Cascade PI-controllers with fuzzy tuning

This paper presents some simple fuzzy logic schemes for online tuning proportional-integral controller parameters to improve system robustness. It is shown that, with fuzzy tuning, the reference response is well-damped and the maximum deviation of the disturbance response is reduced even in the case of changing plant parameters. The fuzzy-tuned controllers can then be applied to multiloop control systems using the conventional cascade control principles. Simulation results for a two-mass servo system indicate that good performance can be achieved in the presence of parameter and load variations, and backlash nonlinearity. Explicit expressions for the controller parameters facilitate the training process at a low computational cost. The proposed method can be applied for a variety of controlled objects suffering from uncertainties.