Abstract
Magnetically suspended flywheel (MSFW) with gimballing capability fulfills requirements of precision and maneuvers for space applications. A novel reluctance force-type hybrid magnetic bearing (RFHMB) is presented based on analysis of demerits of Lorentz force-type magnetic bearing and common RFHMB. It features that radial and axial magnetic bearing units are integrated into a compact assembly with four separate biased permanent magnets and two conical stators; four radial poles with shoes and rotor made of iron-based amorphousness can reduce eddy loss. Equivalent magnetic circuits of permanent magnets and their control currents are presented. Simulation results indicate flux density fluctuates from 0.272 T to 0.41 T; rotor tilting does not affect the suspension force when rotor only tilts aroundX-axis orY-axis. When rotor drifts inX,Y, orZdirection and tilts aroundX-axis orY-axis simultaneously, force in corresponding directions slightly increases with tilting angle’s enlargement, but the maximum change does not exceed 14%. Additional tilting torque mainly determined by uniformity of flux density in conical air gaps is 0.05 Nm which is far smaller than 11 Nm in common RFHMB; magnetic suspension force is effectively decoupled amongX,Y, andZdirections; results prove that MSFW with gimballing capability theoretically meets maneuvering requirement of spacecraft.
Highlights
Flywheel is an inertial actuator in a spacecraft attitude control system to generate suitable attitude control torques for correcting spacecraft attitude deviation or adjusting to an assigned attitude [1,2,3,4]
For the novel reluctance force-type hybrid magnetic bearing (RFHMB), its novelties are the radial and axial magnetic bearing units which are integrated as a compact assembly, permanent magnets are used to generate the radial and axial biased fluxes, the radial stators include 4 stator poles, and their relative permanent magnets are separated into four separate segments to make the magnetic flux of X and Y channels independent from each other
When the rotor tilts around X- or Yaxis, simulation results indicated that the fluctuation of flux density is from 0.272 T to 0.41 T, the additional tilting torques in the novel RFHMB is 0.05 Nm while that in the common reluctance force-type magnetic bearing increases with the angle linearly and its maximum torque is up to 11 Nm
Summary
Flywheel is an inertial actuator in a spacecraft attitude control system to generate suitable attitude control torques for correcting spacecraft attitude deviation or adjusting to an assigned attitude [1,2,3,4]. As for the 5-degree-of-freedom (DOF) MSFW, the rotor of it can be actively controlled in all 5 DOFs, so the momentum vector of the flywheel can be tilted actively with respect to the spacecraft body (named as “vernier gimballing”) to generate control moment in the other two directions [12, 13] For these space applications of an MSFW with gimballing capability, its structure has been studied in [12, 14]. In the presented new MSFW with gimballing capability shown, there are one rotor, one novel reluctance force-type hybrid magnetic bearing (RFHMB), one tilting magnetic bearing, one integrated axial/radial displacement sensor, one motor, two touchdown bearings, one shaft, and one base.
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