Incremental Nonlinear Dynamic Inversion Based Control Allocation Approach for a BWB UAV

Aircrafts with BWB (Blended-Wing-Body) layout have many potential advantages. However, there are also complicated aerodynamic coupling effects in a BWB UAV and nonlinear interferences between its multiple control effectors. These uncertainties pose great challenges to the flight control. Traditional gain scheduling control law and simple linear combination allocation of multiple control effectors fail to provide satisfactory performance confronting the above challenges. In this paper, an incremental nonlinear dynamic inversion based control allocation (INDICA) approach is implemented to a BWB UAV for the purpose of improving the robustness of the control system and exerting the full effectiveness of redundant control effectors. This approach is embedded in a dual-looped attitude control law, exploiting time scale separation principle. The control effectors are allocated efficiently based on a re-distributed pseudo-inverse algorithm in an incremental form, where the actuator limits and nonlinear axis-coupling effects of multiple effectors are taken into account. A fault reconstruction strategy for control effectors is also designed based on the INDICA. The results show that the INDICA controller follows the attitude command accurately while reducing the dependence on model accuracy. And it can be quickly reconstructed under various fault conditions, which provides sound and feasible solutions for the flight control of a BWB UAV.