MCFB_StepLimitSwitch

PLCopen motion icon

Function Block - Homing to a limit switch.

Inputs

Input	Data Type	Range	Unit	Default	Description
Execute	BOOL	FALSE, TRUE	N/A	No default	Request the homing step procedure at the rising edge. Outputs are reset when execute input is FALSE.
AxisID	AXIS_REF	1 to 256	N/A	No default	Name of a declared instance of the AXIS_REF library function. See AXIS_REF Structure.
Direction	BOOL	FALSE, TRUE	N/A	No default	Defines the axis homing direction. 0 (zero) = Clockwise rotation. 1 = Counterclockwise rotation.
LimitSwitchMode	DINT	0, 3	N/A	No default	Limit switch state to complete homing. 0 (zero) = Switch is on. 1 = Switch is off. 2 = Rising edge of switch. 3 = Falling edge of switch.
Velocity	LREAL	No range	User unit/sec	No default	Commanded velocity for the homing move.
Acceleration	LREAL	No range	User unit/sec²	No default	Commanded acceleration for the homing move.
Deceleration	LREAL	No range	User unit/sec²	No default	Commanded deceleration for the homing move.
Jerk	LREAL	No range	User unit/sec³	No default	Commanded jerk for the homing move. If 0 (zero), trapezoidal acc/dec is used.
TorqueLimit	LREAL	No range	User units	No default	Maximum torque applied for the homing move. Entered in thousandths of maximum torque. Example: 250 is 250/1000, or 25%.
TimeLimit	TIME	No range	Sec	No default	Maximum time for homing move to complete. If exceeded, the homing procedure errors out. 0 (zero) = no time limit.
DistanceLimit	LREAL	No range	User units	No default	Maximum distance for homing move to complete. If exceeded, the homing procedure errors out. 0 (zero) = no distance limit.
LimitSwitch	BOOL	FALSE, TRUE	N/A	No default	The limit switch input I/O point.
BufferMode	SINT	0, 5	N/A	No default	Define the homing move start action. 0 = Abort. 1 = Buffer. 2 = Blend to active. 3 = Blend to next. 4 = Blend to low velocity. 5 = Blend to high velocity. See Buffer Modes for detailed information.

Outputs

Output

Data Type

Range

Unit

Description

Done

BOOL

FALSE, TRUE

N/A

Indicates the move completed successfully.
The Command Position has reached the endpoint.

Busy

BOOL

FALSE, TRUE

N/A

High from the moment the Execute input goes high until the time the move is ended.

Active

BOOL

FALSE, TRUE

N/A

Indicates this move is the Active move.

CommandAborted

BOOL

FALSE, TRUE

N/A

Indicates the move was aborted.

Error

BOOL

FALSE, TRUE

N/A

Indicates either:

An invalid input was specified.
The move was terminated due to an error.

ErrorID

INT

Enumerated

N/A

Indicates the error if the Error output is set to TRUE.

Error identifier:

ErrorID	Description
1	TimeLimit exceeded.
2	DistanceLimit exceeded.
3	TorqueLimit exceeded.
4	Axis error stop state.
5	Axis not enabled.
6	Invalid inputs for Velocity-Acceleration-Deceleration.

Remarks

Performs a single-axis home to a limit switch.
The limit switches are used for homing procedure.
- They are always active once moving part working area has been surpassed.

This image shows the function or function block I/O.

Figure 1: MCFB_StepLimitSwitch

Usage

This function block does not modify the actual position.
Home is commanded by the user in the designated homing direction at the selected or programmed Velocity.
This procedure performs a homing function searching for sensor using only LimitSwitches.
- A LimitSwitch has one Off (or On) area.
If LimitSwitch is found On with a rising Execute, the process is started in the opposite direction as specified.
LimitSwitch is searched for Off Edge (released) and process is restarted again in original direction.
- Or On, depending on LimitSwitchMode setting.
- This ensures the end conditions are always the same.
The Torque is limited.
Time and Distance Limits can cause an error if exceeded.
The direction changes only when the specified Velocity is reached.
- This ensures acceleration and deceleration spaces are fixed.

Figure 2: MCFB_StepLimitSwitch Usage 1

Figure 3: MCFB_StepLimitSwitch Usage 2

FBD Language Example

FFLD Language Example

IL Language Example

Not available.

ST Language Example

PositiveDirection :=0;
RisingEdge :=2;
Velocity :=10000.0;
TorqueLimit :=50.0;
TimeLimit :=T#10s;
DistanceLimit :=10000.0;

Inst_MCFB_StepLimitSwitch( True, Axis1, PositiveDirection, RisingEdge, Velocity, 1000, 1000, 0, TorqueLimit, TimeLimit, DistanceLimit, LimitSwitch, 0 );

HomeComplete :=Inst_MCFB_StepLimitSwitch.Done;
HomeBusy :=Inst_MCFB_StepLimitSwitch.Busy;
HomeActive :=Inst_MCFB_StepLimitSwitch.Active;
HomeAborted :=Inst_MCFB_StepLimitSwitch.CommandAborted;
HomeError :=Inst_MCFB_StepLimitSwitch.Error;
HomeErrorID :=Inst_MCFB_StepLimitSwitch.ErrorID;

(* LimitSwitch is a declared I/O point *)