(598b) The Use of a Time Variant IMC Controller for Robust Performance Improvement

The design of the IMC controller requires that the filter time constant be specified as a single tunable parameter with an increase resulting generally in lower system performance but increased system robustness. In this work the effect of using a variable filter time constant for implementation in an Internal Model Control (IMC) system is presented. During an initial closed loop response a high performance filter constant can be employed with it changing during the course of the response to a final value resulting in a robust filter constant. This work will demonstrate the potential performance improvement that can be obtained by this approach for various types of plant model structures. The internal models used will be examined with and without plant model mismatch and the performance improvement quantified. Implementation details of the discrete IMC controller and rules for how to adjust the filter constant over time as a function of the model parameters and model structure will also be presented.