Research on a combinatorial control method for coaxial rotor aircraft based on sliding mode

Aiming at the position and attitude tracking of coaxial rotor aircraft (CRA), this paper proposes a combinatorial control method of sliding mode control (SMC) coupled with proportional-integral-derivative control (PIDC). Considering the complete description of flight dynamics, aerodynamics and airflow interference, the dynamical model of CRA is established. The dynamical model is simplified according to the actual flight, then the simplified dynamical model is divided into two subsystems: a fully-actuated subsystem and an under-actuated subsystem. The controller of the fully-actuated subsystem consists of a SMC controller coupled with a rate bounded PIDC controller, while the controller of the under-actuated subsystem is composed of a SMC controller. The sliding manifold is defined by combining the position and velocity tracking errors of the state variables for each subsystem. Lyapunov stability theory is used to verify the stability of the sliding mode controller, which ensures that all state trajectories of the system can reach and stay on the sliding mode surface, the uncertainty and external interference of the model are compensated. Simulation and experiment compared with the conventional PIDC are carried out, the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.