Embedded algorithm for relative pose measurement between non-cooperative targets

For the spacecrafts with circle and line features, an algorithm for embedded vision applications was proposed for the relative pose measurement between non-cooperative targets. The edge points were detected by a Canny edge detector and the image thinning was performed in a Field Programming Gate Array(FPGA). Then, elliptic characters on the target were detected by a novel ellipse detection algorithm based on edge contour in a Digital Signal Processor(DSP), and line features on the target were detected by a real-time and high accuracy method base on Hough Transform(HT). Finally, a ground simulation experiment was performed for a practical mission on orbit. and the relative attitude between target spacecraft and CCD camera was calculated by the obtained ellipse and lines. Experimental results show that the proposed method have been implemented in the embedded system and the update rate is more than 3 Hz. The measurement accuracy becomes poorer with the increasing of measuring distance and that in three directions is different even in the same measure distance. When the measuring distance is less than 4 m, the measurement accuracy in the depth direction is higher than 100 mm, other directions is higher than 60 mm and the angle accuracy is higher than 1°. The obtained results meet the requirement of the embedded system for the system resource, update rate and the detection accuracy.