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