Improving the Load Disturbance Rejection Performances of Imc-tuned Pid Controllers

In this paper a new methodology for the improvement of regulation performances of PID controllers, tuned according to the concept of Internal Model Control, is presented. Basically, it consists of adding to the PID output, when no change of the set-point is required, a value that depends on the difference between the system output and the PID output itself. In this way the load disturbance rejection capabilities of the control system can be improved significantly, especially for lag-dominant processes. The use of the additional module of the control system does not require any significant extra tuning effort for the operator, because analytical tuning rules are given for the selection of the new parameters. Simulation examples are given in order to show the effectiveness of the technique. Copyright c 2002 IFAC