Quadrotors, sometimes called quadcopters, are part of a broad category of robots called Unmanned Aerial Vehicles (UAVs) that have four motors and propellers to provide lift for the craft. In this chapter, we will introduce some of these flying robots that are controlled by ROS. The chapter will consider both simulations and flying the real thing.

The following figure shows the Crazyflie quadrotor that will be discussed later in this chapter:

Crazyflie quadrotor

In the image of Crazyflie, notice the four propellers or rotors that act to lift the craft vertically for takeoff and keep it in flight at some altitude when flying. First, such crafts are classified as rotocraft because the lift is generated by the rotors shown in the figure, rather than the wings of an airplane. Second, they are not helicopters, because the main propeller and the tail rotor control the flight of a helicopter. The tail rotor of a helicopter keeps the craft from rotating itself due to the rotation...