Design and Implementation of a Fully Actuated Rotor Aerial Manipulator for Contact Operations

The power unit thrust directions of the conventional under-actuated rotor UAV (unmanned aerial vehicle) are parallel, so that it can't generate lateral thrust without changing the attitude, which limits the interaction capability and application scenarios of the aerial manipulator (AM). To solve this problem, a fully actuated rotor AM is designed to change the thrust direction by tilting the installation angle of the power unit. The control distribution matrix based on this structure is designed to verify the full actuation characteristics, and then the independent control of position and attitude is realized by the control structure. A contact force control method of the AM for contact operations is proposed, which divides the contact detection task into the approach state and the moving contact state. A hybrid force/motion controller is used to achieve force control in the normal direction of the contact surface. The outdoor experiment results indicate that the fully actuated rotor AM achieves stable flight and moving contact operation. Compared with the under-actuated platform, the position change during flight doesn't depend on attitude change, and the attitude angle is kept within ±1.5°; the contact force in the normal direction of the contact surface can be controlled during moving contact.