MC_TouchProbe

The function block MC_TouchProbe records an axis position at the time of a digital signal (touch probe function). The position is captured via an external hardware latch and is therefore highly accurate and independent of the cycle time. The function block controls this mechanism and determines the externally recorded position.

	The parameters involved may have to be set in the drive parameters. For the servo terminal the parameters can be found in the objects DMC Setting (0x8030) or DMC Features (0x8031).

	After a measuring probe cycle has been initiated by a rising edge on the "Execute" input, this is only terminated if the outputs "Done", "Error" or" CommandAborted" become TRUE. If the operation is to be aborted in the meantime, the function block MC_AbortTrigger must be called with the same TriggerInput data structure. Otherwise no new cycle can be initiated.

Signal curve

Inputs

VAR_INPUT
    Execute       : BOOL;
    WindowOnly    : BOOL;
    FirstPosition : LREAL;
    LastPosition  : LREAL;
END_VAR

Name	Type	Description
Execute	BOOL	The command is executed with a rising edge, and the external position latch is activated.
WindowOnly	BOOL	If WindowOnly = TRUE, only one position within the window between "FirstPosition" and "LastPosition" is recorded. Positions outside the window are rejected and the external position latch is automatically newly activated. Only if the recorded position lies inside the window, "Done" becomes TRUE. The recording window can be interpreted in terms of absolute or modulo values. For this purpose, the "ModuloPositions" flag must be set accordingly in the TriggerInput data structure. In the case of absolute value positions there is exactly one window. With modulo positions, the window is repeated within the modulo cycle defined in the axis parameters (e.g. 0 to 360°).
FirstPosition	LREAL	Initial position of the recording window, if "WindowOnly" is TRUE. This position can be interpreted as an absolute or modulo value. For this purpose, the "ModuloPositions" flag must be set accordingly in the TriggerInput data structure.
LastPosition	LREAL	End position of the recording window, if "WindowOnly" is TRUE. This position can be interpreted as an absolute or modulo value. For this purpose, the "ModuloPositions" flag must be set accordingly in the TriggerInput data structure.

Inputs/outputs

VAR_IN_OUT
    Axis         : AXIS_REF;
    TriggerInput : TRIGGER_REF; 
END_VAR

Name	Type	Description
Axis	AXIS_REF	Axis data structure
TriggerInput	TRIGGER_REF	Data structure for describing the trigger source. This data structure must be parameterized before the function block is called for the first time.

Outputs

VAR_OUTPUT
    Done             : BOOL;
    Busy             : BOOL;
    CommandAborted   : BOOL;
    Error            : BOOL;
    ErrorId          : UDINT;
    RecordedPosition : LREAL;
    RecordedData     : MC_TouchProbeRecordedData; 
END_VAR

Name	Type	Description
Done	BOOL	TRUE if an axis position was successfully detected. The position is sent to the output "RecordedPosition".
Busy	BOOL	TRUE as soon as the function block is active. FALSE if it is in the default state.
CommandAborted	BOOL	TRUE if the process is interrupted by an external event, e.g. by the call up of MC_AbortTrigger.
Error	BOOL	TRUE, if an error occurs.
ErrorID	UDINT	If the error output is set, this parameter supplies the error number.
RecordedData	MC_TouchProbeRecordedData	Data structure with complementary information relating to the logged axis position at the time of the trigger signal

Requirements

Development environment	PLC libraries to include
TwinCAT 3.1.4024.11	Tc3_DriveMotionControl