#LyX 2.3 created this file. For more info see http://www.lyx.org/ \lyxformat 544 \begin_document \begin_header \save_transient_properties true \origin unavailable \textclass article \use_default_options true \begin_modules customHeadersFooters minimalistic todonotes figs-within-sections \end_modules \maintain_unincluded_children false \language british \language_package default \inputencoding auto \fontencoding global \font_roman "default" "default" \font_sans "default" "default" \font_typewriter "default" "default" \font_math "auto" "auto" \font_default_family default \use_non_tex_fonts false \font_sc false \font_osf false \font_sf_scale 100 100 \font_tt_scale 100 100 \use_microtype true \use_dash_ligatures true \graphics default \default_output_format default \output_sync 0 \bibtex_command default \index_command default \paperfontsize default \spacing single \use_hyperref true \pdf_title "Net-zero Cable Repair Ship" \pdf_author "Andy Pack" \pdf_bookmarks true \pdf_bookmarksnumbered false \pdf_bookmarksopen false \pdf_bookmarksopenlevel 1 \pdf_breaklinks false \pdf_pdfborder true \pdf_colorlinks false \pdf_backref false \pdf_pdfusetitle true \papersize default \use_geometry true \use_package amsmath 1 \use_package amssymb 1 \use_package cancel 1 \use_package esint 1 \use_package mathdots 1 \use_package mathtools 1 \use_package mhchem 1 \use_package stackrel 1 \use_package stmaryrd 1 \use_package undertilde 1 \cite_engine biblatex \cite_engine_type authoryear \biblio_style plain \biblio_options urldate=long \biblatex_bibstyle authoryear \biblatex_citestyle authoryear \use_bibtopic false \use_indices false \paperorientation portrait \suppress_date true \justification true \use_refstyle 1 \use_minted 0 \index Index \shortcut idx \color #008000 \end_index \leftmargin 2cm \topmargin 2cm \rightmargin 3.5cm \bottommargin 2cm \secnumdepth 3 \tocdepth 3 \paragraph_separation skip \defskip medskip \is_math_indent 0 \math_numbering_side default \quotes_style british \dynamic_quotes 0 \papercolumns 1 \papersides 1 \paperpagestyle fancy \bullet 1 0 9 -1 \bullet 2 0 24 -1 \tracking_changes false \output_changes false \html_math_output 0 \html_css_as_file 0 \html_be_strict false \end_header \begin_body \begin_layout Standard \begin_inset CommandInset toc LatexCommand tableofcontents \end_inset \end_layout \begin_layout Standard \begin_inset FloatList table \end_inset \end_layout \begin_layout Standard \begin_inset FloatList figure \end_inset \end_layout \begin_layout Standard \begin_inset Newpage newpage \end_inset \end_layout \begin_layout Right Footer Andy Pack \end_layout \begin_layout Left Footer January 2021 \end_layout \begin_layout Left Header Sustainable Cable Ship - Group 1 \end_layout \begin_layout Part Vessel Study \end_layout \begin_layout Section Propulsion \end_layout \begin_layout Subsection Power Requirements \end_layout \begin_layout Subsubsection Hotel Load [AP] \end_layout \begin_layout Section Efficiency Investigations \end_layout \begin_layout Subsection Solar [AP] \end_layout \begin_layout Section Energy Storage [AP] \end_layout \begin_layout Subsection Battery Chemistry \end_layout \begin_layout Subsection Time-dependent Modelling \end_layout \begin_layout Section Mission Ops \end_layout \begin_layout Subsection Grapnel-based Operations [AP] \end_layout \begin_layout Standard While the use of robotics has made sub-sea cable repair operations more efficient, durable and accurate, as will be discussed there are situations where this is not available and it is worth briefly outlining how grapnels are used in repair operations. \end_layout \begin_layout Standard Grapnels are specialised tools attached to lengths of chain which trail the stern of the ship. For cable repair operations, a cut & hold grapnel is used \begin_inset CommandInset citation LatexCommand citep key "cut-and-hold-paper,cut-and-hold-eta-product" literal "false" \end_inset . With knowledge of the path of the subject cable and the location of the fault, the grapnel is lowered before the boat makes a pass perpendicular to the cable. As the grapnel makes contact it is able to both cut and grip the cable before being raised to the surface vessel. \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout Disadvantages \end_layout \end_inset \end_layout \begin_layout Subsection Unmanned Underwater Vehicle Operations [AP] \end_layout \begin_layout Standard The following section outlines how the use of an unmanned underwater vehicle (UUV) can make mission operations more efficient and precise. The state of current UUV usage throughout cable repair operations is outlined in order to identify the critical capabilities and requirements. The future of the domain is then explored and the challenges identified before exploring how these can be overcome in order to meet the determined requirements. Prior to this, the domain of UUVs as a whole is described in order to outline the scope of available vehicles. \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout Why ROVS? \end_layout \end_inset \end_layout \begin_layout Subsubsection UUV Classes \end_layout \begin_layout Paragraph ROVs and AUVs \end_layout \begin_layout Standard UUVs are generally divided into two categories, remotely operated underwater vehicles (ROV) and autonomous underwater vehicles (AUV) with the distinction being between whether a human is controlling the vehicle or whether it operates independently; as such they have different applications. ROVs have been the vehicle class of choice where intervention and actuation is required such as offshore oil and gas operations and cable repair. A human operator controls the vehicle from the surface vessel, bi-directional communication including data, control, video and power are transmitted through an umbilical cord tether between the two vessels. AUVs on the other hand have primarily been used for survey and research purposes. \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout No umbilical cord? \end_layout \end_inset \end_layout \begin_layout Standard This distinction in responsibilities is not static, however. Like other robotics domains such as auto-mobiles and ships, autonomy is a rapidly developing area of research and development and newer vehicles are able to complete many more complex operations without human intervention and with longer endurance. \end_layout \begin_layout Paragraph Physical Configuration \end_layout \begin_layout Standard The physical layout of a UUV can generally be described by one of two classes, box frames or torpedo shaped. \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout determined by the size and range of the vehicle. \end_layout \end_inset Box frame UUVs are typically larger with more space for instruments and actuators but are not expected to make longer distance journeys as a result of their poor hydrodynamic profile. Torpedo shaped vehicles tend to be smaller without actuators; their hydrodynami c profile makes them well suited for faster, longer distance missions however this comes at the cost of reduced stability and control. \end_layout \begin_layout Subsubsection Current ROV Usage \end_layout \begin_layout Standard Cable repair operations are currently undertaken, where possible, with human-con trolled ROVs. With visual contact and direct actuation at the seabed, the ROV is used to identify, cut and grip the cable for retrieval to the surface-vessel. In doing so the need for repeated motions of the ship across the cable is removed, saving time and fuel. Instead the surface vessel uses dynamic positioning in order to maintain it's position above the ROV and cable. \end_layout \begin_layout Standard While this finer control is a key benefit for ROV use over grapnels, one of the most important benefits is the ability to bury repaired cables in the sea floor using high-powered water jets. 70% of cable damage is caused by man-made activity, of which over a third is a result of fishing activity; another quarter is as a result ship anchors \begin_inset CommandInset citation LatexCommand citep key "ultra-map-cable-damage-causes" literal "false" \end_inset . As such, the ability to protect sub-sea cables in shallower waters by burying them from human intervention is a key parameter in protecting cables from further damage. While this can be completed with a separate plough, this would require more deck space, motion of the surface vessel. Ploughs are also typically extremely heavy pieces of equipment and would make the vessel less efficient overall. \end_layout \begin_layout Standard The need for fine movement control and actuators with which to manipulate cables has led to box frame vehicles dominating this field, figure \begin_inset CommandInset ref LatexCommand ref reference "fig:The-HECTOR-7-ROV" plural "false" caps "false" noprefix "false" \end_inset shows SIMEC Technology's HECTOR-7 ROV, a typical design for sub-sea cable repair vehicles. \end_layout \begin_layout Standard \begin_inset Float figure wide false sideways false status open \begin_layout Plain Layout \noindent \align center \begin_inset Graphics filename hector-7.jpg lyxscale 50 width 50col% \end_inset \end_layout \begin_layout Plain Layout \begin_inset Caption Standard \begin_layout Plain Layout SIMEC Technology's HECTOR-7 ROV used on Orange Marine's Pierre de Fermat, \begin_inset CommandInset citation LatexCommand citep key "rov-hector-7-datasheet" literal "false" \end_inset \begin_inset CommandInset label LatexCommand label name "fig:The-HECTOR-7-ROV" \end_inset \end_layout \end_inset \end_layout \end_inset \end_layout \begin_layout Standard \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout Limited depth \end_layout \end_inset \end_layout \begin_layout Standard Table \begin_inset CommandInset ref LatexCommand ref reference "tab:ROV-specs" plural "false" caps "false" noprefix "false" \end_inset lists the specifications for the ROVs currently being used as part of the ACMA cable repair agreement along with similarly classed vehicles from other providers. \end_layout \begin_layout Standard \begin_inset Float table wide false sideways false status open \begin_layout Plain Layout \noindent \align center \begin_inset Tabular \begin_inset Text \begin_layout Plain Layout \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold HECTOR-7 \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold Atlas \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold ST200 \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold QTrencher 600 \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold Company \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout SIMEC Technology \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Global Marine \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout SMD \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold Vessel \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Pierre de Fermat \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Wave Sentinel \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Cable Innovator \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout N/A \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout C.S Sovereign \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold Depth Rating \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 3,000 m \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 2,000 m \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 2,500 m \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 3,000 m \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold Weight in Air \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 9 t \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 10.6 t \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 6.5 t \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 11 t \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold Power \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 300 kW \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 300 kW \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout - \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 450 kW \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout \series bold Burial Depth \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 2 m \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 2 m \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 1.5 m \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 3 m \end_layout \end_inset \end_inset \begin_inset VSpace smallskip \end_inset \end_layout \begin_layout Plain Layout \begin_inset CommandInset citation LatexCommand citep key "rov-hector-7-datasheet,global-marine-atlas-data-sheet,glboal-marine-st200-datasheet,smd-qtrencher-600-datasheet" literal "false" \end_inset \end_layout \begin_layout Plain Layout \begin_inset Caption Standard \begin_layout Plain Layout Relevant specifications and operating capabilities for sub-sea cable repair ROVs \begin_inset CommandInset label LatexCommand label name "tab:ROV-specs" \end_inset \end_layout \end_inset \end_layout \end_inset \end_layout \begin_layout Paragraph Requirements Specification \end_layout \begin_layout Standard Using this information the requirements for a cable repair UUV could be described as the following, \end_layout \begin_layout Enumerate The UUV should have actuators in order to both cut and grip cables \end_layout \begin_layout Enumerate The UUV should be able to operate to at least 2 km of depth \end_layout \begin_layout Enumerate The UUV should be able to locate the cable without visual information i.e. electromagnetically \end_layout \begin_deeper \begin_layout Enumerate In shallower water the cable is buried and will not be able to be visually identified \end_layout \end_deeper \begin_layout Enumerate The UUV should be able to re-bury the cable in shallower waters \end_layout \begin_deeper \begin_layout Enumerate This should provide more protection to the cable from interference including fishing operations \end_layout \end_deeper \begin_layout Subsubsection Current AUV Usage \end_layout \begin_layout Standard Autonomous underwater vehicles are well suited to survey and research operations , without human intervention they sweep a given area collecting data for analysis. This can include bathymetry \begin_inset Foot status open \begin_layout Plain Layout The measurement of the depth of a body of water \end_layout \end_inset , surveys and chemical composition investigations such as pH and toxin levels. \end_layout \begin_layout Standard \begin_inset Float figure wide false sideways false status open \begin_layout Plain Layout \noindent \align center \begin_inset Graphics filename hugin-superior.jpg lyxscale 30 width 60col% \end_inset \end_layout \begin_layout Plain Layout \begin_inset Caption Standard \begin_layout Plain Layout Kongsberg Maritime's HUGIN Superior AUV, \begin_inset CommandInset citation LatexCommand citep key "auv-hugin-superior-datasheet" literal "false" \end_inset \end_layout \end_inset \end_layout \begin_layout Plain Layout \end_layout \end_inset \end_layout \begin_layout Subsubsection Domain Challenges \end_layout \begin_layout Paragraph Navigation \end_layout \begin_layout Standard One of the main advantages of using an autonomous vehicle for sub-sea cable repairs would be the physical de-coupling of the vehicles, however this also poses the most significant challenge. In typical ROV operations, the operator has knowledge of the location of the ROV relative to the surface vessel. As the surface vessel is GNSS-enabled (Likely GPS) it has knowledge of its position in world co-ordinates and the operator can use this to reduce the ROV's cable search space. \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout Diagram? \end_layout \end_inset \end_layout \begin_layout Standard Decoupling the vehicles introduces complications that are not necessarily typical to the existing use cases for AUVs. The frequency of EM waves used by GNSS systems do not penetrate deep through the water and an AUV must be able to operate without world co-ordinates provided in this manner. As such, navigation systems used by AUVs are typically \emph on dead reckoning \emph default systems. This is a form of navigation that operates relative to a known fixed point (where a UUV is deployed for example) as opposed to one relative to world co-ordinates. \end_layout \begin_layout Standard With an accurate system, this will satisfy many surveying and research use cases where relative location data can be transformed to world-coordinates after the fact. This will prove less effective when the vehicle is expected to autonomously navigate to a specific location (the cable fault). A dead reckoning system as described above uses relative sensors to measure it's speed and infer it's current location however these relative sensors have associated measurement errors which accumulate over time. This would be more pronounced under the water where sea currents are liable to accentuate these errors, the efficacy of an AUV's fault location capabilitie s may be reduced to the point of unacceptability. \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout Kalman filter now? \end_layout \end_inset \end_layout \begin_layout Paragraph Launch & Recovery \end_layout \begin_layout Standard \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout Top hat or garage TMS to act as LARS interface? \end_layout \end_inset \end_layout \begin_layout Subsubsection Proposed Design \end_layout \begin_layout Standard The vehicle will be designed for hybrid ROV/AUV operations. The vehicle should be able to complete missions independently of the surface vessel with the ability to operate in a similar fashion to existing ROVs (human controller, tethered power and data connection). This will have a number of benefits, primarily that the vehicle should be able to benefit from autonomous operation with the ability for direct human control in missions deemed to complex for autonomous control. \end_layout \begin_layout Standard The existing remit of AUV operations is primarily survey, inspection and light intervention, it is likely that the autonomous capabilities of this vehicle would not be capable of conducting all existing cable repair missions which involve a lot more involved intervention. It is important that enabling autonomous operations does not ultimately reduce it's operating capabilities. \end_layout \begin_layout Standard As previously described, box frame UUVs are well suited to sub-sea cable operations where fine movement control and space for actuators are critical. As such a box frame of similar specifications to those currently used, \begin_inset CommandInset citation LatexCommand cite key "global-marine-atlas-data-sheet,rov-hector-7-datasheet" literal "false" \end_inset will be used. The vehicle will likely be at the larger and heavier end of existing ROVs as the vehicle must now have the onboard energy capabilities to complete a mission without a constant power supply from the surface vessel. \end_layout \begin_layout Subsubsection Navigation \end_layout \begin_layout Standard As previously described, the navigation system will primarily be built on the principle of \emph on dead reckoning \emph default using an inertial navigation system (INS). An INS uses input from many types of sensor such as accelerometers and gyroscopes to measure the movement of the vehicle and hence infer it's location. None of these could individually provide an accurate determination of location and as such \emph on sensor fusion \emph default is employed. Each sensor has an associated measurement uncertainty which compounds over time, sensor fusion allows all the sensor measurements to be combined in such a way as to produce a single output measurement with an uncertainty smaller than any of each sensor individually. A common method for implementing sensor fusion is using a \emph on Kalman filter \emph default \begin_inset Flex TODO Note (Margin) status open \begin_layout Plain Layout reference, explain? \end_layout \end_inset . \end_layout \begin_layout Standard However, despite the use of a Kalman filter allowing more precise approximations of the vehicles relative location, the lack of external calibrating updates means that the overall uncertainty will still continually increase over time. In land-based robotics this is mitigated through the use of periodic GPS measurements which have low uncertainty and help to place an upper bound on the overall error. As previously mentioned, GNSS systems do not work deep underwater and as such, another method for providing these external updates must be used. \end_layout \begin_layout Paragraph Underwater Acoustic Positioning \end_layout \begin_layout Paragraph Underwater Acoustic Communications \end_layout \begin_layout Paragraph Acoustic Doppler Current Profiling \end_layout \begin_layout Subsubsection Control \end_layout \begin_layout Subsubsection Summary \end_layout \begin_layout Standard \begin_inset Newpage newpage \end_inset \end_layout \begin_layout Standard \begin_inset CommandInset label LatexCommand label name "sec:bibliography" \end_inset \begin_inset CommandInset bibtex LatexCommand bibtex btprint "btPrintCited" bibfiles "references" options "bibtotoc" \end_inset \end_layout \begin_layout Standard \begin_inset Newpage pagebreak \end_inset \end_layout \begin_layout Section \start_of_appendix appendix placeholder \end_layout \end_body \end_document