EFFECT OF INTERACTIONS
Since most unit operations have multiple loops and streams, interactions can exist where the proportional-integral-derivative (PID) output of one loop affects the PID process variable (PV) of another loop and vice versa. Interactions can cause loops to confusingly burst into oscillations. Here we look at how to reduce the consequences and prevent the initiation of interactions. In the process we realize some principles in the design of control strategies for plantwide control.
Often a production rate control loop affects a quality control loop such as a composition, pH or temperature loop. Action of the temperature loop does not affect the feed loops if cooling and heating ...