Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 439

■Proportional output operation
To perform control with a motor valve, use this function block with a loop tag FB as shown below.
Setting value
of valve
PID
opening
Loop tag
Motor valve opening
Sensor
This function block outputs open/close command bits to operate the motor valve opening according to the deviation (of
opening) between the motor valve opening (PV) and the setting value of valve opening (current) (SVC). This function block
turns on or off command signals according to the following ON/OFF conditions of command signals.
• ON/OFF condition of command signal output
The output ON/OFF conditions are calculated as shown in the following figures.
Output
Output of Open Command Signal
(OPEN)
Output of Close Command Signal
(CLOSE)
Applying a dead band and hysteresis avoids switching ON/OFF of command signal output frequently.
• Dead band (DBND)
When the motor valve opening (PV) and setting value of valve opening (current) (SVC) change frequently, ON/OFF of
command signal output switches frequently.
Setting the dead band (DBND) avoids frequent switching of command signal output.
DBND: Deviation of opening at which open/close command signals are output. (The command signals are not output until the
deviation of opening becomes larger than DBND.)
• Hysteresis (HS0)
Using hysteresis enables the motor valve to open by the amount of the opening set with the hysteresis even though the
deviation of opening is less than or equals to the dead band.
DBND-HS0: Command signal output stops when the deviation of opening falls within the range of DBND-HS0 during the
command signal output.
Position
proportional
Open/
output FB
close
output
M
Motor valve
Condition
SVC - PV > DBND
SVC - PV  DBND - HS0
SVC - PV < DBND
SVC - PV  -(DBND - HS0)
Result
Open command signal (OPEN):
OFF  ON
Open command signal (OPEN):
ON  OFF
Close command signal (CLOSE):
OFF  ON
Close command signal (CLOSE):
ON  OFF
12.39 Position Proportional Output (M+M_PVAL_T_)
Figure
0
DBND
SVC-PV(%)
OFF ON Command
signal output
(OPEN)
0
DBND
SVC-PV(%)
HS0
Command
OFF ON
signal output
(OPEN)
0
DBND
SVC-PV(%)
ON OFF Command
signal output
(CLOSE)
0
DBND
SVC-PV(%)
HS0
Command
ON OFF
signal output
(CLOSE)
12 LOOP TAG
12
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