Mitsubishi FX3U-4AD User Manual page 21

FX /FX /FX PLC User's Manual - Analog Control Edition
3G 3U 3UC
PID Instruction (FNC 88)
1. Outline
1.1 Outline of function ........................................................................................................................ L-3
1.2 Basic Operation Expressions in PID Instruction (Reference)....................................................... L-4
2. How to Use PID Instruction
2.1 Explanation of function and operation.......................................................................................... L-5
2.2 Relationship Between Parameter Setting and Auto-Tuning......................................................... L-6
3. Parameter
3.1 Parameter List: (S3) to (S3) + 28 ................................................................................................. L-7
3.2 Details of Parameters................................................................................................................... L-9
3.2.1 Sampling time (T
3.2.2 Operation setting (ACT):(S3)+1.................................................................................................. L-10
3.2.3 Input filter (α): (S3)+2 ................................................................................................................. L-12
3.2.4 Proportional gain (K
3.2.5 Integral time (T
3.2.6 Differential gain (K
3.2.7 Differential time (T
3.2.8 Alarm output flag: (S3)+24 ......................................................................................................... L-17
4. Auto-Tuning
4.1 Limit Cycle Method..................................................................................................................... L-18
4.1.1 Parameters set in auto-tuning (of limit cycle method) ................................................................ L-18
4.1.2 Auto-tuning procedure ................................................................................................................ L-19
4.1.3 Reference: How to obtain three constants in PID control (limit cycle method)........................... L-20
4.2 Step Response Method.............................................................................................................. L-21
4.2.1 Parameters to be set by auto-tuning (step response method) ................................................... L-21
4.2.2 Auto-tuning procedure ................................................................................................................ L-21
4.2.3 Reference: How to obtain three constants in PID control (step response method).................... L-22
4.3 Cautions on Auto-Tuning Execution........................................................................................... L-22
5. Example of Practical Programs (for Step Response Method)
5.1 Example: System and operation ................................................................................................ L-23
5.2 Program example of auto-tuning (step response method) and PID control ............................... L-24
5.3 Program example of auto-tuning (step response method)......................................................... L-26
6. Troubleshooting
6.1 Error Codes................................................................................................................................ L-28
Warranty...................................................................................................................................... i
Revised History ......................................................................................................................... ii
): (S3) .............................................................................................................. L-9
S
): (S3)+3.................................................................................................... L-13
P
): (S3)+4 ............................................................................................................ L-13
I
): (S3)+5...................................................................................................... L-15
D
): (S3)+6...................................................................................................... L-15
D
Table of Contents
L-3
L-5
L-7
L-18
L-23
L-28
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