Nodes, Work, and Park Searches

ProModel "registers" all cranes to their home nodes at the beginning of a simulation run. When a crane starts to move, ProModel erases registration, and re-establishes it when the crane stops, according to the following rules:

1. Cranes assigned to a task (pick up, drop off, down) remain unregistered throughout intermediate stops and register to the task destination node upon arrival.

2. Idle cranes that are bumped away, or cranes that were unsuccessful in claiming the entire bridge region to go parking register themselves to the node closest to their bridge when they stop. If there are multiple nodes closest to the bridge, ties are broken by the minimum distance to the hoist and then the order of appearance in the nodes edit table. If the hoist is still moving at the time the bridge stops, the registry procedure executes by considering the destination of the hoist.

Please note

Only users can instruct cranes to park on nodes. However, as a result of bump-aways, a crane can end up standing still at positions that do not necessarily correspond to nodes. In any case, ProModel registers an idle stationary crane to a node and places it under the control of work and park searches of that node.

Cranes follow the same rules as regular dynamic resources while searching for assignments (returning to preempted jobs, exclusive & non-exclusive work searches, requests coming from nodes not included in the work search, etc.). There are some additional steps to handle interactions with other cranes operating in the same envelope. Upon completion of its task, a crane goes through these extra steps:

1. Lets other cranes in the same envelope re-attempt their claims, possibly generating an induced claim on its bridge.

2. Even though other cranes might bump away its bridge, the crane executes the work search defined for it at its current node. (If requests are waiting at different locations of the same work search record, ProModel takes the resource request priorities into consideration.)

3. If it was not allocated to a task or bumped away, the crane executes the park search defined for it at its current node, or attempts going home if return home is checked.

Please note

A crane bridge moving to park cannot bump other idle bridges out of its way. In such a case, the bridge goes as far as it can towards its destination and registers itself to the closest node upon stopping (using the rules discussed above).