Multi-objective optimization based design of fractional PID controller

This paper deals with robust fractional order PID controller design via numerical multi-objective optimization. The proposed interval-based design scheme uses frequency-domain specifications to ensure a desired closed-loop behavior. By maintaining the desired phase margin quasi-constant in a pre-specified frequency band, it guarantees more robustness to gain uncertainties. This leads to a closed-loop system with an interesting iso-damping property in a more large frequency band than other design methods. A numerical example is presented to show the efficiency of the proposed method and to discuss about the obtained results.