On the concepts of fail-safety and fail-safe systems
Zhi Wei Zhou · Journal of the China Railway Society · 2002
The paper analyzes the definition of fail safety given by M.Nicolaidis and points out that the present formal definitions for the concept of fail safety are imperfect. On the basis of discussion and analysis of fail safe systems, the paper presents a new formal definition of fail safety, such that the partition of the outputs set of the fail safe system into the fail safe side and the fail dangerous side depends on the external environments of the system. By means of this definition, we can introduce the concepts of the ideal fail safe system, the p FS system, the absolute fail safe side and a new concept of self locking for fail safe systems as well.