OUTPUT EFFECTIVENESS AND SCALING SENSITIVITY FOR SECONDARY MEASUREMENT SELECTION

Often in process control, it is necessary to use extra measurements, o r so-called secondary outputs for monitoring processes. Traditionally, the selection of these outputs is based on criteria which need to be calculated scheme-by-scheme resulting in a combinatorial problem. In t his work, it is shown that these secondary outputs can be selected usi ng an efficient measure, the output effectiveness (OE) when the output s are scaled in a special way. This method does not need any scheme-by -scheme calculation so that the combinatorial problem is avoided. Sinc e the OE measure is dependent on output scaling, its sensitivity to th is scaling is also discussed. A scaling sensitivity matrix is derived for the designer to quickly determine the effect of different choices of scaling factors on the OE measure. This information can then be use d for efficient output selection. This is demonstrated on a distillati on example.