171
The function code P10.01 shall be set for AI analog reference. 1 or 9 shall be set for this terminal function
according to input analog signal (Their directions are all determined by LED’s tens place setting of PLC
current stage).
5: Reserved
6: Process closed loop PID
7: Reserved
Note
When the stage running direction of PLC is determined by running command, the running direction of motor
can be changed from external direction command in real time. For example, the forward and reverse running
can be realized via X terminal. The running direction is the direction determined by the running command; if
the direction is uncertain, then follow the direction of last section.
6.12 Process PID parameters (Group P14)
The PID closed loop control adopts the combinations of proportional control (P), integral control (I) and
differential control (D). This is a control mode which makes the feedback value consistent with the target
value.
Proportional control (P)
The control quantity in proportion to the deviation cannot only rely on P control to eliminate steady-state
error.
Integral control (I)
The control quantity in proportion to the deviation integral value can eliminate steady-state error, but it
cannot control sharp change.
Differential control (D)
The control quantity in proportion to the deviation change rate can predict the change tendency of the
deviation, quickly response to sharp change and improve dynamic performance, but it is vulnerable to
interference, so use D control only when necessary. The PID control block diagram is as shown in Fig.
6-59.
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