Robust Backstepping Controller with Adaptive Sliding Mode Observer for a Tilt-Augmented Quadrotor With Uncertainty Using SO(3)

The conventional quadrotor is incapable of controlling position and orientation independently. To mitigate this deficiency, we use a tilt-augmented quadrotor for greater mobility in a constrained environment. When the rotors tilt in a tilt-augmented quadrotor, it leads to changes in moment- of-inertia. This changes in the moment-of-inertia and external disturbances will introduce uncertainty terms into the model. In this paper, we design an adaptive super twisting sliding mode observer which guarantees finite time estimation of uncertain terms with unknown maximum bound. With the help of this observer, a backstepping controller using SO(3) is developed to establish exponential convergence to the desired trajectory. The exponential convergence of the backstepping controller and finite time convergence of the observer are shown using the Lyapunov approach. Hardware experiments are performed to compare the performance of both the existing controller and our proposed controller and corresponding videos are at https://www.youtube.com/watch?v=brTd5UYvciM.