Pointing mechanisms for LIDAR are suffering from extremely small oscillatory motions, sometimes called swiveling. The amplitudes in these ball bearings are close to the limits for ball bearings, especially when solid lubrication is of interest. The latter may be caused by cleanliness requirements.
Tribological characterization
Qualification of bearings for such mechanisms is related to extremely small oscillating motion in range of few degrees combined with the aim to achieve high oscillating frequencies in order to reduce test durations of life tests. Standard bearing test devices suffer from reasonable rotational masses. They are hardly able to reach a range of 1 Hz. AAC has developed a new setup to overcome these shorts.
New test setup for ball bearings
AAC has designed and built a new device for ball bearing testing which is suitable for testing at ambient conditions and thermal vacuum in a range of -50 to 100°C. In comparison to usual ball bearing testing devices – which perform mostly uni-directional movements – BBT² is also capable of implementing oscillating motions starting at amplitude of 2°combined with frequencies up to a range of 60Hz. Moreover, it also enables complex motion patterns adjustable to special customer and/or mission parameters. The plot shows a custom dynamic movement profile with a sinus vibration of 60 Hz with a duration of 0.4 seconds and an excitation of +/- 2 deg, following a fast movement to 11 deg and back to the starting position.
Two test items per frame are driven by one bearing less motor. One test item consist of a housings which can host one single or a pair of axially pre-loaded ball bearings. Each housing can be adapted to custom hard/soft preloads and ball bearing sizes. It is mounted directly on a torque cell enabling to measure its own torque with high resolution. In total 4 frames enable to test 8 items in parallel.
Ongoing research
This new setup was recently used to run a test campaign on 8 pairs of bearings over 12 weeks in thermal vacuum. It was clearly observed, that for those small oscillating motions the lubrication is a key issue.
Interested in more information or Research and Development of Space Tribology? Get in touch with our team of experts at office@aac-research.at or visit us at Aerospace & Advanced Composites: Space Engineering & Technology
