PID
Inputs
|
Input |
Data type |
Description |
|
AUTO |
BOOL |
TRUE = normal mode - FALSE = manual mode. |
|
PV |
REAL |
Process value. |
|
SP |
REAL |
Set point. |
|
Xout_Manu |
REAL |
Output value in manual mode. |
|
KP |
REAL |
Gain. |
|
TI |
REAL |
Integration factor. |
|
TD |
REAL |
Derivation factor. |
|
TS |
TIME |
Sampling period. |
|
XMIN |
REAL |
Minimum allowed output value. |
|
XMAX |
REAL |
Maximum output value. |
|
I_SEL |
BOOL |
If FALSE, the integrated value is ignored. |
|
INT_HOLD |
BOOL |
If TRUE, the integrated value is frozen. |
|
I_ITL_ON |
BOOL |
If TRUE, the integrated value is reset to I_ITLVAL. |
|
I_ITLVAL |
REAL |
Reset value for integration when I_ITL_ON is TRUE. |
|
DEADB_ERR |
REAL |
Hysteresis on PV. PV will be considered as unchanged if greater than (PVprev - DEADBAND_W) and less that (PRprev + DEADBAND_W). |
|
FFD |
REAL |
Disturbance value on output. |
Outputs
|
Output |
Data type |
Description |
|
Xout |
REAL |
Output command value. |
|
ER |
REAL |
Last calculated error. |
|
Xout_P |
REAL |
Last calculated proportional value. |
|
Xout_I |
REAL |
Last calculated integrated value. |
|
Xout_D |
REAL |
Last calculated derivated value. |
|
Xout_HLM |
BOOL |
TRUE if the Xout output value is greater or equal to XMAX. |
|
Xout_LLM |
BOOL |
TRUE if the Xout output value is less or equal to XMIN. |
Diagram
Remarks
It is important for the stability of the control that the TS sampling period is much bigger than the cycle time.
In LD language, the output rung has the same value as the AUTO input, corresponding to the input rung.
ST Language
MyPID is a declared instance of PID function block.
MyPID (AUTO, PV, SP, XOUT_MANU, KP, TI, TD, TS, XMIN, XMAX,
I_SEL, I_ITL_ON, I_ITLVAL, DEADB_ERR, FFD);
XOUT := MyPID.XOUT;
ER := MyPID.ER;
XOUT_P := MyPID.XOUT_P;
XOUT_I := MyPID.XOUT_I;
XOUT_D := MyPID.XOUT_D;
XOUT_HLM := MyPID.XOUT_HLM;
XOUT_LLM := MyPID.XOUT_LLM;
FBD Language
LD Language
ENO has the same state as the input rung.
Created with the Personal Edition of HelpNDoc: Easily Add Encryption and Password Protection to Your PDFs