The calculation of "Probability of Failure on Demand" (PFH) according to IEC 61508 shows for a 1oo1 and a 1oo2 system using the same initial values that - as expected - a 1oo2 system is a better safety integ...
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The calculation of "Probability of Failure on Demand" (PFH) according to IEC 61508 shows for a 1oo1 and a 1oo2 system using the same initial values that - as expected - a 1oo2 system is a better safety integrity system than a 1oo1 system. This means, that a 1oo2 system has a lower probability of failure than a 1oo1 system. Comparing the same systems operating in a high demand or continuous mode of operation, there will be some cases, especially for systems with high diagnostics, where a 1oo1 system has a lower ¿Probability of Failure per Hour¿ (PFH) value than a 1oo2 system, using the PFH formulas according to IEC 61508. Using the equation according to IEC 61508, it is also possible that the PFH value is apparently better the longer the system runs either in the high mode or continuous mode of operation. Both results are irreproducible in industrial reality. Therefore, this paper will analyze first what conditions are necessary to get a hazard event when using a PFH system. Only those cases are considered in the modified PFH calculation, in which indeed a hazard event occurs. In a second step, it presents a new approach with the help of plausible arguments in order to calculate the PFH value of a PFH system considering a high diagnostic and a very low failure rate. The presented approach can also be correctly verified with mathematics using the advanced Markov model also described in this paper.
OPC is a matured and accepted standard in industries, but hardly used in industrial applications developed at universities, especially in Europe. Publications in this area, either using OPC-communication or developing...
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OPC is a matured and accepted standard in industries, but hardly used in industrial applications developed at universities, especially in Europe. Publications in this area, either using OPC-communication or developing applications have been hardly increased over the past several years. This paper reports the current state of the standard, but also describes current problems and how they can be managed and overcome. The authors also give an overview of the recently published new standard, which is called: OPC unified approach. After the fundamentals are described in this paper, the authors present their experiences with OPC to combine it with methods and procedures to develop a modern maintenance system. It also reports current developments at the Department of computerarchitecture and systemprogramming at the university of kassel.
The authors present their latest research results and developments of a code generator for Matlab / Simulink block diagrams and to download the generated code onto safety related systems such as a safety PLC (Programm...
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The common cause failures (ccf) are the biggest part when calculating the probability of failure for redundant safety integrity systems. A ccf can occur, when a random hardware failure leads to a failure of several co...
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The common cause failures (ccf) are the biggest part when calculating the probability of failure for redundant safety integrity systems. A ccf can occur, when a random hardware failure leads to a failure of several components. There are several methods to calculate the probability of ccf. Three models will be shown in this paper, with the help of which the beta-factor will be calculated. The ccf ratio for the calculation of the overall probability of failure is defined with the beta-factor.
The authors present their latest research results and developments of a code generator for Matlab/Simulink block diagrams and to download the generated code onto safety related systems such as a safety PLC (programmab...
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The authors present their latest research results and developments of a code generator for Matlab/Simulink block diagrams and to download the generated code onto safety related systems such as a safety PLC (programmable logic controller). An example demonstrates the different stages for code generation, evaluation and conversion before such code can be used in process industries. systematic approaches are necessary when such source code is embedded in process units. To the best knowledge of the authors, Matlab/Simulink source code has not been transferred on safety PLC before. Matlab/Simulink is an advanced and matured programming environment, especially for simulations of engineering processes and systems. Hardly no hardware exists, when it comes to download the developed algorithms and to use it in real world applications and so far this approach is the only one for using developed and tested Matlab/Simulink software on an safety related system.
This paper is dealing with redundant optoelectronic data transmission with special respect to laser channels. The concept of the generalized erasure channel (GEC) is used to determine the probability of undetected err...
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This paper is dealing with redundant optoelectronic data transmission with special respect to laser channels. The concept of the generalized erasure channel (GEC) is used to determine the probability of undetected error for some binary symmetric and non-symmetric channels protected by appropriate codes. In detail, communication via different binary symmetric channels (BSCs), generalized erasure channels and symmetrized binary non symmetric channels (BNSCs) is investigated. Simple upper bounds are given, relating the new formulas to that one of the BSC Finally the results in connection with an inequality for proper codes are applied to multi wavelength optical transmission through channels generated by semiconductor lasers.
Safety-related systems mostly comprise hardware and software solutions. Due to the increasing application of complex hardware and software systems, the software systems have to be considered regarding safety as well a...
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The Monte Carlo Simulation is one mean to calculate safety parameters like MTTF for safety related systems. This procedure helps simulating real failure on demand for safety functions using random numbers. The MTTF-va...
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The Monte Carlo Simulation is one mean to calculate safety parameters like MTTF for safety related systems. This procedure helps simulating real failure on demand for safety functions using random numbers. The MTTF-value can be calculated either directly, via Monte Carlo Simulation, using χ2 - or Student-distributions. Relevant is the fact, that a high number of simulation cycles and/or a large simulation time can be used.
We present novel concepts, technologies and potentials of optical data communication, especially for future computerarchitectures. The WDM (wavelength division multiplexing) and the optical wiring technologies are ex...
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The standard IEC/EN61508 provides the developer with guidelines to develop and implement safety related systems according to the international standard. The standard supplies qualitative and quantitative criteria to e...
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