Mitsubishi Electric FX3G User Manual page 25

FX /FX /FX /FX /FX
3S 3G 3GC 3U
M. PID Instruction (FNC 88)
1. Outline
1.1 Outline of function ....................................................................................................................... M-3
1.2 Basic Operation Expressions in PID Instruction (Reference)...................................................... M-4
2. How to Use PID Instruction
2.1 Explanation of function and operation......................................................................................... M-5
2.2 Relationship Between Parameter Setting and Auto-Tuning........................................................ M-6
3. Parameter
3.1 Parameter List: (S3) to (S3) + 28 ................................................................................................ M-7
3.2 Details of Parameters.................................................................................................................. M-9
3.2.1 Sampling time (T
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
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 ........................................................................................................ M-17
4. Auto-Tuning
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)
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
6.1 Error Codes............................................................................................................................... M-28
Warranty...................................................................................................................................... i
Revised History ......................................................................................................................... ii
PLC User's Manual - Analog Control Edition
3UC
): (S3) ............................................................................................................. M-9
S
): (S3)+3................................................................................................... M-13
P
): (S3)+4 ........................................................................................................... M-13
I
): (S3)+5..................................................................................................... M-15
D
): (S3)+6..................................................................................................... M-15
D
Table of Contents
M-3
M-5
M-7
M-18
M-23
M-28
19