Modelling of Diagnostics Influence on Control System Safety

If the control system besides the standard control functions also realizes the functions (known as safety functions), failures of which can influence safety of the controlled process, then the control system may be a source of risk for assets, that are within the scope of the controlled process. Early detection of these failures and subsequent negation of their effects can have a significant influence on the safety integrity level of the safety function and thus also on the elimination of risks related to the controlled process. Therefore, the diagnostics is the means which, if appropriately applied, can increase not only the availability, but also the safety of the control system. The paper deals with using the homogeneous Markov chains to influence the evaluation of on-line diagnostics on the hardware safety integrity of the safety function, depending on the application method of several simultaneously operating diagnostics mechanisms and their basic parameters - the failures diagnostic coverage coefficient and the failure diagnostics time

THE INFLUENCE OF DIAGNOSTICS ON THE RELIABILITY AND SAFETY OF THE CONTROL EQUIPMENT

U ovome radu analizira se utjecaj dijagnostike i redundancije za poboljšanje pouzdanosti i sigurnosti upravljačkih uređaja na brodskim električnim strojevima. Pri projektiranju upravljačkog uređaja važni zahtjevi su sigurnost, pouzdanost i raspoloživost sustava. Ako sustav nema ugrađenu dijagnostiku i redundanciju svaki kvar može dovesti do smanjivanja sigurnosti sustava. Analiziraju se koncepcije samodijagnostike i dijagnostike, mogućnosti primjene samodijagnostike i dijagnostike na različite strukture sistema, te utjecaj na pouzdanost i sigurnost sistema upravljanja, a time i na pouzdanost i sigurnost brodskog elektroenergetskog sistema u cjelini. Problem se analizira s dva aspekta. Prvo, koriste se kombinirane tehnike modeliranja za procjenu poboljšanja pouzdanosti i sigurnosti kada se uključuje redundancija u sustav. Drugo, koristi se Markovljev model u istraživanju sigurnosnog aspekta određene arhitekture za projektiranje redundantnog dijagnostičkog sustava. Na taj način vrši se vrednovanje mogućih rješenja kojima se brodska elektroenergetska postrojenja mogu voditi uz znatno povoljniju bezotkaznost (toleriranje grešaka), i analizira se utjecaj kvalitete dijagnostike na ta rješenja.The paper aims at analyzing the influence of diagnostics and redundancy on the improvement of reliability and safety of the control equipment of the ship electrical engines. Safety, reliability and availability of the system are important requirements when designing the control equipment. If diagnostics and redundancy are not built in the system, any engine failure may lead to a gradual decrease of the system safety. The conception of self diagnostics and diagnostics, possibilities of its application on different system structures, as well as its influence on the reliability and safety of the control system, and consequently on the overall ship’s electric power plant reliability and safety are analyzed. The analysis is carried out from two aspects: first, we have used the combined modelling techniques to estimate the improvement of reliability and safety when redundancy is included in the system; and, secondly, we have used the Markov’s model to research into the safety aspect of two architectures for the design of a redundant diagnostic system. The procedure enables the evaluation of potential solutions by means of which the ship’s electric power plant can operate with more suitable fault tolerance. The influence of the quality of diagnostics on these solutions has been also analyzed

Human African trypanosomiasis : current status and eradication efforts

Epidemics of human African trypanosomiasis (HAT) in the 20th century led to millions of deaths. However, since the start of the twenty-first century, there is been a continued decline in the number of reported cases, due to increased investment and prioritisation of control efforts. Systematic screening of at-risk areas and widespread access to increasingly advanced diagnostics and treatments, along with much improved vector control, have all helped to make disease elimination achievable in the near future. Despite the progress, the danger of disease resurgence is well-known for HAT and continued surveillance and treatment availability is essential. Additionally, many uncertainties regarding HAT transmission remain and combine to make potential disease eradication a complete unknown

Supporting group maintenance through prognostics-enhanced dynamic dependability prediction

Condition-based maintenance strategies adapt maintenance planning through the integration of online condition monitoring of assets. The accuracy and cost-effectiveness of these strategies can be improved by integrating prognostics predictions and grouping maintenance actions respectively. In complex industrial systems, however, effective condition-based maintenance is intricate. Such systems are comprised of repairable assets which can fail in different ways, with various effects, and typically governed by dynamics which include time-dependent and conditional events. In this context, system reliability prediction is complex and effective maintenance planning is virtually impossible prior to system deployment and hard even in the case of condition-based maintenance. Addressing these issues, this paper presents an online system maintenance method that takes into account the system dynamics. The method employs an online predictive diagnosis algorithm to distinguish between critical and non-critical assets. A prognostics-updated method for predicting the system health is then employed to yield well-informed, more accurate, condition-based suggestions for the maintenance of critical assets and for the group-based reactive repair of non-critical assets. The cost-effectiveness of the approach is discussed in a case study from the power industry

Dependable Digitally-Assisted Mixed-Signal IPs Based on Integrated Self-Test & Self-Calibration

Heterogeneous SoC devices, including sensors, analogue and mixed-signal front-end circuits and the availability of massive digital processing capability, are being increasingly used in safety-critical applications like in the automotive, medical, and the security arena. Already a significant amount of attention has been paid in literature with respect to the dependability of the digital parts in heterogeneous SoCs. This is in contrast to especially the sensors and front-end mixed-signal electronics; these are however particular sensitive to external influences over time and hence determining their dependability. This paper provides an integrated SoC/IP approach to enhance the dependability. It will give an example of a digitally-assisted mixed-signal front-end IP which is being evaluated under its mission profile of an automotive tyre pressure monitoring system. It will be shown how internal monitoring and digitally-controlled adaptation by using embedded processors can help in terms of improving the dependability of this mixed-signal part under harsh conditions for a long time

Model Data Fusion: developing Bayesian inversion to constrain equilibrium and mode structure

Recently, a new probabilistic "data fusion" framework based on Bayesian principles has been developed on JET and W7-AS. The Bayesian analysis framework folds in uncertainties and inter-dependencies in the diagnostic data and signal forward-models, together with prior knowledge of the state of the plasma, to yield predictions of internal magnetic structure. A feature of the framework, known as MINERVA (J. Svensson, A. Werner, Plasma Physics and Controlled Fusion 50, 085022, 2008), is the inference of magnetic flux surfaces without the use of a force balance model. We discuss results from a new project to develop Bayesian inversion tools that aim to (1) distinguish between competing equilibrium theories, which capture different physics, using the MAST spherical tokamak; and (2) test the predictions of MHD theory, particularly mode structure, using the H-1 Heliac.Comment: submitted to Journal of Plasma Fusion Research 10/11/200

Overview of the JET results in support to ITER

The 2014–2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L–H power threshold in Deuterium and Hydrogen are given, stressing the importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H = 1 at βN ~ 1.8 and n/nGW ~ 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D–T campaign and 14 MeV neutron calibration strategy are reviewed.European Commission (EUROfusion 633053

The safety case and the lessons learned for the reliability and maintainability case

This paper examine the safety case and the lessons learned for the reliability and maintainability case

Validation of gyrokinetic modelling of light impurity transport including rotation in ASDEX Upgrade

Upgraded spectroscopic hardware and an improved impurity concentration calculation allow accurate determination of boron density in the ASDEX Upgrade tokamak. A database of boron measurements is compared to quasilinear and nonlinear gyrokinetic simulations including Coriolis and centrifugal rotational effects over a range of H-mode plasma regimes. The peaking of the measured boron profiles shows a strong anti-correlation with the plasma rotation gradient, via a relationship explained and reproduced by the theory. It is demonstrated that the rotodiffusive impurity flux driven by the rotation gradient is required for the modelling to reproduce the hollow boron profiles at higher rotation gradients. The nonlinear simulations validate the quasilinear approach, and, with the addition of perpendicular flow shear, demonstrate that each symmetry breaking mechanism that causes momentum transport also couples to rotodiffusion. At lower rotation gradients, the parallel compressive convection is required to match the most peaked boron profiles. The sensitivities of both datasets to possible errors is investigated, and quantitative agreement is found within the estimated uncertainties. The approach used can be considered a template for mitigating uncertainty in quantitative comparisons between simulation and experiment.Comment: 19 pages, 11 figures, accepted in Nuclear Fusio