Scanlab RTC 5 PC Interface Board - set_fly_tracking_error

RTC
®
5 PC Interface Board
Rev. 1.9 e
10 Commands And Functions
428
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Ctrl Command set_fly_tracking_error
Function activates or deactivates tracking error compensation of encoder values for Processing-on-
the-fly applications.
Call
set_fly_tracking_error( TrackingErrorX, TrackingErrorY )
Parameters TrackingErrorX ,
TrackingErrorY
Tracking error in units of [10 µs] for each axis (signed 32-bit values)
allowable range: [0 … 65535], excessive bits are ignored.
Comments • Tracking error compensation is a first-approximation correction:
EC = E + ( E – EP ) *
TrackingError ,
whereby E is the current encoder value, EP is that of the previous cycle and EC is the
compensated encoder value (used for Processing-on-the-fly correction).
• To avoid step-like galvanometer movements, the used encoders should have a suffi-
ciently high resolution (counts per 10 µs cycle).
•If
TrackingErrorX,Y = 0 (initialization value), then compensation will be switched off.
•The commands store_encoder, read_encoder and get_encoder still use the original,
uncorrected encoder values.
• This compensation is practical only for linear motions (chapter 8.7.2, page 179), not for
rotary motions (chapter 8.7.3). For the latter,
TrackingErrorX,Y should be set to 0.
• If the encoders get reset via the start trigger (set_control_mode(bit #9 = 1)), then the
output value of the first 10 µs cycle might be incorrect to an unforeseen extent. Resets
via the set_fly_x and set_fly_y commands automatically wait internally for an empty
cycle.
• This compensation only functions for Processing-on-the-fly applications with encoders,
but not with position signals via the McBSP interface.
RTC
®
4  RTC
®
5 new command
Version info Available beginning with version DLL 533, OUT 534, RBF 524