Robust fault-tolerant adaptive integral dynamic sliding mode control using finite-time disturbance observer for coaxial octorotor UAVs

In this paper, the dynamics modeling of coaxial octorotor UAVs is described taking into account the majority of uncertain factors such as actuator faults, parametric deviations, and external disturbances. Then, a robust and fault-tolerant controller is designed for both position and attitude dynamics using a higher-order integral dynamic sliding mode controller (I-DSMC). The robustness and fault-tolerant capabilities of the proposed I-DSMC are further improved by using a nonlinear finite time disturbance observer (FTDO). The adaptive I-DSMC provides correction terms for unknown lumped uncertainty in real-time by use of FTDO estimates. Lyapunov stability is provided for the closed-loop system. The efficacy of the proposed controller is supported by simulation studies. The results reveal that multiple actuator failures are accommodated in the octorotor UAV without loss of controllability in any channel. Further, the simulation results show that the selected multirotor configuration along with the proposed controller combination provides an effective solution for multiple actuator failures in presence of other uncertainties.