MCFB_StepBlock

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Function Block A function block groups an algorithm and a set of private data. It has inputs and outputs. - Homing The Homing procedure allows, based on a position measurement, to set a position offset to the motor in order to ensure it is physically at the home position to a physical object, mechanically blocking the movement.

Inputs

Input	Data Type	Range	Unit	Default	Description
Execute	BOOL	0, 1	N/A	No default	Request the homing step procedure at the rising edge A rising edge is the transition of a digital signal from low to high. It is also called positive edge. Outputs are reset when execute input is FALSE.
AxisID	AXIS_REF	1, 256	N/A	No default	Name of a declared instance of the AXIS_REF library function. See AXIS_REF Structure for more information.
Direction	DINT	0, 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 In physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time	LREAL	No range	User unit/sec³	No default	Commanded jerk In physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time for the homing move. If 0 (zero), trapezoidal acc/dec is used.
TorqueLimit	LREAL	No range	User units	No default	Maximum torque Torque is the tendency of a force to rotate an object about an axis. Just as a force is a push or a pull, a torque can be thought of as a twist 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, 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 more information.

Outputs

Output

Data Type

Range

Unit

Description

Done

BOOL

N/A

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

Busy

BOOL

N/A

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

Active

BOOL

N/A

Indicates this move is the Active move.

CommandAborted

BOOL

N/A

Indicates the move was aborted.

Error

BOOL

N/A

Indicates either:

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

ErrorID

INT

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 When the step gets activated, the action is activated for a single execution, and possibly once again when the step is deactivated.
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 6-100: 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 Torque is the tendency of a force to rotate an object about an axis. Just as a force is a push or a pull, a torque can be thought of as a twist 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.

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;