Nonlinear output-transition control for nonminimum-phase systems: The VTOL example

Achieving the optimal output-transition control for nonlinear systems remains challenging and requires complex calculation. This paper investigates the use of a polynomial-based output-transition trajectory together with three different types of inversion-based feedforward for nonminimum-phase vertical take-off and landing (VTOL) aircraft. The necessity of pre-actuation and post-actuation is examined by comparing the input and output of the VTOL system obtained from these three nonlinear output-transition control methods. Based on simulation results, pre-actuation and post-actuation can be omitted but at the expense of the input magnitude and the smoothness of the output transition. This study offers alternative nonlinear output-transition control for nonminimum-phase systems when pre-actuation and/or post-actuation are not available.