Robust PI tuning for an elastic two-mass system

Elastic two-mass systems represent a wide class of industrial applications for which Proportional Integral controllers are common for speed control. The problem to set up the PI gains is crucial: the inner resonances could lead to undamped oscillations affecting the system behaviour. Moreover, in the literature the PI tuning problem is usually solved "experimentally" with a trial and error procedure starting by a cautious PI realization. Here we give bounds on the PI gains assuring robust performance. The bounds are functions of the plant parameters. Therefore, a systematic procedure to tune the PI can be easily implemented.