Decoupling Control for Hovering Flight Vehicle with Parameter Uncertainties

Abstract

*† ‡ § This paper proposes a new approach to consider nonlinear H∞ control of hovering vehicles described by six-degree-of-freedom nonlinear dynamics with plant uncertainties due to the variation of moments of inertia caused by fuel consumption and/or payload operation. Taking into account nonlinear effect, plant uncertainty, and exogenous disturbances caused by 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. Nomenclature dx, dy, dz, and dl , dm , dn = applied exogenous forces and moments Fx, Fy , Fz , and L, M ,N = applied forces and moments g = acceleration due to gravity xx I , xz I , …, = the moments of inertia of the flight vehicle s m = vehicle's mass U, V, W, and P, Q, R = linear and angular velocities ,, φ θψ = Euler angles 0 θ = main rotor collective pitch angle 0T θ = tail rotor collective pitch angle 1c θ = lateral cyclic pitch 1s θ = longitudinal cyclic pitch