Adaptive Controller Performance Evaluation: Foxboro EXACT and ASEA Novatune

The work described in this paper was focused on two recently commercialized adaptive self-tuning controllers, the Foxboro EXACT and the ASEA Novatune. Tests were performed in pulp and paper mill processes. The Foxboro EXACT demonstrated a dramatic performance improvement on a recovery boiler specific gravity control loop and on a paper machine pH loop. It was clear that addition of adaptive derivative control to adaptive PI control caused a substantial increase in performance. The ASEA Novatune adaptive feedforward feature was found to add significantly to performance improvements over adaptive feedback control alone. In addition to mill tests, both controllers were tested with two different real-time process simulations. These were: 1) a digital non-linear second-order model; 2) a digital fifth-order linear model with time delay. These digital simulations were implemented with an IBM PC-compatible personal computer.