Dependability Evaluation of Watchdog Processors

Abstract Many control systems need a good safety level, this can be done with the help of a Watchdog Processor, that not involve a high increase in the system's cost compared with other fault tolerant structures. This paper presents Markov models for studying the safety, reliability and availability of a Watchdog Processor. To carry out a benefit analysis, the results of the models of the three systems: Simplex Systems, Reconfigurable Duplication Systems, and Stanby Sparing Systems, are cornpared. The influence of parameters, suchcoverage, permanent faults, fault rate, etc, in all models is considered. For solving the models in the transient mode, a program based in the randomization method is used.