Maximum sensitivity constrained region based tuning of active disturbance rejection control for industrial applications in presence of time-varying disturbances.

Linear active disturbance rejection control (ADRC) uses conventional Luenberger type linear extended state observer (LESO) and a simple proportional derivative (PD) controller for anti-disturbance applications. Limitation of the linear ADRC lies in its inability to adequately reject time-varying disturbances. Modified ADRC strategies discussed in this manuscript, including LESO-based proportional integral derivative-ADRC (LESO-PID-ADRC) and proportional resonant-ADRC (LESO-PR-ADRC), exhibit the capability to proficiently track ramp and sinusoidal references while effectively suppressing similar disturbances. Additionally, a quasi-generalized integrator-extended state observer based PID-ADRC (QGI-PID-ADRC) is proposed which is capable of tracking both step and ramp references while simultaneously rejecting ramp and sinusoidal disturbances. Furthermore, maximum sensitivity constrained region (MSCR) based graphical tuning approach is presented for the PID and PR controllers. Frequency domain analysis is conducted to illustrate reference tracking and disturbance rejection capability of the designed controllers. Moreover, stability of the closed loop system is illustrated using Nyquist plots. Simulation study is conducted in MATLAB for two complex systems (ship motion model and pressurized water reactor (PWR)) which have associated nonlinearities, time-varying system parameters and modeling uncertainties. The research demonstrates that LESO-PID-ADRC, QGI-PID-ADRC and LESO-PR-ADRC, when tuned using the proposed graphical approach, outperform recently introduced control strategies, excelling in both reference tracking and disturbance rejection.