PID

 Function Block A function block groups an algorithm and a set of private data. It has inputs and outputs. - PID Proportional-Integral-Derivative - A PID controller is a generic control-loop feedback mechanism widely used in industrial control systems. An error occurs when an event or a disturbance triggers off a change in the process variable. A PID controller attempts to correct the error between a measured process variable and a desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly. loop.

See Regulation for more information.

Inputs

Input	Data Type	Range	Unit	Default	Description
AUTO	BOOL				TRUE = normal mode FALSE = manual mode
DEADB_ERR	REAL				Hysteresis on PV. PV is considered as unchanged if it is both: Greater than (PVprev - DEADBAND_W). Less than (PRprev + DEADBAND_W).
FFD	REAL				Disturbance value on output.
I_ITL_ON	BOOL				If TRUE, the integrated value is reset New start of the microprocessor. to I_ITLVAL.
I_ITLVAL	REAL				Reset value for integration when I_ITL_ON is TRUE.
I_SEL	BOOL				If FALSE, the integrated value is ignored.
INT_HOLD	BOOL				If TRUE, the integrated value is frozen.
KP Proportional gain of a control loop. AKA: P-gain.	REAL				Gain.
PV	REAL				Process value.
SP	REAL				Set point.
TD	REAL				Derivation factor.
TI	REAL				Integration factor.
TS	TIME				Sampling period Motor systems having a reciprocating or oscillating motor that operates synchronously with the periodicity of the source which supplies the electrical energy. The period of execution of a pipe is the time spent between two successive computations of set values for the same pipe. The period of execution of a pipe is specified by the PERIOD parameter of the input pipe block..
XMAX	REAL				Maximum output value.
XMIN	REAL				Minimum allowed output value.
Xout_Manu	REAL				Output value in manual mode.

Outputs

Output	Data Type	Range	Unit	Description
ER	REAL			Last calculated error.
Xout	REAL			Output command value.
Xout_D	REAL			Last calculated derivated value.
Xout_HLM	BOOL			TRUE if the output value is saturated to XMAX.
Xout_I	REAL			Last calculated integrated value.
Xout_LLM	BOOL			TRUE if the output value is saturated to XMIN.
Xout_P	REAL			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

(* MyPID is a declared instance of PID function A function calculates a result according to the current value of its inputs. 
A function has no internal data and is not linked to declared instances. block. *)
Op1: 	CAL MyPID (AUTO, PV, SP, XOUT_MANU, KP, TI, TD, TS, XMIN, XMAX, I_SEL, I_ITL_ON, I_ITLVAL, DEADB_ERR, FFD)
	FFLD  MyPID.XOUT
	ST Structured text - A high-level language that is block structured and syntactically resembles Pascal.  XOUT
	FFLD  MyPID.ER
	ST  ER
	FFLD  MyPID.XOUT_P
	ST  XOUT_P
	FFLD  MyPID.XOUT_I
	ST  XOUT_I
	FFLD  MyPID.XOUT_D
	ST  XOUT_D
	FFLD  MyPID.XOUT_HLM
	ST  XOUT_HLM
	FFLD  MyPID.XOUT_LLM
	ST  XOUT_LLM

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;