Fault tolerant path following for a quadrotor

This paper presents a path following controller for a quadrotor UAV experiencing a single rotor failure. A smooth, dynamic feedback control law is proposed that allows the quadrotor to follow both closed and non-closed embedded curves while maintaining a desired velocity profile along the path when one out of four motors is completely disabled due to failure. The nonlinear model of the quadrotor is transformed into a partially linear model by a coordinate and feedback transformation. A path following controller is designed for transformed system that guarantees invariance of the path. The uncontrolled nonlinear portion of the dynamics (internal dynamics) are shown to be bounded.