FB_CTRL_PT3

FB_CTRL_PT3 1:

The function block provides a non-oscillating PT3 transfer element in the functional diagram.

Transfer function

Step response

FB_CTRL_PT3 3:

VAR_INPUT

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

Name	Type	Description
fIn	FLOAT	Input value of the PT3 element
fManValue	FLOAT	Input value that is output in manual mode.
eMode	E_CTRL_MODE	Input that specifies the operation mode of the function block.
bHold	BOOL	A TRUE at this input will hold the internal state (and therefore also the output) constant at its current value, independently of the input value.

VAR_OUTPUT

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

Name	Type	Description
fOut	FLOAT	Output of the PT3 element
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_PT3_PARAMS;
END_VAR

Name	Type	Description
stParams	ST_CTRL_PT3_ PARAMS	Parameter structure of the PT3 element

stParams consists of the following elements:

TYPE
ST_CTRL_PT3_PARAMS :
STRUCT
    tCtrlCycleTime  : TIME := T#0ms; 
    tTaskCycleTime  : TIME := T#0ms; 
    fKp             : FLOAT := 0; 
    tT1             : TIME := T#0ms; 
    tT2             : TIME := T#0ms; 
    tT3             : TIME := T#0ms; 
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.
fKp	FLOAT	Controller amplification / transfer coefficient
tT1	TIME	Time constant T1
tT2	TIME	Time constant T2p
tT3	TIME	Time constant T3