Robust adaptive attitude control for agile maneuver of quadrotors based on finite-time geometric extended state observer

This paper is concerned with the robust attitude tracking problem for quadrotors on the three-dimensional special orthogonal group SO(3) with finite-time convergence via disturbance-observer-based control technique. A finite-time geometric extended state observer is deduced on SO(3), which is an almost-global stable one without singularity or unwinding phenomenon happening in large-scale attitude control systems. Notably, the estimated performance is significantly enhanced compared to other conventional disturbance observers as no coordinate parameterization is made. Based on the estimated results, an adaptive geometric fast terminal sliding mode control law on SO(3) is introduced to alleviate the chattering effect and guarantee robust attitude tracking. An auxiliary system is then constructed to deal with the input saturation problem. The almost-global finite-time stability of the whole closed-loop system is then verified via Lyapunov analysis. Finally, simulations and flight experiments demonstrate the strong robustness and fast convergence rate of the proposed method against other geometric controllers and those utilizing attitude representations in Euler angle form.