General model and improved global sliding mode control of the four-rotor aircraft

In order to improve the versatility of the control method of the four-rotor aircraft, a general mathematical model, the rectangular four-rotor aircraft, is modeled, and two special cases, square cross structure and square X structure, are deduced. Based on the conventional global sliding mode control, an improved global sliding mode control is proposed to control the position and the attitude of the four-rotor aircraft. The dynamic sliding mode surface of the improved global sliding mode control can evolve into the linear sliding mode surface in a limited time by changing the decay function of the dynamic sliding mode surface. In this way, the controlled system has not only the strong global robustness but also the quick response rate. Simulation results show that the position and the attitude of the four-rotor aircraft can be controlled by the improved global sliding mode control, and the control performances, for instance the response speed, can be improved.