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Station Object

The Station object provides a fixed location for a Mover to stop at until it is ready to be released. A Station is a type of Objective, and provides a handle to the Mover object that is currently docked with the Station, allowing further motion commands to be issued to the Mover.



Setup & Execution

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// Declaration
Station     : ARRAY [0..GVL.NUM_STATIONS-1] OF Station;

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// Initialization
Station[1].Position     := 250;
Station[2].Position     := 500;
Station[3].Position     := 750;

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// Call this method cyclically
FOR i := 0 TO GVL.NUM_STATIONS - 1 DO
    Station[i].Cyclic();
END_FOR



Mover Registration

Unlike other types of Objectives, Stations manage mover registration automatically. Any mover that is commanded with a MoveToStation is also automatically registered with that station. As an example, this implementation would be redundant:

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Mover[2].MoveToStation( Station[3] );
Station[3].RegisterMover( Mover[2] );       // unnecessary

Stations also automatically unregister movers that have been redirected with another move command, even if that command's destination is the same as the Station.

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Mover[2].MoveToStation( Station[3] );
Mover[2].MoveToPosition( Station[3].Position );

Here, the Station will not report MoverInPosition.



Methods

Cyclic

Cyclic()

Stations require a cyclic call in the Main program. This allows the station to automatically unregister movers from its Tracked list who have been redirected and are no longer destined for this Station.

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FOR i := 0 TO GVL.NUM_STATIONS - 1 DO
    Station[i].Cyclic()
END_FOR



Properties

.MoverInPosition

Status boolean indicating that a mover is currently docked with the Station



.CurrentMover

Reference variable that refers to the Mover that is docked with the Station

When no mover is present in the Station, .CurrentMover is an invalid reference. In this case, an ErrorMover will replace the invalid reference. The user will receive notifications when this happens in the TwinCAT Event Logs.

It is recommended that all evaluations are nested inside IF checks for .MoverInPosition.



.TrackedMoverCount

Simply reports the number of Movers that are currently registered with the Station. Because Stations automatically deregister movers that are not currently destined for this Station, this value also represents the current number of incoming movers.



.Position

Current placement of the Station along the track



.TrackId

DINT

Track that the station is assigned to when using track management. See the Track object.



Extra Examples

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// Basic Station implementation with a 1s dwell time
IF Station[0].MoverInPosition THEN
    StationTimer( IN := TRUE, PT := T#1000MS ); // TON

    IF StationTimer.Q THEN
        Station[0].CurrentMover.MoveToStation( Station[1] );
    END_IF
ELSE
    StationTimer( IN := FALSE );
END_IF

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// Immediately redirect all incoming shuttles to Station 1 instead of Station 0
FOR i := 0 TO Station[0].TrackedMoverCount-1 DO
    Station[0].TrackedMovers[i]^.MoveToStation( Station[1] );
END_FOR