Flatness-Based Discrete Active Disturbance Rejection Control for the Flexible Transmission System

The flexible transmission system benchmark was proposed to evaluate the robustness of digital controllers. The multi-model uncertainty coupled with the non-minimum phase (NMP) zero is a challenging issue for the controller design. Therefore, a flatness-based discrete active disturbance rejection control (ADRC) scheme is formulated in this work, constituting an extended state observer, a linear feedback law and a set-point filter. The NMP zero issue is overcome by the flatness-based transformation, and the multi-model uncertainty is compensated by the discrete ADRC. The performances of set-point tracking and disturbance rejection are analyzed theoretically. Furthermore, the proposed control scheme is simulated and discussed in the time domain and the frequency domain.