Output tracking for nonlinear non-minimum phase systems and application to PVTOL aircraft

In this paper, we consider a class of multi-input multi-output (MIMO) nonlinear non-minimum phase systems. For such nonlinear system, an output tracking control approach based on decomposition is presented and applied to a planar vertical takeoff and landing (PVTOL) aircraft. The external dynamics of the system can be separated into minimum-phase and non-minimum-phase parts. The internal dynamics of the system is separated to linear part and nonlinear part, and the linear part of the internal dynamics is only related with the non-minimum phase part of the external dynamics and the states of itself. Consequently, two low-dimensional controllers are designed separately to stabilize the two subsystems, and make the overall closed-loop system stable in spite of the existence of disturbances. Through this method, the design of the controller parameters is very simple. The theoretical results are confirmed by computer simulations.