Multivariable Observer-Based Deadtime Control

A closed-loop form of observer is presented for multivariable control of processes exhibiting time delay or "dead time" characteristics. With this method under ideal conditions (i.e., a perfect fit of the model to the process), the separation of the system poles does not include any deadtime effects. Thus, higher controller gains could normally be used under these conditions. Here, response results are shown for simulation tests on a (2×2)-interactive first order lag plus deadtime process which originated in the literature as a dynamic model for a binary distillation column. Response comparisons are made between the observer-based system with proportional-plus-integral (PI) control and the systems with a main "multi-Pi" controller alone and in combination with the multivariable (Smith) type of open-loop predictor. The performances with respect to load (signal) disturbances and process parametric changes or forcing are mainly considered.