ESA GNC Conference Papers Repository
EPOS: A Hardware-in-the-Loop Robotic Simulation Assembly for Testing Automated Rendezvous and Docking GNC Sensor Payloads
We present a newly built robotic testbed for the verification of the docking sensor payload of an On-Orbit-Servicing spacecraft performing Automated Rendezvous and Docking (ARVD). EPOS 2.0 is the second generation of the European Proximity Operations Simulator, a facility serving Proximity Operations Simulation since the late 1980s at the German Aerospace Center site in Oberpfaffenhofen, Germany. This paper describes the motivation for the hardware-in-the-loop-simulation of ARVD and outlines the technical challenge of the new facilitys construction such as achieving highly precise robot accuracy as well as creating realistic environmental conditions. Currently the EPOS testing assembly consists of two industrial robotic arms capable to carry up to 200kg of sensor hardware to generate realistic camera images of the Rendezvous and Docking of two spacecraft. The setup allows the simulation of the rendezvous process starting at a distance of 25m down to contact. The facility general layout and performance parameters are described with a focus on positioning accuracy, computational speed and workspace. Sunlight simulation yet remains subject of ongoing development activity, an outline of the work done around this issue is given. In a first experimental testcampaign, using the visual based navigation sensor system "Vibanass" the EPOS-simulator is utilized for the first time in an open loop testcase with a complete environmental setup. Vibanass provides precise relative navigation capabilities and shall be tested in the close distance range under high-power laser illumination. This project requires environmental lighting conditions with a power spectral density close to sunlight in order to generate a realistic environment. This is a challenging design-task and currently under development. The experience gained in this test shall improve the understanding of vision based GNC algorithms and will be used for upcoming On-Orbit-Servicing missions. Another important issue is the incorporation of contact dynamics to enable docking simulation. The time of contact between the two spacecraft remains one of the most critical parts of ARVD and is most demanding for the simulation facility in terms of the required computational speed for the control algorithm. The new facility will be endowed with contact dynamics capabilities, which is currently subject of ongoing research. An outlook of the intended future use of EPOS and the potential benefits to Proximity Operations and On-Orbit-Servicing missions concludes.