinear WEC control methodology based on pseudospectral methods. The continuous time energy maximization problem is fully discretised (both state and control), and the optimal solution is obtained by solving the resulting finite dimensional optimization problem. By way of example, the nonlinear viscous damping for a hinged ap WEC is incorporate into the control model. It is shown that the ratio of energy captured to energy dissipated is significantly increased with the nonl...
http://mural.maynoothuniversity.ie/6781/
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Numerical Optimal Control of Wave Energy Converters
(2015)
Bacelli, Giorgio; Ringwood, John
Numerical Optimal Control of Wave Energy Converters
(2015)
Bacelli, Giorgio; Ringwood, John
Abstract:
Energy maximizing control for wave energy converters (WECs) is a nonstandard optimal control problem. While the constrained optimal control problem for WECs has been addressed by modelpredictive control strategies, such strategies need to employ cost function modifications due to convexity problems and the algorithms are computationally complex, making realtime implementation difficult. The recently developed family of direct transcription methods offer a promising alternative, since they are computationally efficient and a convex problem results. Moreover, constraints on both the device displacement and velocity, and power take off force, are easily incorporated. Both singlebody and multibody device models can be used, as well as arrays of singlebody or multibody devices.
http://mural.maynoothuniversity.ie/9435/
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On the solution of multibody wave energy converter motions using pseudospectral methods
(2015)
Paparella, Francesco; Bacelli, Giorgio; O’Cathain, Michael; Ringwood, John
On the solution of multibody wave energy converter motions using pseudospectral methods
(2015)
Paparella, Francesco; Bacelli, Giorgio; O’Cathain, Michael; Ringwood, John
Abstract:
Multibody wave energy converters are composed of several bodies interconnected by joints. Two different formulations are adopted to describe the dynamics of multibody systems: the Differential and Algebraic Equations (DAEs) formulation and the Ordinary Differential Equations (ODEs) formulation. While the number of variables required for the description of the dynamics of a multibody system is greater in the DAE formulation than in the ODE formulation, the ODE formulation involves an extra computational effort in order to describe the dynamics of the system with a smaller number of variables. In this paper, pseudospectral methods are applied in order to solve the dynamics of multibody wave energy converters using both DAE and ODE formulations. Apart from providing a solution to the dynamics of multibody systems, pseudospectral methods provide an accurate and efficient formulation for the control of multibody wave energy converters. As an application example, this paper focuse...
http://mural.maynoothuniversity.ie/6680/
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Optimal control of wave energy converters
(2014)
Bacelli, Giorgio
Optimal control of wave energy converters
(2014)
Bacelli, Giorgio
Abstract:
Wave Energy Converters (WECs) are devices designed to absorb energy from ocean waves. The particular type of Wave Energy Converter (WEC) considered in this thesis is an oscillating body; energy conversion is carried out by means of a structure immersed in water which oscillates under forces exerted by waves. This thesis addresses the control of oscillating body WECs and the objective of the control system is to optimise the motion of the devices that maximises the energy absorption. In particular, this thesis presents the formulation of the optimal control problem for WECs in the framework of direct transcription methods, known as spectral and pseudospectral optimal control. Direct transcription methods transform continuous time optimal control problems into Non Linear Programming (NLP) problems, for which the literature (and the market) offer a large number of standard algorithms (and software packages). It is shown, in this thesis, that direct transcription gives the possibility o...
http://mural.maynoothuniversity.ie/6753/
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State space model of a hydraulic power take off unit for wave energy conversion employing bondgraphs
(2008)
Bacelli, Giorgio; Gilloteaux, JeanChristophe; Ringwood, John
State space model of a hydraulic power take off unit for wave energy conversion employing bondgraphs
(2008)
Bacelli, Giorgio; Gilloteaux, JeanChristophe; Ringwood, John
Abstract:
In this work, the modeling of a Power Take Off (PTO) unit for a point absorber wave energy converter is described. The PTO influences the energy conversion performance by its efficiency and by the damping force exerted, which affects the motion of the body. The state space model presented gives a description of the damping force and of the internal dynamics of the PTO. The aim of this work is to develop a model for the PTO as a part of a complete wavetowire model of a wave energy converter as in Figure 1, used for the design control techniques. Figure 1: Wavetowire model structure A bondgraph is employed to model the physical system that provides transparent and methodical means of formulating state space equations and of visualizing energy transfer throughout the system. Bondgraphs have already been shown to be a very useful tool for the modeling of PTO for wave energy converters (2). The dynamic of the mathematical model is then analyzed respect to the variation of parameters...
http://mural.maynoothuniversity.ie/4419/
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