Browsing by Subject "scheduling"

Now showing 1 - 5 of 5

Open Access
An analysis of FMS scheduling problem: a beam search based algorithm and comparison of scheduling schemes
(1994) Karabük, Süleyman
FMS scheduling procedures in the literature can be classified into on-line and off-line schemes according to the number of scheduling decisions made at a point in time. Online scheduling attempts to schedule operations one at a time when it is needed and off-line scheduling refers to scheduling operations of available jobs for the entire scheduling period. In the literature there is no unified argument for or against either of these scheduling schemes. This research has two main objectives: development of a new scheduling scheme called quasi on-line that makes a trade-off between on-line and off-line schemes and comparison of the proposed scheme with others under various experimental conditions. A new algorithm is proposed on which the quasi online scheme is based. The proposed algorithm is a heuristic and utilizes a beam search technique. It considers finite buffer capacity, routing and sequence flexibilities and generates machine and AGV schedules for a given scheduling period. A simulation model is also developed to implement and test scheduling schemes.
Open Access
An analysis of pure robotic cycles
(2008) Yıldız, Serdar
This thesis is focused on scheduling problems in robotic cells consisting of a number of CNC machines producing identical parts. We consider two different cell layouts which are in-line robotic cells and robot centered cells. The problem is to find the robot move sequence and processing times on machines minimizing the total manufacturing cost and cycle time simultaneously. The automation in manufacturing industry increased the flexibility, however it is not widely studied in the literature. The flexibility of machines enables us to process all the required operations for a part on the same machine. Furthermore, the processing times on CNC machines can be increased or decreased by changing the feed rate and cutting speed. Hence, we assume that a part is processed on one of the machines and the processing times are assumed to be controllable. The flexibility of machines results in a new class of cycles named pure cycles. We determined efficient pure cycles and corresponding processing times dominating the rest of pure cycles in the specified cycle time regions. In addition, for in-line robotic cells, the optimum number of machines is determined for given parameters.
Open Access
Experimental investigation of an FMS due-date scheduling problem: Evaluation of machine and AGV scheduling rules
(Kluwer Academic Publishers, 1993) Sabuncuoglu I.; Hommertzheim, D.L.
Although extensive research has been conducted to solve design and operational problems of automated manufacturing systems, many of the problems still remain unsolved. This article investigates the scheduling problems of flexible manufacturing systems (FMSs). Specifically, the relative performances of machine and automated guided vehicle (AGV) scheduling rules are analyzed against various due-date criteria. First, the relevant literature is briefly reviewed, and then the rules are tested under different experimental conditions by using a simulation model of an FMS. The sensitivity to AGV workload, buffer capacity, and processing-time distribution is also investigated to assess the robustness of the scheduling rules. © 1993 Kluwer Academic Publishers.
Open Access
An information system based on system analysis approach for course scheduling in universities
(1996) Karataş, Koray
The basic aim of this study is to provide additional insights on the subject of course scheduling in universities. Course scheduling is a very time consiuning effort, and involves different parties like students, instructors and administration, with conflicting interests. Generation of a schedule to satisfy all of the parties seems like an art, rather than an ordinary planning work. Most of the solutions to the course scheduling problem so far is based on algorithms and data structures from operations research, and programmed as batch sequences. In this study, the main argument is that the solution procedure to the course scheduling problem can be based on a system analysis approach, and with the help of an interactive software, the amount of information that a user can pass to the system is increased. This, in turn, may result in a more realistic solution. In addition to the described methodology, a computer software is developed in order to implement and test the solution algorithm.
Open Access
Two-machine flowshop scheduling with flexible operations and controllable processing times
(2011) Uruk, Zeynep
In this study, we consider a two-machine flowshop scheduling problem with identical jobs. Each of these jobs has three operations, where the first operation must be performed on the first machine, the second operation must be performed on the second machine, and the third operation (named as flexible operation) can be performed on either machine but cannot be preempted. Highly flexible CNC machines are capable of performing different operations as long as the required cutting tools are loaded on these machines. The processing times on these machines can be changed easily in albeit of higher manufacturing cost by adjusting the machining parameters like the speed of the machine, feed rate, and/or the depth of cut. The overall problem is to determine the assignment of the flexible operations to the machines and processing times for each job simultaneously, with the bicriteria objective of minimizing the manufacturing cost and minimizing makespan. For such a bicriteria problem, there is no unique optimum but a set of nondominated solutions. Using ǫ constraint approach, the problem could be transformed to be minimizing total manufacturing cost objective for a given upper limit on the makespan objective. The resulting single criteria problem is a nonlinear mixed integer formulation. For the cases where the exact algorithm may not be efficient in terms of computation time, we propose an efficient approximation algorithm.