Fault-Tolerant Control of Lifting-Wing Multicopter Based on Nonlinear MPC

This letter proposes a fault-tolerant control (FTC) framework for a novel type of aircraft—lifting-wing multicopters. The core of the framework is an attitude controller based on nonlinear model predictive control (NMPC), where the objective function of the NMPC is designed on the basis of the relaxed hover solution for lifting-wing multicopters, derived theoretically in this letter. The existence of the relaxed hover solution demonstrates that, despite the complex aerodynamic forces and moments introduced by the lifting wings, stable attitude control can still be achieved by sacrificing yaw control. Additionally, the FTC framework incorporates a disturbance observer based on the Extended Kalman Filter (EKF), allowing the lifting-wing multicopter to maintain FTC even in the presence of model errors, sensor noise, and actuator response delays. Initially, Model-in-the-Loop (MIL) simulations were conducted to verify the feasibility of the control logic. Subsequently, real-world experiments using onboard sensors and GPS demonstrated that the lifting-wing multicopter could maintain stable attitude control and perform outer-loop position control under single rotor failure as well as two opposite rotor failure conditions.