On time-constant robust tuning of fractional order proportional derivative controllers

This paper deals with analyzing a newly introduced method for tuning of fractional order [ proportional derivative ] ( FO[ PD ] ) controllers to be used in motion control. By using this tuning method, not only the phase margin and gain crossover frequency are adjustable, but also robustness to variations in the plant time-constant is guaranteed. Conditions on the values of control specifications ( desired phase margin and gain crossover frequency ) for solution existence in this tuning method are found. Also, the number of solutions is analytically determined in this study. Moreover, experimental verifications are presented to indicate the applicability of the obtained results.