ASMC and ARSMC Cascaded Controller Design for QUAVs With Time-Varying Load and Unknown Disturbances

In this paper, cascaded controllers, which combine adaptive sliding mode control and recursive techniques, are presented to control quadrotor unmanned aerial vehicles with time-varying load and unknown disturbances. In the outer-loop control subsystem, an adaptive sliding mode controller, which includes adaptive laws estimating the time-varying load and unknown disturbances, is presented to control the position of the quadrotor. In the inner-loop control subsystem, an adaptive recursive sliding mode controller, which includes a self-turning law estimating the unknown inner-loop disturbances, is designed to control the attitude of the quadrotor. Moreover, a nonsingular terminal sliding mode surface is used to converge the tracking error of attitude angles to zero in finite time; and an integral sliding mode surface is designed in the adaptive recursive sliding mode controller to improve the attitude control performance of the quadrotor. Simultaneously, adaptive gain adjustment laws were applied to estimate those unknown upper bounds of the disturbances in the system. In the end, the efficiency and feasibility of the proposed control method are demonstrated by some computer simulations.