Quadrotor Fault-Tolerant Control at High Speed: A Model-Based Extended State Observer for Mismatched Disturbance Rejection Approach

Fault-tolerant control of a quadrotor in extreme conditions, such as rotor failure and strong winds, is exceptionally challenging due to its underactuated nature, strong mismatched disturbances, and highly nonlinear multi-input and multi-output properties. This letter proposes a reduced attitude control approach that combines a model-based extended state observer (MB-ESO) and mismatched disturbance decoupling to control a quadrotor under strong winds and complete loss of two opposing rotors. Our MB-ESO based control provides a new theoretical framework for more general nonlinear systems by utilizing all measurable outputs, thereby maximizing the use of all available information to design a robust controller. Testing in a high-fidelity simulator shows that our approach outperforms the state-of-the-art Incremental Nonlinear Dynamic Inversion method.