Realtime Operating Systems For Distributed Process Control Systems

Abstract

Conventional process control systems today are organized around a single computer with a realtime operating system as the key element. The function of the realtime operation system is to control resources in the system shared by application tasks including input/output devices, computer memory, and the CPU itself.Two developments forthcoming will affect realtime operating systems for process control. They are first, the trend toward line sharing and remote intelligent terminals; and second, the trend toward the use of multiple computers and microprocessors in semi-dedicated control functions but still integrated into the overall computer control system.Both of these trends indicate that the major impact on the realtime operating system will be in the distribution of the data base and intertask communication since both devices and data and tasks will be resident in possibly different computers. The objective of this paper is to examine techniques for communication between computers which can realize effective interprogram communication even when the tasks and data base are distributed among several process control computers or special purpose controllers. Some experimental results are presented.