6. Conclusions
In this paper we have explored the impact of the RFID technology
on the management of the storage/retrieval operations in a
warehouse. We have considered six order management environments
as the result of combining two types of policies (static, dynamic)
with three technological environments (no RFID tags,
RFID tags are attached on racks, RFID tags are attached on racks
and pallets) in all possible ways. A solution for the problem has
consisted of an order management policy that, given a set of orders
to be fulfilled, indicates a sequence of order fulfilment and assigns
a route and a forklift for each order. The objective has been the
minimisation of the expected tardiness. We have introduced a
set of order management policies whose performances have been
compared via simulation on a set of randomly generated realistic
test instances of different complexity. Given an instance and an order
management policy, the developed simulator simulates the
fulfilment of the storage/retrieval orders by simulating the movements
of the forklifts inside the warehouse and making decisions
at certain decision times according to the given policy.
A first conclusion that can be drawn from this work is that the
dynamic order management environments are significantly more
efficient, as far as tardiness and total flow time is concerned, than
the static ones mainly because a dynamic environment allows us
to incorporate information about the current status of the warehouse
into the decision making process. In particular, the priority
rules that take into account the concept of expected congestion
in the working zones and the due dates yield the best results.
Regarding the RFID technology the main conclusion is that
using this technology instead of a technology that requires human
intervention to identify and locate items greatly improves the efficiency
of an order management policy. We can conclude also that
RFID tagging both racks and pallets is more efficient than tagging
only racks. In fact, we consider that applying a dynamic policy in
a warehouse where both racks and pallets are RFID tagged is an
excellent option in practice.
Another issue that we are considering as a future work is to
investigate the benefits of also attaching RFID tags on the warehouse
floor at the depot, at the aisle intersections and in front of
the columns. These additional tags would allow the automatic
identification and location of the forklifts inside the warehouse
in real time. This information could be used to dynamically assign
routes to the forklifts taking into account the current status of the
warehouse, for example, taking into account the current working
zone congestion.