MCFB_StepLimitSwitch
Description
This function block performs a single-axis home to a limit switch. In this case the limit switches (always active once moving part working area has been surpassed) are used for homing procedure.
The following figure shows the function block I/O:
Figure 7-249: MCFB StepLimitSwitch
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. Outputs are reset when execute input is false. |
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Data type |
BOOL |
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Range |
[0 , 1] |
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Unit |
N/A |
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Default |
— |
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AxisID |
Description |
Name of a declared instance of the AXIS_REF library function |
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Data type |
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Range |
[1 , 256] |
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Unit |
N/A |
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Default |
— |
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Direction |
Description |
Define the axis homing direction
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Data type |
BOOL |
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Range |
[0 , 1] |
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Unit |
N/A |
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Default |
— |
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LimitSwitchMode |
Description |
Limit switch state to complete homing
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Data type |
DINT |
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Range |
[0 , 3] |
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Unit |
N/A |
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Default |
— |
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Velocity |
Description |
Commanded velocity for the homing move |
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Data type |
LREAL |
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Range |
— |
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Unit |
User unit/sec |
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Default |
— |
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Acceleration |
Description |
Commanded acceleration for the homing move |
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Data type |
LREAL |
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Range |
— |
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Unit |
User unit/sec2 |
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Default |
— |
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Deceleration |
Description |
Commanded deceleration for the homing move |
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Data type |
LREAL |
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Range |
— |
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Unit |
User unit/sec2 |
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Default |
— |
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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) |
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Data type |
LREAL |
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Range |
— |
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Unit |
User unit/sec3 |
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Default |
— |
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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 entered in thousandths of maximum torque, e.g. "250" is 250/1000, or 25%. |
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Data type |
LREAL |
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Range |
— |
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Unit |
User unit |
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Default |
— |
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TimeLimit |
Description |
Maximum time for homing move to complete. If exceeded the homing procedure will error out. 0= no time limit |
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Data type |
TIME |
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Range |
— |
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Unit |
sec |
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Default |
— |
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DistanceLimit |
Description |
Maximum distance for homing move to complete. If exceeded the homing procedure will error out. 0= no distance limit |
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Data type |
LREAL |
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Range |
— |
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Unit |
User unit |
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Default |
— |
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LimitSwitch |
Description |
The limit switch input I/O point |
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Data type |
BOOL |
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Range |
[0 , 1] |
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Unit |
N/A |
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Default |
— |
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BufferMode |
Description |
Define the homing move start action
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Data type |
SINT |
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Range |
[0 , 5] |
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Unit |
N/A |
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Default |
— |
Output
Done |
Description |
Indicates the move completed successfully. The Command Position has reached the endpoint |
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Data type |
BOOL |
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Unit |
N/A |
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Busy |
Description |
High from the moment the Execute input is one-shot to the time the move is ended |
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Data type |
BOOL |
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Unit |
N/A |
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Active |
Description |
Indicates this move is the active move |
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Data type |
BOOL |
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Unit |
N/A |
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CommandAborted |
Description |
Indicates the move was aborted |
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Data type |
BOOL |
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Unit |
N/A |
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Error |
Description |
Indicates an invalid input was specified or the move was terminated due to an error |
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Data type |
BOOL |
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Unit |
N/A |
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ErrorID |
Description |
Indicates the error if Error output is set to TRUE
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Data type |
INT |
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Unit |
N/A |
Usage
This homing procedure performs a homing function searching for sensorA sensor is a type of transducer that converts one type of energy into another for various purposes including measurement or information transfer using only LimitSwitches. (A LimitSwitch has 1 “Off” (or “On”) area).
- Home is commanded by user in the desired homing direction at the selected Velocity.
- If LimitSwitch is found ‘On’ on rising ‘Execute’, then the process is started in the opposite direction as specified, LimitSwitch is search for ‘Off’ (or On, depending on LimitSwitchMode setting) Edge (released), and process is restarted again in original direction. This ensures that the end conditions are always the same.
- The torque is limited.
- The Time and Distance Limits can cause error if exceeded
- The Direction changes only when the specified Velocity is reached, this ensures acceleration and deceleration spaces are fixed
- This Function BlockA function block groups an algorithm and a set of private data. It has inputs and outputs. doesn’t modify actual position
Related Functions
Example
Structured Text
PositiveDirection :=0; RisingEdge :=2; Velocity :=10000.0; TorqueLimit :=50.0; TimeLimit :=T#10s; DistanceLimit :=10000.0;
Inst_MCFB_StepLimitSwitch( True, Axis1, PositiveDirection, RisingEdge, Velocity, 1000, 1000, 0, TorqueLimit, TimeLimit, DistanceLimit, LimitSwitch, 0 );
HomeComplete :=Inst_MCFB_StepLimitSwitch.Done; HomeBusy :=Inst_MCFB_StepLimitSwitch.Busy; HomeActive :=Inst_MCFB_StepLimitSwitch.Active; HomeAborted :=Inst_MCFB_StepLimitSwitch.CommandAborted; HomeError :=Inst_MCFB_StepLimitSwitch.Error; HomeErrorID :=Inst_MCFB_StepLimitSwitch.ErrorID;
(* LimitSwitch is a declared I/O point *)
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Ladder Diagram
Function Block Diagram