Nonlinear H_∞ decoupling hover control with parameter uncertainties

This paper proposes a new approach to nonlinear H_∞ control of hovering vehicles described by six-degree-of-freedom nonlinear dynamics with plant uncertainties due to variation of moments of inertia caused by fuel consumption and/or payload operation. Taking into account nonlinear effect, plant uncertainty, and wind gust, we show in this paper that the six-degree-of-freedom nonlinear H_∞ controller can be exactly decoupled into two three-degree-of-freedom controllers, one for translational motion and the other for rotational motion, even though longitudinal and lateral dynamics of flight vehicle in hover are highly nonlinear and severely coupled. At the same time, the paper shows that the nonlinear H_∞ decoupling controls in hover are robust to plant uncertainty and wind gust.