A. Kavusturucu et Sm. Gupta, Expansion method for the throughput analysis of open finite manufacturing/queueing networks with N-policy, COMPUT OPER, 26(13), 1999, pp. 1267-1292
In this paper we consider arbitrary topology manufacturing (queueing) syste
ms with finite buffers and N-policy. N-policy involves a queueing system in
which the machine (server) is assigned to alternative jobs when it becomes
idle and becomes available only after the queue builds up to a predetermin
ed level of N jobs. We use the decomposition, isolation and expansion metho
dologies to calculate the throughput of the system. The methodology is test
ed rigorously by using orthogonal arrays to design the experiments in order
to cover a large experimental region. The results of the methodology are c
ompared with simulation results. To this end, we also develop a simulation
model (which in itself is quite challenging). The differences in the two re
sults are investigated using t-tests. Based on the results, the methodology
proves to be remarkably accurate and robust over a broad range of paramete
rs.
Scope and purpose
Manufacturing systems these days are complex networks of service stations w
ith finite capacities. In order to model such networks, researchers usually
resort to simulation modeling just to capture the finite capacity restrict
ion. However, a recently reported approximation technique, called the expan
sion methodology, has proven to be extremely robust. In this paper, an addi
tional complication is introduced to the manufacturing system. In order to
increase the utilization of machines (or minimize machine idle time), the w
ork at a station is actually accumulated while the machine at that station
is assigned to alternative jobs as soon as it becomes idle. The machine kee
ps processing these alternative jobs till the accumulated work at the stati
on reaches a predetermined level of N jobs, In order to capture all these c
omplications, this paper uses decomposition, isolation and expansion method
ologies to develop an analytical (approximation) technique to model such a
system. System throughput is used as the overall measure of performance. Th
e technique is thoroughly tested and is found to be reliable, easy to progr
am and robust. (C) 1999 Elsevier Science Ltd. All rights reserved.