4 Autonomous charging principle: independently calling in the charging stations Active markers: infrared LEDs for communication with the cameras Intelligent monitoring: the system enables both the formation and individual flight of the spheres Fast calibration of the system In order to know where a flying object is located in the space, the computer must first know the positions of the cameras. The necessary calibration of the system can be carried out quickly and easily. To do so, a manually controlled sphere with a measuring cross flies through the space freely for about 15 minutes and is recorded by the cameras whilst doing so. The recording process enables the main computer to recalculate the exact locations and alignments of all the cameras in the coordinate system. From here on, it acts like an air traffic controller, coordinating both the manoeuvres and the free movements of the spheres. No direct communication takes place between the spheres in this respect. Long flight times due to autonomous charging Depending on the flight speed, buoyancy and manoeuvres that are flown, the average flight time of a sphere comes to two hours. As the spheres stop at their charging stations regularly and autonomously, they can be used as flying objects for several days without a person having to intervene. Exact positioning thanks to infrared technology The ten cameras are positioned so that they map out the flight area as a whole, and each sphere is recorded by at least two cameras. Due to their special filters, the cameras only capture infrared light and are not sensitive to other light. By means of the four infrared LEDs on the outside of each sphere, they detect their position and orientation in the space and, additionally, can tell the optically identical flying objects apart. Large spatial coverage with low power consumption Whilst passive reflectors first have to be illuminated, the active markers on the spheres emit the infrared light by themselves. The light only has to cover the distance between the sphere and camera. Compared to passive markers, a larger space can therefore be recorded with the same number of cameras. The markers are not permanently lit, but instead flash for only a millisecond. This makes them extremely long-lasting and energy efficient. Synchronised with the flashing, the cameras record an image that they send to the main computer.
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