Reliability Allocation for a System with Complex Redundancy

The paper deals with the possibilities of allocating reliability requirements for a system using complex redundancy. It means system consists of a few identical subsystems and for its common function it is quite enough if only certain part of these subsystems operates. The subsystems not operating at a certain moment serve as redundancy in case that the subsystems which are operating fail. All the system, however, is not a trivial parallel structure, because if the system is to work properly, always more than one subsystem should operate and the subsystems can function only in configurations set in advance. Practical application of the suggested method of reliability allocation is demonstrated for a pantograph system of a high-speed train. In order to provide the proper function of the system, the minimum number of operating pantographs in pre-set configurations providing safe current collection has to be always available. Using some pantograph configurations (e.g. two pantographs being one after another very closely) is in fact not possible for safety reasons. The article presents the procedure of reliability allocation for this specific system. Suggested method is based on a truth table and Boolean algebra application.