Mitsubishi Electric MELSEC-Q/L - Example of Practical Program (Step Response Method)

7 APPLICATION INSTRUCTIONS
7.18 PID Instruction
747
7
Example of practical program (step response method)
This section provides a sample program to implement auto tuning using the step response method in the following system.
System and operation example
■System configuration
■Description
X2: Auto tuning command
X3: PID control command
Y20: Error display
Y21: Heater output
Setting item During auto tuning During PID control
Set value (SV) (S1) 500(+50) 500(+50)
Parameters Sampling time (T
S
) (S3) 3000 ms 500 ms
Input filter () (S3)+2 70% 70%
Derivative gain (K
D
)(S3)+50% 0%
Upper limit of output value (S3)+22 2000 (2 seconds) 2000
Lower limit of output value (LLV) (S3)+23 0 0
Action setting
(ACT)
Alert for rate of
change in input
(S3)+1(bit 1) None None
Alert for rate of
change in output
(S3)+1(bit 2) None None
Settings of upper
and lower limits of
output value
(S3)+1(bit 5) Yes Yes
Manipulated value (MV) (D) 1800 According to arithmetic
operation
PV
MV
PV
MV
CPU module
PID control
D/A
converter
module
A/D
converter
module
Sensor
Control target
(example:
constant
temperature
bath)