MCFB_StepRefPulse

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Function Block - Homing to a zero angle reference.

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.
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.
SwitchMode	DINT	0 to 3	N/A	No default	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.
SetPosition	LREAL	No range	User units	No default	Value of the absolute position to be set when the homing move is done.
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.
BufferMode	SINT	0 to 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

This function modifies actual position and sets to the SetPosition input value at the end.
Performs homing by searching for Zero pulse in encoder.
- Also called Marker or Reference Pulse.
The pulse appears once per encoder revolution.
The advantage in using Reference Pulse for homing is the higher accuracy and precision achieved compared to traditional optical, mechanical, or magnetic sensors.

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

Figure 1: MCFB_StepRefPulse

Usage

Home is commanded by the user in the designated homing direction at the selected or programmed Velocity.
First occurrence of the Reference Pulse, Homing is finished.
The Torque is limited.
Time and Distance Limits can cause an error if exceeded.

Figure 2: MCFB_StepRefPulse Usage 1

Figure 3: MCFB_StepRefPulse Usage 2

It is common that a first approach is performed against a mechanical sensor at higher velocity, and after a Reference Pulse, at a lower velocity.
This is a traditional 2-Step homing (Coarse by external Switch in reverse and Fine by Reference Pulse in forward).

Figure 4: MCFB_StepRefPulse Usage 3

FBD Language Example

FFLD Language Example

IL Language Example

Not available.

Structured Text

PositiveDirection :=0;
Velocity :=10000.0;
SetPosition :=0.0;
TorqueLimit :=50.0;
TimeLimit :=T#10s;
DistanceLimit :=10000.0;

Inst_MCFB_StepRefPulse( True, Axis1, PositiveDirection, Velocity, 1000, 1000, 0, SetPosition, TorqueLimit, TimeLimit, DistanceLimit, 0 );

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