New desaturation strategy for digital PID controllers

The phenomenon of `integral wind-up¿¿ in a process controller, when a plant´s actuation reaches its limits, is well known, and can cause severe problems. This is particularly so for batch reactors, in which the start-up phase, when such saturation occurs, is a significant proportion of the total process time. This short paper presents a new technique which has been used successfully in several processes. A practical example, relating to an industrial batch reaction process, is described in detail. The new method has proved to be very effective in this demanding application.