Onboard CNN-Based Processing for Target Detection and Autonomous Landing for MAVs

In this work, we address the problem of target detection involved in an autonomous landing task for a Micro Aerial Vehicle (MAV). The challenge is to detect a flag located somewhere in the environment. The flag is posed on a pole, and to its right, a landing platform is located. Thus, the MAV has to detect the flag, fly towards it and once it is close enough, locate the landing platform nearby, aiming at centring over it to perform landing; all of this has to be carried out autonomously. In this context, the main problem is the detection of both the flag and the landing platform, whose shapes are known in advanced. Traditional computer vision algorithms could be used; however, the main challenges in this task are the changes in illumination, rotation and scale, and the fact that the flight controller uses the detection to perform the autonomous flight; hence the detection has to be stable and continuous on every camera frame. Motivated by this, we propose to use a Convolutional Neural Network optimised to be run on a small computer with limited computer processing budget. The MAV carries this computer, and it is used to process everything on board. To validate our system, we tested with rotated images, changes in scale and the presence of low illumination. Our method is compared against two conventional computer vision methods, namely, template and feature matching. In addition, we tested our system performance in a wide corridor, executing everything on board the MAV. We achieved a successful detection of the flag with a confidence metric of 0.9386 and 0.9826 for the Landing platform. In total, all the onboard computations ran at an average of 13.01 fps.