Design and Antidisturbance Control for an H-Configuration Tiltable QuadRotor: Enabling Narrow Space Crossing

Focusing on the problem of narrow space crossing in search and rescue missions, an H-configuration Tiltable QuadRotor (HTQR) with four additional servos is designed in this article. The essential large roll angle during crossing magnifies the deviation between the centers of aerodynamics and gravity (DCAG), and results in the nonnegligible ground effect torque due to different height of rotors. An antidisturbance control scheme is proposed to achieve safe crossing against the disturbances from the DCAG and the ground effect. A dynamic allocation relationship related to the servo tilt angle is first deduced to map the control forces and torques to the hybrid actuators. Based on quantitative disturbance analysis, the translational and rotational controllers are improved by integrating with a disturbance observer and a fixed-time sliding mode observer. Flight experiments illustrate that the designed HTQR with the antidisturbance control scheme can cross narrow space under disturbances from the DCAG and the ground effect.