Reliable judgement for gray-zone in monitoring system

This paper discusses a safety monitoring system design that consists of sensors with gray zone signal outputs, where the gray zone signal expresses no judgement for situations of uncertainty. This type of sensor is expected to prevent model-induced failures that may be induced by a failure to alarm or by generating false alarms, since the model-induced failures occur in the gray zone. Our problem of interest is in determining the optimal judgement method for the gray zone. Firstly, one-sensor system with three-value outputs is analyzed, and under certain conditions the two-step judgement method utilizing information from another sensor only for gray zone outputs are shown to be better than both deterministic and stochastic judgement. Secondly, a heterogeneous type of sensor system model is introduced where a judgement of safety or danger is always made after integrating information from a two-value sensor that monitors another characteristic of the real state. Lastly, it is suggested that these monitoring models are applicable to the analysis of the human collaboration problem