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XPS-Q8 Controller
XPSDocumentation V1.4.x (EDH0301En1060 — 10/17)
Example 2
The time flasher function is of particular use with high precision (direct drive) stages.
At high speeds, these stages typically provide very good speed stability. In other words,
the position change over a short time interval is highly consistent and repeatable. Hence,
time spaced pulses can be used for synchronization with similar, in some cases even
higher precision as distance spaced pulses. The time spaced pulse configuration,
however, provides some further flexibility with regards to the nominal distance between
successive triggers.
Consider an XM stage for instance. XM stages feature an analog encoder with 4 µm
signal period. The max. resolution of the distance spaced pulses is 20 nm (setting
PositionerHardInterpolatorFactorSet(200)). If the goal is to get pulses at a nominal
distance of 268 nm at a speed of 200 mm/s speed, this is not possible using the distance
spaced pulse configuration. Either 260 nm or 280 nm are possible, but not 268 nm. With
some minor adjustments to the target speed, however, this is possible using the time
spaced pulse configuration:
• The target speed is 200 mm/s, the desired distance between successive pulses is
268 nm. So the nominal time interval between successive pulses is:
268 nm / 200 mm/s = 1.340 µs
• Round this nominal value to the next possible time interval, means to the next
integer multiple of 25 ns: 1.350 µs
Use this rounded time interval to calculate a corrected velocity:
268 nm / 1.350 µs = 198.51852 mm/s
GroupMoveAbsolute(MyStage.X, -50)
PositionerSGammaParametersSet(MyStage.X, 198.51852, 2500, 0.02, 0.02)
PositionerTimeFlasherSet(MyStage.X, -30, 30, 0.00000135)
PositionerTimeFlasherEnable(MyStage.X)
GroupMoveAbsolute(MyStage.X)
PositionerTimeFlasherDisable(MyStage.X)
In this example, a first pulse is generated when the stage crosses the position -30 mm.
Further pulses are generated every 1.350 µs until the stage reaches the maximum
position of +30 mm. Since the stage moves at a speed of 198.51852 mm/s, the nominal
distance between successive pulses is: 198.51852 mm/s * 1.35 µs = 268 nm.
13.3.5
AquadB Signals on PCO Connector
In the AquadB signals configuration, AquadB encoder signals are provided on the PCO
connector, see Appendix E, PCO connector for details and pinning. These signals are
either output always (Always configuration), or only when the positioner is within a
defined position window (Windowed configuration).
When used with stages that feature a digital encoder (AquadB), the AquadB signals are
the same as the encoder signals of the stage. When used with SinCos encoders
(AnalogInterpolated), the resolution of the AquadB signal is defined by the signal
period of the encoder and the settings of the hardware interpolator by the function
PositionerHardInterpolatorFactorSet ().
Example
XM stages feature an analog encoder with a signal period of 4 µm. With the setting
PositionerHardInterpolatorFactorSet (200) the post-quadrature resolution of the AquadB
signals is: 4 µm / 200 = 0.02 µm. In this case one full period of the AquadB signals
equals 0.08 µm.
The following functions are used to configure AquadB signals:
PositionerPositionCompareAquadBWindowedSet
PositionerPositionCompareAquadBWindowedGet
PositionerPositionCompareEnable
PositionerPositionCompareAquadBAlwaysEnable
PositionerPositionCompareDisable
168
Motion Tutorial
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