Development of parallel linked quadrotor for increment of flight freedom, attitude control and improvement of transient response

The quadrotors are useful for periodic inspections of tunnels and bridges. However, the conventional quadrotor has a problem such that it is impossible to control the rotational motion and the translational motion independently. Therefore, if the camera is attached on the bottom of the quadrotor, it is difficult to observe its upward direction. In this paper, we develop a novel quadrotor that has a parallel link to tilt itself. By increasing one degree of freedom of the quadrotor, we resolve the problems described above. And we derive a model of the developed quadrotor. Then, we consider a PID controller for the stabilization of the quadrotor at a specified hovering state. We derive gain parameters of the PID controller by which the controlled quadrotor is stabilized.