Direct digital process control: Practice and algorithms for microprocessor application

Process control applications and control algorithms suited for microprocessors are surveyed. Applications are noted both in large, general purpose process control systems and in specialized applications that have been made possible by the availability of computing power in small packages. Distributed control and use of extended data buses (data highways), both made possible by extensive use of microprocessors, are becoming standard in general purpose systems. General purpose process control systems still utilize proportional-integral-derivative (PID) algorithms and variants of them for the most part. Some recent research results on algorithms designed for use in stand-alone, single-loop calculator or microprocessor-based controllers are presented. These algorithms, which could also be used in direct digital control (DDC) systems, are specifically tailored for simple implementation in a relatively low computing power, discrete-time environment.