Modified Derivative Decoupling Control of Nonlinear Interactive System

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 on-line microcomputer. Liquid levels and temperature in tanks mixing hot and cold water inflow streams ore controlled. The results are compared with those obtained by the instantaneously optimal control and by the Inverse Nyquist Array technique. Both simulated and experimal performances of the modified derivative decoupling controller are found to be better in comparison with those obtained by the controller based on the Inverse Nyquist Array. Further, experiments showed that the modified derivative decoupling controller reduced the interaction to a negligible level.