Distributed process control system

摘要

A method and apparatus for carrying out the control of a process using a distributed process controller wherein each controller receives during consecutive time slots of a scan cycle inputs from the process representing measured values of process variables to be controlled by the control loops of the system. Control is provided by the use of a preselected algorithm in each of the slots with the output of that algorithm being used to control certain of the loops or to provide input to another slot or to a control program. Control programs which can be written by the user are run sequentially in the background to provide additional loops of control or inputs to the slots so that the number of algorithms which can be used is increased without drastically increasing the equipment required.