Example of Feed Forward Control
This section describes the time when the bias value is written and the value to be written. For example, suppose that there is an
oven temperature control and the PID control has already been adjusted to achieve the best performance. See the illustration
below. When the operator opens the oven door, the PID control bias adapts to heat loss, the temperature drops slightly, and the
temperature rises above the SP until the loop adapts again when the door closes. Feed-forward control can reduce this effect.
Records the amount of bias generated by the loop controller when the door is opened or closed. Next, write a ladder program to
monitor the position of the oven door limit switch. When the door opens, the ladder program reads the current bias value from
R+04 and writes the required change to R+04. When the door closes, the required change is subtracted. The following figure
shows the results.
Step changes in bias are the result of twice-feedforward writing to the bias value. It can be seen that PV variation is significantly
inhibited. The same technology can also be applied when a set point is changed.
PV
バイアス
閉じる
オーブンの
ドア
閉じる
開く
PV
降下
PV
超過
PV
バイアス
閉じる
オーブンの
ドア
閉じる
開く
フィード
フィード
The door of
the oven
Bias
Close
Open
Close
descent
excess
The door of
the oven
Bias
Close
Open
Close
Feed
Feed
Summary of Contents for Kostac SJ-Ether Series
Page 1: ...English version of the KOSTAC SJ Ether series user s manual SJ ETHER USER M...
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Page 113: ...3 24 Note Refer to 6 3 3 Module Assembly for connections and locks between modules...
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Page 156: ...flashing OFF Not sent H W RX Green flashing Receiving H W OFF Not received H W...
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Page 310: ...Chapter 7 Maintenance...
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