Loop-Shaping and Easy Tuning of Fractional-Order Proportional Integral Controllers for Position Servo Systems

This paper develops simple formulas directly relating performance specifications to control parameters of fractional-order proportional integral (PI) controllers for position servo systems. With the proposed controller settings, the open-loop frequency response achieves a good phase margin, that remains constant in a wide range around the crossover frequency. Consequently, the tuning results in high stability robustness to gain variations in the loop. Moreover, the fractional order integration also leads to limited overshoot and short settling time. Laboratory experiments confirm simulation results.