Multiple-loop PID controller tuning by the goal attainment trade-off method

An interactive multi-objective optimisation method has been introduced in this study for tuning multi-loop PID controllers. Several design specifications may be simulta-neously considered in this optimisation problem. The multi-objective PID tuning, problem was then reformu-lated into the goal attainment framework. Minimisation of the attainment factor was used as a design index for checking the system whether it met the goals. A trade-off procedure should be performed to achieve the acceptable control effects if the goals were unsatisfied. The one-parameter tuning PID controller was introduced in this work so that the number of the tuning parameters of the multi-loop controllers was reduced. The interactive optimisation search was accordingly lightened. Two examples, a two-loop and a three-loop process, were given to illustrate the design concept