Acknowledgements

Thermal

Simulation

Future Work

Design Introduction

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

• 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

This research is supported by CENTER OF EXCELLENCE in Aeronautics and Astronautics and Stanford University.

We thank COMSOL technical support for their useful feedback.

.

• 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.

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.

Magnetic analysis: • Used COMSOL to analyze the coil and

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.

Magnetic sphere

Levitation coil

IR source

Photodiode

Experiment Levitation

Experiment Spinning

0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

0.2

0.4

0.6

0.8

1

Distance from the Coil (mm)

Ele

ctro

ma

gn

etic

Fo

rce

(N

)

Electromagnetic force VS. Distance

Coil I=0.10 A.

Coil I=0.12 A.

Coil I=0.14 A.

Coil I=0.16 A.

Coil I=0.18 A.

Coil I=0.20 A.

Sphere Gravity Force

Magnetic force

Gravity force

Spinning coils

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.

.F=qv X B

Coil In vacuum with current 0.26A ~2 hours Multislice: Magnetic flux density

norm (T) Arrow Volume: Magnetic

field

Vacuum top lid

Lens between sphere and detector

Detector

Lens between

sphere and

laser source

Laser source

Experiment running in air before it is moved to vacuum.

Was able to spin the sphere up to 11Hz in vacuum.

4 coils Sphere is spinning in vacuum