Abstract
In a real manufacturing environment, the set of tasks that should be scheduled is changing over the time, which means that scheduling problems are dynamic. Also, in order to adapt the manufacturing systems with fluctuations, such as machine failure and create bottleneck machines, various flexibilities are considered in this system. For the first time, in this research, we consider the operational flexibility and flexibility due to Parallel Machines (PM) with non-uniform speed in Dynamic Job Shop (DJS) and in the field of Flexible Dynamic Job-Shop with Parallel Machines (FDJSPM) model. After modeling the problem, an algorithm based on the principles of Genetic Algorithm (GA) with dynamic two-dimensional chromosomes is proposed. The results of proposed algorithm and comparison with meta-heuristic data in the literature indicate the improvement of solutions by 1.34 percent for different dimensions of the problem.
Highlights
Scheduling is one of the most important decisions in the optimal utilization of facilities and equipment
The Flexible Dynamic Job-Shop with Parallel Machines (FDJSPM) problem is defined as follow: there are m processing steps for n tasks in Job-Shop Scheduling (JS) where each task needs a set of operations
In studies conducted in 2004, for task scheduling, the Random Keys Genetic Algorithm (RKGA) method was used in the first step SPT Cyclic Heuristic (SPTCH) contributions and the Johnson rule were used for assigning tasks and SPT Cyclic Heuristic (SPTCH) contributions and the Johnson rule were used for assigning to machines in such a way that each task was allocated to a machine which can process the allocated tasks to machines in such a way that each task was allocated to a machine which can process the task at the earliest time
Summary
Scheduling (assigning resources to tasks) is one of the most important decisions in the optimal utilization of facilities and equipment. Consider the flexibility of operation and flexibility due to parallel machines in addition to considering the dynamic manufacturing environment (due to the non-zero entry time of tasks to the workshop). Most manufacturing systems keep several versions of each machine at each workstation (flexibility due to parallel machines) to solve the bottleneck problem (due to long processing times for some components or due to machine failure) and to increase production and improve performance. The aim of this paper is to model the problem and solve the problem of minimizing the workflow ( Fmax ) by considering the dynamics generated in the workshop, i.e., operation flexibility and the flexibility of the parallel machines with non-uniform speed. For the first time, we consider the operational flexibility and the flexibility due to parallel machines with non-uniform speed for a dynamic job shop. The following, literature review and research background in the field of “job-shop”, “flexible job-shop” and “scheduling by parallel machines with uniform and non-uniform speeds” are presented
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