MCFB_StepLimitSwitchFastInput

Description

This function block performs a homing function by searching for an external physical switch. The switch must be connected to one of the two fast inputs The inputs are taken into account at each cycle depending on the system periodicity (for example each millisecond). Under certain circumstances this can be insufficient when more accuracy is needed, or if a quick response is required from the system. To fill the gap, a drive may have some Fast Input connections (generally one or two). When an event happens that triggers a Fast Input (e.g. when a sensor sends a rising edge), the detection of a signal occurs faster (which can be 1000 times more accurate than the system periodicity). Then the timestamp associated with this input can be provided to the IPC to take corrective action on the Axis' AKD drive. The Axis will move and when a fast input The inputs are taken into account at each cycle depending on the system periodicity (for example each millisecond). Under certain circumstances this can be insufficient when more accuracy is needed, or if a quick response is required from the system. To fill the gap, a drive may have some Fast Input connections (generally one or two). When an event happens that triggers a Fast Input (e.g. when a sensor sends a rising edge), the detection of a signal occurs faster (which can be 1000 times more accurate than the system periodicity). Then the timestamp associated with this input can be provided to the IPC to take corrective action is triggered, the triggered axis will then perform an absolute move to the latched position.

The following figure shows the function block I/O:

MCFB StepLimitSwitchFastInput

Figure 7-254: MCFB StepLimitSwitchFastInput

Input

Execute

Description

Request the homing step procedure at 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.

Data type

BOOL

Range

[0 , 1]

Unit

N/A

Default

—

AxisID

Description

Structure for specified Axis desired to home

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

—

LimitSwitchMode

Description

Limit switch state to complete homing

Value	Description
0	when rising edge of sensor A sensor is a type of transducer that converts one type of energy into another for various purposes including measurement or information transfer
1	when falling edge

Data type

DINT

Range

[0 , 1]

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

—

Jerk In physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time

Description

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 zero, then trapezoidal acc/dec is used)

Data type

LREAL

Range

—

Unit

User unit/sec³

Default

—

TorqueLimit

Description

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

Data type

LREAL

Range

—

Unit

User unit entered in thousandths of maximum torque, e.g. "250" is 250/1000, or 25%.

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

—

FastInputNum

Description

0 for first fast input (X7 Pin 10), 1 for second fast input (X7 pin 9)

Data type

BOOL

Range

[0 , 1]

Unit

N/A

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

Set when the function block is active

Data type

BOOL

Unit

N/A

CommandAborted

Description

Indicates the move was aborted

Data type

BOOL

Unit

N/A

Error

Description

Signals that an error has occurred within the function block

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-Accel-Decel

Data type

INT

Unit

N/A

Usage

The homing is commanded in the most likely direction were the sensor can be found. In this example (-).

UDFB StepLimitSwitchFastInput: usage

Related Functions

MCFB_StepAbsSwitchFastInput

Example

Structured Text

Execute_1 :=1;

Inst_MCFB_StepLimitSwitchFastInput( Execute_1, Axis1, 0, 0, 10000.0, 10000.0, 10000.0, 0, 0, 0, 0, 0, 0);

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

FBD

Ladder Diagram

UDFB StepLimitSwitchFastInput: LD example

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