7-14
Chapter 7. PARAMETER SETUP
●
●
I
O
U
t
(PID operation initial MV)
PID operation is started in the following cases using the
I
O
U
t
set-
ting value:
• When the mode changes from READY AUTO to RUN AUTO
• When the power is turned ON in the RUN AUTO (or HOLD,
FAST, END AUTO) mode
• At completion of auto-tuning
As the PV, SP and PID parameters settings bear a relation to PID
operation, the first MV
resulting from PID operation will not necessarily match the
I
O
U
t
setting value.
●
●
R
P
I
D
(PID operation initialization)
When SP changes suddenly by ADV (advance) operation, rate ac-
tion in PID operation may cause the MV in the operation to change
excessively. For this reason, excessive changes can be suppressed by
initializing PID operation.
However, as initialization of PID operation may result in lost conti-
nuity, initialization may adversely influence PID operation depend-
ing on the circumstances in which the controller is being used.
Initialization ON/OFF and conditions can be selected by the
R
P
I
D
setting.
●
●
S
t
(smart-tuning method selection)
0: Smart-tuning is disabled.
1: The brake value is fixed to inhibit overshoot.
2: Overshoot is inhibited while automatically reviewing the brake
value.
• When the control direction is set to reverse action, overshoot is
inhibited. When set to direct action, undershoot is inhibited. Both
functions are referred to collectively as “overshoot inhibit.”
When set to 1, the value of PID parameter setting item
B
R
is used
as it is to inhibit overshoot.
When set to 2, the value of
B
R
is reviewed at each rise (reverse
action) or fall (direct action, and overshoot is inhibited while the
value is automatically rewritten.
Review is executed only in the direction in which the
B
R
value is
increased (overshoot inhibit effect becomes more apparent).
When operation is carried out for a long time with this parameter
set to 2, overshoot inhibit may function too strongly, and it may
take a long time to arrive at SP. So, when overshoot disappears,
note down the
B
R
value at that time, set
S
T
to 1, and reset the
B
R
value to the noted down value.
