Quad Rotorcraft Switching Control: An Application for the Task of Path Following

This paper addresses the problem of road following using a quad rotorcraft equipped with an onboard image processing system. The main objective consists of estimating and tracking the road without a priori knowledge of the path to be tracked. Special interest is also given to the development of efficient estimation and control strategies for dealing with situations when the road is not detected in the camera image. Aiming at this goal, two operational regions are defined: one for the case when the road is detected and another for the case when it is not. A switching between the measurements of imaging and inertial sensors enables estimation of the required vehicle parameters in both operational regions. In addition, for dealing with both aforementioned cases, a switching control strategy for stabilizing the vehicle lateral position is proposed. The system stability is verified not only in the two operational regions, but also in the switching boundaries between them. The performance of the switching estimation and control strategies is tested in numerical simulations and real-time experiments, successfully validating the effectiveness of the proposed approaches.