Composite observer based finite time control for nonlinear systems subjecting to multiple disturbances

Composite observer based finite time control of nonlinear systems in case of multiple disturbances is studied in this article, wherein the disturbances contain two parts, the first type is the harmonic disturbance with modeling errors, and all other disturbances are classified as the second type, known as lumped disturbances. To give estimation of the harmonic disturbance and the lumped disturbances, a disturbance observer (DO) and the extended state observer are constructed, respectively. On this basis, a finite-time elegant anti-disturbance controller is presented by combing DO-based control, active disturbance rejection control, backstepping technique and the finite time command filter method. Eventually, it is proved that the design method put forward in this article is correct and feasible.