EXPERIMENTAL EVALUATION OF SATURATION ALGORITHMS FOR ADVANCED DIGITAL CONTROLLERS.

Simulations and experiments were performed to confirm that the anti-reset windup method results in a much slower output response than the algorithms proposed in this paper and, in some cases, the method itself becomes a constraint to controller tuning. Four saturation algorithms were studied, ranging from the anti-reset windup method to a full-scale, on-line constrained optimization. These saturation algorithms not only provide considerable improvement over the anti-reset windup method, but also reduce the 'ringing' problem in 'model-based' controllers. As a result, the advanced controller can be more tightly tuned. The simulations and experiments were performed on a pilot-scale stirred-tank process involving dead-time. They show that it is worthwhile to include these saturation algorithms in advanced digital controller designs.