XPS-Q8 Controller Motion Tutorial
Saves the gathering data from memory in a file gathering.dat in the
..admin/public folder of the XPS.
In this example, one set of data will be gathered every 10 ms on the trajectory between
the start of the 3rd and the end of the 5th element.
13.3 Distance, Time Spaced Pulses or AquadB Position Compare
13.3.1 Position compare settings and limits of use
13.3.1.1 Position compare calibration
EncoderIndexOffset (stages.ini) is a configuration parameter (measured in position unit
like mm, deg. …), used to correct the offset between stage raw encoder position and
stage hard interpolator position values.
To measure EncoderIndexOffset value, do the followings:
- Set EncoderIndexOffset = 0 in stages.ini then reboot the controller.
- Send the following commands to the controller:
GroupInitialize() then GroupHomeSearch().
PositionerHardInterpolatorPositionGet()
Example: PositionerHardInterpolatorPositionGet( (XY.X, double *)
Controller response: 0,Value1 (example 0,0.001).
- Set EncoderIndexOffset = Value1 in stages.ini then reboot the controller once again.
Send the same commands: GroupInitialize(), GroupHomeSearch() then
PositionerHardInterpolatorPositionGet().
Controller response: 0,Value2 (example 0, 2.71051e-20). Value2 must be closed
to 0, meaning that the position compare is now calibrated.
Note
It is not mandatory to calibrate the PCO and its accuracy is application dependent.
13.3.1.2 Valid settings as a function of scan velocity and PCO pulse settling time
- Determine PCO encoder frequency:
AquadB encoder:
PCO encoder frequency = ScanVelocity / EncoderResolution
Analog Sin/Cos encoder:
PCO encoder frequency = ScanVelocity * HardInterpolatorFactor / EncoderScalePitch
Example: ScanVelocity = 10 mm/s, EncoderScalePitch = 0.004 mm,
HardInterpolatorFactor = 200 => PCO encoder frequency = 10 * 200 / 0.004 =
500000 = 500 kHz
- The valid settings are shown in the following table:
Pulse settling
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