This research aims to design a control and protection system that can exhibit high reliability through the use of fault tolerance. While many fault-tolerant computer systems have been developed, an integrated systems approach demands that other factors must be included. We are particularly concerned with the interfaces between the various subsystems or elements of the total system. The necessary properties to achieve fault tolerance are (1) all errors must be detected and corrected, (2> all nominally independent systems must be isolated to the extent that errors or other faults in them cannot disturb the performance of the other elements or subsystems, and (3) each subsystem must be able to detect the status of other subsystems so that it may determine if that subsystem is in a fault-free state, or is in a state whereby a fault exists but has been properly handled, or is in a state where a fault or multiple faults exist that disable the particular subsystem. The approach used is one of hierarchical abstraction. At the top level of the hierarchy the performance goals and reliability goals of the target system are specified. At the next levels, each subsystem will be defined in terms of its goals and the interconnection between them will be examined. At each subsequent sublevel of the hierarchy, the sub-subsystem specification and interconnection will be examined to achieve the goals of the higher level subsystem. The development of validation techniques is essential if such systems are to be used. The particular validation technique that is proposed rests heavily on the hierarchical design technique described above.Anticipated Results/Potential Commercial Applications as described by the awardee:The results of the study are anticipated to be a specification of the interfaces between subsystems and the specifications of those subsystems to achieve the required reliability goals. Of particular importance is the design of subsystem control to achieve proper control under various normal and non-normal plant conditions and the ability to optimize the complete system. It is expected that a detailed validation plan will be developed using formal proof techniques based on the hierarchical design approach.
