Control for autonomous VTOL aircraft with restricted inputs

This study presents simple controllers for achieving global stability in a Vertical Take-off and Landing (VTOL) aircraft with bounded thrust input. While previous studies apply nonlinear combinations of nested saturation functions for stabilizing the equilibrium point of the system, the proposed controllers are based on smooth uniformly bounded functions that can easily be implemented. A procedure for synthesizing a control function that steers the aircraft to an acceptable configuration while reducing the applied control effort is also presented. Using the flatness property the approach is based on a simple solution to a (sub) optimal control problem with a quadratic index of performance.