MAGNETIC LEVITATION FOR SPHERICAL DRAG-FREE SENSOR TESTING
Abdul
*
Alfauwaz ,
Abdulaziz Alhusain, John Lipa and Dan Debra
CENTER OF EXCELLENCE in Aeronautics and Astronautics (CEAA)
Stanford University
*alfauwaz@stanford.edu
Introduction
Magnetic force
Gravity force
Design
• Design and build a system that can levitate and hold a
hollow sphere in vacuum, “simulating zero-g
operation”
• Spin the TM by using 4 coils to produce a rotating
magnetic field around the equator of the sphere.
.F=qv X B
Thermal
System features:
• Coil designed to run in vacuum for at least 2
hours without any damage.
•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.
Levitation coil
Photodiode
IR source
Magnetic sphere
Coil Power Dissipation
• Used COMSOL to simulate thermal simulation in air and vacuum.
• Install 2 temperature sensor in the coil
• Run the coil in vacuum for about 3 hours.
Spinning coils
Simulation
Magnetic analysis:
• Used COMSOL to analyze the coil and
Coil In vacuum with current 0.26A ~2 hours
simulate the magnetic field which is produce
by coil.
• Calculate the magnetic force on the sphere
for different situation
• The figure below shows the electromagnetic
force versus the distance between the coil
and the sphere for different currents.
Multislice: Magnetic flux density
norm (T) Arrow Volume: Magnetic
field
Electromagnetic force VS. Distance
Vacuum top lid
Detector
Electromagnetic Force (N)
Experiment Levitation
Coil
Coil
Coil
Coil
Coil
Coil
1
0.8
0.6
0.4
I=0.10
I=0.12
I=0.14
I=0.16
I=0.18
I=0.20
A.
A.
A.
A.
A.
A.
Sphere Gravity Force
0.2
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Distance from the Coil (mm)
Lens between
sphere and
laser source
Experiment Spinning
Laser source
Lens between sphere and detector
Experiment running in air before it is moved to vacuum.
Future Work
• The system will be used to test the three-axis optical sensor system,
DOSS, that is being developed separately, by rapidly switching to the
DOSS sensor while the ball is levitated.
• Small magnetic pulses will be used to simulate thruster perturbations
in the plane orthogonal to the support axis
4 coils
Sphere is spinning in vacuum
Was able to spin the sphere up to 11Hz in vacuum.
Acknowledgements
This research is supported by CENTER OF EXCELLENCE in Aeronautics and Astronautics and Stanford University.
We thank COMSOL technical support for their useful feedback.
.