Mathematical modeling and control of a quadrotor aerial vehicle with tiltrotors aimed for interaction tasks

With a wide spectrum of applications ranging from entertainment to military use, quadrotors, in their conventional construction with four fixed rotors, have proven to be sufficiently capable of robustly performing numerous tasks. However, the capability to generate thrust just in one direction, i.e., normal to its main plane, is very restrictive and drastically reduces the maneuverability and agility of the vehicle. In this paper, an alternative model of the quadrotor is presented. Constructively, the difference lies in the addition of a mechanism that tilts the rotors in the longitudinal direction, which in practice adds maneuverability by enabling the longitudinal translation uncoupled from the pitching movement. In addition to this new thrust component in the longitudinal direction, this configuration also yields a significant increase in the yaw torque. These are highly desired features in a UAV used to execute tasks that require physical interaction with the surrounding environment. The mathematical model of the entire system is obtained by employing the Euler-Lagrange formalism and a multi-body approach. In addition, a basic control scheme is used to verify, through simulation, the obtained model.