Robust combined feedback/feedforward control for fractional FOPDT systems

Abstract

SUMMARYIn this paper, a combined feedback/feedforward design methodology is proposed for fractional systems in order to cope with model uncertainty and to minimize performance degradation. Based on a fractional commensurate uncertain model, a parametric robust controller is first designed. Then, a parametric command signal for the unity feedback loop is designed. Finally, an optimal set of tuning parameters is found by solving a constrained min-max optimization problem in order to minimize the worst-case settling time. Simulation results show the effectiveness of the methodology.

Inversion-based set-point filter design for fractional control systems

“…In this case the operators commutation is guaranteed, independently form the adopted definition because of the strict properness of zero order dynamics, provided (20) to be satisfied. In [0, ], considering that the Laplace transform of the convolution integrals equals the product of the Laplace transforms and that ℒ[ ] = Γ( + 1) 1 +1 , starting from (19) and using the same procedure employed to obtain (11), we can derive its differintegral as an explicit expression in terms of MittagLeffler functions (10). For > a similar result is achievable by considering that the transition polynomial (19) can be represented as the summation of a polynomial and a delayed one.…”

“…Another approach that can be pursued to achieve satisfactorily set-point tracking performance is the use of a feedforward control law [6], [7]. Among the recent research in this topics, in [8], [9], [10] the problem of the design of a feedforward (model-based) control law has been considered for fractional systems, based on the input-output inversion concept for a standard unity-feedback linear control system. We propose here a novel approach to design a setpoint filter based on a dynamic inversion technique.…”