FB_CTRL_PT3
The function block provides a non-oscillating PT3 transfer element in the functional diagram.
Transfer function:
Step response:
VAR_INPUT
VAR_INPUT
fIn : FLOAT;
fManValue : FLOAT;
eMode : E_CTRL_MODE;
bHold : BOOL;
END_VAR
fIn : Input value of the PT3 element.
fManValue : Input value that is output in manual mode.
eMode : Input that specifies the block's operating mode.
bHold : 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
fOut : Output of the PT3 element.
eState : State of the function block.
eErrorId : Supplies the error number when the bError output is set.
bError : Becomes TRUE, as soon as an error occurs.
VAR_IN_OUT
VAR_IN_OUT
stParams : ST_CTRL_PT3_PARAMS;
END_VAR
stParams : Parameter structure of the PT3 element. This consists of the following elements:
TYPE
ST_CTRL_PT3_PARAMS :
STRUCT
tCtrlCycleTime : TIME := T#0ms; (* controller cycle
time [TIME] *)
tTaskCycleTime : TIME := T#0ms; (* task cycle time
[TIME] *)
fKp : FLOAT := 0; (* proportional gain
*)
tT1 : TIME := T#0ms; (* T1 *)
tT2 : TIME := T#0ms; (* T2 *)
tT3 : TIME := T#0ms; (* T3 *)
END_STRUCT
END_TYPE>
tCtrlCycleTime : 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 : 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 : Controller amplification / transfer coefficient
tT1 : Time constant T1
tT2 : Time constant T2p
tT3 : Time constant T3