Influence of ROV umbilical on power quality when supplying electrical loads

The paper investigates the effects of a 3 km electrical umbilical cable on power transmission for an "island" supply onboard an all/more electric 'work-class' remote operated vehicle (ROV). It is shown how the chosen transmission voltage and frequency influence efficiency and the selection of power transmission components. A key feature of the paper is a discussion on the use of matrix converters for the propulsion thruster drive system; thereby allowing the input displacement factor to be varied to maintain maximum power transmission efficiency, independent of the thruster power factor. The natural impedance characteristics of the umbilical cable are also considered as means of reducing the input filter requirements for such converter

Drive systems for operation on deep-sea ROVs

Power systems for thruster actuators and other auxiliaries employed on work-class deep-sea ROVs subject to 300bar ambient pressures, are considered. Emphasis on 3×3 matrix converters for thrusters and 3×2 matrix converters for system auxiliaries, is given, along with experimental results showing operation during pressure cycling consistent with typical operational duties

Sensorless control of deep-sea ROVs PMSMs excited by matrix converters

The paper reports the development of model-based sensorless control methodologies for driving PMSMs using matrix converters. In particular, experimental results show that observer-based state-estimation techniques normally employed for sensorless control of PMSMs using voltage source inverters (VSIs), can be readily exported to matrix converter counterparts with minimal additional computational overhead. Furthermore, zero speed start-up and speed reversal are experimentally demonstrated. Finally, the observer is designed to be fault tolerant such that upon detection of a broken terminal (phase fault), the PMSM remains operational and could be utilized to provide a limp-home capabilit

Qualitative assessment of the entry of capripoxviruses into Great Britain from the European Union through importation of ruminant hides, skins and wool

Sheep pox and goat pox (SPGP) virus and lumpy skin disease (LSD) virus belong to the genus Capripoxvirus and cause disease with economic impacts in sheep/goats and cattle respectively. In 2013/14, outbreaks of SPGP were reported in sheep in Greece and Bulgaria and LSD outbreaks were reported in cattle in Turkey, Egypt and some countries in the Middle East. Clinical signs for both diseases include pox lesions, papules and scabs on the skin which may contain virus. This, together with the fact that Great Britain (GB) currently imports cattle hides, sheep skins and wool from European Union (EU) countries without the requirement for treatment prior to export, raises concern that capripoxviruses could be introduced into GB. A qualitative assessment presented here concluded that the current risk of entry of SPGP virus into GB through the importation of one untreated sheep skin, hide or wool bale from an EU Member State (MS) with similar flock prevalence to that in sheep in Greece in 2013/14 is low. In terms of SPGP virus levels, those infected sheep skins/hides entering GB are more likely to be from infected animals with normal skin (i.e., not showing lesions) and hence carrying lower levels of virus than those from animals showing papules and scabs which contain very high virus levels and are easier to detect. The predicted risk of importation of LSD virus per cattle hide/skin is also low (assuming LSD were to emerge in an EU MS with similar herd prevalence to that reported for SPGP in Greece in 2013/14). The levels of LSD virus on an infected cow's hide, if imported, may be very low. It is recommended that the risks for entry of capripoxviruses are recalculated if outbreaks occur elsewhere within the EU

Pathways for entry of livestock arboviruses into Great Britain : assessing the strength of evidence

The emergence of bluetongue virus and Schmallenberg virus in Great Britain (GB) during the last decade has highlighted the need for understanding the relative importance of the various pathways of the entry of livestock arboviruses so as to help focus surveillance and mitigation. This study summarizes what is known for the main routes of entry and assesses the strength of the current evidence for and against. Entry through infected arthropod vectors is considered at the level of each life cycle stage for tick-, biting midge- and mosquito-borne viruses, and while there is evidence that this could happen through most tick and mosquito stages, strong evidence that only exists for entry through adult midges. There is also strong evidence that entry through immature midge stages could not happen. The weight of supporting evidence is strongest for importation of viraemic livestock including horses. While there is some indication of a common pathway for midge-borne viruses from sub-Saharan Africa to GB via Continental Europe, other factors such as maternal transmission in dogs and sheep need to be considered in the light of recent findings

Assessing the impact of climate change on vector-borne viruses in the EU through the elicitation of expert opinion

Expert opinion was elicited to undertake a qualitative risk assessment to estimate the current and future risks to the European Union (EU) from five vector-borne viruses listed by the World Organization for Animal Health. It was predicted that climate change will increase the risk of incursions of African horse sickness virus (AHSV), Crimean-Congo haemorrhagic fever virus (CCHFV) and Rift Valley fever virus (RVFV) into the EU from other parts of the world, with African swine fever virus (ASFV) and West Nile virus (WNV) being less affected. Currently the predicted risks of incursion were lowest for RVFV and highest for ASFV. Risks of incursion were considered for six routes of entry (namely vectors, livestock, meat products, wildlife, pets and people). Climate change was predicted to increase the risk of incursion from entry of vectors for all five viruses to some degree, the strongest effects being predicted for AHSV, CCHFV and WNV. This work will facilitate identification of appropriate risk management options in relation to adaptations to climate change

Q fever through consumption of unpasteurised milk and milk products – a risk profile and exposure assessment

Q fever is a zoonotic disease caused by the bacterium Coxiella burnetii which is endemic in cattle, sheep and goats in much of the world, including the United Kingdom (UK). There is some epidemiological evidence that a small proportion of cases in the developed world may arise from consumption of unpasteurised milk with less evidence for milk products such as cheese. Long maturation at low pH may give some inactivation in hard cheese, and viable C. burnetii are rarely detected in unpasteurised cheese compared to unpasteurised milk. Simulations presented here predict that the probability of exposure per person to one or more C. burnetii through the daily cumulative consumption of raw milk in the UK is 04203. For those positive exposures, the average level of exposure predicted is high at 1266 guinea pig intraperitoneal infectious dose 50% units (GP_IP_ID50) per person per day. However, in the absence of human dose–response data, the case is made that the GP_IP_ID50 unit represents a very low risk through the oral route. The available evidence suggests that the risks from C. burnetii through consumption of unpasteurised milk and milk products (including cheese) are not negligible but they are lower in comparison to transmission via inhalation of aerosols from parturient products and livestock contact

Qualitative import risk assessment : a proposed method for estimating the aggregated probability of entry of infection

In the absence of sufficient numerical data, qualitative risk assessment is recognised as an important tool for providing risk managers with evidence-based predictions on which to formulate their decisions. Such approaches have been used in the area of animal health for import risk assessment for both livestock and zoonotic pathogens. Very few qualitative import risk assessments have, however, considered the aggregated probability of introduction, that is, the probability of at least one infected/contaminated entry per group of import units. Those that have are generally based on specific cases and do not follow a generic approach. In this paper, we consider whether or not it is feasible to develop a generic method and under what circumstances such an approach could be applied in practice. Our conclusion is that it would be difficult to specify a generic method because any such approach would rely on specifying numerical bounds for qualitative categories of probability as well as an idea of the number of imports and would thus be case-specific. As an alternative we propose a way of using case by case information to create a simple graphical reference tool which removes some of the subjectivity that is often associated with deriving qualitative risk. The reference tool considers various qualitative categories of individual probability and determines the relationship between this probability, the number of imports and the aggregated probability of entry. Applying the reference tool to a previously published case-study demonstrated some differences in conclusions and suggests that more subjective approaches can under-estimate probability and thus risk. It is concluded that this approach may be useful for future qualitative assessments of aggregated probability, provided that bounds for qualitative probabilities can be defined for the specific case situation

Matrix converters for sensorless control of PMSMs and other auxiliaries on deep-sea ROVs

The use of matrix converter technologies for the control of actuators and other auxiliaries onboard work-class, deep-sea, remotely operated vehicles (ROVs) is reported. Key requirements for such systems are the ability to sustain operation at high ambient pressures, up to 300 bar, commensurate with operation of ROVs at depths of 3000 m, and to minimise the number of external connections and cabling mass to improve reliability and reduce drag. Emphasis is given to 32 matrix converters for 3f–1f AC voltage/frequency for conversion control of system auxiliaries, with experimental results showing circuit functionality during pressure cycling consistent with typical operational duties, and the use of 33 matrix converters for control of actuators driven by brushless permanent magnet synchronous machines (PMSMs). A principal feature of the paper is the development of model-based sensorless control methodologies for driving PMSMs using matrix converters. In particular, it is shown that observer-based state estimation techniques normally employed for sensorless control of PMSMs using voltage source inverters, can be readily exported to matrix converter counterparts with minimal additional computational overhead. Experimental results from a 0.7 kW PMSM driven by a matrix converter, suitable for a subsea actuator pump, are included to demonstrate the ability of the sensorless techniques to provide reliable estimates of machine rotor position under transient load conditions, and the subsequent exploitation for matrix converter/motor combinations is discussed