MCFB_StepRefPulse

Description

This function block performs homing by searching for Zero pulse (also called Marker or reference pulse) in encoder. The reference pulse appears once per encoder revolution. The advantage in using Reference PulseWhen the step gets activated, the action is activated for a single execution, and possibly once again when the step is deactivated for homing is the higher accuracy and precision that can be achieved compared to traditional optical, mechanical or magnetic sensors.

The following figure shows the function block I/O:

Figure 7-250: MCFB StepRefPulse

Arguments

Input

Execute	Description	Request the homing step procedure at rising edgeA rising edge is the transition of a digital signal from low to high. It is also called positive edge
	Data type	BOOL
	Range	[0 , 1]
	Unit	N/A
	Default	—
AxisID	Description	Name of a declared instance of the AXIS_REF library function
	Data type	AXIS_REF
	Range	[1 , 256]
	Unit	N/A
	Default	—
Direction	Description	Define the axis homing direction Value Description 0 clockwise rotation 1 counterclockwise rotation
	Data type	BOOL
	Range	[0 , 1]
	Unit	N/A
	Default	—
SwitchMode	Description	Switch state to complete homing Value Description 0 switch is on 1 switch if off 2 rising edge of switch 3 falling edge of switch
	Data type	DINT
	Range	[0 , 3]
	Unit	N/A
	Default	—
Velocity	Description	Commanded velocity for the homing move
	Data type	LREAL
	Range	—
	Unit	User unit/sec
	Default	—
Acceleration	Description	Commanded acceleration for the homing move
	Data type	LREAL
	Range	—
	Unit	User unit/sec2
	Default	—
Deceleration	Description	Commanded deceleration for the homing move
	Data type	LREAL
	Range	—
	Unit	User unit/sec2
	Default	—
JerkIn physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time	Description	Commanded jerkIn physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time for the homing move (if zero, then trapezoidal acc/dec is used)
	Data type	LREAL
	Range	—
	Unit	User unit/sec3
	Default	—
SetPosition	Description	Value of the absolute position to be set when the homing move is done
	Data type	LREAL
	Range	—
	Unit	User unit
	Default	—
TorqueLimit	Description	Maximum torqueTorque 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
	Data type	LREAL
	Range	—
	Unit	User unit
	Default	—
TimeLimit	Description	Maximum time for homing move to complete. If exceeded the homing procedure will error out. 0= no time limit
	Data type	TIME
	Range	—
	Unit	sec
	Default	—
DistanceLimit	Description	Maximum distance for homing move to complete. If exceeded the homing procedure will error out. 0= no distance limit
	Data type	LREAL
	Range	—
	Unit	User unit
	Default	—
BufferMode	Description	Define the homing move start action Value Description 0 abort 1 buffer 2 Blend to active 3 blend to next 4 blend to low velocity 5 blend to high velocity See table in Buffer Modes
	Data type	SINT
	Range	[0 , 5]
	Unit	N/A
	Default	—

Output

Done	Description	Indicates the move completed successfully. The Command Position has reached the endpoint
	Data type	BOOL
	Unit	N/A
Busy	Description	High from the moment the Execute input is one-shot to the time the move is ended
	Data type	BOOL
	Unit	N/A
Active	Description	Indicates this move is the active move
	Data type	BOOL
	Unit	N/A
CommandAborted	Description	Indicates the move was aborted
	Data type	BOOL
	Unit	N/A
Error	Description	Indicates an invalid input was specified or the move was terminated due to an error
	Data type	BOOL
	Unit	N/A
ErrorID	Description	Indicates the error if Error output is set to TRUE Value 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
	Data type	INT
	Unit	N/A

Usage

This function Block performs homing by searching for Zero pulse (also called Marker or reference pulse) in encoder. The reference pulse appears once per encoder revolution.

• Home is commanded by user in the desired homing direction at the programmed velocity.
• First occurrence of the Reference Pulse, HomingThe 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 is finished
• TorqueTorque 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 error if exceeded
• This FunctionA function calculates a result according to the current value of its inputs. A function has no internal data and is not linked to declared instances. modifies actual position and sets to the “SetPosition” input value at the end

 

It is common that a first approach is performed against a mechanical sensorA sensor is a type of transducer that converts one type of energy into another for various purposes including measurement or information transfer 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).

Related Functions

MCFB_StepAbsolute

MCFB_StepAbsSwitch

MCFB_StepBlock

MCFB_StepLimitSwitch

Example

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;

Ladder Diagram

Function Block Diagram

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