Robust nonlinear control and stability analysis of a 7DOF model-scale helicopter under vertical wind gust

The helicopter manoeuvres naturally in an environment where the execution of the task can easily be affected by atmospheric turbulences, which lead to variations of its model parameters. The originality of this work relies on the nature of the disturbances acting on the helicopter and the way to compensate them. The disturbance consists in vertical wind gusts. Here, a 7DOF nonlinear Lagrangian model of VARIO helicopter with unknown disturbances is used. This model presents quite interesting control challenges due to nonlinearities, aerodynamical forces, underactuation and its dynamics are non-minmum phase. Two approaches of robust control are compared via simulations: an approximate feedback linearization and an active disturbance rejection control (ADRC) using the approximate feedback linearization procedure. Several simulations show that adding the observer can compensate the effect of disturbances.