Implicit NDI robust nonlinear control design with acceleration feedback

In order to improve the robustness of the regular explicit nonlinear dynamic inversion (NDI) control law, an incremental version of the NDI control law is designed via the implicit dynamic inversion (DI) and singular perturbation methods, in which the state acceleration (derivative) is used as feedback to measure the effects of the aircraft model perturbation and the current position information of the effector. The complete aerodynamic model is unnecessary because there is no nonlinear direct state feedback based on the nominal aircraft model, and as a result, the sensitivity to aircraft model is reduced. The angular acceleration is established utilizing a special geometrical method through overloading information, and the other state acceleration is obtained using an algebraic method based on aircraft dynamic equations. The control structure is simple, and the isolation of measurement signals, reestablishing of feedback signal, re-allocation of control power and the reconfiguration of control law can be achieved conveniently and rapidly. The control law design and computer simulation for an aircraft with aerodynamic perturbation demonstrate that the robustness of the control law is increased.