On convergence of nonlinear active disturbance rejection control for MIMO systems

In this paper, the global and semi-global convergence of nonlinear active disturbance rejection control (ADRC) for a class of multi-input multi-output (MIMO) nonlinear systems with large uncertainties that come from both dynamical modeling and external disturbance are proved. A class of linear systems with external disturbance that can be dealt with by ADRC is classified, from which a comparison with internal model principle is made both analytically and numerically. Numerical simulations illustrate the efficiency and advantage of ADRC in dealing with unknown dynamics, fast tracking, and lower overstriking.