The Shield Advance UC 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, ShieldadvanceStatus is set to FINISHED.

If necessary and applicable, the Shearer can use the Roof Support System’s ShieldadvanceStatus in 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 3 contains the sequence diagram of this UC.


Figure 3 – Sequence diagram of the Shield Advance Use Case