Paramount ME User’s Guide
69
Polynomial/Sine Curve
Please read the Important Note in the “XPeriodic Error Correction (PEC)X” section on page X65X
before continuing.
The Paramount ME’s motor to worm reduction assembly uses gears with the ratio of
3.3333 : 1 and 3.000 : 1. These additional pulleys add higher order frequencies to the
recorded periodic error. Using the Polynomial option, the Curve Fit button computes a
least squares polynomial fit of the order entered in the Polynomial Order text box. The
default order is fifth, which will typically result in a very nice curve representing the
recorded data.
In addition to the nth order polynomial curve fit, you can also manually fit a sine curve to
the PEC data. After recording the periodic error, click the Sine Curve option. You will see
a small white square plotted in the curve area. Drag this square to change the amplitude
and phase of the sine curve. Once you are satisfied with the sine curve data fit, click
Curve Fit to copy the sine wave into the fitted curve memory. Then click Upload to
transfer this data into the control system permanent flash memory.
Note: The adjustable sine curve only appears when the Table to Display group is set to
Recorded.
The beginning and end values of the recorded table (that is, the left-most and right-most
values on the graph) must be of similar amplitude. If they are not, this may indicate that
the polar alignment is poor, causing a significant non-periodic error drift during the
recording phase.
XFigure 42X shows how the graph looks after clicking Curve Fit. Both the original recorded
data (the bumpy line) and the computed fit curve are shown. If the higher frequency
information is not modeled with the curve, you can change the Polynomial Order of the
curve to attempt a better fit.
After the Curve Fit button is clicked, the equation for the nth order polynomial line, or the
amplitude and phase of the sine curve is displayed at the bottom of the dialog box.
Uploading the PEC Curve
Please read the Important Note in the “XPeriodic Error Correction (PEC)X” section on page X65X
before continuing.
Once you have an acceptable fit to the recorded data (if required), it must be transferred to
the MKS 4000. When you click Upload, you will be asked to verify replacement of the
existing PEC table.
Figure 43: Replace existing PEC table dialog box (TheSky6 Professional Edition).
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