  Quadrotor is often used to accomplish various missions related to
surveillance, territory mapping, search and rescue, and other purposes.
Quadrotor is a nonlinear system with multiple input multiple output and has
stability issue due to external disturbance. These characteristics lead to
difficulty in cruise control of quadrotor automatically. Decoupling method is
used to eliminate the interaction of other control on rotational motion, then
the roll, pitch, and yaw angle can be controlled independently. Nonlinear PD
controller is obtained from invers model of control signal on a quad rotor and
it is used to control the translational motion in x and y axis with nonlinear
dynamics because of the influence the rotational angle. Simulation results show
that the proposed method can eliminate the control interaction of roll, pitch
and yaw angle, hence it works like single input single output system and
translational motion on x andy axis can achieve the expected trajectory
precisely.
