A Systematic Comparison of Identification Techniques Used in Industrial Systems of Autotuning

The paper illustrates a systematic procedure to evaluate the suitability of different identification technique for control purposes. These techniques, commonly used in industrial autotuners, are: open loop step, closed loop step and relay feedback. A review of basic characteristics with emphasis on pros and cons is firstly presented. The comparison is stated in terms of achievable performance, duration of experiments, robustness to noise and sensitivity to external disturbances. Simulations for different classes of process have been performed in order to find general conclusions and to draw guidelines for the choice of the most suitable technique. Main features of a software package, expressly developed to train and assist the control engineer, are finally illustrated