MC_DigitalCamSwitch (FB)¶

FUNCTION_BLOCK MC_DigitalCamSwitch

This function block is analogous to switching on a motor shaft: The function block commands a group of discrete output bits to switch in analogy to a set of mechanical cam controlled switches connected to an axis. Forward and backward movements are allowed.

Note

Changing the VAR_IN_OUT-parameters requires a new rising edge of the Enable input.
See SMC_DigitalCamSwitch_HighPrecision for a similar function block that can provide more precise timing information.

Hint

This functionality is sometimes called PLS – Phase or Position or Programmable Limit Switch.

Example

Assume the following parameter values set:

Parameter

Type

Switch01

Switch02

Switch03

Switch04

TrackNumber

INT

1

1

1

2

FirstOnPosition [u]

REAL

2000

2500

4000

3000

LastOnPosition [u]

REAL

3000

3000

1000

-

AxisDirection

INT

1=Pos

2=Neg

0=Both

0=Both

CamSwitchMode

INT

0=Position

0=Position

0=Position

1=TIME

Duration

TIME

-

-

-

1350

Assume further, that no on/off compensation nor hysteresis is employed. The figure demonstrates the behavior of the outputs, when the axis is moving continuously in positive direction. The axis is a modulo axis with a modulo length of 5000 u.

Example of DigitalCamSwitch¶

Now assume that on compensation (-125ms) and off compensation (+250ms) are employed.

Detailed description of Switch01¶

The resulting behavior of the outputs, when the axis is moving continuously in negative direction without on/off compensation and without hysteresis.

Example in negative direction¶

InOut:

Scope	Name	Type	Initial	Comment
Inout	`Axis`	AXIS_REF_SM3		Reference to axis the switches are connected to
	`Switches`	MC_CAMSWITCH_REF		Reference to switching actions
	`Outputs`	MC_OUTPUT_REF		Reference to signal outputs that are directly related to the referenced tracks
	`TrackOptions`	MC_TRACK_REF		Reference to structure containing track related properties, e.g. the on/off compensations per output/track.
Input	`Enable`	`BOOL`		`TRUE`: Enables execution of function block.
	`EnableMask`	`DWORD`	16#FFFFFFFF	32 bits of `BOOL` enabling the different tracks. Least significant data is related to the lowest `TrackNumber`.
	`TappetMode`	MC_TAPPETMODE	tp_mode_auto	Mode for position outputs
Output	`InOperation`	`BOOL`		`TRUE`: Commanded tracks have been enabled.
	`Busy`	`BOOL`		`TRUE`: Execution of function block has not been finished yet.
	`Error`	`BOOL`		`TRUE`: Error has occurred within the function block.
	`ErrorID`	`SMC_ERROR`		Error identification
	`SwitchCorrupted`	`INT`		Signals potential problems that arise from compensation times: Compensation times may lead to the case that the extrapolated position passes one switching point several times before passing the other switching point again. As a consequence, a non-inverted switch may become inverted (and the other way around). In this case, this variable indicates the switch in concern. There are two possible reasons: noisy velocity-values, “big” difference between on- and off-compensation. -1 means that such behaviour hasn’t occured.

Structure: