Hexacopter outdoor flight test results of an Extended State Observer based controller

Extended State Observers (ESO) provide the appealing capability of estimating states and disturbances (like modeling errors) simultaneously. In this paper we present a modified full-state linear ESO as an augmentation of a baseline attitude tracking controller for a hexacopter. The baseline controller is designed using Nonlinear Dynamic Inversion with relative degree 2. By feeding back the estimated modeling error from the ESO, the performance as well as the robustness of the overall control system is significantly improved. These capabilities are demonstrated in outdoor flight tests with a hexacopter, where controlled flight is achieved even under severe actuator degradation. Due to the linear structure of the presented ESO, this might be an alternative to adaptive controllers in view of certification issues.