Multicopters are usually under-actuated systems and have four independent DOF. The x,y position in the body frame is coupled to the roll and pitch angles. In order to overcome the under-actuated problem and to achieve independent control in all six DOF, a change in the multicopter platform needs to be implemented. Different solutions on how to improve the platform have been proposed, most of them suggest the tilting rotors concept in which the rotation is done by additional motors; the down side of adding motors is the additional weight without increasing the lifting power. In this paper we suggest a tilting rotors solution to the under-actuated problem without the down side mentioned.
The paper presents a novel type of a multicopter with a unique platform. The platform gives the aerial vehicle the ability to control the roll angle and the y axis translational movement independently. The proposed hexacopter design features four rotors attached to the vehicle body and another two rotors attached to a seesaw, the seesaw is connected to the main body in the center of mass and can rotate along one body frame`s axis, by that the seesaw adds the fifth DOF. This design makes the aerial vehicle more maneuverable without adding non-supplying lifting power actuators.
The paper contains the dynamic modeling of a seesaw hexacopter, which lead to the equations of motion of the body (position, attitude) and the seesaw angle. Furthermore, a non-linear controller is developed to achieve a five DOF trajectory tracking capability.
