Research Article

A Two-Stage Path Planning Method for the Rearrangement Problem in Modular Puzzle-Based Storage System

Table 2

Additional notation.

SymbolDefinition

A = [source(A), direction(A)]A single move, where source(A) denotes the source slot to be moved and direction(A) denotes the moving direction. For an internal move, direction(A) = 1 or -1, which means clockwise or anticlockwise, respectively; for an exchange move, direction(A) = 2 or -2, which means moving-in or moving-out, respectively.
slot(s)The slot index of item
 = {Ak}A sequence of single moves, where Ak is a single move.
A single move plan of the module.
previous(i)The previous (anticlockwise adjacent) slot index of slot i.
next(i)The next (clockwise adjacent) slot index of slot i.
matched(i)Slot index in corresponding to slot i in .
between(i1, i2)A set of items between slot i1 and slot i2 in a current state
d= [type(d), distance(d)]An exchange demand generated by the picking module, where type(d) denotes the type of required item, and distance(d) denotes the remaining steps for exchange move of d.
D = {d}A set of exchange demands generated by the picking module.
i pThe index of port slot.