Attitude Control of a Tilt Trirotor Using Fast Nonsingular Terminal Integral Sliding Mode

This paper presents a fast nonsingular terminal integral sliding mode (FNTISM) controller for attitude tracking of a tilt trirotor unmanned aerial vehicle (UAV) in vertical takeoff and landing (VTOL) flight mode. The rotation of UAV is described by the matrix group SO(3) to eliminate gimbal lock. Besides, the proposed controller offers fast response, high tracking accuracy, and strong disturbance rejection characteristics. It employs a sliding surface function that includes integral terms which effectively estimates disturbances by integrating control deviation. Additionally, an arctangent function is utilized to limit the angular command within a specific boundary, thereby achieving rapid control while minimizing system overshoot. The flight experiment results demonstrate that the proposed controller exhibits superior performance in response speed, tracking accuracy, and robustness compared to the existing fast nonsingular terminal sliding mode (FNTSM) controllers on tilt trirotor UAV.