A bi-directional flow-rack automated storage and retrieval system for unit-load warehouses

Storage allocation in a warehouse based on the forklifts fleet availability

“…Some of the studies focused on the racks layout to develop some configurations other than traditional parallel picking aisles layout to reduce the total traveled distance by the forklift fleet, [5][6][7][8] some other studies focused on applying the new technologies such as autonomous vehicle storage retrieval systems to more efficiently ship the products. [9][10][11][12] Moreover, there are studies that focused on reducing the overall time and cost of material handling in the warehouse, [13][14][15][16] (routing the forklifts to have both put-away and order-picking operations in a same cycle, 17 and reducing the consumed energy and released emissions by the warehousing operations, 18 and so on.…”

“…Each single-deep rack includes many bins/bays, which are called unit-load or store. 12 In some of the traditional unit-load allocation problems, there is a rule to assign the units of a same product type to a same area of the warehouse. But, Ho and Sarma 13 showed that there is no need to store all units of a product type in a same area or near together.…”

Cycle time models for the bidirectional flow-rack AS/RS

“…[17] introduced some modifications to the classical flow-rack AS/RS to hold out with a brand-new system that needs only one S/R machine for storage and retrieval operations. [21] came up with a "mix" of the two previous cited systems to design a bidirectional flow-rack storage system (BDF AS/RS). It is a two S/R machines based system, one on each face of the rack to perform both storage and retrieval operations.…”

“…As far as we know, even if this system has been often cited in many papers to position investigation works related to flow-racks, this latter has not been studied to perform such investigations. [43,44] remains to this day the only instigations on the bi-directional flow-rack after its introduction in [21]. In [43] the presented study was to propose a batching-greedy heuristic to generate dual-command operations in the bidirectional flow-rack AS/RS.…”

“…This flow-rack system is used in the industry in the case of items with low size and weight, such as pharmaceutical products, food, textile, and electronic components [20]. In [21], while presenting the bidirectional flow -rack AS/RS, the authors have also proposed mathematical models of retrieval and dual cycle times, but by considering each machine separately according to a certain type of running. Nevertheless, what information about system performance can be obtained if the AS/RS is considered in a systemic approach?…”