At the time of commonplace automation, robotization and the rapid development of IT, high qualifi... more At the time of commonplace automation, robotization and the rapid development of IT, high qualifications of employees have become the critical element of every industry system. This follows from their limited availability, frequently high costs of procurement and possible employee absenteeism. Moreover, the concept of Industry 4.0 will transform current industry employees into knowledge employees. This is due to the fact that hard and routine tasks will be executed by robots and computers. This constitutes change in the required employee competences. Unfortunately, the aspect of management and configuration of employee competences is often overlooked in industrial practice. In response to the existing problem, the article puts forward the original model of employee competence configuration which is a basis for responses to numerous questions of managers of production processes, both general ones, e.g., Do we have a sufficient set of competences to execute a production schedule? as well as detailed ones, e.g., Which and how many competences are missing? etc. An important novelty of the presented model is the possibility of its application with both proactive and reactive questions. Due to the discrete and combinatorial nature of the problem under consideration, the use of mathematical programming methods was limited only to small data instances. Therefore, a proprietary dedicated genetic algorithm was proposed to solve this problem, which turned out to be extremely effective. The use of this genetic algorithm has enabled finding a solution depending on the instance data up to 70 times faster than by use of the mathematical programming.
Constraints, although ubiquitous in production and distribution planning, scheduling and control,... more Constraints, although ubiquitous in production and distribution planning, scheduling and control, often lead to inconsistencies in the decision-making process. The constraint-based modeling helps circumvent many organizationimpacting issues. To address this, we developed a multi-level approach to the modeling and solving of combinatorial optimization problems. It is versatile and effective owing to the use of multi-level presolving and multiple paradigms, such as constraint programming, logic programming, mathematical programming and fuzzy logic, for their complementary strengths. The capability of this framework and its advantage over mathematical programming alone or over hybrid frameworks is shown in the illustrative example, in which combinatorial optimization is used as a benchmark to prove the effectiveness of the proposed approach. Knowledge of the problem is stored in the form of facts.
Manufacturing enterprises today have to face the volatility of markets, characterized by a decrea... more Manufacturing enterprises today have to face the volatility of markets, characterized by a decreasing production volume and an increasing number of product variants to meet customer expectations. Traditional dedicated manufacturing lines (DML) have been replaced by flexible manufacturing systems (FMS) and, recently, by the systems that combine features of DML and FMS, i.e., by reconfigurable manufacturing systems (RMS). Appropriate manufacturing support and optimization systems for FMS and RMS will advance the quality and effectiveness of reconfigurable manufacturing. This paper proposes an original mixed integer linear programming (MILP) model for decision support in configuration and reconfiguration of the manufacturing system. The modeled problem is a certain development of the known machine loading problem MLP. In this approach, we generate a highly parameterized model based on a set of constraints and a set of questions. Different mathematical programming (MP) -based solvers are proposed to solve this model.
Production and Manufacturing Research: An Open Access Journal, 2014
The paper presents a concept and implementation of a novel approach to the modelling and solving ... more The paper presents a concept and implementation of a novel approach to the modelling and solving of the Two-Echelon Capacitated Vehicle Routing Problem (2E-CVRP). Multi-echelon distribution systems are quite common in supply-chain and logistic systems. Two environments, mathematical programming (MP) and constraint logic programming, in which constraints are treated in different ways and different methods are implemented, were combined to use the strengths of both. The proposed approach is particularly important for the decision models with an objective function and many discrete decision variables added up in multiple constraints. The 2E-CVRP is an extension of the classical Capacitated Vehicle Routing Problem (CVRP) where the delivery depot-customers pass through intermediate depots (called satellites). The 2E-CVRP was selected as a known and documented example for verification and evaluation of the effectiveness of the proposed approach. The presented approach will be compared with classical MP on the same data-sets in computational tests. The proposed approach will be used also for extensions of the modelled problem beyond the standard.
Production optimization is a complex process because it must take into account various resources ... more Production optimization is a complex process because it must take into account various resources of the company and its environment. In this process, it is necessary to consider the enterprise as a whole, taking into account the interaction between its key elements, both in the technological and business layer. For this reason, the article proposes the use of enterprise architecture, which facilitates the interaction of these layers in the production optimization process. As a result, a proprietary meta-model of enterprise architecture was presented, which, based on good practices and the assumptions of enterprise architecture, facilitates the construction of detailed optimization models in the area of planning, scheduling, resource allocation, and routing. The production optimization model formulated as a mathematical programming problem is also presented. The model was built taking into account the meta-model. Due to the computational complexity of the optimization model, a method...
At the time of commonplace automation, robotization and the rapid development of IT, high qualifi... more At the time of commonplace automation, robotization and the rapid development of IT, high qualifications of employees have become the critical element of every industry system. This follows from their limited availability, frequently high costs of procurement and possible employee absenteeism. Moreover, the concept of Industry 4.0 will transform current industry employees into knowledge employees. This is due to the fact that hard and routine tasks will be executed by robots and computers. This constitutes change in the required employee competences. Unfortunately, the aspect of management and configuration of employee competences is often overlooked in industrial practice. In response to the existing problem, the article puts forward the original model of employee competence configuration which is a basis for responses to numerous questions of managers of production processes, both general ones, e.g., Do we have a sufficient set of competences to execute a production schedule? as w...
Distributed Computing and Artificial Intelligence, 14th International Conference, 2017
The efficient and timely distribution of freight is critical for supporting the demands of modern... more The efficient and timely distribution of freight is critical for supporting the demands of modern urban areas. Without optimal freight distribution, urban areas could not survive and develop. The paper presents the concepts of hybrid approach to optimization of urban freight distribution. This approach proposed combines the strengths of mathematical programming (MP) and constraint logic programming (CLP), which leads to a significant reduction in the search time necessary to find the optimal solution and allows solving larger problems. It also presents the formal model for optimization of urban freight distribution with different types of time constraints. The application of the hybrid approach to the optimization of urban freight distribution is the primary contribution of this paper. The proposed model was implemented using both the hybrid approach and pure mathematical programming for comparison. Several experiments were performed for both computational implementations in order to evaluate both approaches.
Decision support systems (DSS) provide decision-makers with an interactive environment for analys... more Decision support systems (DSS) provide decision-makers with an interactive environment for analyses of information with various models to help solve unstructured and NP-hard problems. The important aspect of DSS is a technical and technological approach to the design and implementation of the above systems. A traditional approach to DSS engineering and implementation requires a great deal of effort for its maintenance. However, the enterprises would like to concentrate on its core competitiveness instead of non-core activities like IT maintenance. As a result of this, IT outsourcing has became a very popular event. Thus there is a growing need for intelligent decision support tools capable of assisting a decision maker in many problems in SMEs (Small and Medium Sized Enterprises). In this paper we present the use of declarative programming (constraint logic programming and relational SQL database) as an environment and framework for such decision support systems in an application se...
Streszczenie: W artykule przedstawiono autorski model optymalizacji łańcucha dostaw z punktu widz... more Streszczenie: W artykule przedstawiono autorski model optymalizacji łańcucha dostaw z punktu widzenia operatora logistycznego. Model został sformułowany w postaci zagadnienia programowania liniowego całkowitoliczbowego z funkcją celu określającą koszty dystrybutora, producenta oraz transportu. Przeprowadzono szczegółową dyskusję modelu z omówieniem ograniczeń, parametrów i zmiennych decyzyjnych. Dodatkowo w artykule zaprezentowano aktualny stan outsourcingu usług logistycznych.
Constraints, although ubiquitous in production and distribution planning, scheduling and control,... more Constraints, although ubiquitous in production and distribution planning, scheduling and control, often lead to inconsistencies in the decision-making process. The constraint-based modeling helps circumvent many organizationimpacting issues. To address this, we developed a multi-level approach to the modeling and solving of combinatorial optimization problems. It is versatile and effective owing to the use of multi-level presolving and multiple paradigms, such as constraint programming, logic programming, mathematical programming and fuzzy logic, for their complementary strengths. The capability of this framework and its advantage over mathematical programming alone or over hybrid frameworks is shown in the illustrative example, in which combinatorial optimization is used as a benchmark to prove the effectiveness of the proposed approach. Knowledge of the problem is stored in the form of facts.
The paper presents a concept and implementation of a novel approach to the modelling and solving ... more The paper presents a concept and implementation of a novel approach to the modelling and solving of the Two-Echelon Capacitated Vehicle Routing Problem (2E-CVRP). Multi-echelon distribution systems are quite common in supply-chain and logistic systems. Two environments, mathematical programming (MP) and constraint logic programming, in which constraints are treated in different ways and different methods are implemented, were combined to use the strengths of both. The proposed approach is particularly important for the decision models with an objective function and many discrete decision variables added up in multiple constraints. The 2E-CVRP is an extension of the classical Capacitated Vehicle Routing Problem (CVRP) where the delivery depot-customers pass through intermediate depots (called satellites). The 2E-CVRP was selected as a known and documented example for verification and evaluation of the effectiveness of the proposed approach. The presented approach will be compared with classical MP on the same data-sets in computational tests. The proposed approach will be used also for extensions of the modelled problem beyond the standard.
The paper presents an optimization model and its implementation using a hybrid approach for the C... more The paper presents an optimization model and its implementation using a hybrid approach for the Capacitated Vehicle Routing Problem with Pick-up and Alternative Delivery (CVRPPAD). The development of the CVRPPAD was motivated by postal items distribution issues. The model proposed combines various features of Vehicle Routing Problem variants. The novelty of this model lies in the introduction of alternativeness of item delivery points, differentiation of delivery point types in terms of their capacity (parcel lockers) and possibility of collecting the items during the execution of delivery routes. The model also takes into account a possibility of introducing time windows related to delivery time. The proposed data structure in the form of sets of facts facilitates the implementation of the model in all environments, Constraint Logic Programming (CLP), Mathematical Programming (MP), metaheuristics, databases, etc. The model is implemented in the MP, hybrid CLP/MP, and hybrid CLP/heuristic environments. The hybrid CLP/MP approach is the authors' original solution, which has already been used to solve Supply Chain Management problems, scheduling problems, routing problems etc. For large size problems, considering their combinatorial character, the proposed CLP/MP approach is ineffective. Its effectiveness will improve when MP is replaced by a heuristic. All implementations were performed on the same data instances (facts), which made it possible to compare them according to the solution search time, number of decision variables and number of constraints. The directions into which the model can be further developed were also presented.
Scheduling and resource allocation problems are widespread in many areas of today’s technology an... more Scheduling and resource allocation problems are widespread in many areas of today’s technology and management. Their different forms and structures appear in production, logistics, software engineering, computer networks, project and human resources management, services, etc. The literature (problem classification, scheduling and resource allocation models, solutions) is vast and exhaustive. In practice, however, classical scheduling problems with fixed structures and standard constraints (precedence, disjoint, etc.) are rare. Practical scheduling problems include also logical and nonlinear constraints, and they use nonstandard criteria of schedule evaluations. Indeed, in many cases, decision makers are interested in the feasibility and/or optimality of a given schedule for specified conditions formulated as general and/or specific questions. Thus, there is a need to develop a programming framework that will facilitate the modeling and solving of a variety of diverse scheduling prob...
Grouping Products in a Follow-Up Production Control System for Parallel Partitioned Flow Production Lines
IFAC Proceedings Volumes, 2001
Abstract The paper deals with the system of parallel flow production lines. Each line can be dyna... more Abstract The paper deals with the system of parallel flow production lines. Each line can be dynamically divided into partitions designated to concurrent processing different products. The production flow through machines belonging to the partition is synchronized. The set of products which can be manufactured in a given line depends on tools the line is equipped with. Each feasible set of products processed concurrently in the line has been named the preparedness variant. There are many algorithms to control switching the lines between their preparedness variants e.g. priority rules or the Follow-up Scheduling. The quality of current control for the flow production lines strongly depends on previous decision of the preparedness variants configuration. An optimization model for this problem and computational example have been presented in the paper.
This paper presents a hybrid method for modeling and solving supply chain optimization problems w... more This paper presents a hybrid method for modeling and solving supply chain optimization problems with soft, hard, and logical constraints. Ability to implement soft and logical constraints is a very important functionality for supply chain optimization models. Such constraints are particularly useful for modeling problems resulting from commercial agreements, contracts, competition, technology, safety, and environmental conditions. Two programming and solving environments, mathematical programming (MP) and constraint logic programming (CLP), were combined in the hybrid method. This integration, hybridization, and the adequate multidimensional transformation of the problem (as a presolving method) helped to substantially reduce the search space of combinatorial models for supply chain optimization problems. The operation research MP and declarative CLP, where constraints are modeled in different ways and different solving procedures are implemented, were linked together to use the str...
Uploads
Papers by Pawel Sitek