Multicriteria hybrid flow shop scheduling problem: literature review, analysis, and future research

This research focuses on the Hybrid Flow Shop production scheduling problem, which is one of the most difficult problems to solve. The literature points to several studies that focus the Hybrid Flow Shop scheduling problem with monocriteria functions. Despite of the fact that, many real world problems involve several objective functions, they can often compete and conflict, leading researchers to concentrate direct their efforts on the development of methods that take consider this variant into consideration. The goal of the study is to review and analyze the methods in order to solve the Hybrid Flow Shop production scheduling problem with multicriteria functions in the literature. The analyses were performed using several papers that have been published over the years, also the parallel machines types, the approach used to develop solution methods, the type of method develop, the objective function, the performance criterion adopted, and the additional constraints considered. The results of the reviewing and analysis of 46 papers showed opportunities for future researchon this topic, including the following: (i) use uniform and dedicated parallel machines, (ii) use exact and metaheuristics approaches, (iv) develop lower and uppers bounds, relations of dominance and different search strategiesto improve the computational time of the exact methods,  (v) develop  other types of metaheuristic, (vi) work with anticipatory setups, and (vii) add constraints faced by the production systems itself

Approximation algorithms for solving multi-objective optimization problems

This paper tries to cover the main aspects/properties related to scheduling problems, approximation algorithms, and multi-objective combinatorial optimization. Then, we try to describe the main techniques that can be used to solve such problems. In this paper, the reviews results relate to multi-objective optimization problems, exact and approximation search, with the aim of getting all Pareto optimal solutions for some NP-hard problems

A Bicriteria Simulated Annealing Algorithm for Scheduling Jobs on Parallel Machines with Sequence Dependent Setup Times

The study considers the scheduling problem of identical parallel machines subject to minimization of the maximum completion time and the maximum tardiness expressed in a linear convex objective function. The maximum completion time or makespan is the date when the last job to be completed leaves the system. The maximum tardiness is indicated by the job that is completed with the longest delay relative its due date. Minimizing both criteria can help assuring a high utilization of the production system as well as a high level of service towards the client. Due to the complexity of the problem, a Simulated Annealing (SA) heuristic has been implemented to be able to obtain an efficient solution in a reasonable running time. A set of n jobs is assigned, to one of the m identical parallel machines. Each job is processed in only one operation before its completion after which it leaves the system. Constraints, such as due dates for each job and setup times for the machines, are considered. The resolution procedure consists of two phases and begins with an initial solution generator. Then a SA heuristic is applied for further improvement of the solution. 4 generators are used to create an initial solution and 3 to generate neighbour solutions. To test and verify the performance of the proposed resolution procedure, a computational experimentation has been realized on a set of test problems generated ad-hoc

Hybrid flowshop scheduling with dual resources in a supply chain

This dissertation addresses a hybrid-flow shop scheduling problem with dual resource constraints in a supply chain. Most of the traditional scheduling problems deal with machine as the only resource. However, other resources such as labor is not only required for processing jobs but are often constrained. Considering the second resource (labor) makes the scheduling problems more realistic and practical to implement in industries. In this research labor has different skill levels and the skill level required to perform the setup could be different from that needed to perform the run. The setup time is sequence-dependent, and job release times and machine availability times are dynamic. Also machine skipping is allowed. In tactical supply chain decisions such as scheduling, the goal is to minimize the cost of producer. However, when looking at the whole network, minimizing the cost of the producer alone may not lead to minimizing the cost of the whole supply chain. In fact the coordination between the producer and other entities in the network can minimize the cost. In this dissertation coordination between producer and customers is considered in order to make effective scheduling decisions. The goal of this research is to minimize the work-in-process inventory for the producer and maximize customers' service level to maintain producer-customers coordination. A linear mixed-integer mathematical programming model is proposed and CPLEX solver is used to find solutions for generated example problems with branch-and-bound technique. As the problem is NP-hard in the strong sense three different meta-search heuristic algorithms based on tabu search are developed in order to quickly solve the scheduling problems. A total of 243 examples were generated in small, medium and large size problems. Search algorithms performance in small size problems can be assessed by comparing them with the optimal solution from branch-and-bound method. However, in medium and large size problems, branch-and-bound method cannot find the optimal solution and therefore for assessing the performance of search algorithms three different lower bounding methods are proposed. The first method is based on Logic-Based Benders Decomposition and the second and third methods are two different variations of iterative selective linear programming (LP) relaxation called fractional LP relaxation and positive LP relaxation. An experimental analysis based on a nested-factorial design with blocking is developed in order to identify statistically significant differences between the effectiveness and efficiency of the lower bounding methods and search algorithms. The results showed that the proposed search algorithms and lower bounding methods are very effective and efficient. On average the developed lower bounding methods tighten the lower bound found by branch-and-bound by 11.93%. The quality of search algorithms is the same as the upper bound found by branch-and-bound. However, the search algorithms are on average 3.8 times faster than the branch-and-bound method

Non-permutation flowshop scheduling in a supply chain with sequence-dependent setup times

In this paper, we consider a flowshop scheduling problem with sequence-dependent setup times and a bicriteria objective to minimize the work-in-process inventory for the producer and to maximize the customers' service level. The use of a bicriteria objective is motivated by the fact that successful companies in today's environment not only try to minimize their own cost but also try to fulfill their customers' need. Two main approaches, permutation and non-permutation schedules, are considered in finding the optimal schedule for a flowshop. In permutation schedules the sequence of jobs remains the same on all machines whereas in non-permutation schedule, jobs can have different sequence on different machines. A linear mathematical model for solving the non-permutation flowshop is developed to comply with all of the operational constraints commonly encountered in the industry, including dynamic machine availabilities, dynamic job releases, and the possibility of jobs skipping one or more machines, should their operational requirements deem that it was necessary. As the model is shown to be NP-hard, a metasearch heuristic, employing a newly developed concept known as the Tabu search with embedded progressive perturbation (TSEPP) is developed to solve, in particular, industry-size problems efficiently. The effectiveness and efficiency of the search algorithm are assessed by comparing the search algorithmic solutions with that of the optimal solutions obtained from CPLEX in solvable small problem instances.Keywords: Sequence-dependent setup time, Mixed-integer linear programming, Non-permutation scheduling, Flowshop, Tabu search with embedded progressive perturbations, Bicriteri

A MIXED-INTEGER PROGRAMMING MODEL FOR THE JOB SCHEDULING PROBLEM IN A PRODUCTION COMPANY

Purpose: In this study, a mixed-integer programming model is developed to minimize the total lateness and total completion time of the jobs in an automotive company. In order to respond rapidly to the continuous customer demand through the production, the work schedule of engineers in the research and development department is considered flexibly. Methodology: In the study, the mixed-integer programming model is supported by the analytical hierarchy process model to determine the weighted values of total tardiness and total completion times. The developed model is applied to the automotive company using the real data and the problem is solved using the GAMS CPLEX 24.1.3 software. Findings: In this job scheduling problem, the total completion time is decreased to 622 hours from 10149 hours, maximum tardiness is decreased to 9 hours from 104 hours and total tardiness is decreased to 13 hours from 860 hours by using the proposed model. Originality: The proposed model is used for the job scheduling purpose in compliance with the structure of the automotive industry company using the machine scheduling modeling principles and Analytical Hierarchy Process together. Keywords: Parallel Machine Scheduling, Optimization, Mixed Integer Programming, Analytical Hierarchical Process

Sequence-dependent group scheduling problem on unrelated-parallel machines

In this research we address a sequence-dependent group scheduling problem on a set of unrelated-parallel machines where the run time of each job differs on different machines. To benefit both producer and customers we attempt to minimize a linear combination of total weighted completion time and total weighted tardiness. Since the problem is shown to be NP-hard, meta-heuristic algorithms based on tabu search are developed to find the optimal/near optimal solution. For some small size yet complex problems, the results from these algorithms are compared to the optimal solutions found by CPLEX. The result obtained in all of these problems is that the tabu search algorithms could find solutions at least as good as CPLEX but in drastically shorter computational time, thus signifying the high degree of efficiency and efficacy attained by the former.Keywords: Bi-criteria, Group scheduling, Sequence-dependent setup time, Mixed-integer linear programming, Unrelated-parallel machines, Tabu searc