Robust Hybrid Tracking Control of Coaxial Octorotors Based on Super‐Twisting Lumped Disturbance Observation

ABSTRACT

A control strategy is proposed for coaxial octorotors based on model predictive control (MPC) and backstepping (BS) control approaches incorporating a high‐order sliding mode disturbance observer which is based on a super‐twisting algorithm and can track the lumped disturbance in finite time. The proposed approach employs MPC and the disturbance observer to control the position variables of the system, while the BS method and the disturbance observer stabilise the attitude variables. The proposed control method adopts two loops to provide control laws required to stabilise the extracted nonlinear dynamics of the system. Implementing feedforward compensation with a super‐twisting disturbance observer (STDO) enhances the control system capability to effectively reject disturbances. Once control inputs have been obtained by the designed controllers, a constrained control allocation method provides rotor speed within an acceptable range. An evaluation of the proposed approach is performed in terms of accuracy and computational complexity compared to other methods. Simulation results indicate that the developed control strategy is capable of accurate trajectory tracking, stable flight under different conditions, and coping with disturbances arising from external and internal sources.