Design of super-twisting controller for rotor vehicle based on high-order sliding mode observer with laser rangefinder

Unmanned aerial vehicles (UAVs) carrying a laser rangefinder can provide more accurate aircraft height information than conventional GPS or barometer measurements in actual flights, however, they can't provide the altitude velocity. This article addresses the problem of altitude tracking of aircrafts and proposes a control strategy based on the combination of a high-order sliding mode observer and a super-twisting sliding mode controller, which can respectively control and estimate the altitude velocity. First, the dynamic model of altitude direction of a rotor aircraft is established, then the high-order sliding mode observer is established to estimate state variables, and the super-twisting controller is designed. Then, a comprehensive stability analysis of the combined controller-observer based on the Lyapunov stability theory is presented, thus ensuring the asymptotic convergence of the tracking error under external bounded disturbances. The experimental results show that the super-twisting sliding mode controller can evaluate the altitude velocity accurately by using the information output from the high-order sliding mode observer, and the convergence time is 0.5 s. The combination of the super-twisting controller and high-order sliding mode observer can realize the accurate altitude control of aircrafts.