Rockwell Automation 1771-QB Linear Pos. - Manual (Page 98)

Formatting Module Data (WRITES)
Chapter 7
7Ć19
If gain is relatively high, following error will be relatively small, because the
system will be more sensitive to changes in following error. If gain is low,
following error becomes relatively larger, because the system is not as
responsive to changes in following error. Choose a gain value to match the
capabilities of your equipment and provide an adequate system response.
The proportional gain that you choose must provide a stable system and
maintain desired positioning accuracy. If the gain is too high, the axis may
overshoot programmed endpoints and oscillate around them. If the gain is too
low, the axis may stop before it is within the desired in-position or PID bands.
Gain Break Speed (words 18 and 47)
At speeds equal to and above the gain break speed, the proportional gain is
increased or reduced by the gain factor parameter (words 19 and 48). Below the
gain break speed, the proportional gain is unchanged.
Figure 7.25
Gain Break Speed Word
50011
Gain break speed,
BCD 99.99 ips or 999.9 mmps max
Binary 327.67 ips or 3276.7 mmps max
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
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The gain break plot in Figure 7.26 illustrates the concept of gain break.