FB_CTRL_NORMALIZE

FB_CTRL_NORMALIZE 1:

This function block can be used to linearize a non-linear transfer element, with the aid of an inverse characteristic curve.

The characteristic curve of the transfer element that is to be linearized is stored in the table associated with this function block. The function block uses this to calculate the inverse characteristic curve with which the linearization can be carried out.

Sample

The following valve characteristic curve is stored in the table with 4 interpolation points.

FB_CTRL_NORMALIZE 2:

Control value	Valve position
arrTable[1,1] := -6;	arrTable[1,2] := -100;
arrTable[2,1] := -1;	arrTable[2,2] := -70;
arrTable[3,1] := 1;	arrTable[3,2] := 70;
arrTable[4,1] := 6;	arrTable[4,2] := 100;

The inverse characteristic curve is calculated from this characteristic curve:

FB_CTRL_NORMALIZE 3:

In the ideal case, applying these two characteristic curves in series will result in a linear transfer behavior.

FB_CTRL_NORMALIZE 4:

VAR_INPUT

VAR_INPUT
    fIn           : FLOAT;
    fManValue     : FLOAT;
    bExtrapolate  : BOOL;
    eMode         : E_CTRL_MODE;
END_VAR

Name	Type	Description
fIn	FLOAT	Input value
fManValue	FLOAT	Input value that is output in manual mode.
bExtrapolate	BOOL	If this input is FALSE, then the value of the last interpolation point is output if the limits of the table are exceeded. If, however, it is TRUE, then extrapolation is performed on the basis of the last two interpolation points.
eMode	E_CTRL_MODE	Input that specifies the operation mode of the function block.

VAR_OUTPUT

VAR_OUTPUT
    fOut                        : FLOAT;
    bInIsGreaterThanMaxElement  : BOOL;
    bInIsLessThanMinElement     : BOOL;
    eState                      : E_CTRL_STATE;
    eErrorId                    : E_CTRL_ERRORCODES;
    bError                      : BOOL;
END_VAR

Name	Type	Description
fOut	FLOAT	Table value from linear interpolation
bInIsGreaterThanMaxElement	BOOL	A TRUE at this output indicates that the input value is greater than the largest interpolation point.
bInIsLessThanMinElement	BOOL	A TRUE at this output indicates that the input value is smaller than the smallest interpolation point.
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_NORMALIZE_PARAMS;
END_VAR

Name	Type	Description
stParams	ST_CTRL_NORMALIZE_PARAMS	Parameter structure of the function block

stParams consists of the following elements:

TYPE ST_CTRL_NORMALIZE_PARAMS:
STRUCT
    tCtrlCycleTime           : TIME := T#0ms;
    tTaskCycleTime           : TIME := T#0ms;
    pDataTable_ADR           : POINTER TO FLOAT := 0;
    nDataTable_SIZEOF        : UINT     := 0;
    nDataTable_NumberOfRows  : UINT     := 0;
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.
tTaskCycleTime	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.
pDataTable_ ADR	POINTER TO FLOAT	Address of the n x 2 array on which linear interpolation is to be carried out.
nDataTable_ SIZEOF	UINT	Size of the n x 2 array
nDataTable_ NumberOfRows	UINT	Number of rows in the array