ControlP

ControlP (FB)

FUNCTION_BLOCK ControlP

Short description

Proportional-acting controller (P-controller) The direction of action (inverted / direct) is also adjustable. Typical application: control loops with actuators that have an integrating/storage character.

Representation

Interfaces

Inputs

Name	Data type	Value range	Initial value	Function
rX	REAL			Analog measured value
rW	REAL			Analog setpoint
xEn	BOOL			Enable of the controller

Outputs

Name	Data type	Value range	Initial value	Function
rY	REAL		0.0	Controller output signal
rDiff	REAL			Control deviation
xLimitActive	BOOL			Status - limit exceeded

Setpoints / parameters

Name	Data type	Value range	Initial value	Function
rMax	REAL		100.0	Upper absolute limit of the output signal
rMin	REAL		-100.0	Lower absolute limit of the output signal
rKp	REAL	0.0 …	2.0	Gain factor
rOffset	REAL		0.0	Offset
rYDisabled	REAL		0.0	Disabled value
eAction	eControlMode		eControlMode.Inverted	Direction of action of the controller (Inverted, Direct)
eManModeN	eManNum		eManNum.Auto	Operating mode for the controller output signal
rManValue	REAL			Output signal in manual mode

Function description

General

This function block contains a proportional-acting controller (P-controller). The controller's output signal rY is calculated when the controller is enabled (xEn = TRUE) and in the controller's automatic operating mode (eManModeN = eManNum.Auto) is calculated as follows: rY = rKp * ((measured value + offset) - (setpoint)) Depending on the controller's direction of action eAction the measured and set values are determined as follows:

eAction	measured value	setpoint	Formula	Function
eControlMode.Inverted	rW	rX	rY = rKp * ((rW + rOffset) - (rX))	Direction of action - Inverted
eControlMode.Direct	rX	rW	rY = rKp * ((rX + rOffset) - (rW))	Direction of action - Direct

Enable input xEn

If the enable input is not active (xEn = FALSE) the disabled value rYDisabled is transferred to the output rY (precondition: eManModeN = eManNum.Auto) and limited by the absolute limits. With the enable input active (xEn = TRUE) the output signal is calculated according to the formula above and passed to the output rY (precondition: eManModeN = eManNum.Auto) and limited by the absolute limits.

Control deviation rDiff

The control deviation is calculated according to the following formula and passed to the output rDiff . rDiff = measured value - setpoint

Absolute limits rMin and rMax

The controller's output signal rY is limited downwards by the absolute limit rMin and upwards by rMax . The absolute limit rMin is set to the current value of rMax - 0.1 if it is >= the current value of rMax . The only exception is manual operation for the controller output signal (eManModeN = eManNum.Man).

Status - limit exceeded xLimitActive

The limit-exceeded status is activated (xLimitActive = TRUE) if a limit exceedance exists. The status of the limit exceedance is not set (xLimitActive = FALSE) if no limit exceedance exists. A limit exceedance exists if the controller's output signal rY reaches / exceeds the upper limit rMax or reaches / falls below the lower limit rMin .

Operating mode for the controller output signal eManModeN

The parameter eManModeN allows switching the output signal rY from automatic to manual mode and vice versa. In manual mode the output signal rY takes over the output signal in manual mode rManValue. The setpoint / parameter rManValue is overwritten with the current value of the output signal at every transition into automatic mode rY .

eManModeN	rY	Function
eManNum.Auto	signal according to formula / disabled value	Automatic mode - output signal
eManNum.Man	rManValue	Manual mode - output signal

CODESYS

InOut:

Scope	Name	Type	Initial
Input	rX	REAL
Input	rW	REAL
Input	xEn	BOOL
Input Const	rYMax	REAL	100
Input Const	rYMin	REAL	-100
Input Const	rKp	REAL	2
Input Const	rOffset	REAL	0
Input Const	rYDisabled	REAL	0
Input Const	eAction	eControlMode	eControlMode.Inverted
Input Const	eManModeN	eManNum	eManNum.Auto
Input Const	rManValue	REAL
Output	rY	REAL	0
Output	rDiff	REAL
Output	xLimitAktiv	BOOL