Design and experimental verification of a robust control to avoid individual calibration of multiple reaction wheels in satellites

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Momentum exchange devices like momentum wheels and reaction wheels are widely used in spacecraft attitude control. Managing their internal momentum, so that it is interchanged with the angular momentum of the rest of the spacecraft, usually involves controlling the angular velocity of these devices. This can be done by characterizing and performing a precise calibration on the wheel. However, this approach has some drawbacks, as small manufacturing differences require characterizing each individual wheel that is used, and the performance of each wheel can suffer small changes through the lifecycle of the satellite. This can be especially laborious in the case of spacecrafts with several reaction wheels, constellation of satellites or, more generally, when a set of reaction wheels are manufactured with the same specifications, since it would require calibrating each of the wheels.This paper presents a new control design concept that avoids the necessity of calibrating all the wheels by formulating the calibration variations as a disturbance rejection problem, where the errors introduced by the absence of a dedicated calibration curve are treated as an external low frequency noise added to the command velocity, and a H∞ controller is synthesized to reject it. Experimental results have been obtained with a set of laboratory satellites, showing that the proposed methodology is able to handle out-of-calibration configurations, and improves the performance even when all wheels are well calibrated.