Visual tracking and following of a quadrocopter by another quadrocopter

We present a follow-the-leader scenario with a system of two small low-cost quadrocopters of different types and configurations. The leader is a Parrot AR.Drone which is controlled by an iPad App utilizing the visual odometry provided by the quadrocopter and pilots it autonomously. The follower is an Asctec Hummingbird which is controlled by an onboard 8-bit microcontroller. Neither communication nor external sensors are required. A custom-built pan/tilt unit and the camera of a Nintendo Wii remote tracks a pattern of infrared lights and allows for online pose estimation. A base station allows for monitoring the behavior but is not required for autonomous flights. Our efficient solution of the perspective-3-point problem allows for estimating the pose of the camera relative to the pattern in six degrees of freedom at a high frequency on the microcontroller. The presented experiments include a scenario in which the follower follows the leader with a constant distance of two meters flying different shapes in narrow, GPS-denied indoor environment.