Increasing system reliability-a survey of redundant control methods

Several redundant system architectures are discussed, including hot standby systems, CPU redundancy, full dual redundancy, and fault tolerant systems. Each architecture is examined in terms of its potential for increased reliability, complexity, and cost. It is concluded that the range of redundant controllers available today provides a level of reliability suitable to any process. The control system designer, in selecting a controller, must consider not only the probability of failure but also the consequence of a failure. Since the design of the controller can affect the consequences, it must be carefully evaluated