Abstract
A particular structure of a four rotors mini-flying robot where two rotors are directional (X4 bidirectional rotors) is presented in the paper. The two internal degree of freedom leads to a transformation between the equivalent system of the control-inputs and the rotor force-inputs which is not a diffeomorphism. This makes our system different from that of classical flyer robot (X4 flyer). The dynamic model involves five control inputs which will be computed to stabilize the engine with predefined trajectories. For the underactuated system we show that the nonlinear model can be locally-asymptotically stabilized by a smooth time-varying control law. The simulation results are presented to illustrate the control strategies.