User Manual

High−level Instructions
3 − 770
Explanation of operation
Specify set value (SP) with the instruction or an indicator before the operation.
If auto−tuning is requested with a device such as indicator, the above auto−tuning request program is not
necessary.
When R1 turns on, work area DT100 to DT129 will be initialized. (However, only DT100 (MV) can be held.)
The control conditions are that operation cycle is 1 sec, derivative type reverse operation (heating), and
PWM resolution is 1000.
PID control starts from the next scan, and PWM output is executed for Y0.
Note) If execution condition R1 has turned off during PID control, PWM output Y0 also turns off. However,
output value MV is held.
Program as described above to start auto−tuning with the instruction, and turn on R1 after turning on R0.
When auto−tuning has completed successfully, R11 turns on and KP, TI and TD is set.
If R1 is on continuously, it will change to PID control automatically, and PWM output will be executed for Y0.
When changing control conditions
The area of S4+1 to S4+9 must be changed to change control conditions. Change it before the second
execution of the F356 instruction.
<Details of S4>
S4: It is divided into output (MV), specified area of control mode, auto−tuning related area and PID
processing work area. It is recommended to allocate it in the non−hold area. Also, do not use the data in
this area for other purposes.
Output (MV) and control mode area
(Normally, the default values are used.) Default value Range
S4: The output value (MV) of PID processing is stored. k0
k−10000 to 10000
S4+1: Set the lower limit value of output value (MV). k0 Min. k−10000
S4+2: Set the upper limit value of output value (MV). k10000 Max. k+10000
S4+3: Set 100% output band (range where PID control is not performed). k0 k0 to 80(%)
S4+4: Set control cycle (TS). Setting unit=10ms, default value=1sec. k100
k1 to 3000(0.01 to 30s)
S4+5: Set control mode. (Refer to the table below.) k0 k0 to 3
Control mode Val-
ue
e.g.
Derivative type
Reverse k0 Heating
Forward k1 Cooling
Proportional−
derivative
type
Reverse k2 Heating
derivative type
Forward k3 Cooling
Auto−tuning related area (The default value is normally used.)
S4+6: Set bias value for performing auto−tuning. k0 from k0
S4+7: Set correction data (a1) of auto−tuning result (KP). k125 k50 to k500%
S4+8: Set correction data (a2) of auto−tuning result (TI). k200 k50 to k500%
S4+9: Set correction data (a3) of auto−tuning result (TD). k100 k50 to k500%
S4+10: The status while auto−tuning is being performed is stored. k0 k0 to k5
PID processing work area
S4+11: The area up to S4+29 is 0
to the work area for PID processing and auto−tuning processing. to
S4+29: 0
Reverse operation and forward operation
Reverse operation: If the measured value drops, “Reverse
operation” is specified to boost the output (heating, etc.).
Forward operation: If the measured value increases, “Forward
operation” is specified to boost the output (cooling, etc.).
Derivative type (PI−D)/Proportional−derivative type (I−PD)
Derivative type: The speed is faster to get to set value, but it is
easily overshooted.
Proportional−derivative type: The speed is slow to get to set
value, but it is not easily overshooted.