Pid Control Instruction List - Mitsubishi Electric MELSEC-Q series Programming Manual

Operation expressions
The operation expressions for PID operation using PID control instructions are indicated below.
Name
Process value Forward
differentiation Complete operation
derivative
Reverse
operation
*1 PV is calculated using the following expression.
fn
Therefore, it is the same as the PV (process value) of the input data as long as the filter coefficient is not set for the input data.
Process Value after Filtering PV
PV : Process value of the present sampling cycle
n
: Filter coefficient
PV : Process value of the preceding sampling cycle (after filtering)
fn-1
PV is stored in the I/O data area. ( Page 51 I/O Data)
fn

PID control instruction list

A list of the instructions used to execute PID control is given below.
: Usable, : Unusable
Instruction Processing Details
Name
PIDINIT Sets the reference data for PID operation.
PIDCONT Executes PID operation with the SV (set value) and the PV (process value).
PID57 Used to monitor the results of PID operation at an AD57(S1).
PIDSTOP Stops or starts PID operation for the set loop No.
PIDRUN
PIDPRMW Changes the operation parameters for the designated loop number to PID control
data.
*1 For the Basic model QCPU, High Performance model QCPU, Redundant CPU, Universal model QCPU, and LCPU, "with or without PID
limits" can be selected.
Refer to Sections 5.1 and 5.2 for details of the setting range when "with/without PID limits" has been selected.
 Page 36 PID Control Data,  Page 51 I/O Data
Operation Expressions
+ (PV
= PV - PV )
fn n fn-1 n
Meanings of Symbols
EV : Deviation in the present sampling cycle
n
EV : Deviation in the preceding sampling cycle
n-1
SV: Set value
PV : Process value of the present sampling cycle (after
fn
filtering)
PV : Process value of the preceding sampling cycle (after
fn-1
filtering)
PV : Process value of the sampling cycle two cycles before
fn-2
(after filtering)
MV: Output change value
MV : Present manipulation value
n
D : Present derivative term
n
K : Proportional constant
P
T : Sampling cycle
S
T : Integral constant
I
T : Derivative constant
D
CPU
QCPU, LCPU QnACPU
*1
 
*1
 
 
 
*1
 
3 PID CONTROL SPECIFICATIONS
3.2 PID Control by Complete Derivative
3
21