Modified derivative decoupling control of nonlinear interactive system

Abstract

A new technique is presented to overcome difficulties encountered in designing controller based on the nonlinear derivative decoupling control approach. The method, which is limited only to a set point change, is extended to a load change (unknown disturbance). This modified method is investigated on noninteracting control of laboratory-scale mixing tanks in series both by digital simulation and by experiment using online microcomputer. Liquid levels and temperature in tanks mixing hot and cold water inflow streams are controlled. The results are compared with those obtained by the instantaneously optimal control and by the inverse Nyquist array technique. Experiments show that modified derivative decoupling controller reduced the interaction to a negligible level while controlling the variables by three conventional proportional controller results in considerable interactions.