Intelligent power management for unmanned vehicles

Unmanned Air Vehicles (UAVs) are becoming more widely used in both military and civilian applications. Some of the largest UAVs have power systems equivalent to that of a military strike jet making power management an important aspect of their design. As they have developed, the amount of power needed for loads has increased. This has placed increase strain on the on-board generators and a need for higher reliability. In normal operation these generators are sized to be able to power all on-board systems with out overheating. Under abnormal operating conditions these generators may start to overheat, causing the loss of the generator's power output. The research presented here aims to answer two main questions: 1) Is it possible to predict when an overheat fault will occur based on the expected power usage defined by mission profiles? 2) Can an overheat fault be prevented while still allowing power to be distributed to necessary loads to allow mission completion? This is achieved by a load management algorithm, which adjusts the load profile for a mission, by either displacing the load to spare generators, or resting the generator to cool it down. The result is that for non-catastrophic faults the faulty generator does not need to be fully shut down and missions can continue rather than having to be aborted. This thesis presents the development of the load management system including the algorithm, prediction method and the models used for prediction. Ultimately, the algorithms developed are tested on a generator test rig. The main contribution of this work is the design of a prognostic load management algorithm. Secondary contributions are the use of a lumped parameter thermal model within a condition monitoring application, and the creation of a system identification model to describe the thermal dynamics of a generator

Managing loads on aircraft generators to prevent overheat in-flight

On future UAVs it is envisaged that the power requirements of all on-board electrical systems will increase. In most flight (mission) situations the installed power generation will have adequate capacity to operate the aircraft. It is possible that during abnormal situations such as coolant blockage the generators on-board may be forced to operate under very high load conditions. The main failure mechanism for a generator is overheating and subsequent disintegration of windings, hence the research problem being addressed here is to manage the loads upon the generator to prevent overheats. The research presented here summarizes the modeling of the generator and formation of the load management system. Results are presented showing the system reallocating loads after a fault during flight, preventing overheat of the generators and successfully completing the mission

<i>Xanthomonas</i> biofilm rupture by DNAse I.

<p>A, DNAse treatment of 1 h duration. B, DNAse treatment for an overnight period. The absorbance values were normalized to the control XVM2 plus buffer in order to compare the response for different strains. Error bars represents the standard deviation. Graphs are a representative assay of at least three assays with three replicates per assay</p

Strains of <i>Xanthomonas</i> spp. used in the study.

<p>Strains of <i>Xanthomonas</i> spp. used in the study.</p

Presence of eDNA at the early stages of biofilm formation in <i>Xcc</i>.

<p>Representative light (crystal violet, CV staining) and fluorescence (SYTO-9 staining) images of 72 h static cultures on LB or XVM2 media. Fibers were observed after both staining for strains <i>Xcc</i> 306 and <i>Xcc</i> 12879 A^w at the early stages of biofilm formation. Fibers interconnected cells at different stages of aggregation, from one to several cells are shown. In XVM2 medium, fibers were thicker and more uniform after staining with CV and SYTO-9. eDNA in XVM2 medium appeared to cover the surface like a sheet in contrast to individual fibers produced in LB medium.</p

Presence of eDNA in preformed biofilms of <i>Xcc</i>.

<p>Representative light (CV staining) and fluorescence (SYTO-9 staining) images of mature biofilms on LB or XVM2 media. Both <i>Xcc</i> 306 and <i>Xcc</i> 12879 A^w strains were more aggregated in XVM2 than LB. A high level of aggregation for strain <i>Xcc</i> 12879 A^w in XVM2 made it difficult to observe eDNA fibers in aggregates. In XVM2, strain <i>Xcc</i> 306 was less aggregated and CV and SYTO-9 staining revealed eDNA surrounding the cells. In LB both staining revealed long fibers interconnecting aggregates.</p

Presence of Extracellular DNA during Biofilm Formation by <i>Xanthomonas citri</i> subsp. <i>citri</i> Strains with Different Host Range

<div><p><i>Xanthomonas citri</i> subsp. <i>citri</i> (<i>Xcc</i>) A strain causes citrus bacterial canker, a serious leaf, fruit and stem spotting disease of several <i>Citrus</i> species. <i>X</i>. <i>alfalfae</i> subsp. <i>citrumelonis</i> (<i>Xac</i>) is the cause of citrus bacterial spot, a minor disease of citrus nursery plants and <i>X</i>. <i>campestris</i> pv. <i>campestris</i> (<i>Xc</i>) is a systemic pathogen that causes black rot of cabbage. <i>Xanthomonas</i> spp. form biofilms <i>in planta</i> that facilitate the host infection process. Herein, the role of extracellular DNA (eDNA) was evaluated in the formation and stabilization of the biofilm matrix at different stages of biofilm development. Fluorescence and light microscopy, as well as DNAse treatments, were used to determine the presence of eDNA in biofilms and bacterial cultures. DNAse treatments of <i>Xcc</i> strains and <i>Xac</i> reduced biofilm formation at the initial stage of development, as well as disrupted preformed biofilm. By comparison, no significant effect of the DNAse was detected for biofilm formation by <i>Xc</i>. DNAse effects on biofilm formation or disruption varied among <i>Xcc</i> strains and <i>Xanthomonas</i> species which suggest different roles for eDNA. Variation in the structure of fibers containing eDNA in biofilms, bacterial cultures, and in twitching motility was also visualized by microscopy. The proposed roles for eDNA are as an adhesin in the early stages of biofilm formation, as an structural component of mature bacterial aggregates, and twitching motility structures.</p></div

Effect of DNAse in the extracellular matrix of <i>Xcc</i>.

<p>Transmission Electron Microscopy of <i>Xcc</i> 306 and 12879 A^w strains in exponential growth phase, after DNAse and no-DNAse (Buffer) treatments. DNAse treated bacteria showed less extracellular structures than de buffer control. The remaining structures observed after treatment could be associated to extracellular proteins. Bacterial cell division is shown under DNAse treatment.</p

Effect of DNAse I during biofilm formation in <i>Xanthomonas</i>.

<p>Biofilm formation after treatment with DNAse I at different times after bacterial seeded with different <i>Xanthomonas</i> species and strains (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156695#pone.0156695.t001" target="_blank">Table 1</a>). A, DNAse added at 0 h post seeding (hps); B, DNAse added at 24 hps; C, DNAse added at 48 hps; and D, DNAse added at 72 hps. The absorbance values were normalized to the control XVM2 plus buffer in order to compare the response for different strains. Error bars represent the standard deviation. Graphs are a representative assay of at least three assays with three replicates per assay. Statistical analyses were performed using STATGRAPHICS Plus, version 5.1 (Copyright Manugistics Inc.).</p