Mitsubishi Electric FX5 - Basic Operation Expressions in PID Instruction; Basic Operation Expression for PID Control

10 PID CONTROL FUNCTION
10.2 Basic Operation Expressions in PID Instruction
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10.2 Basic Operation Expressions in PID Instruction
The PID instruction executes using the speed type or measured value differential type operation expression. According to the
contents of (s3)+1, bit 0 (operation setting (ACT)) specified by (s3) in the PID control, either forward operation or backward
operation is executed. Each value required in the operation is specified by a corresponding parameter (s3) or later.
Basic operation expression for PID control
Expression for calculating the measured value (after the filter) in sampling at this time
(PVnf)
The value "PVnf" is obtained from the following expression based on the read measured value.
Measured value after filter: PVnf = PVn+L (PVnf-1-PVn)
Operation
setting (ACT)
(s3+1: b0)
Operation expression The meaning of the signs
Forward operation
(OFF)
EVn: Deviation in sampling at this time
EVn-1: Deviation in previous cycle
SV: Target value
PVnf: Measured value in sampling at this time
(after filter)
PVnf-1: Measured value in previous cycle
(after filter)
PVnf-2: Measured value in two cycles before
(after filter)
ΔMV: Output variation
MVn: Operation quantity at this time
Dn: Differential term at this time
Dn-1: Differential term in previous cycle
TS: Sampling cycle
KP: Proportional gain
TI: Integral constant
TD: Differential constant
KD: Differential gain
Backward operation
(ON)
PVn: Measured value in sampling at this time
L: Filter coefficient
PVnf-1: Measured value in previous cycle (after filter)
ΔMV=KP{(EVn-EVn-1)+
EVn=PVnf-SV
Dn=
MVn=ΣΔMV
TS
TI
TD
TS+KD•TD
KD•TD
TS+KD•TD
EVn+Dn}
(-2PVnf-1+PVnf+PVnf-2)+ •Dn-1
ΔMV=KP{(EVn-EVn-1)+
EVn=SV-PVnf
Dn=
MVn=ΣΔMV
TS
TI
TD
TS+KD•TD
KD•TD
TS+KD•TD
EVn+Dn}
(2PVnf-1-PVnf-PVnf-2)+
•Dn-1