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Showing 2 results for Tavakkoli Moghaddam
Dr. Mehdi Foumani, Dr. Reza Tavakkoli Moghaddam, Volume 10, Issue 1 (7-2019)
Abstract
This paper analyzes the performance of a robotic system with two machines in which machines are configured in a circular layout and produce non-identical parts repetitively. The non-destructive testing (NDT) is performed by a stationary robotic arm located in the center of the circle, or a cluster tool. The robotic arm integrates multiple tasks, mainly the NDT of the part and its transition between a pair of machines. The robotic arm cannot complete the transition if it identifies a fault in the part. The main feature of the NDT technology is that its required time is changed by altering the testing cost. This generates a trade-off between cost and cycle time. Initially, the problem of robotic arm scheduling and part sequencing is jointly solved to supports the decision making for reliability improvement of small-scale robotic systems with NDT technologies. We show how the case of non-identical parts can be converted into a travelling salesman problem (TSP). Then, we provide a generalization of the framework based on three characteristics: pickup criterion, layout and travel time metric. The results are extended for the interval and no-wait pickup criteria, and then some notes are provided for travel time saving of different layout and travel time metric. It is shown whether circular systems are equivalent to linear systems, or they dominate linear cases in general terms.
Miss Fateme Ghaffarifar, Seyed Hadi Nasseri, Reza Tavakkoli Moghaddam, Volume 14, Issue 1 (6-2023)
Abstract
One of the most important and widely used problems in the logistics part of any supply chain is the location-routing problem (LRP) of vehicles. The purpose is to select distribution centers to supply goods for customers and create suitable travel routes for vehicles to serve customers. Studies conducted in the field of supply chain logistics systems have shown that if vehicle travel routing is neglected when locating supply centers, the costs of the logistics system may increase dramatically. Therefore, in the LRP problem, the location of supply centers and the routing of vehicles are considered simultaneously. In this paper, we will present a multi-objective model for vehicle location-routing problems with a flexible fuzzy approach. Its' goals are to make strategic decisions to deploy candidate supply centers at the beginning of the planning horizon, as well as form the vehicle travel at the tactical level to serve the customers in short-term periods of time. Therefore, in order to adapt the mathematical model to the real conditions, the constraints related to the capacity of the vehicles have been considered in a flexible fuzzy state, and also the problem has been modeled in a multi-period state along with the presence of the distance limit and the accessibility factor for each vehicle. The evaluation criterion is to minimize costs related to the establishment of candidate supply centers, the fixed cost of using vehicles and transportation costs, as well as maximizing customer satisfaction by reducing shortage costs and reducing harmful environmental effects. To solve the model, it is first converted into a single-objective model using the weight method and then solved using the proposed algorithm. Finally, using a numerical example in the field of waste management, the effectiveness of the proposed solution method is shown. It should be mentioned that the model was solved using GAMS software and the results are shown.
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