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XPS-Q8 Controller
XPSDocumentation V1.4.x (EDH0301En1060 — 10/17)
The amplitude mismatch between sine and cosine signals generates 0.17% interpolation
error per percent amplitude mismatch. With a 20 µm scale pitch, 1% amplitude
mismatch generates 33 nm peak to peak interpolation error.
Positive amplitude is the distance between the signal's maximum value and the
signal axis. Negative amplitude is the distance between the signal's minimum value
and the signal axis. If the positive amplitude and negative amplitude are not equal,
there is amplitude mismatch.
Phase Shift
The phase shift between sine and cosine generates 0.28% interpolation error per degree
phase shift. With a 20 µm scale pitch, 1 degree phase shift between sine and cosine
generates 55.5 nm peak to peak error.
Combined Errors
The combination of these errors is not a simple sum but is more likely a root mean
square relationship. With a 20 µm scale pitch, 1% sine offset, 1% cosine offset, 1%
phase mismatch and 1 degree phase error between sine and cosine generates 132.5 nm
peak to peak error.
20000 (0.32%)
Note that the calculated value, 111.373 nm is lower than the measured 132.5 nm.
Analog encoder compensation feature
The compensation for repeatable distortions of the analog encoder input signals is
always active. It uses the following parameters read from the stages.ini file. The default
values are 0 for all stages:
EncoderSinusOffset = 0 volts
EncoderCosinusOffset = 0 volts
EncoderDifferentialGain = 0
EncoderPhaseCompensation = 0 deg
The function GroupInitializeWithEncoderCalibration() initializes the positioner and
runs the encoder calibration process. During calibration, the stage moves for 25
EncoderScalePitch and the controller determines the appropriate calibration values. The
controller though, will not automatically apply these values.
186
Note
Figure 61: Phase Shift.
+ (0.32%)
+ (0.164%)
2
2
Motion Tutorial
+ (0.28%)
= 111.373
2
2
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