FB_CTRL_3POINT

FB_CTRL_3POINT 1:

The function block provides a 3-point transfer element in the functional diagram.

Behavior of the output

FB_CTRL_3POINT 2:

VAR_INPUT

VAR_INPUT
    fSetpointValue  : FLOAT;
    fActualValue    : FLOAT;
    nManSyncValue   : INT;
    bSync           : BOOL;
    eMode           : E_CTRL_MODE;
END_VAR

Name	Type	Description
fSetpointValue	FLOAT	Setpoint of the controlled variable
fActualValue	FLOAT	Actual value of the controlled variable
nManSyncValue	INT	Input with which the 3-point link can be set to one of the three junctions. `nManSyncValue >= 1 → bPosOut = TRUE, bNegOut = FALSE nManSyncValue <= -1 → bPosOut = FALSE, bNegOut = TRUE otherwise → bPosOut = FALSE, bNegOut = FALSE`
bSync	BOOL	A rising edge at this input sets the 3-point element to the value "bManSyncValue".
eMode	E_CTRL_MODE	Input that specifies the operation mode of the function block.

VAR_OUTPUT

VAR_OUTPUT
    bPosOut    : BOOL;
    bNegOut    : BOOL;
    eState     : E_CTRL_STATE;
    eErrorId   : E_CTRL_ERRORCODES;
    bError     : BOOL;
END_VAR

Name	Type	Description
bPosOut	BOOL	This output from the 3-point element is TRUE if the upper junction of the characteristic curve is active.
bNegOut	BOOL	This output from the 3-point element is TRUE if the lower junction of the characteristic curve is active.
eState	E_CTRL_STATE	State of the function block
eErrorId	E_CTRL_ERRORCODES	Supplies the error number when the output `bError` is set.
bError	BOOL	Becomes TRUE, as soon as an error occurs.

VAR_IN_OUT

VAR_IN_OUT
    stParams    : ST_CTRL_3POINT_PARAMS;
END_VAR

Name	Type	Description
stParams	ST_CTRL_3POINT_PARAMS	Parameter structure of the 3-point element

stParams consists of the following elements:

TYPE
ST_CTRL_3POINT_PARAMS :
STRUCT
    tCtrlCycleTime    : TIME := T#0ms;
    tTaskCycleTime    : TIME := T#0ms;
    fPosOutOn         : FLOAT;
    fPosOutOff        : FLOAT;
    fNegOutOn         : FLOAT;
    fNegOutOff        : FLOAT;
END_STRUCT
END_TYPE

Name	Type	Description
tCtrlCycleTime	TIME	Cycle time with which the control loop is processed. This must be greater than or equal to the TaskCycleTime. The function block uses this input value to calculate internally whether the state and the output values have to be updated in the current cycle.
tTaskCycle Time	TIME	Cycle time with which the function block is called. If the function block is called in every cycle this corresponds to the task cycle time of the calling task.
fPosOutOn	FLOAT	Control deviation that will result in bPosOut = FALSE being switched to bPosOut = TRUE (bNegOut = FALSE).
fPosOutOff	FLOAT	Control deviation that will result in bPosOut = TRUE being switched to bPosOut = FALSE (bNegOut = FALSE).
fNegOutOn	FLOAT	Control deviation that will result in bNegOut = FALSE being switched to bNegOut = TRUE (bPosOut = FALSE).
fNegOutOff	FLOAT	Control deviation that will result in bNegOut = TRUE being switched to bNegOut = FALSE (bPosOut = FALSE).