Cascade control with low order active disturbance rejection controller for higher order nonlinear cascade system

Aiming at a class of higher order, strong coupling, uncertainty nonlinear systems such as ball and plate system, a cascade control strategy with low order active disturbance rejection control (ADRC) is proposed when the nonlinear system is converted into cascade system of several low order nonlinear systems. The difficulty of parameter setting with higher order ADRC is resolved through this strategy. Because the disturbance and coupling are treated as an additional state variable, which is then estimated and compensated for in real time through the ESO of low order ADRC, the problems of uncertain, nonlinear, coupling and disturbance rejection are all solved. At the same time, the simulation studies of ESO and trajectory tracking with ball and plate system are made to verify the effectiveness of the strategy which is proposed. The results of simulation experiments indicate that the proposed strategy has better dynamic, robust characteristics aiming at the higher order, complicated nonlinear plant.