A New Variable Fractional-Order Pi Algorithm

In this paper the authors present a novel control algorithm based on control error sign dependent variable-fractional-order PI controller. The algorithm is being optimized via ITSE criterion for control error. It is tested both for unconstrained control signal and a more real-case scenario, i.e. 2.5 saturation on control signal. The algorithm is tested for A-,Band E-type variable-order PI controllers and compared to basic PI and fractional-PI (FPI) controllers. Important parameters, including rise and settling time, overshoot and peak time of unit-step response, as well as graphical representation of unit-step response are presented. Conducted numerical simulations show some interesting behaviour of the A-type definition both in non-limited and limited control signal cases, i.e. switching between derivation and integration action. Moreover, collected unit-step response parameters indicate the A-type definition to be the best behaving in all considered criteria. However, some unwanted minor oscillations in the unit-step response are to be observed, whose origin will be investigated in further research. (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.