Incremental Nonlinear Dynamic Inversion Control for Coaxial Compound Helicopter

In this paper, incremental nonlinear dynamic inversion (INDI) methods, which have been widely applied in fixed-wing aircraft to manage model uncertainties and external disturbances, are investigated for coaxial compound helicopters (CCH) across full envelope flight modes. Firstly, a comprehensive nonlinear dynamic model of the CCH is developed. Then, a control surface switching strategy, designed for three distinct flight modes within the entire flight envelope, is introduced. Central to this research is the design of inner-loop angular rate control laws, employing INDI to effectively handle both modeling uncertainties and external disturbances. Subsequently, an outer-loop attitude control law is established, aligned with the specific response characteristics of the CCH and leveraging the dynamic inversion method. The efficacy of the proposed control law in achieving precise attitude tracking, even in the presence of notable model uncertainties and external disturbances, is demonstrated through simulation results.