FB_BA_Anlg3Pnt

The function block FB_BA_Anlg3Pnt is intended for control of three-point actuators for valves or dampers. A continuous control signal for positioning an actuator is converted into the binary commands for opening and closing.
If the deviation between the position setpoint fIn and the calculated actual position value fPos of the actuator is greater than the set threshold fHys / 2, the function block starts to correct the position by switching the outputs bOpn or bCls, depending on the amount of the control deviation:

	bOpn	bCls
fIn - fPos > fHys / 2	TRUE	FALSE
fIn - fPos < - fHys / 2	FALSE	TRUE

If the function block reaches an end position fOut = 0 or fOut = 100 through a corresponding input value fIn, the corresponding switching output remains permanently set in order to safely reach this end position at the valve or damper:

	bOpn	bCls
fOut = 0	FALSE	permanently TRUE
fOut = 100	permanently TRUE	FALSE

Any deactivation of the continuous signal must be implemented by the user through external programming.

The input fIn is automatically limited internally to the range of 0...100 %.
This also applies to the inputs fHys and fRefVal. The travel times nTiCls as well as nTiOpn are both limited downwards to 10 (milliseconds).
A rising edge at bRef triggers a referencing command (setting the calculated actual position to fRefVal).
If the drive has limit switches, these can also be detected directly by means of a digital input and used for referencing at bRef.

Inputs

VAR_INPUT
  fIn         : REAL;
  fHys        : REAL;
  nTiCls      : UDINT;
  nTiOpn      : UDINT;
  bRef        : BOOL;
  fRefVal     : REAL;
  bCloseInit  : BOOL;
END_VAR

Name	Type	Description
fIn	REAL	Setpoint for the actuator position [0…100 %]. Internally limited to values between 0 and 100.
fHys	REAL	Hysteresis for the actuator position [0…100 %]. Internally limited to values between 0 and 100.
nTiCls	UDINT	Run time of the actuator from open to closed [ms]. Internally limited to values between 0 and 100.
nTiOpn	UDINT	Run time of the actuator from closed to open [ms]. Internally limited to values between 0 and 100.
bRef	BOOL	Edge references the internal position memory of the drive to value of fRefVal [0…100 %].
fRefVal	REAL	Value for referencing the actuator with bRef [0…100 %]. Internally limited to values between 0 and 100.
bCloseInit	BOOL	If this input is TRUE, output bCls is TRUE for the time udiTiOpn_ms.

Outputs

VAR_OUTPUT
  bCls    : BOOL;
  bOpn    : BOOL;
  fPos    : REAL;
END_VAR

Name	Type	Description
bCls	BOOL	Output for closing the actuator.
bOpn	BOOL	Output for opening the actuator.
fPos	REAL	Current calculated actuator position [0…100 %].

Requirements

Development environment	Required PLC library
TwinCAT from v3.1.4024.22	Tc3_BA2 from v5.2.5.0