The basic principle of the RTG/Forklift calculator is to minimize crane delay. To achieve this, AutoStow selects RTGs in the following way:
It looks for an RTG that is already in the section and selects the RTG that is closest so that it does not cause a delay.
If it cannot find a suitable RTG, it selects another RTG from another section.
Finally if no more RTGs are available, based on the AutoStow parameter CFGRTL (on page 1), which specifies the total number of available RTGs, AutoStow selects the RTG that causes the least delay.
Forklifts are chosen in a similar way, except that they are not limited by the maximum number in a block or lane, as defined for RTGs by the configuration parameters CFGRBL (on page 1) and CFGRLN (on page 1).
When selecting and deploying equipment, AutoStow uses a set of preference rules to:
Reduce truck pool clashes within an RTG roadway
Reduce the number of yard rehandles within sections
Flexibly adjust the crane program based on operation demands.
AutoStow always considers the total primary CHEs (RTGs) available.
These are the preference rules that AutoStow uses to reduce truck pool clashes and yard rehandles within sections, and to have the flexibility to adjust the crane program:
Consider the move distance between the 1st move per crane per stow factor for a better chance to start in a) the best block and b) the best block end.
In order of priority, consider for a given POW and a given stow factor to a) start in an independent block, b) stay there, and c) stay within a lane.
Feed from a single section (preferred for single POW) but do not ignore crane rates.
Clear a stack for rehandle movements within a row.
Prefer to feed from the roadside.
Sweep sections from a block or lane in a logical direction before moving to the next block or lane.
Prefer to isolate by block in a different POW.
If it is unavoidable for multiple POWs to feed to a single section, isolate stacks per POW but do not ignore rehandling.
AutoStow tries to minimize the sum of all crane delays. Depending upon parameter settings, an RTG can easily move a few rows and still feed the crane in time. Therefore, if AutoStow considers moving an RTG, it checks to see whether it will introduce a crane delay by comparing whether the estimated time of move completion would occur later than the scheduled move.
To calculate the estimated time of move completion, AutoStow adds travel + startup + actual lift/drop times to the time of the last move. The scheduled move time (the productivity set in Quay Commander (on page 1) determines the time an RTG has to complete moves) is defined as: 30 mph corresponds to 2 min/move, which means the scheduled move times are two minutes apart.
The estimated time of move completion is defined as: Last Move Time + Travel Time + Fetch/Drop Time
Travel Time is defined as: Start/Stop Time (Constant) + Gantry Time (Speed x Distance) + Lane Change Time (if applicable)