Component-led integrative optimisation methodology for avionic thermal management

The modern military aircraft can be defined as a System of Systems (SoS); several distinct systems operating simultaneously across boundary interfaces. As the on-board subsystems have become more complex and diverse, the development process has become more isolated. When considering thermal management of distributed heat loads, the aircraft has become a collection of individually optimised components and subsystems, rather than the implementation of a single system to perform a given task. Avionic thermal management is quickly becoming a limiting factor of aircraft performance, reliability and effectiveness. The challenge of avionic thermal management is growing with the increasing complexity and power density of avionic packages. The aircraft relies on a heat rejection growth capacity to accommodate the additional through-life avionic heat loads. Growth capacity is defined as an allowable thermal loading growth designed into the system by the underutilisation of spatial and cooling supply at aircraft introduction; however, this is a limited resource and aircraft subsystem cooling capability is reaching a critical point. The depleted growth capacity coupled with increased avionic power demands has led to component thermal failure. However, due to the poor resolution of existing data acquisition, experimental facilities or thermodynamic modeling, the exact inflight-operating conditions remain relatively unknown. The knowledge gap identified in this work is the lack of definitive methodology to generate high fidelity data of in-flight thermal conditions of fast-jet subsystems and provide evidence towards effective future thermal management technologies. It is shown that, through the development of a new methodology, the knowledge gap can be reduced and as an output of this approach the unknown system behaviour can be defined. A multidisciplinary approach to the replication, analysis and optimisation of a fast-jet TMS is detailed. The development of a new Ground Test Facility (GTF) allows previously unidentified system thermal behaviour to be evaluated at component, subsystem and system level. The development of new data to characterise current thermal performance of a fast jet TMS allows recommendations of several new technologies to be implemented through a component led integrative system optimisation. This approach is to consider the TMS as a single system to achieve a single goal of component thermal management. Three technologies are implemented to optimise avionic conditions through the minimisation of bleed air consumption, improve avionic reliability through increased avionic component isothermalisation and increase growth capacity through improved avionic heat exchanger fin utilisation. These component level technologies improved system level performance. A reduction in TMS bleed air consumption from 1225kg to 510kg was found to complete a typical flight profile. A peak predicted aircraft specific fuel consumption saving of 1.23% is seen at a cruise flight condition because of this approach to avionic thermal management

In-flight calibration and verification of the Planck-LFI instrument

In this paper we discuss the Planck-LFI in-flight calibration campaign. After a brief overview of the ground test campaigns, we describe in detail the calibration and performance verification (CPV) phase, carried out in space during and just after the cool-down of LFI. We discuss in detail the functionality verification, the tuning of the front-end and warm electronics, the preliminary performance assessment and the thermal susceptibility tests. The logic, sequence, goals and results of the in-flight tests are discussed. All the calibration activities were successfully carried out and the instrument response was comparable to the one observed on ground. For some channels the in-flight tuning activity allowed us to improve significantly the noise performance.Comment: Long technical paper on Planck LFI in flight calibration campaign: 109 pages in this (not final) version, 100 page in the final JINST versio

Bayesian learning of models for estimating uncertainty in alert systems: application to air traffic conflict avoidance

Alert systems detect critical events which can happen in the short term. Uncertainties in data and in the models used for detection cause alert errors. In the case of air traffic control systems such as Short-Term Conflict Alert (STCA), uncertainty increases errors in alerts of separation loss. Statistical methods that are based on analytical assumptions can provide biased estimates of uncertainties. More accurate analysis can be achieved by using Bayesian Model Averaging, which provides estimates of the posterior probability distribution of a prediction. We propose a new approach to estimate the prediction uncertainty, which is based on observations that the uncertainty can be quantified by variance of predicted outcomes. In our approach, predictions for which variances of posterior probabilities are above a given threshold are assigned to be uncertain. To verify our approach we calculate a probability of alert based on the extrapolation of closest point of approach. Using Heathrow airport flight data we found that alerts are often generated under different conditions, variations in which lead to alert detection errors. Achieving 82.1% accuracy of modelling the STCA system, which is a necessary condition for evaluating the uncertainty in prediction, we found that the proposed method is capable of reducing the uncertain component. Comparison with a bootstrap aggregation method has demonstrated a significant reduction of uncertainty in predictions. Realistic estimates of uncertainties will open up new approaches to improving the performance of alert systems

Aeronautical life-cycle mission modelling framework for conceptual design

This thesis introduces a novel framework for life cycle mission modelling during conceptual aeronautical design. The framework supports object-oriented mission definition using Geographical Information System technology. Design concepts are defined generically, enabling simulation of most aeronautical vessels and many non-aeronautical vehicles. Moreover, the framework enables modelling of entire vessel fleets, business competitors and dynamic operational changes throughout a vessel life cycle. Vessels consist of components deteriorating over time. Vessels carry payload that operates within the vessel environment.An agent-based simulation model implements most framework features. It is the first use of an agent-based simulation utilising a Geographical Information System during conceptual aeronautical design. Two case studies for unmanned aircraft design apply the simulation. The first case study explores how the simulation supports conceptual design phase decisions. It simulates four different unmanned aircraft concepts in a search-and-rescue scenario including lifeboats. The goal is to learn which design best improves life cycle search performance. It is shown how operational and geographical impacts influence design decision making by generating novel performance information. The second case study studies the simulation optimisation capability: an existing aircraft design is modified manually based on simulation outputs. First, increasing the fuel tank capacity has a negative effect on life cycle performance due to mission constraints. Therefore, mission definition becomes an optimisation parameter. Changing mission flight speeds during specific segments leads to an overall improved design

Neural basis of a visuo-motor transformation in the fly

How the outputs of populations of sensory neurons are used by motor systems to generate appropriate behaviour is a long standing question in neuroscience. I address this problem by studying a comparatively simple model system. In the fly, Neck Motor Neurons control gaze-stabilising head movements that occur during wholebody rotations. These motor neurons receive several sensory inputs including one from well-characterized visual interneurons, Tangential Cells (TCs), which respond to panoramic image shifts induced during self-motion. In chapter one, I provide a general introduction to sensory-motor circuits and the fly gaze-stabilisation system. In chapter two, I report that the visual receptive fields of Neck Motor Neurons are similar to those of the TCs. Using this result, I show an alignment between the coordinate systems used by the visual and the neck motor systems to process visual information. Thus, TCs encode visual inputs in a manner already closely matched to the requirements of the neck motor neurons, considerably facilitating the visual-motor transformation In chapter three, I analyse the gating of neck motor neuron visual responses by convergent mechanosensory inputs from the halteres. Some neck motor neurons do not fire action potentials in response to visual stimuli alone, but they will in response to haltere movements. I show that visual stimuli produce sustained sub-threshold depolarisations in these neurons. These visual depolarisations increase the proportion of haltere-induced action potentials in neck motor neurons. Thus, visual inputs can only affect the spiking output if the halteres are moving. This simple mechanism could explain why flies only make visually induced head movements during walking or flight: behaviours that involve beating the halteres. By analysing how the outputs of a model sensory system are used, I have shown a novel alignment between sensory and motor neuron populations and a simple mechanism underlying multisensory fusion

Autonomous 3D Exploration of Large Structures Using an UAV Equipped with a 2D LIDAR

This paper addressed the challenge of exploring large, unknown, and unstructured industrial environments with an unmanned aerial vehicle (UAV). The resulting system combined well-known components and techniques with a new manoeuvre to use a low-cost 2D laser to measure a 3D structure. Our approach combined frontier-based exploration, the Lazy Theta* path planner, and a flyby sampling manoeuvre to create a 3D map of large scenarios. One of the novelties of our system is that all the algorithms relied on the multi-resolution of the octomap for the world representation. We used a Hardware-in-the-Loop (HitL) simulation environment to collect accurate measurements of the capability of the open-source system to run online and on-board the UAV in real-time. Our approach is compared to different reference heuristics under this simulation environment showing better performance in regards to the amount of explored space. With the proposed approach, the UAV is able to explore 93% of the search space under 30 min, generating a path without repetition that adjusts to the occupied space covering indoor locations, irregular structures, and suspended obstaclesUnión Europea Marie Sklodowska-Curie 64215Unión Europea MULTIDRONE (H2020-ICT-731667)Uniión Europea HYFLIERS (H2020-ICT-779411

State-of-the-art in aerodynamic shape optimisation methods

Aerodynamic optimisation has become an indispensable component for any aerodynamic design over the past 60 years, with applications to aircraft, cars, trains, bridges, wind turbines, internal pipe flows, and cavities, among others, and is thus relevant in many facets of technology. With advancements in computational power, automated design optimisation procedures have become more competent, however, there is an ambiguity and bias throughout the literature with regards to relative performance of optimisation architectures and employed algorithms. This paper provides a well-balanced critical review of the dominant optimisation approaches that have been integrated with aerodynamic theory for the purpose of shape optimisation. A total of 229 papers, published in more than 120 journals and conference proceedings, have been classified into 6 different optimisation algorithm approaches. The material cited includes some of the most well-established authors and publications in the field of aerodynamic optimisation. This paper aims to eliminate bias toward certain algorithms by analysing the limitations, drawbacks, and the benefits of the most utilised optimisation approaches. This review provides comprehensive but straightforward insight for non-specialists and reference detailing the current state for specialist practitioners