Evaluation of acceleration-based disturbance observation for multicopter control

Small UAVs flying in narrow passages require robustness to turbulence caused by self-induced vortices. Aerial manipulation introduces modeling errors due to payload and parameter changes. When large external forces are applied, small helicopters must fly at orientations far outside hover conditions. The compensation of such uncertainties can be achieved through disturbance observation (DO). An onboard IMU makes the platform well-suited for acceleration-based DO. In this paper, we evaluate a cascaded attitude and position tracking controller for a quadrotor. Quaternions are used for attitude control to allow large orientation angles. We investigate attitude tracking by the boundary-layer integral sliding mode control coupled with acceleration-based DO. The position controller generates singularity-free quaternion and angular velocity signals. The presented controller is experimentally verified and compared to PID and backstepping controllers for trajectory tracking and hovering in turbulent conditions. Compensation of large external forces in the horizontal plane is shown through a stable 45° hover.