Distributed Fault-Tolerant Formation Tracking of Networked Quadrotors Using Cascade Estimators

This paper presents a distributed fault-tolerant control strategy that consists of a fully distributed position controller and an attitude constrained controller for the leader-follower formation of networked quadrotor unmanned aerial vehicle (UAV) systems in the presence of actuator fault and external disturbance. A distributed position controller is first developed for each follower quadrotor to ensure the formation tracking to the leader, where cascade estimators consisting of a filter-based dynamics estimator and a fixed-time estimator are exploited to completely counteract the actuator fault and external disturbance. Then, based on the cascade estimators development, by introducing a nonlinear transformation, a robust attitude constrained controller is proposed to guarantee the command attitude tracking singularity free. Stability analysis demonstrates that the closed-loop systems are asymptotically stable. Experiment results further verify and assess the proposed control strategy.