Sintonia iterativa de margens de ganho e fase.

Abstract

The automatic control improves process efficiency, guarantees the process safety and product quality. There is still a large demand for controller tuning and opportunities to propose new techniques. The techniques for iterative identification and control under closed loop operation are very attractive for industrial applications because it doesn't cause stops in system operation, guarantees safe operation, handles unstable processes and satisfies usual production restrictions. The use of simple models accurate closed to interesting frequencies for control together with experimental frequency data is a good approach especially for complex dynamics. In this work it is proposed an iterative procedure for closed loop controller tuning applying a relay experiment. The phase margin is evaluated and a continuous-time model is identi ed using constraints. This model is improved at high frequencies employing frequency data from the same experiment, the improved model is used to estimate the gain margin. The controller redesign is performed minimizing a frequency domain criterion based on gain and phase margins that are classical measures of robustness in addition to the crossover frequency. The procedure is applicable for a large number of processes types and safely approach specifications using a few experiments.