Gemini GV6K and Gemini GT6K Programmer's Guide
Gemini GV6K and Gemini GT6K Programmer's Guide
Gemini GV6K and Gemini GT6K Programmer's Guide
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The b<strong>and</strong>width of the low-pass filter is controlled with the FFILT comm<strong>and</strong>:<br />
FFILT Setting<br />
Low pass Filter B<strong>and</strong>width<br />
Ø infinite (no filtering) – default setting<br />
1 120 Hz<br />
2 80 Hz<br />
3 50 Hz<br />
4 20 Hz<br />
When considering whether or how much master position filtering to use, consider the<br />
application requirement itself. The application requirements related to filtering can be<br />
categorized into these three types:<br />
Type I:<br />
Type II:<br />
Type III:<br />
If an application requires smooth motion but also high follower tracking accuracy,<br />
then a heavy filtering should not be used. It should not be used because it may<br />
introduce too much velocity phase lag, although the motion may be smooth. In<br />
other words, the master axis in the first place should produce very smooth motion<br />
<strong>and</strong> low sensor measurement noise such that a higher level of master filtering is<br />
not needed.<br />
If follower axis velocity tracking error is not critical but smooth follower axis<br />
motion is desired, then you can use a higher level of master filtering to deal with<br />
sensor noise or master vibration problems.<br />
If it is determined that under certain dynamic conditions the master position's<br />
oscillatory measurement is purely caused by its vibration motion (noise is<br />
insignificant), <strong>and</strong> it is necessary for the follower to follow such motion, then the<br />
filter comm<strong>and</strong> should not be used or only use the highest b<strong>and</strong>width (FFILT1).<br />
Following Status (TFSF, TFS, <strong>and</strong> FS) bit 18 indicates the status of master position filtering.<br />
Following Error<br />
As soon as an axis becomes configured as a follower, the follower's position comm<strong>and</strong> is<br />
continuously updated <strong>and</strong> maintained. At each update, the position comm<strong>and</strong> is calculated<br />
from the current master position <strong>and</strong> velocity, <strong>and</strong> the current ratio or velocity of the follower.<br />
Whenever the comm<strong>and</strong>ed position is not equal to the actual follower position, a Following<br />
error exists. This error, if any, may be positive or negative, depending on both the reason for<br />
the error <strong>and</strong> the direction of follower travel. Following error is defined as the difference<br />
between the comm<strong>and</strong>ed position <strong>and</strong> the actual position.<br />
Following Error = Comm<strong>and</strong>ed position - Actual position<br />
If the follower is traveling in the positive direction <strong>and</strong> the actual position lags the<br />
comm<strong>and</strong>ed position, the error will be positive. If the follower is traveling in the negative<br />
direction <strong>and</strong> the actual position lags the comm<strong>and</strong>ed position, the error will be negative. This<br />
error is always monitored, <strong>and</strong> may be read into a numeric variable (VAR) at any time using<br />
the PER comm<strong>and</strong>. The error value in follower steps is scaled by SCLD for the axis. This<br />
value may be used for subsequent decision making, or simply storing the error corresponding<br />
to some other event.<br />
188 Gem6K Series Programmer’s <strong>Guide</strong>
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