Beckhoff TS5066, Руководство пользователя

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PLC API
TS5066 17 Version: 1.0
3.3 FB_AxisExtrapolateValues
This function block is used for extrapolating kinematic axis parameters. The set position (and optionally the
set velocity) are extrapolated based on the set velocity (and set acceleration) around the specified correction
time.
NOTE
By default, the parameter for using the set acceleration for extrapolating the velocity and position is _acti-
vated_. Accordingly, adequately smooth, i.e. noise-free and spike-free acceleration values (e.g. analytical
values from PTP axes) have to be present in the AxisIn structure. Encoder axes do not meet these acceler-
ation requirements through sampling and dual position differentiation. Application of the acceleration has to
be deactivated by setting parameter stAxisExtrapolateParameters.bUseAccForExtrapolation=FALSE.
Description
Beat effects described in the introduction [
}
7] lead to loss or duplicate reading of sent information. If this
information contains set values for axes, the result are step changes in the kinematic variables (set position
and set velocity). In axes that are operated directly with these variables, this will cause periodic disturbance.
The situation can be rectified by correcting the set values using higher derivative terms (set velocity or set
acceleration) and a correction time. The latter is configured (see
FB_TimeSync [ } 14] ) to ensure that beat
effects and set value fluctuations can be compensated through the extrapolation.
Figure 1 shows the received (continuous line) and the corrected (dashed line) position, with the axis being
driven with the position interface of the uncorrected values. This results in increasing fluctuations of the
actual velocity (dotted line). Figure 2 shows an overview of the situation.
Fig. 10: Figure 1: Uncorrected (black, continuous) and corrected (red, dashed) set position and actual
velocity (blue, dotted) of the axis driven with the _uncorrected_ position in the position interface.