Scaling down the attitude control hardware-in-the-loop test facility for CubeSats and introduction of the auto-calibration

Air bearings have long served as a cornerstone in the development, testing, and validation of attitude control systems (ACS). Utilizing such test platforms presents a balance between pure analytical and software evaluations of attitude determination and control algorithms versus the integration of hardware-in-the-loop simulation (HILS) and software-in-the-loop simulation (SILS) alongside an air bearing test setup. Past experiences [1], [5-7] show that these test platforms often unearth errors not always detectable in purely software-based verification environments, particularly evident in novel missions, processes, or personnel unfamiliar with established verification tools and strategies. Detecting critical software or algorithmic flaws pre-launch can significantly impact mission success. This paper provides an overview of the testbed and details the development of the NanoSat testbed, including its general setup and findings regarding disturbance torques. Furthermore, it explains the autocalibration of the CoG using a model-based approach and presents corresponding test results.