3,186 research outputs found
Analysis of causation of loss of communication with marine autonomous systems: a probability tree approach
No full textThe last decade has seen the eagerly anticipated introduction of marine autonomous systems as a pragmatic tool for ocean observation. However, outstanding reliability problems means that these vehicles are not yet fulfilling their true potential. Of the classes of problems, loss of communication with a marine autonomous system is both fundamental and difficult to diagnose. In our view, this is due to two reasons: first in many cases users are not technologists and secondly if a vehicle is lost the task of diagnosing the root cause is subject to epistemic uncertainty that users are often reluctant to quantify in a formal manner. As a result users may accept the first hypothesis considered as the main root cause for loss of communication. We show that this approach can result in an increased unreliability of marine autonomous systems through failure to ascertain and then address the true root causes. Consequently, we propose a probability tree approach to help diagnose root cause(s) for loss of communication with a marine autonomous system (MAS). The model was developed based on the results of two detailed investigations and a body of failure data collected from 205 undersea glider operations
Reliability Case Notes No. 10. Board of Inquiry: Circumstances surrounding the stranding of the AutoNaut ‘Gordon’ on the Plymouth coast on 7th November 2014
No full textThe Marine Autonomous Systems in Support of Marine Operations (MASSMO) was a project funded by the Natural Environment Research Council, United Kingdom.Autonaut ‘Gordon’ met all objectives set out in MASSMO mission plan. The vehicle has survived extreme storms in phase 1, whilst gathering valuable science data using state of the art sensors, such as novel passive acoustic devices. In phase 2, the vehicle was successfully deployed to detect tagged fish.In phase 2, Autonaut ‘Gordon’ was deployed on 4th November 2014, at 11.10 am, from Plymouth bay, and transited out 7.2 km East to position 50.337°Latitude, ? 4.13367°Longitude, to start ranging tests and the campaign. The mission was terminated, under NERC’s instructions, on November 6th. During recovery, in the early hours of November 7th, Autonaut ‘Gordon’ was grounded. This resulted in severe damage to the vessel. This Inquiry report looks at the circumstances that have led to the grounding of Autonaut ‘Gordon’ with the aim of diagnosing the most likely root cause for the accident. The grounding of Autonaut ‘Gordon’ was caused by severe weather. However, this report concludes that planning error was the most influential root cause for the accident. The last waypoint, WPT1, was approximately 0.5 miles from Shagstone and lee shore on east side of Harbour entrance. This has put the vehicle in a vulnerable position. The report also concludes that rushed planning was the second most influential root cause for planning error.This report presents analysis of all other potential root causes considered by the Inquiry panel and raises recommendations to mitigate the risk of marine autonomous systems grounding in future deployments
Reliability Case Notes No. 9. Autosub Long Range risk assessment report: expert elicitation and risk discussion record
No full textA Risk Assessment Workshop was convened on the 17th November 2014, in Southampton, to quantify the likelihood of loss of Autosub Long Range (ALR) autonomous underwater vehicle in the forthcoming campaign for the UK FASTNEt (Fluxes Across Sloping Topography of the North East Atlantic) science project. The ALR is an autonomous underwater vehicle developed by the National Oceanography Centre, Southampton; its development is funded by the Natural Environment Research Council, UK.This report presents a summary of the discussions, which comprises a review and assessment of potential failure modes and a summary of the risk mitigation actions
Reliability Case Notes No. 8. Risk and reliability analysis of Autosub 6000 autonomous underwater vehicle
No full textAutosub 6000 is an autonomous underwater vehicle developed and operated by the National Oceanography Centre, Southampton. The vehicle development was funded by the United Kingdom’s Natural Environment Research Council (NERC). The credibility of Autosub 6000 to perform science missions is directly related to its reliability and availability. The aim of this report is to provide reliability and availability analysis of Autosub 6000 based on the vehicle operational history. This report considers the operational history from September 2007 to September 2012, during which seven campaigns were conducted and a total of 68 missions were carried out by Autosub 6000. Eight of the missions ended prematurely.The two most frequently observed failure modes in its fault history were GPS and battery failures. Both failures raised design errors that have since then been addressed.The report concludes that Autosub 6000 failure rate is correlated with two factors: 1. the maximum operating depth and 2. whether or not new technology is being used. Operations at depth greater than 3000 metres are 92% more likely to have an abort than operations at water depth lower than 3000 metres. Adding new technology to the vehicle increases the failure rate by approximately 200%. Of the 110 faults that emerged during the seven campaigns fifty five were mitigated through design corrections, this resulted in a 10% increase in reliability for a 60 km mission, the reliability of which is 0.7.Autosub 6000 software reliability was assessed using two models, the time?related Poisson and the Littlewood. Using both models we can conclude that Autosub 6000 has a reliability of 95% for a 20 hr mission.Lithium?Ion battery reliability was quantified using the FIDES approach. An Autosub 6000 battery pack contains approximately 400 battery cells. The probability of at least one out of four battery packs failing, in 1 year, is 0.20. We concluded that one extra battery pack should be onboard of the vehicle to have at least 96% confidence that the mission will be completed successfully
GC-FID data of biocatalytic esterification reactions & NMR data of lignin characterization
No full textTabulated chromatographic data (GC-FID) from butyl butyrate esterification reactions. 13C and 31P NMR data from pine kraft lignin (BIOPIVA 100) and cationic pine kraft lignin. A list of sample code identifiers with their descriptions is available upon request from the author.<br
A Systems Dynamics Framework for Risk Management of Multiple Autonomous Underwater Vehicles
No full textAutonomy: Risk Assessment
No full textOceanography and ocean observation in general is ever trending toward both automated in situ observation and working in extreme environments. These goals can only be met by de?risking the technology and deployment practices to acceptable levels of risks. A number of industries have standardised risk management processes to support the design and development of their systems. The lack of formal risk assessment of autonomous ocean vehicles has hindered the potential for true autonomy, which is required for exploring unstructured and unexplored environments. When discussing risks different stakeholders may have different consequences foremost in mind. For example the vehicle owner may be interested in risk of loss, whereas the user is interested in risk of vehicle unavailability. Other risks, such as legal risks and risk of collision, affect all stakeholders. This chapter presents a risk management process using several methods tailored to autonomous oceanvehicles in which risk assessment is a key component
Meetresultaten Kunststof GC-elementen: Project C2: Oever- en Bodembescherming met GC
No full textAnome BV en het Innovatie Test Centrum van Rijkswaterstaat-DWW zijn samen met verschillende partners aan het onderzoeken in hoeverre Ground Consolidators (GC\u92s) interessant zouden kunnen zijn voor gebruik in Oever- en bodembescherming. De eerste fase van het onderzoek is afgerond en er is besloten om verdergaand onderzoek te doen. In verband met duurzaamheid van het materiaal, is ervoor gekozen om verder onderzoek te verrichten naar GC-elementen van kunststof. Dit onderzoek is gedaan door een drietal studenten van de TU Delft aan de faculteit Civiele Techniek. Voorliggend document bevat de meetresultaten van de kwali- en kwantitatieve experimenten die zijn uitgevoerd om de eigenschappen van kunststoffen GC\u92s en een pakket GC\u92s te bepalen
Estimating and managing blowout risk during access to subglacial Antarctic lakes
No full textAs Antarctic subglacial lake research progresses to in situ exploration an important topic is the lake's probable gas concentration. Depending on hydrological setting, subglacial lakes may contain large amounts of dissolved gas or gas trapped within clathrates. Consequently, access can be potentially dangerous due to the risk of blowout where depressurization could lead to high-speed ejection of water and gas from a borehole. We present a structured approach to assess the blowout risk in subglacial lake exploration. The approach integrates a generic event tree, applicable to open and closed hydrological systems, with site-specific expert judgment incorporating rigorous probabilistic formulations. The methodology is applied to a motivating example: Ellsworth Subglacial Lake. Judgments elicited through a formal process were provided by five experts with 88 years combined experience that, after aggregation, gave a median risk of blowout of 1 in 2186 with a lower quartile of 1 in 3433 and an upper quartile of 1 in 1341. This approach can be applied to any subglacial lake given a modicum of knowledge on its hydrological setting, as uncertainty can be captured through the elicited judgments. Additionally, the event tree analysis informs blowout mitigation strategies to reduce risk of injury or death
Meetresultaten Kunststof GC-elementen: Versie 4
No full textAnome BV en het Innovatie Test Centrum van Rijkswaterstaat-DWW zijn samen met verschillende partners aan het onderzoeken in hoeverre Ground Consilidators (GC\u92s) interessant zouden kunnen zijn voor gebruik in Oever- en bodembescherming. De eerste fase van het onderzoek is afgerond en er is besloten om verdergaand onderzoek te doen. In verband met duurzaamheid van het materiaal, is ervoor gekozen om verder onderzoek te verrichten naar GC-elementen van kunststof. Dit onderzoek is gedaan door een drietal studenten van de TU Delft aan de faculteit Civiele Techniek. Voorliggend document bevat de meetresultaten van de kwali- en kwantitatieve experimenten die zijn uitgevoerd om de eigenschappen van kunststoffen GC\u92s en een pakket GC\u92s te bepalen
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