State-feedback-based fractional-order control approximation for a rotary flexible joint system

In recent years, fractional-order controllers have been used more extensively in applied research and industrial applications. In this article, a state-feedback-based fractional integral control scheme is proposed and implemented in a rotary flexible joint system. For this modified state-feedback control approach, two different approximation methods are used: CRONE (Commande Robuste d'Ordre Non Entier, meaning noninteger-order robust control), developed by A. Oustaloup, and the FOMCON (fractional-order modelling and control) MATLAB toolbox. For comparison, pure state-feedback control and the modified technique are both implemented for a simulation and an experiment involving a rotary flexible joint system. The tracking performance of the rotary arm and the degree to which the tip vibration is minimized are evaluated and compared between the pure state-feedback control scheme and the modified state-feedback-based fractional integral control scheme.