Edge-based approach to estimate the drift of a helicopter during flight

Abstract

The Institute of Flight Systems at the German Aerospace Center (DLR) site in Braunschweig Germany has set its goal into making helicopter flying as safe as possible. The new DLR research project "Rettungshubschrauber 2030" addresses the topic of aiding helicopter rescue missions. Research will be conducted to increase the safety of these missions as well as to enable the conduct of missions in circumstances where nowadays a helicopter would not be allowed to operate. One aspect of this research is to increase or maintain the situational awareness of the pilot by processing data from camera images. The paper will focus on the field of visual odometry. It examines, if an edge-based approach for extracting features is a possible alternative or addition to established feature extractors. In the paper, two algorithms for edge extraction will be compared: an algorithm that is based on Hough transform and an algorithm that is based on the Douglas-Peucker method. They are tuned for working with images of rather low resolution and are tested on their ability to detect a sufficient amount of features in camera images as well as on their computational complexity. Then, their ability to detect the drift of a helicopter is assessed using recorded data from flight tests with the advanced control technology/flying helicopter simulator (ACT/FHS) of the DLR. Their performance will be tested on the basis of reference data from the ACT/FHS which have been recorded by the use of a highly accurate INS/DGPS system. The evaluation of the algorithms yields the result that both achieve the proposed accuracy regarding the velocity estimation with the Hough-based method achieving better accuracy while taking significantly more computational time.