Innovative Approach to Use Air Bearings in Cubesat Ground Tests
Résumé
In the fast-growing society of CubeSat developers, the necessity of CubeSat ground tests is apparent. One of the more complex and discussed system-level tests is the Attitude Determination and Control System (ADCS) examination. It requires motions of the CubeSat and environment conditions close to space. Most of the ADCS testbeds involve an air bearing as one of the main component of a rotating table since it allows reducing the friction between the moving CubeSat and fixed elements. However, such rotating tables have common drawbacks. Notably, they allow CubeSat rotations only in a limited range of angles, usually within ±45°. In this paper, an innovative approach to use air bearings, which allows circumventing this limitation, is discussed. The proposed testbed involves 4 air bearings instead of only one. The air bearings are placed so that their effective surfaces lie on a sphere. This (virtual) sphere is large enough to place a CubeSat inside, while its influence on the dynamic parameters of the CubeSat is minimal. Nevertheless, some issues should be tackled to ensure the feasibility of such an air bearing testbed. In the proposed design, the concentricity of the air bearing active elements and the floating spherical elements might be perturbed and thus affect the lift force. In addition, the total lift force of the air bearing sphere highly depends on the angular attitude of the sphere. This paper presents results of the study of the air bearing sphere behavior and the progress of the work which has been previously introduced at the 4S Symposium in 2014.
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