Attitude Flight Control System Design of UAH using Fuzzy Sliding Mode Controller with Parameter Uncertainty and External Disturbance

Unmanned Aerial Helicopters (UAHs) pose a multi-input and multi-output (MIMO) nonlinear dynamic structure. In this paper, a robust control method is formulated to improve the performance of nonlinear UAH Euler angles (i.e., roll, pitch, and yaw), taking the UAH flight attitude as the main control outputs. Examining the dynamic equations of the nonlinear model reveals that the UAH control inputs do not appear directly in the model. This means that Euler angles can be controlled through the angular velocities to fulfill control the UAH having nonlinear model dynamic equations which are in a non-affine structure. For this purpose, the sliding mode control (SMC) is employed as a robust control method via a new technique having a two-loop structure in the presence of disturbance and uncertainty. The slopes of sliding surfaces of the sliding mode controller are tuned according to a fuzzy logic, also by using Lyapunov Theory, the stability of the closed-loop system is guaranteed. A set of tests is conducted on an UAH simulation case study to explore its performance under different scenarios. The results clearly demonstrate well performances in the face of the induced disturbance and uncertainty.