For a class of nonlinear MIMO system, a novel decoupling control method is proposed. Firstly, equivalent
input of each subsystem is designed by using backstepping method. Then, the total uncertainties, including coupling effect,
external disturbance and parameter time-varying of each subsystem, are estimated by an extended state observer(ESO), and
the estimate is introduced into the backstepping controller to compensate. Finally, decoupling and control are achieved. The
convergence of the new method is proved by using Lyapunov stability theory. Simulation result shows that the method can
achieve fast response, good decoupling effect and good robustness.