Browsing by Subject "Cyclic scheduling"

Now showing 1 - 4 of 4

Open Access
Robotic cell scheduling with operational flexibility
(Elsevier, 2005) Akturk, M. S.; Gultekin, H.; Karasan, O. E.
In this paper, we study the problem of two-machine, identical parts robotic cell scheduling with operational flexibility. We assume that every part to be processed has a number of operations to be completed in these two machines and both machines are capable of performing all of the operations. The decision to be made includes finding the optimal robot move cycle and the corresponding optimal allocation of operations to these two machines that jointly minimize the cycle time. We prove that with this definition of the problem 1-unit robot move cycles are no longer necessarily optimal and that according to the given parameters either one of the 1-unit robot move cycles or a 2-unit robot move cycle is optimal. The regions of optimality are presented.
Open Access
Robotic cell scheduling with operational flexibility
(2002) Gültekin, Hakan
In this thesis, we study the problem of two-machine, identical parts robotic cell scheduling with operational flexibility. We assume that every part to be processed has a number of tasks to be completed in these two machines and both machines are capable of performing all of the tasks. The decision to be made includes finding the optimal robot move cycle and the optimal allocation of tasks to these two machines corresponding to this robot move cycle that jointly minimize the cycle time. We proved that 1-unit robot move cycles are not necessarily optimal with this definition of the problem any more and that according to given parameters either one of the 1-unit robot move cycles or a 2-unit robot move cycle is optimal. We proposed a new robot move cycle, which is a result of the assumption of operational flexibility. This cycle is not only simple and practical but also dominates all of the common cycles reported in the literature. Finally, we considered the change of layout and showed that the cycle time of the proposed cycle can be further reduced by a change in the layout while the cycle times of all other cycles remain the same. Keywords: Robotic cell, cyclic scheduling, automated manufacturing.
Open Access
Scheduling in a three-machine robotic flexible manufacturing cell
(Elsevier, 2007) Gultekin, H.; Akturk, M. S.; Karasan, O. E.
In this study, we consider a flexible manufacturing cell (FMC) processing identical parts on which the loading and unloading of machines are made by a robot. The machines used in FMCs are predominantly CNC machines and these machines are flexible enough for performing several operations provided that the required tools are stored in their tool magazines. Traditional research in this area considers a flowshop type system. The current study relaxes this flowshop assumption which unnecessarily limits the number of alternatives. In traditional robotic cell scheduling literature, the processing time of each part on each machine is a known parameter. However, in this study the processing times of the parts on the machines are decision variables. Therefore, we investigated the productivity gain attained by the additional flexibility introduced by the FMCs. We propose new lower bounds for the 1-unit and 2-unit robot move cycles (for which we present a completely new procedure to derive the activity sequences of 2-unit cycles in a three-machine robotic cell) under the new problem domain for the flowshop type robot move cycles. We also propose a new robot move cycle which is a direct consequence of process and operational flexibility of CNC machines. We prove that this proposed cycle dominates all 2-unit robot move cycles and present the regions where the proposed cycle dominates all 1-unit cycles. We also present a worst case performance bound of using this proposed cycle.
Open Access
Scheduling in robotic cells: process flexibility and cell layout
(Taylor & Francis, 2008) Gultekin, H.; Akturk, M. S.; Karasan, O. E.
The focus of this study is the identical parts robotic cell scheduling problem with m machines under the assumption of process and operational flexibility. A direct consequence of this assumption is a new robot move cycle that has been overlooked in the existing literature. We prove that this new cycle dominates all classical robot move cycles considered in the literature for m = 2. We also prove that changing the layout from an in-line robotic cell to a robot-centered cell reduces the cycle time of the proposed cycle even further, whereas the cycle times of all other cycles remain the same. For the m-machine case, we find the regions where the proposed cycle dominates the classical robot move cycles, and for the remaining regions present its worst case performance with respect to classical robot move cycles. Considering the number of machines as a decision variable, we also find the optimal number of machines that minimizes the cycle time of the proposed cycle.