Merigaud, Alexis; Gilloteaux, Jean-Christophe; Ringwood, John

Abstract:

To date, mathematical models for wave energy devices typically
follow Cummins equation, with hydrodynamic parameters
determined using boundary element methods. The resulting models
are, for the vast majority of cases, linear, which has advantages
for ease of computation and a basis for control design to
maximise energy capture. While these linear models have attractive
properties, the assumptions under which linearity is valid
are restrictive. In particular, the assumption of small movements
about an equilibrium point, so that higher order terms are not
significant, needs some scrutiny. While this assumption is reasonable
in many applications, in wave energy the main objective
is to exaggerate the movement of the device through resonance,
so that energy capture can be maximised. This paper examines
the value of adding specific nonlinear terms to hydrodynamic
models for wave energy devices, to improve the validity of such
models across the full operational spectrum.

Gaussian Process (GP) model interpolation is used
extensively in geostatistics. We investigated the effectiveness
of using GP model interpolation to generate
maps of cortical activity as measured by Near Infrared
Spectroscopy (NIRS). GP model interpolation also produces
a variability map, which indicates the reliability of
the interpolated data. For NIRS, cortical hemodynamic
activity is spatially sampled. When generating cortical
activity maps, the data must be interpolated. Popular NIRS
imaging software HomER uses Photon Migration Imaging
(PMI) and Diffuse Optical Imaging (DOI) techniques
based on models of light behaviour to generate activity
maps. Very few non-parametric methods of NIRS imaging
exist and none of them indicate the reliability of the interpolated
data. Our GP model interpolation algorithm and
HomER produced activity maps based on data generated
from typical functional NIRS responses. Image results
in HomER were taken as the bench mark as the images
produced are co...

Electrocardiography (ECG) is a test that measures the electrical
activity of the heart. The use of ECG for recording in
ambulatory settings is becoming more prominent due to an
increase in in-home monitoring. By virtue of the ambulatory
nature of the recordings, artifacts have a large effect on
the signals, with the most significant artifact a result of motion.
This paper describes an accelerometer system used to
detect differential movement between the recording electrodes
on the body. This system is then used to determine
a Quality of Signal (QOS) metric for the ECG signal. The
results show that the use of differential movement of the
recording electrodes with respect to one another is a better
representative of the motion artifact, then overall body
movement.
This simple Signal Quality metric is used to more accurately
flag the appropriate noisy ECG data which can be
rejected from the signal. The simplicity of this system also
allows it to be easily embedded into any in-home moni...

In this chapter we present an overview of the area of electroencephalographyfunctional
near infrared spectroscopy (EEG-fNIRS) measurement as an activity
monitoring technology for brain computer interfacing applications. Our interest in
this compound neural interfacing technology is motivated by a need for a motor
cortical conditioning technology suitable for use in a neurorehabilitation setting
[15, 50]. Specifically we seek BCI technology that allows a patient with a paretic
limb (as a consequence of stroke) to engage in movement-based rehabilitation
exercises which will, we hope, encourage neuroplastic processes in the brain so that
recovery and function is ultimately restored [38]. As we are interested in rehabilitation
following stroke haemodynamic signatures of motor cortical activity coupled
with the corresponding direct measures of the electrical activity of the neurons
involved could be a rich source of new information on the recovering brain areas.
While most neural enginee...

As the number of radio standards increase and spectrum resources come under more pressure, it becomes ever less efficient to reserve bands of spectrum for exclusive use by a single radio standard. Therefore, this work focuses on channelization structures compatible with spectrum sharing among multiple wireless standards and dynamic spectrum allocation in particular. A channelizer extracts independent communication channels from a wideband signal, and is one of the most computationally expensive components in a communications receiver. This work specifically focuses on non-uniform channelizers suitable for multi-standard Software-Defined Radio (SDR) base stations in general and public mobile radio base stations in particular.
A comprehensive evaluation of non-uniform channelizers (existing and developed during the course of this work) shows that parallel and recombined variants of the Generalised Discrete Fourier Transform Modulated Filter Bank (GDFT-FB) represent the best trade-off ...

Carlos, Rovira; Coyle, Shirley; Corcoran, Brian; Diamond, Dermot; McCoy, Aaron; Stroiescu, Florin; Daly, Kieran; Ward, Tomas E.

Abstract:

This paper presents a system for remote monitoring
of respiration of individuals that can detect respiration rate,
mode of breathing and identify coughing events. It comprises a
series of polymer fabric-sensors incorporated into a sports vest,
a wearable data acquisition platform and a novel rich internet
application (RIA) which together enable remote real-time
monitoring of untethered wearable systems for respiratory
rehabilitation. This system will, for the first time, allow
therapists to monitor and guide the respiratory efforts of
patients in real-time through a web browser. Changes in
abdomen expansion and contraction associated with respiration
are detected by the fabric sensors and transmitted wirelessly via
a Bluetooth-based solution to a standard computer. The
respiratory signals are visualized locally through the RIA and
subsequently published to a sensor streaming cloud-based
server. A web-based signal streaming protocol makes the
signals available as real-time streams to...

Wave Energy Converters (WECs) based on oscillating bodies can
achieve optimal energy absorption under certain conditions associated
with reactive control. These conditions, in general, are not realisable in
practice because non-causal and future values of the excitation force
need to be known. In this paper, an alternative approach is presented,
where the relationship between the optimal velocity and the excitation
force is realised through a simple coefficient of proportionality, thus
removing the problem of non-causality. From theoretical considerations
and numerical simulations over a range of heaving WECs in different
sea conditions, it is shown that such suboptimal and causal approximation,
while significantly reducing the complexity and improving
the robustness of reactive control, allows the achievement of values of
energy capture very close to the ideal optimum.

Mangourova, Violeta; Ringwood, John; Van Vliet, Bruce

Abstract:

Guyton’s original integrative physiology model was a milestone in integrative physiology,
combining significant physiological knowledge with an engineering perspective to develop
a computational diagrammatic model. It is still used in research and teaching, with a
small number of variants on the model also in circulation. However, though new research
has added significantly to the knowledge represented by Guyton’s model, and significant
advances have been made in computing and simulation software, an accepted common
platform to integrate this new knowledge has not emerged. This paper discusses the issues
in the selection of a suitable platform, together with a number of current possibilities, and
suggests a graphical computing environment for modelling and simulation. Byway of example,
a validated version of Guyton’s 1992 model, implemented in the ubiquitous Simulink
environment, is presented which provides a hierarchical representation amenable to extension
and suitable for teachin...

Signorelli, Chris; Villegas, Carlos; Ringwood, John

Abstract:

The technical challenges in developing PTO systems
for wave energy converters are enormous as they have to
accommodate both power absorption and survival of extreme
waves. The design of PTO systems and their controllers requires
complex simulations, taking into account the interaction with the
wave energy converter (WEC). However, many of the properties
for continuous operation are difficult to reproduce in simulation.
PTO and control design for WECs can be facilitated using
onshore hardware-in-the-loop (HIL) test-rigs. By performing
HIL simulations, it is possible to test the actual PTO and its
control equipment under typical operating conditions. To
demonstrate the concept we have adapted the scale model of a
two degree-of-freedom heaving point-absorber to be tested in this
manner. To recreate typical operating conditions, we created and
validated a real-time simulation of the WEC, enabling its motion
to be emulated using a hydraulic prime mover. The degree of
novelty with this wo...

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 1-body point absorber oscillating in heave and a 2-body 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...

Hydraulic Power Take Off (PTO) systems for wave
energy usually fall into two broad categories. These are, firstly,
variable pressure systems where control of the primary
force/torque is achieved by pressure modulation, and secondly,
constant pressure systems where control of the primary
force/torque is achieved by valve transitions that select between
discrete effort levels determined by the approximately constant
accumulator pressure and alternative piston areas. Energy storage
is integral to the constant pressure category while, in the purest
form of the variable pressure category, it is not provided. Hybrid
systems which combine elements of both categories are also
possible.
This paper reports an analysis of the most elementary of systems
from each of these categories. The analysis uses a coupled
hydrodynamic-hydraulic time domain model. The model is used to
assess the effectiveness of the hydrodynamic power absorption and
the efficiency of the hydraulic power transmission.
The r...

Wave Energy Converters (WECs) consisting of oscillating
bodies can gain significant benefit from a real-time
controller that is able to appropriately tune the system operation
to the incident wave, thus allowing for a higher energy capture
in a wider variety of wave conditions. Some of the proposed
controllers, however, are non-causal and need predictions of the
excitation force to be implemented in practise. A frequencydomain
model is proposed, for the estimation of the effects that
the wave- excitation-force prediction error has on the reference
velocity that is calculated from the non-causal control law and,
ultimately, on the absorbed power. The model can easily be
derived exclusively from the predictor and from the non-causal
law, with no additional information about the excitation force.
Such a frequency-domain model can be valuable for the design
of a robust control architecture, where the prediction error
has a limited effect on the performance (power absorption).
Focus is p...

Westphalen, J; Bacelli, G; Balitsky, P; Ringwood, John

Abstract:

In this paper, we investigate the differences between
two control strategies for a two-device 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 single-body device with diameter of
5 m and a draught of 25 m we simulate the device motions for
...

Nolan, G.A.; Ringwood, John; Leithead, W.E.; Butler, S.

Abstract:

This paper explores optimal damping profiles for a heaving buoy wave energy converter (WEC). The approach is mathematical and the model of Eidsmoen (1995) is used as a basis. In order to permit analytical development, the model is initially simplified and an optimal damping profile is determined using numerical optimization. Having found the
optimal damping profile, a semi-analytical solution methodology is developed to determine the optimal damping parameters. Finally, the procedure is validated on the original model and some aspects related to the control problem are addressed.

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 24-hour 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 cross-correlation'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 inter-correlated. This suggests that 24-hour 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 24-hour electrical load data as a time series th...

This paper investigates the possible use of artificial neural networks (ANN), more precisely multi-layer perceptrons (MLPs), for the nonlinear modelling and predictive control of a milk pasteurisation plant. Model predictive control (MPC) schemes require the development of a predictive model. Using data gathered from an industrial milk plant, a nonlinear multi-step ahead neural network predictor model (NNM) was established. A neural predictive controller (NPC) was then designed on the same basis for the control of milk pasteurisation temperature. Simulation results are presented and conclusions are drawn.

In this paper, a number of approaches to the modelling of electricity demand, on a variety of time-scales, are considered. These approaches fall under the category of 'intelligent' systems engineering, where techniques such as neural networks, fuzzy logic and genetic algorithms are employed. The paper attempts to give some motivation for the
employment of such techniques, while also making some effort to be realistic about the limitations of such methods, in particular a number of important caveats that should be borne in mind when utilising these techniques within the current application domain. In general, the electricity demand data is modelled as a time series, but one application considered involves application of linguistic modelling to capture operator expertise.

Malpas, Simon C.; Leonard, Bridget L.; Guild, Sarah-Jane; Ringwood, John; Navakatikyan, Michael; Austin, Paul C.; Head, Geoffrey A.; Burgess, Don E.

Abstract:

This article focuses on how sympathetic nerve activity (SNA) contributes to the variability seen in blood pressure. Specifically, it examines the following questions: why do oscillations occur at certain frequencies, why do only certain frequencies of oscillations in SNA induce oscillations in the vasculature, and what may be the functional purpose of these oscillations.

Gaussian process prior models are known to be a powerful non-parametric tool for stochastic data modelling. It employs the methodology of Bayesian inference in using
evidence or data to modify or refer some prior belief. Within the Bayesian context, inference can be used for several purposes, such as data analysis, filtering, data
mining, signal processing, pattern recognition and statistics. In spite of the growing popularity of stochastic data modelling in several areas, such as machine learning and mathematical physics, it remains generally unexplored within the realm of nonlinear dynamic systems, where parametric methods are much more mature and more widely accepted.
This thesis seeks to explore diverse aspects of mathematical modelling of nonlinear dynamic systems using Gaussian process prior models, a simple yet powerful
stochastic approach to modelling. The focus of the research is on the application of non-parametric stochastic models to identify nonlinear dynamic systems fo...

Soraghan , C.J.; Markham, Charles; Matthews, F.; Ward, Tomas E.

Abstract:

A dedicated triple wavelength LED driver is presented for optical
brain–computer interfacing (BCI). The solution caters for the constraints
of a common-anode grounded case and modulation up to
several kilohertz that allows source separation of light that has backscattered
from the brain. With total harmonic distortion of 0.95% and
a frequency range of ~40 kHz, the driver has application in a continuous
wave optical BCI. Other modulation strategies such as time division
multiplexing (TDM) are catered for, owing to input DC
coupling. Linearity in the optical output is maintained by the ‘load
sensing’ differential op-amp on the LED’s current limiting resistor,
which is the basis for the V-I conversion.

Coyle, S.; Ward, Tomas E.; Markham, Charles; Roche, Bryan; McDarby, G.; McLoone, Sean F.

Abstract:

The use of electrodermal activity (EDA) has become the most widely used measure in
psychophysiological studies and has been identified as perhaps the best general index of
autonomic activity [Dawson et al 1990]. Recent work in near-infrared (NIR) technology,
however, has made possible the development of another psychophysiological recording
device that may match EDA as a general index of autonomic arousal.

Motor imagery and motor task execution has been shown to activate similar areas of the
sensorimotor area of the cerebral cortex [Beisteiner et al.]. This has been studied using fMRI,
PET and EEG. Four right-handed male subjects aged 25-45 participated in this study. The
optical response was measured from the sensorimotor area of the cerebral hemisphere contralateral
to hand movement. Cerebral blood volume changes, evident from a decrease in the
detected light signal, were observed during the voluntary hand movement tasks and also from
the imagined hand movement tasks. Not only do the results of this study further validate the
theory that real and imagined movements activate similar cortical areas, but it also brings to
light a novel approach to brain-computer interface development. Classification of EEG
features during motor imagery has been applied to EEG-based brain-computer interfaces
[Pfurtscheller et al]. Cerebral blood flow changes due to motor imagery detected using NIRS
have...

A stochastic model for visual evoked response
generation is proposed based on a compound neurological
generator approach. Participation of individual
generators is stochastically modelled in a physiologically
realistic manner that captures the inherent variability in
latencies and amplitudes associated with the component
phases of the response. The model is invertible such that
decomposition of real responses to reveal individual unit
generator participation is possible and suggests that
conventional averaging techniques may provide a truer
picture of the visual evoked response than previously
thought.

Soraghan , C.; Matthews, F.; Markham, Charles; Pearlmutter, Barak A.; O'Neill, R.; Ward, Tomas E.

Abstract:

A continuous wave near-infrared spectroscopy (NIRS) instrument for brain-computer interface (BCI) applications is presented. In the literature, experiments have been carried out on subjects with such motor degenerative diseases as amyotrophic lateral sclerosis, which have demonstrated the suitability of NIRS to access intentional functional activity, which could be used in a BCI as a communication aid. Specifically, a real-time, multiple channel NIRS tool is needed to realise access to even a few different mental states, for reasonable baud rates. The 12-channel instrument described here has a spatial resolution of 30mm, employing a flexible software demodulation scheme. Temporal resolution of ~100ms is maintained since typical topographic imaging is not needed, since we are only interested in exploiting the vascular response for BCI control. A simple experiment demonstrates the ability of the system to report on haemodynamics during single trial mental arithmetic tasks. Multiple tr...

Nerve conduction studies (NCS) are one of the basic tools of the electrodiagnostic clinician and are performed in order to evaluate the integrity of peripheral nerve function . Using such techniques diagnosis of various diseases and disorders of nerve are possible. During NCS a peripheral nerve is stimulated using an electrical pulse of sufficient intensity to recruit as many nerve fibres as possible. This elicits a volley of action potentials (APs) in the individual nerve fibres which is then recorded at a distal point usually using surface electrodes. Usually only two components of the recorded response (called the compound action potential or CAP), the distal amplitude and the distal/peak latency are routinely recorded though the proximal latency is also used to construct an average measure of conduction velocity (CV). In this study a model of the sensory CAP of the median nerve as measured using bipolar electrodes is proposed and using this model an additional measure is extract...