An ApproximationFree Simple Control Scheme for Uncertain Quadrotor Systems: Theory and Validations In this paper, a simple tracking control scheme is proposed for quadrotor systems with uncertain dynamics. It precludes the necessity for prohibitive analytic computation of the derivatives of the desired (virtual) attitude that is typically employed in controlling quadrotor systems. Moreover, this control scheme is approximationfree in the sense that it does not incorporate any adaptive laws, observers, or command filters to compensate for unknown parameters in the dynamics and the absence of the analytic differentiation, thus exhibiting remarkably low complexity levels and making its implementation straightforward. The thrust saturation is approached in the position control design which also enables the singularity in desired attitude extraction to be avoided entirely. It is demonstrated that based on the proposed scheme, the tracking errors can be made arbitrarily small by appropriately selecting design parameters. Extensive simulations and experiments are performed to verify the effectiveness of our scheme.

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 EulerLagrange formalism and a multibody approach. In addition, a basic control scheme is used to verify, through simulation, the obtained model.