Design & development of air bearing table for on ground testing of AOCS hardware

Air bearing table is used to validate attitude control strategies for small satellites and to validate the performance of satellite sensors and actuators on ground with frictionless environment before launch. It can only be done by using a test platform that floats on the continuous airstream and hence allowing free rotation around all three axes. The system is employed to develop, improve, and carry out tests of sensors (magnetometer, sun sensor), actuators (reaction wheel, magnetic torquer), and algorithms in the experimental framework. In order to simulate weightlessness, it is essential for the platform to be completely balanced in all axes. Another important consideration is that the combined center of gravity (COG) of the lifted structure should be coincident or very close to the center of rotation (COR) of bearing. In this paper the design detail of developed air bearing table is discussed. It provides a cost effective mean to test small satellites and their AOCS hardware. The diameter of air bearing is selected as 5 inch as it fulfilled the loading requirement which is integrated with the platform. The designed load is selected to be 100kg class satellites. Modular design approach is adopted in order to accommodate different sizes of air bearing and hence enhancing the lifting capability of the platform. The sensitivity of platform is tested to be as small as 5 grams. The vertical balancing of the system (Z-axis) is done by adding counter weights at each corner of the platform, while horizontal balancing is carried out with the help of trimming masses in two axes(X, Y). The platform allows tilt angle of 30° about X and Y axes while free rotation of 360° about Z-axis. The system is tested for the dummy weight of 75kg at continuous pressure of 4bar. For the desired lifting mass, appropriate air compressor is selected that can supply maximum pressure of 8 bar. A control panel is also provided to regulate the air flow according to the experimental needs. FEM analysis is carried out for the platform to check the maximum lifting capability of the system. The results were found within safe limits.