The Application Case Longwall Operationis composed of the Use Cases for underground longwall mining systems. Figure 1presents the Application Case “Longwall” including the Use Cases “Conveying”, “Initialization”, “Shield Advance”, “Push AFC”, “Anti-Collision” “Horizon Control” and “Face Alignment”. Furthermore, the involved Users, which are the “Shearer”, “AFC”, “RoofSupport” and “Face Alignment System are displayed in Figure 1as well.

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Figure 1– Use Case Diagram for the Application Case Longwall Operation

The InitializationUC is utilized for the initial exchange of system dimensions or non-mutable data between the communication partners. It is mandatory and needs to be run every time the connection to one of the partners is (re-)established. Figure 2shows the sequence diagram of the Initializationuse case.

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Figure 2– Sequence diagram of the Initialization Use Case

The Shield AdvanceUC describes the process of moving shields towards the coal face depending on the Shearer’s position.

The Roof Support System cyclically reads the position and the running direction of the Shearer. By taking the Shearer’s position and dimensions and the actual position of the shields into account, the Roof Support System calculates which shields shall be pulled. The Roof Support System advances the corresponding shields, if necessary. This state is reflected by setting the ShieldadvanceStatus-Variable to ONGOING. Once the shield advance action is finished, i.e. all shields are in the desired position, ShieldadvanceStatusis set to FINISHED.

If necessary and applicable, the Shearer can use the Roof Support System’s ShieldadvanceStatusin its automation states.

For advanced operation, the Shearer’s drum heights can be used by the Roof Support System to determine the desired shield positions, if shield advance above the machine body is allowed. Figure 3contains the sequence diagram of this UC.

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Figure 3– Sequence diagram of the Shield Advance Use Case

This Push AFCUC describes the process of pushing the AFC towards the coal face depending on the Shearer’s position.

The Roof Support System cyclically reads the position and the running direction of the Shearer. By taking the Shearer’s position and dimensions and the actual position of the AFC sections into account, the Roof Support System calculates which sections shall be pushed. The Roof Support System advances the corresponding sections, if necessary. This state is reflected by setting the AFCPushStatusto ONGOING. If the AFC has successfully advanced all sections (i.e. all sections are in the desired position), the AFCPushStatusis set to FINISHED. The Shearer can use the AFC’s AFCPushStatusin its automation states if necessary. Figure 4illustrates the sequence diagram of this UC.

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Figure 4– Sequence diagram of the Push AFC Use Case

The ConveyingUC describes the automatic adaption of the Shearer’s speed depending on the AFC’s load.

The Shearer cyclically reads the Stateof the AFC. If the AFC’s Stateis RUNNING, the Shearer reads the Load-Variable from the AFC. If the AFC’s Load exceeds a parameterizable threshold, the Shearer’s speed is limited to a certain value. For advanced operation, the AFC’s Loadcan be used for a linear increase of the Shearer’s maximum speed. Figure 5displays the sequence diagram of this UC.

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Figure 5– Sequence diagram of the Conveying Use Case

The Anti-CollisionUC describes the automated process of preventing collisions between the Shearer cutting drums and the Roof Support Shields. The Shearer receives information about the clear area and is responsible for decreasing speed or stopping before a collision would occur.

The Roof Support System cyclically reads the Shearer’s position. By taking the Shearer’s position, dimensions and the actual position of the shields into account, the Roof Support System calculates clearance values for each side of the machine (ClearanceLeftand ClearanceRight). These values reflect the area, in which it is safe for the shearer to move. The values are based on the Shearer’s center of machine.

Depending on the current project/mine, the clearance values will be determined in different ways and will include different factors. Depending on the application, the Roof Support System can check sensor values of flipper, forepole canopy, setting pressure and advance ram.

The Shearer cyclically reads the clearance value for the current movement direction (ClearanceLeftor ClearanceRight) and reduces its maximum speed, if the clearance is below a warning threshold, or even stops, if it is lower than a halt threshold.

For advanced operation, the Roof Support System’s clearance can be used for a linear increase of the Shearer’s maximum speed. Figure 6displays the sequence diagram of this UC.

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Figure 6– Sequence diagram of the Anti-Collision Use Case

The Face AlignmentUC describes the automated process for straightening the conveyor line respective to an aerial view.

The Face Alignment System cyclically reads the Shearer’s position for determining the completion of a full shear. If a full shear was detected, the Face Alignment System uses its measurements to calculate offset values for each shield. After the calculation is finished, the Face Alignment System increases its SequenceNumber.

The Roof Support System cyclically reads the SequenceNumberof the Face Alignment System. If a new SequenceNumberwas detected, the Roof Support System reads the new calculated offsets from the Face Alignment System and applies these offsets for the next shear. Figure 7contains the sequence diagram of this UC.

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Figure 7– Sequence diagram of the Face Alignment Use Case

The Horizon ControlUC describes the process of manually correcting the cutting heights to optimize coal extraction and reduce rock cutting in specific areas. The operator uses the Roof Support System’s control panel to send correction data to the shearer.

If a new user input for either the roof or the floor offset is done, the Roof Support System sends the offset for the corresponding area (identified by StartShieldand EndShield) to the Shearer.

The Shearer uses these offsets for controlling the arm heights in the next shear. Optionally, the Roof Support System can read the present FloorOffsetand RoofOffsetof all shields from the Shearer to allow the user to see the currently applied values. Figure 8contains the sequence diagram of this UC.

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Figure 8– Sequence diagram of the Horizon Control Use Case

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