Model-plant mismatch detection using the plant-model ratio : the influence of multivariable systems containing both fast and slow dynamics

Abstract

The plant-model ratio, developed to diagnose model-plant mismatch present in model-based controllers, inherits the same limitations from the frequency-based analysis that the method is based on. Nonetheless, the plant-model ratio shows the capacity to counteract the effect of non-linear dynamics within processes due to the ability to diagnose parametric model-plant mismatches for first-order plus time delay models. The plant-model ratio is developed before being validated on the Wood-Berry distillation column. One of the prominent limitations of frequency analysis, the filtering effects of time constant differences, is investigated and quantified for the Wood-Berry distillation column, showing the effect of time constant differences on each parametric model-plant mismatch diagnosis.