Post on 13-Dec-2015
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
Duncan Scott: Spinning Wheel April 2009
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
Duncan Scott: Spinning Wheel April 2009
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
Duncan Scott: Spinning Wheel April 2009
Mean Torque Vs Displacement (27/3/09)
Error bars are large for standard deviation …
Duncan Scott: Spinning Wheel April 2009
Mean Torque Vs Displacement (27/3/09)
… or small for standard error (σ/√N)
Duncan Scott: Spinning Wheel April 2009
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
Duncan Scott: Spinning Wheel April 2009
Fourier Transform of Torque Displacement Data
We can also take the Fourier Transform of the torque data, e.g. 40mm displacement data from before
Duncan Scott: Spinning Wheel April 2009
Fourier Transform Displacement Data
Close up and do some peak finding
Duncan Scott: Spinning Wheel April 2009
Fourier Transform Displacement Data
However 1 large unexplained peak at ~135 Hz
Wheel Harmonics, etc
Duncan Scott: Spinning Wheel April 2009
Fourier Transform Displacement Data
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
Duncan Scott: Spinning Wheel April 2009
Fourier Transform Displacement Data
Plot Intensity of each peak Doesn’t look like much of a pattern
Duncan Scott: Spinning Wheel April 2009
Fourier Transform Displacement Data
No real pattern for peaks due to the wheel freq, 8.3 Hz
Duncan Scott: Spinning Wheel April 2009
Fourier Transform Displacement Data
Or spoke frequency , 5 x 8.3 Hz
Duncan Scott: Spinning Wheel April 2009
Acceleration Data
Also looked at accelerating the wheel to 500 rpm This is measured directly in the .280 data (800Hz)…
Duncan Scott: Spinning Wheel April 2009
… 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
Duncan Scott: Spinning Wheel April 2009
Acceleration Data
Time Taken for one revolution Overlaps .280 data
Duncan Scott: Spinning Wheel April 2009
MI Calculation
MI = Torque \ Angular acceleration Angular Acceleration = Δω\ΔT We’ve already calculated the time for each revolution
Duncan Scott: Spinning Wheel April 2009
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…
Duncan Scott: Spinning Wheel April 2009
Duncan Scott: Spinning Wheel April 2009