Spinning Wheel Data Analysis Duncan Scott Magnetics and Radiation Sources group ASTeC STFC Daresbury...

Spinning Wheel Data Analysis

Duncan ScottMagnetics and Radiation Sources group

ASTeCSTFC Daresbury Laboratory

Duncan Scott: Spinning Wheel April 2009

In this data the wheel is being moved in relation to the magnet poles Displacement refers to wheel edge and pole edge

Changing Displacement Data March 27th 2009

Magnet PoleWheel

Displacement


Changing Displacement Data March 27th 2009

Wheel spun at 8.3 Hz for 120 seconds Wheel moved in and out of poles Example torque transducer reading 40mm displacement zero field (2.4Khz)

Mean Torque


Mean Torque Vs Displacement (27/3/09) Find means for each data set Colours define direction wheel is moved Looks like a systematic error – backlash in the wheel movement device

(although only one way) Can’t move the wheel completely out of the field

Edge of Wheel at edge of pole

Wheel Inside pole

Wheel outside pole


Mean Torque Vs Displacement (27/3/09)

Error bars are large for standard deviation …


Mean Torque Vs Displacement (27/3/09)

… or small for standard error (σ/√N)


Line fit Displacement Data

When compared to 1 line fit 2 line fit (separated at edge of wheel at edge of poles) looks better

Correcting for systematic errors due to wheel direction could improve fit


Fourier Transform of Torque Displacement Data

We can also take the Fourier Transform of the torque data, e.g. 40mm displacement data from before


Fourier Transform Displacement Data

Close up and do some peak finding



However 1 large unexplained peak at ~135 Hz

Wheel Harmonics, etc



Can look at the intensity of each peak as the wheel moves in and out of the field. E,g for peak at ~50Hz

Colours similar to before to indicate direction of wheel



Plot Intensity of each peak Doesn’t look like much of a pattern



No real pattern for peaks due to the wheel freq, 8.3 Hz



Or spoke frequency , 5 x 8.3 Hz


Acceleration Data

Also looked at accelerating the wheel to 500 rpm This is measured directly in the .280 data (800Hz)…


… or can be calculated from the angle data in the .180 files (2.4 kHz)

I.e. look for complete revolutions

Acceleration Data

Initial Angle

1 Turn


Acceleration Data

Time Taken for one revolution Overlaps .280 data


MI Calculation

MI = Torque \ Angular acceleration Angular Acceleration = Δω\ΔT We’ve already calculated the time for each revolution


MI calculation

Torque is more tricky Try mean torque over revolution period (?) MI

=2.2, σ=0.51 =2.5, σ=0.48 =3.5, σ=0.44

There must be other ways to calculate this…

Spinning Wheel Data Analysis Duncan Scott Magnetics and Radiation Sources group ASTeC STFC Daresbury...

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