A NEW-TYPE OF RELIABLE CONTROL-SYSTEM USING DECISION BY MAJORITY

Recently, safety measures for a control system against control device failures, especially against sensor failures, has become important. Co ntrol theory for designing a compensator such that the stability of th e total control system can be maintained against possible failures in such control devices has been studied. This is called reliable control . However, because of problems with performance deterioration when som e sensors are out of order and the restricted class of control systems to which it can be applied, reliable control has not been put to prac tical use. Based on the same concept as passive redundancy, this paper considers a situation in which several redundant sensors for the outp ut of a controlled object are in operation simultaneously and independ ently. We direct attention to a method for using the redundant informa tion from the sensors and propose a new type of control system where d ecision by majority is introduced. This idea of tolerance to sensor fa ilures presents a way of overcoming the problems with conventional rel iable control. (C) 1998 Scripta Technica.