Active disturbance rejection solution for single water tank systems with high-precision

Due to the nonlinearities, disturbances and uncertainties of the single water tank system, an active disturbance rejection control (ADRC) solution with high-precision was proposed. Firstly, a nonlinear mechanism model was built based on the theories of fluid dynamics for water tank system. Then, the nonlinear model was linearized in static work point to get its simplified model. Secondly, first-order linear ADRC solutions for the system models with unknown order were designed. With a simple “integrator series” as the normalized type of the feedback system, the parts of dynamic system is different from the normalized type are treated as the total disturbance. So it was estimated by the second-order linear extended state observer and canceled out in the control law. The system, with disturbances, uncertainties and nonlinearities, is reduced to the canonical form of the linear chain of integrators. Simulation results show that both the ADRCs have better performances than PID controller on disturbance-rejection and robustness.