In order to build a realistic drag-free proof mass system for the MGRS, a ground test system is needed. Therefore, a magnetic levitation system was built that can levitate and hold a hollow sphere in vacuum, simulating zero-g operation. An electronics board has been built that is required for a stable feedback control system to drive the coil and hold the ball in a stable levitated position. The board has a switch to reverse the current direction through the coil in case the sphere becomes magnetized and sticks to the coil in vacuum. The ball position sensor is optical and is made up of an infrared emitter and a pair of phototransistors. The system is designed to restore the ball to the levitated position if it drops out of lock, as it might be needed while it is running in vacuum. The heat generated by the coil is an issue in vacuum, so it is designed carefully so that it can run continually for at least 3 hours without any damage or side effect. COMSOL is used for simulation and analysis of the system.
 
Ultimately the sphere needs to be spinning while it is levitated. To do this, four coils are used which are driven by digitally generated sine and cosine functions to produce a rotating magnetic field around the equator of the sphere. Once the system is complete and successfully tested it will be integrated to the MGRS experiment setup.
 
A video of the levitated, spinning sphere is attached below.

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Last modified Mon, 15 Apr, 2013 at 16:48