MCFB_StepBlock

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Function Block - Homing to a physical object, mechanically blocking the movement.

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	DINT	0 to 1	N/A	No default	Defines the axis homing direction. 0 (zero) = Clockwise rotation. 1 = Counterclockwise rotation.
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.
BufferMode	SINT	0 to 5	N/A	No default	Switch state to complete homing. 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 homing against a physical object, mechanically blocking the movement.
In this mode, there is no limit switch or Reference Pulse.
Adequate torque limits are required for not damaging mechanics during homing process.
The StepBlock condition is that we have reached the torque limit and real velocity falls below 5% of demanded.

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

Figure 1: MCFB_StepBlock

Usage

Homing against a physical object, mechanically blocking the movement require adequate torque limits for not damaging mechanics during homing process.

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.
The Torque is limited.
Time and Distance Limits can cause an error if exceeded.
Process is finished when Torque is in limit condition and real velocity is below 5% of selected Velocity.

Figure 2: MCFB_StepBlock Usage 1

Figure 3: MCFB_StepBlock Usage 2

FBD Language Example

FFLD Language Example

IL Language Example

Not available.

ST Language Example

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

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

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