Development of Robust Fractional-Order Reset Control

In this paper, a framework for the combination of robust fractional-order CRONE control with nonlinear reset is given for both first and second generation CRONE control. General design rules are derived and presented for these CRONE reset controllers. Within this framework, fractional-order control allows for better tuning of the open-loop responses on the one hand. On the other hand, reset control enables a reduction in phase lag and a corresponding increase in phase margin compared to linear control for similar open-loop gain profile. Hence, the combination of the two control methods can provide well-tuned open-loop responses that can overcome the fundamental linear control limitation of Bode's gain-phase relationship. Moreover, as established loop-shaping concepts are used in the controller design, CRONE reset can be highly compatible with the industry. The designed CRONE reset controllers are validated on a one degree-of-freedom Lorentz-actuated precision positioning stage. On this setup, CRONE reset control is shown to provide better tracking performance compared to linear CRONE control, which is in agreement with the predicted performance improvement.