CHARACTERISTICS AND PERFORMANCE OF AN AUTOTUNING PROPORTIONAL INTEGRAL DERIVATIVE CONTROLLER FOR DISSOLVED-OXYGEN CONCENTRATION

The characteristics and performance of an autotuning proportional inte gral derivative (PID) controller developed by us have been investigate d. The parameters for this controller, proportional gain, K, the integ ral time constant, tau(i), and the derivative time constant, tau(d), a re on-line-tuned by using heuristic rules, requiring no a priori tunin g. The controller showed a stable and robust performance, even when on ly K was online-tuned. However, the dynamic (or time delay) of the mem brane-type dissolved oxygen (DO) probe caused oscillations in the DO c oncentration unless it was properly compensated. This required a predi ction method. When all three controller parameters were on-line-adjust ed, the DO probe dynamic could be effectively overcome with no separat e prediction step.