Newport XPS-Q8 - Theta Encoder and XY Correction

XPS-Q8 Controller Motion Tutorial
10.7 “Theta” Encoder and XY Correction
In a Theta-XY group, a motion in Theta will induce an offset of the center of the Theta-
axis. Utilizing the 3 encoders of the Theta stage, a correction in X and Y can be
implemented to correct for the induced eccentricity, effectively keeping the Theta axis
in the same position relative to the base. The “Theta” axis is composed of three
encoders A, B and C. The encoder type is defined in the stages.ini file by
“EncoderType”. It must either be “AquadBTheta” or “AnalogInterpolatedTheta”.
EncoderType = ; AquadBTheta or AnalogInterpolatedTheta
To enable “Theta correction”, an XY group must be associated with the
SingleAxisTheta group. It is defined in the system.ini file by:
ThetaCorrectionXYGroupName =
ThetaCorrectionLowPassCutOffFrequency = 20 ; Hz
The radius “r” and the XY correction limits are defined in the stages.ini file by:
EncoderRadius = ; units XY * rad / units Theta
MaximumEncoderCorrectionX = ; units XY
MaximumEncoderCorrectionY = ; units XY
O : Center
1,2,3 : Encoders
r : EncoderRadius
t1, t2, t3 : delta encoder counter
T1 : Encoder position 1
T2 : Encoder position 2
T3 : Encoder position 3
R : Rotation
T : Translation
127 XPSDocumentation V1.4.x (EDH0301En1060 — 10/17)