Our visual tracking approach differs from other methods by using low-cost, lightweight commodity consumer hardware. As main sensor we use a Wii remote infrared (IR) camera, which allows robust tracking of a pattern of IR lights in conditions without direct sunlight. The system does not need to communicate with the ground vehicle and works with an onboard 8-bit microcontroller. Nevertheless the position and orientation relative to the IR pattern is estimated at a frequency of approximately 50,Hz. This enables the UAV to fly fully autonomously, performing flight control, self-stabilisation and visual tracking of the ground vehicle.
Our latest developments enable our quadrocopter to automously take off, tracking and landing on a moving carrier vehicle. The data coming from the infrared camera contains the pixel position of the four blobs and optional information as intensity and bounding box. The task of calculating the position of a camera from a known pattern of control points and their projection onto the camera's image plane is well known as the perspective-n-point (PnP) problem. We used an algorithm which is optimized to solve this special case of the PnP, resulting in faster processing. We also focus on getting the position and yaw angle from the IR-Pattern, while the pitch and roll angle of the quadrocopter are obtained from the IMU.
Further information can be found on the project site:
http://www.ra.cs.uni-tuebingen.de/forschung/flyingRobots/welcome_e.html
