Fault detection of redundant sensors used in reliable sampled-data control systems

Suyama and Zhang (1997) and Suyama (1998) presented a new reliable control system using decision by majority among redundant sensors with tolerance against sensor failures. It solves some questions of the conventional reliable control without loss of the advantage that explicit and urgent sensor failure detection is not needed. Even in this system, sensor failure detection is needed for avoiding simultaneous failures in each sensor set so that decision by majority functions effectively. It is difficult to detect the first sensor failure because the stability and the performance of the proposed system is expected not to deteriorate when one sensor is out of order. This paper presents new fault detection mechanism for redundant sensors used in the system, which is derived from making the best use of the characteristics of decision by majority. In a new framework of tolerance against sensor failures by the proposed system with the fault detection mechanism, urgent measures against sensor failures are taken by decision by majority, when the mechanism detects them