A fault-tolerant interface for self-validating sensors

Much effort has been expended in recent years on the development of fault detection and isolation (FDI) techniques for industrial plant. The increasing availability of localised computational power together with the richness of communication provided by digital bus technology offers the necessary infra-structure for FDI techniques to be applied in a more systematic manner throughout industry. The author outlines a scheme in which the self-validating sensor generates an uncertainty value together with an additional status datum for every measurement value. It is suggested that these parameters are applicable to any type of sensor, and convey sufficient information for appropriate control action to be determined. In order to achieve this, the concept of uncertainty must be extended to accommodate the occurrence of faults, while the status value indicates one of a small number of possible generic fault states. Using uncertainty calculus it is possible to evaluate the effect of single of multiple sensor failures upon data quality elsewhere in the control scheme