Feedback linearization control for a tandem rotor UAV robot equipped with two 2-DOF tiltable coaxial-rotors

In this paper, computed torque control as one method of feedback linearization techniques is considered for an unmanned aerial vehicle (UAV) robot that has two tiltable coaxial rotors so as to realize multifunctional locomotion modes, where each rotor has 2-DOF tilt mechanism. First, a dynamical model of such an UAV robot is derived following the Newton–Euler law. Next, under the assumptions that the anti-torque of the tiltable coaxial rotors is zero and the gyro moment effect of the tiltable coaxial rotors can be ignored, a computed torque controller is derived, because the resultant model of the UAV robot can be simplified to a fully actuated model, which has six motion inputs and six generalized coordinate outputs. In addition, a control allocation problem of the system, in which the control inputs designed using the dynamical model are assigned to all motors for tilting the rotor as well as rotating it, is solvable by using a Moore–Penrose pseudo-inverse, where a coordinate transformation is used to simply the allocation problem. Finally, some simulations are demonstrated to verify the effectiveness of the computed torque control strategy for the robot.