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Abstract

In the last decades, several interesting applications of fractional calculus appeared in the process control field. The usage of fractional elements for description of ideal Bode's control loop is one of the most promising. In authors' previous work, the concept of model set suitable for description of typical industrial processes was presented. In this paper, the problem of reaching the ideal Bode's shape for several process models arising from the model set is considered. In contrast to the other known approaches, the exactly computed filter frequency response is approximated. This approximation is done using standard MATLAB constrained multivariable optimization. The comparison with other methods shows that the direct approximation leads to the significant reduction of the filter order. Arising filters can be useful especially for processes with large gain variations.