Self-classification of assembly database using evolutionary method

Abstract

Purpose The purpose of the paper is to develop a method of automatic classification of the components of the assembly units. The method is crucial for developing an automatic ship assembly planning tools. The proposed method takes into account the assumptions specific for shipbuilding technology processes: high complexity of structures, difficult expert-based classification of components, fixed priority relations between connections resulting from geometrical constraints and demands of welding processes. Design/methodology/approach The set of ex post determined liaisons and assembly sequences constitutes the database of structures which have been made-up earlier. The components classification problem is solved using matrix coding of graphs. Information in such form is stored in the database. The minimization of number of cycles in the graph of classes sequence and minimization of diversity of classes within all constructions has been proposed as criteria of optimization. The genetic algorithm has been proposed as a solution method. Findings The proposed method solves the problem of components’ classifications. It allows setting the pattern of priorities between classes of various connections. This gives a chance to determine the relationship constraints between the connections of new structures for which assembly sequences are not established. Research limitations/implications Mathematical formulation of the database is quite laborious. The possibility of partial automation of this process should be considered. Owing to the complexity of the problem, a relatively simple objective function has been proposed. During a ship hull assembly, additional criteria should be taken into account, what will be the direction of further research. Practical implications Automatic classification of components is dedicated for implementation in shipyards and similar assembly systems. Tests performed by the authors confirm efficiency of presented method in supporting management of the database and assembly of new structures planning. Suggested activity-oriented approach allows for easy conversion of any assembly unit structure to the form of a matrix. Originality/value The new approach for components classification according to its assembly features distinguishes the proposed method from others. The use of nilpotent matrix theory in an acyclicity of graphs analysis is also a unique achievement. Original crossover and mutation operators for assembly sequence were proposed in the article.

A Review of Optimization Algorithms for University Timetable Scheduling

“…Others adopt soft restrictions and utilize them to assess the quality of the solution, while there are instances where student preferences or the spacing between classes has been employed to achieve the same goal. Authors in [4] consider a matrix of conflicts between learners taking two courses i and j simultaneously. The objective function considers the minimization of the number of cases where i and j are scheduled at the same time.…”

“…Because university course timetabling is an NP-hard problem, there are several methods that have been explored in attempts to find optimal solutions. The manual approach requires several days of work and often results in inefficient outcomes [4,14]. However, there are several other procedures that can be used to schedule academic activities and in which restrictions related to the type of problem considered must be respected.…”

“…In general, resolving such challenges and obtaining exact optimal solutions is computationally intractable. Therefore, the university timetabling problem is an example of a Non-Polynomial (NP)-hard problem [4]. These are problems with no particular efficient solutions.…”

Optimizing Faculty Workloads and Room Utilization using Heuristically Enhanced WOA

“…Timetabling problem was solved manually through trial and error, but this was not the greatest option. At present, scientific methods are used to address the problem [1], [2]. Timetabling problems, better known as the university course timetabling problem (UCTTP), are known to be NP-hard, meaning the problem cannot be solved exactly in polynomial time as its size and complexity increase exponentially [3].…”