2,111 research outputs found
Design and operational control of an AGV system
In this paper we first deal with the design and operational control of Automated Guided Vehicle (AGV) systems, starting from the literature on these topics. Three main issues emerge: track layout, the number of AGVs required and operational transportation control. An hierarchical queueing network approach to determine the number of AGVs is decribed. Also basic concepts are presented for the transportation control of both a job-shop and a flow-shop. Next we report on the results of a case study, in which track layout and transportation control are the main issues. Finally we suggest some topics for further research
Policy Design for Controlling Set-Point Temperature of ACs in Shared Spaces of Buildings
Air conditioning systems are responsible for the major percentage of energy
consumption in buildings. Shared spaces constitute considerable office space
area, in which most office employees perform their meetings and daily tasks,
and therefore the ACs in these areas have significant impact on the energy
usage of the entire office building. The cost of this energy consumption,
however, is not paid by the shared space users, and the AC's temperature
set-point is not determined based on the users' preferences. This latter factor
is compounded by the fact that different people may have different choices of
temperature set-points and sensitivities to change of temperature. Therefore,
it is a challenging task to design an office policy to decide on a particular
set-point based on such a diverse preference set. As a result, users are not
aware of the energy consumption in shared spaces, which may potentially
increase the energy wastage and related cost of office buildings. In this
context, this paper proposes an energy policy for an office shared space by
exploiting an established temperature control mechanism. In particular, we
choose meeting rooms in an office building as the test case and design a policy
according to which each user of the room can give a preference on the
temperature set-point and is paid for felt discomfort if the set-point is not
fixed according to the given preference. On the other hand, users who enjoy the
thermal comfort compensate the other users of the room. Thus, the policy
enables the users to be cognizant and responsible for the payment on the energy
consumption of the office space they are sharing, and at the same time ensures
that the users are satisfied either via thermal comfort or through incentives.
The policy is also shown to be beneficial for building management. Through
experiment based case studies, we show the effectiveness of the proposed
policy.Comment: Journal paper accepted in Energy & Buildings (Elsevier
Monte Carlo Simulation to Compare Markovian and Neural Network Models for Reliability Assessment in Multiple AGV Manufacturing System
We compare two approaches for a Markovian model in flexible manufacturing systems (FMSs) using Monte Carlo simulation. The model which is a development of Fazlollahtabar and Saidi-Mehrabad (2013), considers two features of automated flexible manufacturing systems equipped with automated guided vehicle (AGV) namely, the reliability of machines and the reliability of AGVs in a multiple AGV jobshop manufacturing system. The current methods for modeling reliability of a system involve determination of system state probabilities and transition states. Since, the failure of the machines and AGVs could be considered in different states, therefore a Markovian model is proposed for reliability assessment. The traditional Markovian computation is compared with a neural network methodology. Monte Carlo simulation has verified the neural network method having better performance for Markovian computations.We compare two approaches for a Markovian model in flexible manufacturing systems (FMSs) using Monte Carlo simulation. The model which is a development of Fazlollahtabar and Saidi-Mehrabad (2013), considers two features of automated flexible manufacturing systems equipped with automated guided vehicle (AGV) namely, the reliability of machines and the reliability of AGVs in a multiple AGV jobshop manufacturing system. The current methods for modeling reliability of a system involve determination of system state probabilities and transition states. Since, the failure of the machines and AGVs could be considered in different states, therefore a Markovian model is proposed for reliability assessment
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