Robust compensation for active disturbance rejection control of a class of high-order systems with large time delay: Simulation and experimental studies

Rejection of unknown disturbances and uncertainties in high-order nonlinear systems with large delays is an important control problem. Active disturbance rejection control (ADRC) solves disturbances and uncertainties in a simple and effective way. In engineering, low-order ADRC is often used to control high-order large-delay systems because of its ease of implementation and simplicity of operation. However, this leads to the problem that the low-order ADRC has a limited ability to configure the high-order nonlinear systems. The desired dynamics and the closed-loop dynamics are almost always very biased. For a class of high-order nonlinear systems with delay, a bias feedback compensation (BFC) approach to ADRC is suggested. This strategy works by adding a feedback loop based on the desired dynamics over the ADRC loop. The BFC strategy can improve the poor performance of low-order ADRC for higher-order nonlinear systems. In addition, a synthesis parameter tuning procedure of BFC-ADRC is proposed in this article. Then, the stability problem is analyzed in this article. Finally, high-fidelity simulation studies on a 1000 MW power plant for superheater steam temperature control and experiments on three interacting water tanks for level control are performed to verify the tracking, disturbance rejection, and robustness of the control strategy. Both simulation and experiments show that the method is highly robust and significantly improves both disturbance rejection and tracking performance.