On-line micro-vibration measurement method for Lorentz-type magnetic-bearing space actuators

A novel, cost-effective, real-time and on-line method for measuring the generated micro-vibrations and iden- tifying the forces in a magnetic bearing space actuator is proposed. For its validation, an actively-controlled electrodynamic (Lorentz-type) magnetic bearing reaction wheel (MBRW) demonstrator is used, where the mag- netic bearing coils’ current is used as a measurable magnitude to identify the exertion of forces to the satellite’s structure. Due to the Lorentz-type magnetic bearing, a linear relation between current and force is considered and a validation campaign is undertaken, taking a micro-vibration test set-up as a reference. The results obtained using the proposed method are comparable, to a sub-newton level, to the micro-vibration amplitude measured us- ing a state-of-the-art piezoelectric-based dynamometric equipment, which is usually employed for reaction wheel on-ground qualification. The proposed method does not rely on any external and costly measurement equipment, as it only employs internal sensors, already required for control purposes in any active magnetic bearing (AMB), and it can be used for control or on-line and in-situ monitoring purposes.