Tracking control for a velocity-sensorless VTOL aircraft with delayed outputs

This paper presents a nonlinear output-feedback control method to force an underactuated vertical take-off and landing (VTOL) aircraft with delayed measurement outputs to asymptotically track a given reference trajectory. The control development is based on a delayed-output observer. The proposed observer consists of two-step observation algorithms reconstructing the system state with multi-delayed time instants. Conditions are given ensuring global exponential convergence to zero of the observation error for the given the delays in the measurements. Moreover, two low-dimensional controllers are designed separately to stabilize the two decomposed flight dynamics, and make the overall closed-loop system stable. The merits of method include its simple implementation and interesting application. Numerical simulations illustrate the effectiveness of the proposed control method.