PID

 Function Block - PID loop.

See Regulation.

Inputs

Input	Data Type	Range	Unit	Default	Description
AUTO	BOOL	FALSE, TRUE	N/A	N/A	TRUE = normal mode FALSE = manual mode
DEADB_ERR	REAL	No range	Process Value Units	N/A	Hysteresis on PV. PV is considered as unchanged if it is both: Greater than (PVprev - DEADBAND_W). Less than (PRprev + DEADBAND_W).
FFD	REAL	No range	Process Value Units	N/A	Disturbance value on output.
I_ITL_ON	BOOL	FALSE, TRUE	N/A	N/A	If TRUE, the integrated value is reset to I_ITLVAL.
I_ITLVAL	REAL	No range	Process Value Units	N/A	Reset value for integration when I_ITL_ON is TRUE.
I_SEL	BOOL	FALSE, TRUE	N/A	N/A	If FALSE, the integrated value is ignored.
INT_HOLD	BOOL	FALSE, TRUE	N/A	N/A	If TRUE, the integrated value is frozen.
KP	REAL	No range	No Units	N/A	Gain.
PV	REAL	No range	Process Value Units	N/A	Process value.
SP	REAL	No range	Process Value Units	N/A	Set point.
TD	REAL	No range	1/sec	N/A	Derivation factor.
TI	REAL	No range	Sec	N/A	Integration factor.
TS	TIME	No range	Time Units	N/A	Sampling period.
XMAX	REAL	No range	Process Value Units	N/A	Maximum output value.
XMIN	REAL	No range	Process Value Units	N/A	Minimum allowed output value.
Xout_Manu	REAL	No range	Process Value Units	N/A	Output value in manual mode.

Outputs

Output	Data Type	Range	Unit	Description
ER	REAL	No range	Process Value Units	Last calculated error.
Xout	REAL	No range	Process Value Units	Output command value.
Xout_D	REAL	No range	Process Value Units	Last calculated derivated value.
Xout_HLM	BOOL	FALSE, TRUE	N/A	TRUE if the output value is saturated to XMAX.
Xout_I	REAL	No range	Process Value Units	Last calculated integrated value.
Xout_LLM	BOOL	FALSE, TRUE	N/A	TRUE if the output value is saturated to XMIN.
Xout_P	REAL	No range	Process Value Units	Last calculated proportional value.

Remarks

• It is important for the stability of the control that the TS sampling period is much bigger than the cycle time.
• Output of the PID block always starts with zero.
  • The value varies per the inputs provided upon further cycle executions.

Diagram

FBD Language Example

FFLD Language Example

• In the FFLD Language, the output rung has the same value as the AUTO input, corresponding to the input rung.
• ENO has the same state as the input rung.

IL Language Example

Not available.

ST Language Example

(* 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;