Models to calculate safety and reliability parameters for embedded systems

This paper intends to demonstrate that embedded systems have to fulfil high safety and reliability requirements if they are implemented in safety loops. It describes reliability and safety methods especially for the SIL classification of hardware components. Mathematical equations determine safety parameters using the Weibull distribution. Further two types of models are demonstrated: safety architectures with and without redundancy. Since the industrial experience has shown that special architectures such as 1oo1, 1oo2 or 2oo4 are necessary, relevant equations are shown in this paper. Safety considerations must take into account both hardware and software. The measures required for the SIL classification will also be shown in this paper.