P.R.P Hoole

AIRCRAFT-LIGHTNING ELECTRODYNAMICS USING THE TRANSMISSION LINE MODEL PART I: REVIEW OF THE TRANSMISSION LINE MODEL

This work presents a self-consistent and self-contained model to study and analyze aircraft-lightning electrodynamics. In this paper, we review the well developed and reported transmission line model of the cloud-to-ground (CG) lightning return stroke. Subsequently, the incorporation of a circuit model of the aircraft into the return stroke model is considered. The direct hit characteristics of aircraft body lightning currents for both CG and GC (ground- to-cloud) are important when designing protection, shielding and flltering systems for airborne electronic and electrical systems within the aircraft system. Moreover, the model will allow design of aircraft structure and geometry to minimize energy dissipation into the aircraft structure and systems. Basic electromagnetic theory is used to show the validity of considering the return stroke as a transverse magnetic wave along a transmission line. A distributed transmission line model for the aircraft and the return stroke channel of the lightning is used to simulate the return strokes of CG and GC ∞ashes. The efiects of the aircraft geometry with sharp edges are included in the computation of aircraft capacitance values, both distributed as well as lumped values.

Autism, EEG and brain electromagnetics research

There has been a significant increase in the incidence of autism. We report the work on autism by our international group, on the growing attention paid to EEG based diagnosis and the interest in tracing EEG changes to brain electromagnetic signals (BEMS), seeking the cause of autism and the brain regions of its origin. The time- and frequency domain and principal component analysis (PCA) of these EEG signals with a Multilayer Perception Neural Network (MLP) identifies an autistic subject and helps improve classification accuracy. We show differences between a working brain and a relaxed brain, especially in the Alpha waves used for diagnosis.

Flip-teaching engineering optimization, electromagnetic product design, and nondestructive evaluation in a semester's course

Teaching practical design to students requires first a numerical course such as on finite elements and then a course on optimization. However, because of curricular constraints, it is very difficult to get students to take two courses. This paper describes a new semesters course at Michigan State University that accomplishes this through flip teaching to tackle the challenges of time. It is the flip teaching that made it possible to cover two large courses as one. The traditional order of (a) delivering theory (b) programming ancillary tools (mesh generators, solvers), and (c) programming and solving design problems, is flipped. Pre‐constructed meshes described by design parameters and ancillary programs (solvers, mesh generators, and equipotential plotters) are given to students. They familiarize themselves with these at home so that class discussion is focused on the tough concepts inherent to finite element optimization. Further to manage time, students do the massive homework in teams of two and in the last 3 weeks, each student masters one optimization method working closely with the instructor in face‐to‐face sessions. Flip teaching was praised by all students. The final assignment with a realistic design problem (using a method specific to each student) involved a seminar where students presented their results and taught their specific method to the others. A survey proved the learning accomplished.

A new electric dipole model for lightning-aircraft electrodynamics

Purpose – As commercial and military aircraft continue to be subject to direct lightning flashes, there is a great need to characterize correctly the electrical currents and electric potential fluctuations on an aircraft to determine alternative design approaches to minimizing the severity of the lightning-aircraft dynamics. Moreover, with the increased severity of thunderstorms due to global warming, the need arises even more to predict and quantify electrical characteristics of the lightning-aircraft electrodynamics, which is normally not measurable, using a reliable electric model of the aircraft. Such a model is advanced here. The paper aims to discuss these issues. Design/methodology/approach – The case considered in this paper is that of an aircraft directly attached to an earth flash lightning channel. The paper develops a new approach to modelling the aircraft using electric dipoles. The model has the power to represent sharp edges such as wings, tail ends and radome for any aircraft with differen...

Applying a 3D Dipole Model for Lightning Electrodynamics of Low-Flying Aircraft

ABSTRACT In this paper we apply a detailed electrostatic model of an aircraft to be used in an experimentally validated, new electric-charge-based circuit model for studying aircraft-lightning electrodynamics. The model is used to evaluate the electrodynamics of an aircraft under a thundercloud. As commercial and military aircraft continue to be subject to direct lightning flashes, we have previously developed a dipole model to characterize electrical currents and electric potential fluctuations on an aircraft for alternative design strategies to minimizing the severity of lightning-aircraft dynamics. With the increased severity of thunderstorms due to global warming, the need to predict and quantify electrical characteristics of the lightning-aircraft electrodynamics is greater, but they are normally not measurable. That dipole model is used here in a new a simple matrix formulation and applied to low-flying aircraft to compute the lightning channel voltages and currents after the aircraft is struck by lightning.

Ground to Cloud Lightning Flash Currents and Electric Fields: Interaction with Aircraft and Production of Ionosphere Sprites

This paper presents for the first time a case for the importance of ground to cloud (upward leader) lightning flash parameters for safety testing of direct aircraft-lightning interaction and protection of wind turbines, as well as the importance of radiated electric fields for indirect lightning-aircraft interaction and generation of electric discharges called sprites and halos in the ionosphere. By using an electric circuit model of the transverse magnetic waves along the return stroke channel, electric currents at ground level as well as cloud level are determined for both the cloud to ground lightning flash and the ground to cloud lightning flash. We show that when an aircraft triggers lightning, the electric currents will be much more severe in current magnitude, rate of rise of currents, and frequency spectrum than otherwise and are more severe than the parameters observed for the usual and well monitored (and measured) cloud to ground (downward leader) flashes. The rate of rise of currents and the frequency spectrum of the ground to cloud lightning flash are also given here. The electric fields radiated by the lightning flashes that would appear in the ionosphere are presented for both the earth flash and the ground to cloud flash.

Electromagnetic field computation: The beginnings and current directions in optimization

This paper traces the discipline of electromagnetic field computation from the early days of network models to finite differences, integral equation solutions and now the all encompassing finite element method. The discipline enjoyed phenomenal growth under the sponsorship of the IEEE Magnetics Society. The pioneers took a broad view of this subspecialty of electrical engineering as a discipline intersecting with mathematical physics, numerical mathematics and computer science. This liberal non-confining view has spawned further sub-disciplines leading to CAD techniques, and inverse problems, matrix solution methods and parallel processing. The paper then focuses on what is currently the most active area of research, inverse problem solution and optimization where much of the new work lies.

Parameters of cloud to cloud and intra-cloud lightning strikes to CFC and metallic aircraft structures

This paper presents for the first time an assessment of the impact of direct cloud-to-cloud (CC) and intra-cloud (IC) lightning flash on a commercial and a military aircraft. In contrast to cloud-to-ground (CG) lightning strikes to aircraft, where measurements of CG flash measurements may be extended to aircraft strikes, CC and IC flashes are not so accessible. The effects of CC and IC flashes differ from CG flash largely owing to the earth resistance present in CG flashes which imposes limits on the lightning return stroke. It applies the experimentally-attested transmission line model which was reviewed in a previous companion paper to assess the impact on metallic and carbon fiber composite (CFC) structures of modern aircraft. It compares the electrical impact of CC lightning flash on aircraft made of CFC and metallic structures. The simulations and analysis of voltages and the first return stroke current waveforms demonstrate the important distinctions in the characteristics of direct CC lightning effects on metallic and non-metallic airframes. Among the significant results observed are large differences in current time derivatives on the surface of the carbon fiber composites and metallic airframes. Further observations show that there are rise times for the voltage and currents which fall within the subnano and submicro seconds yielding large time derivatives for both the voltages and the currents. This can have important implications for the shielding and protection of the aircraft electrical and electronics systems.

Intelligent localisation of signals using the signal wavefronts: A review

This paper reviews the use of Artificial Neural Networks in lightning related problems, and especially in locating the lightning using a signal sensor with a three element antenna and signal processor. A model to correctly represent both lighting return stroke currents and the radiated lightning electromagnetic pulses (LEMP) is presented with carefully chosen damping coefficients, or frequencies, following a previous work on this. The designed lighting return stroke model is shown to clearly demonstrate the distinct patterns of the LEMP at different distances. This model is used as a test bed to demonstrate the intelligent tracking three element antenna (using inverse computation signal processor) that may be used with a neural network classifier to locate the distance of lightning strike from the three element antenna sensor.

Cloud to Ground and Ground to Cloud Flashes in Lightnin g Protection: And Future Severe Lightnin g and Climate Change

The two common types of lightning flashes that interact with both land systems and airborne systems are the cloud to ground (CG), or downward flashes, and the ground to cloud (GC), or upward flashes. In this paper we report on the direct effect of lightning strike on an aircraft when subject to both GC and CG flashes. The paper utilizes the transmission line based model simulation of both CG and GC flashes and compares the engineering parameters of both types of earth flashes. The paper also examines the first return current stroke and voltages induced when aircraft is subject to a direct lightning strike at various altitudes. A significant increase of current and voltage was observed on the aircraft frame due to direct lightning strike. Thus, the magnitudes of peak current and voltage observed are capable of inducing a higher electric field along the surface since the time transient is short which can have severe effects on the aircraft electrical and electronics systems.