A Fuzzy-Logic-Based Programmable Electronic System for the Control of Safety-Critical Processes

Abstract

The architecture of a fuzzy controller especially suited for safety-critical applications such as temperature control in nuclear reactors is developed. Its main chacteristics are fuzzification by low-resolution analogue-to-digital converters and inference by look-up in a table containing a fuzzy rule set. Although originally based on fuzzy logic, the resulting controller is not “fuzzy” at all in its behaviour. Owing to its simplicity both in hardware and in software, safety-licensing of the controller is facilitated. With regard to software, this can easily be carried out by back translation of the table content. Working in a strictly cyclic fashion, the controller features fully predictable real-time behaviour. The controller’s hardware operation is supervised by a fail-safe logic immediately initiating an emergency shut-down in case of a malfunction.