Object-oriented Simulation Model Research Articles

PARETO-OPTIMIZATION OF THE PRODUCTION SCHEDULE BASED ON THE METHOD OF ANTS OF COLONIES

To optimize the functioning of the automated machining technological complex together with a modified ant algorithm an object model of the organizational and technological process of loading equipment was developed, representing a system of interacting classes of its typical components. The object model describes the structure of the classes that make up the production process system, their attributes, operations, relationships with other classes. The model allows to calculate the values of the objective function and evaluate quality of potential solutions. For the first time, the use of ant algorithms in conjunction with object-oriented simulation modeling is proposed to optimize the production schedule. Every artificial ant finds a potential solution to the problem. The concentration of artificial pheromone is determined by the quality of the solution with respect to the optimization criteria used. For artificial ants formulas for calculating the concentration of pheromone are proposed and transition rules that control the process of searching for the optimal solution are defined. Multi criteria optimization with adaptive weights is proposed, where in the search process the weights of the objective function are corrected. The following variants of choosing the optimality criteria are considered: maximization of the average load factor of the process equipment, minimization of the violation of the deadlines for manufacturing the order with the minimum duration of the manufacturing cycle of the parts, minimization of the violation of the deadlines for the manufacture of the order, minimization of the time limits for manufacturing the order, and the time of adjustment of equipment. Experimental studies were performed to solve the problem of two and three-criteria optimization using the example of an automated technological complex for machining.

A simulation modeling framework for multiple-aisle automated storage and retrieval systems

This paper presents a simulation model framework for unit-load automated storage and retrieval systems (AS/RS) able to cope with most of the features found in industrial settings like, for example, multiple aisles, non aisle-captive cranes or double-deep unit-load AS/RS. Although these features characterize most of the industrial applications, they have been simply neglected by most of the previously published research oriented papers, which explains at least partially the low impact of the research output in practice. To help mitigating this drawback, this paper first presents an up-to-date chronological literature survey, which includes works that use any form of simulation in the modeling process. It then proposes an Object-Oriented Simulation Model for unit-load AS/RS developed with a purely generic mindset. In this model, the physical design decisions are separated from the operational decisions, which makes it possible, first, to obtain a better understanding of AS/RS dynamics and, second, to increase the model's flexibility and generality, thus allowing many interesting scenarios to be represented. In particular, the simulation modeling framework has been used to develop a simulator and to conduct a preliminary study on a multi-aisle AS/RS.

An object-oriented model for simulating agricultural in-field machinery activities

Field operations planning is essential for the operational efficiency in terms of time and cost, especially in complex operations involving capacity constraints and cooperating units. In order to deal with such type of planning problems an object-oriented simulation model which simulates in detail in-field machine activities during the execution phase, was developed and applied. The developed simulation model regards the material input operations with capacity constraints, where a quantity of a “commodity” is transported by the machine and is distributed in the field area. The case of the organic fertilizing application was used as the basis for the description of the object oriented model involving the description of all related programming entities (i.e., classes, attributes, and methods). Combined state and activity diagrams were provided as the basic elements of the simulation model. It was shown that the simulation model provides all the key operational parameters necessary for the evaluation of a selected scenario. This makes it feasible the use of the simulation model as an integral part of a decision support system for advising farmers about in-field operational decisions (e.g., traffic system, driving direction, refilling position) and machinery dimensioning (e.g., tank capacity, operating width, etc.).

Simulation Research on Performance of All Electric Brake System in Tracked Vehicles

In order to improve brake performance of military tracked vehicles, a novel all electric brake system (AEBS) is studied in this paper. Besides its system scheme and construction are presented, its Object Oriented simulation models are built with Simulink to analyze its two operating modes, parking button brake and foot pedal brake. Screw linear speed and brake compressive stress in the parking brake and running brake under various given condition are simulated with the model. Simulation results prove that the performance of the all electric brake system improve remarkably and satisfy the design requirement of military tracked vehicles.

Modeling of Workflow Congestion and Optimization of Flow Routing in a Manufacturing/Warehouse Facility

This paper discusses the notion of workflow congestion in the context of material handling equipment interruptions in a manufacturing or warehousing facility. Development of a combination of probabilistic and physics-based models for workflow interruptions permits evaluation of the expected link travel time. The problem is then of routing in a way that minimizes total expected travel time. The rerouting problem is modeled as a multicommodity flow problem with link capacity design. A greedy upper bounding and Lagrangean relaxation algorithm are developed to solve this efficiently. To calibrate our modeling process we develop an object-oriented simulation model that explicitly considers various workflow interruptions. Our major finding is that rerouting traffic in a congested facility can significantly alleviate congestion delays and improve the efficiency of material movement. A managerial insight derived from this work is that rerouting is most effective in medium traffic-intensity situations.

A Simulation-Based Methodology for Lot-Size Optimization

In the process of lot size optimization, various factors such as machine capability and parts assembly lead time need to be considered. Within small batch and multi-items production environment, kitting parts entering to assembly systems in time may valid shorten product manufacturing period, and reduce the quantity of work-in-process (WIP). This paper built up a mathematical model with the objective function of reducing set up costs, shortening cycle of part production and reducing WIP and with constraints of machine capabilities, part process planning and kitting requirement. An object-oriented simulation model is established to control the behavior of logistics objects to meet the target functions through rules aggregation and constraints at the control points, resulting in an optimal production result.

Simulation-based maintenance support system for multi-functional complex systems

We define a complex system with a complex structure that performs several functions as a multi-functional complex system, and represent it as a pseudo-tree structure using gates. In addition, we develop an object-oriented simulation model to estimate the reliability, availability, and maintainability of the multi-functional system with complex structures. We define attributes, methods, and events for objects and develop logics for the random number generation, breakdowns, maintenance, etc. for simulation. We obtain simulation statistics on availability, utilisation of repairmen and stock probability of spare parts. The user-friendly simulation model is implemented as simulation software using general object-oriented language. Its potentials for application are demonstrated in the case of a transfer crane, which can be considered a representative example of a multi-functional complex system.

An XML-centred approach to creating object-oriented supply chain simulation models

We propose an eXtensible Markup Language (XML)-centred approach to object-oriented simulation modelling of supply chains. Our approach is fundamentally different from previous work in that it uses XML to describe the supply chain itself, as opposed to using XML to store the simulation model. We define a system that includes an XML-based markup language and a 'simulator' that contains a library of fundamental supply chain simulation classes and a simulation 'model mapper'. The simulator processes the supply chain description document and generates an object-oriented simulation model using the class library. We detail working reference implementations of the markup language (Supply Chain Modelling Language (SCML)) and the simulator (Simulator for Integrated Supply Chain Operations (SISCO)).

Assessment of pathogen pollution in watersheds using object-oriented modeling and probabilistic analysis

A limited number of research trials have been reported in the past to model pathogenic organisms in streams and large water bodies at a watershed scale. In this paper, modeling of fecal coliform in streams is proposed from a management perspective at the watershed level. To model the fate and transport of fecal coliform in a watershed in Southeastern Kentucky, an object-oriented (OO) simulation model, based on the concepts of system dynamics (SD) approach, is proposed in this study. The approach combines both data-driven approaches and insights gained from a process-based approach. Different management scenarios, based on flow conditions and pollution sources, are generated and evaluated to validate the proposed approach. Deterministic and conceptually simple probabilistic analyses are carried out to understand several water quality management alternatives that aim to reduce pollutant loadings. Results point to the potential use of the proposed OO–SD framework in addressing environmental policy issues and also to the need for relying on probabilistic analysis to obtain more credible results and recommendations in data-poor conditions. The proposed approach helps direct limited funding and watershed management efforts to be focused on areas that have the greatest impact on the surface water quality conditions.

A hybrid knowledge discovery model using decision tree and neural network for selecting dispatching rules of a semiconductor final testing factory

One of the most challenging production decisions in the semiconductor testing industry is to select the most appropriate dispatching rule which can be employed on the shop floor to achieve high manufacturing performance against a changing environment. Job dispatching in the semiconductor final testing industry is severely constrained by many resources conflicts and has to fulfil a changing performance required by customers and plant managers. In this study we have developed a hybrid knowledge discovery model, using a combination of a decision tree and a back-propagation neural network, to determine an appropriate dispatching rule using production data with noise information, and to predict its performance. We built an object-oriented simulation model to mimic shop floor activities of a semiconductor testing plant and collected system status and resultant performances of several typical dispatching rules, earliest-due-date (EDD) rule, first-come-first-served rule, and a practical dispatching heuristic taking set-up reduction into consideration. Performances such as work-in-process, set-up overhead, completion time, and tardiness are examined. Experiments have shown that the proposed decision tree found the most suitable dispatching rule given a specific performance measure and system status, and the back propagation neural network then predicted precisely the performance of the selected rule.

Modeling Water Quality Management Alternatives for a Nutrient Impaired Stream Using System Dynamics Simulation

A system dynamics (SD) simulation model is developed using an object-oriented modeling environment to simulate and analyze water quality management strategies for a nutrient impaired stream. An object-oriented simulation environment, STELLA, conceived on the principles of system dynamics (SD) is used for the development of the model. The modeling process consists of developing stock-flow diagrams and carrying out computer simulations using difference equations to integrate stocks and flows. The model structure and behavior of the system is validated using dimensionality, replication and sensitivity tests; and calibration along with validation is carried out using an appropriate model performance measure. The model helps the user to separate policy questions from the data and provides the facility to generate "what-if" scenarios while keeping the modeling process transparent. Case study application of this model is illustrated by developing a total maximum daily load (TMDL) allocation strategy for a nutrient impaired stream in the southeastern region of Kentucky, USA. Results suggest that the fate and transport process of total phosphorus in a river system can be simulated using a conceptually simple object-oriented simulation model.

Building an object oriented simulation model by means of arena templates

Building an object oriented simulation model by means of arena templates

Distributed production planning using a graph-based negotiation protocol

A distributed model for allocating a single job to be processed through multiple machines and alternative routings so that the job flow time is experimentally shown to reach its minimum is presented. Issues are addressed pertaining to dynamic and fully distributed decision-making for determining the job flow time in a cooperative manner between system agents (i.e. machines and a job), and for selecting a good routing (i.e. a short flow time) for a job when alternative routings are available. Two cases with confirmed jobs and without confirmed jobs are examined. The proposed protocols can deal with job shop scheduling with multiple product types in a sequential manner. The model is developed on the basis of a distributed shortest path algorithm using asynchronous job-initiated protocols. These protocols are examined using object-oriented simulation models and it is shown how the agents converge to the optimal path in a finite time.

An object-oriented model of the morphological development and digestibility of perennial ryegrass

An object-oriented simulation model was developed to integrate detailed analyses of perennial ryegrass ( Lolium perenne) plant part dimensions, and their mass, cell wall content (CWC) and cell wall digestibility (CWD). The model was validated against data from two field experiments, carried out in The Netherlands (52°N) and Norway (67°N). In the experiments, the effects of temperature × daylength interactions on development, growth and digestibility were determined. Three cultivars differing in heading date were used, and undisturbed growth and regrowth after early (only in The Netherlands) and late cutting were studied. The sensitivity of the model was tested for changes in parameters determining morphological development. A grass plant was modelled as an aggregation of shoot objects. A shoot is an aggregation of phytomers, plus an inflorescence in the reproductive development stage. A phytomer consists of a leaf blade, a leaf sheath, a stem internode and a root. Each phytomer has an axillary bud, which can develop into a new shoot. Morphological development, organic matter (OM) growth and composition were simulated well by the model. Only for regrowing crops in The Netherlands CWC was lower and CWD was higher in the simulations than observed in the field, whereas the differences increased when stem development was more advanced at the moment of cutting. This was attributed to residual stems in the stubble after cutting due to difficulties with machine cutting of lodged crops on the experimental plots. The model can be considered as sufficiently accurate to simulate OM yield and composition of grass cultivars differing in heading date and growing under strongly contrasting temperature and daylength conditions. When the leaf appearance rate, width or length of the leaf blade were increased in the sensitivity analysis, OM yield enhanced, but composition and digestibility of the reproductive grass crops were not systematically affected.

An object-oriented model of the morphological development and digestibility of perennial ryegrass

An object-oriented simulation model was developed to integrate detailed analyses of perennial ryegrass (Lolium perenne) plant part dimensions, and their mass, cell wall content (CWC) and cell wall digestibility (CWD). The model was validated against data from two field experiments, carried out in The Netherlands (52°N) and Norway (67°N). In the experiments, the effects of temperature × daylength interactions on development, growth and digestibility were determined. Three cultivars differing in heading date were used, and undisturbed growth and regrowth after early (only in The Netherlands) and late cutting were studied. The sensitivity of the model was tested for changes in parameters determining morphological development. A grass plant was modelled as an aggregation of shoot objects. A shoot is an aggregation of phytomers, plus an inflorescence in the reproductive development stage. A phytomer consists of a leaf blade, a leaf sheath, a stem internode and a root. Each phytomer has an axillary bud, which can develop into a new shoot. Morphological development, organic matter (OM) growth and composition were simulated well by the model. Only for regrowing crops in The Netherlands CWC was lower and CWD was higher in the simulations than observed in the field, whereas the differences increased when stem development was more advanced at the moment of cutting. This was attributed to residual stems in the stubble after cutting due to difficulties with machine cutting of lodged crops on the experimental plots. The model can be considered as sufficiently accurate to simulate OM yield and composition of grass cultivars differing in heading date and growing under strongly contrasting temperature and daylength conditions. When the leaf appearance rate, width or length of the leaf blade were increased in the sensitivity analysis, OM yield enhanced, but composition and digestibility of the reproductive grass crops were not systematically affected.

Design of a Two-Card Dynamic Kanban System Using a Simulated Annealing Algorithm

The design of a kanban system addresses the selection of two important parameters, i.e. the number of kanbans and lot sizes of part types. Kanban-based operational planning and control issues have been tackled in a number of studies by means of analytical or simulation modelling. However, the estimation of these parameters becomes complicated because of issues such as variation in demand, variation in processing times, different types of products, etc. The combinatorial property of such problems warrants the development of efficient methodology or heuristics to obtain a good solution. In this paper, an attempt has been made to select the number of production and withdrawal kanbans at each workstation and the lot size for each part type required to achieve the best performance using a simulated annealing algorithm technique. An object-oriented simulation model of a two-card dynamic kanban system capable of handling different types of part with different demand requirements has been developed and used for the analysis. Each part type has its own number of production ordering kanbans and withdrawal kanbans at each workstation. The lot size can also be different for different part types. A bicriteria objective function comprising mean throughput rate and aggregate average kanban queue has been used for evaluation. Different types of problem have been tried out and the performance of the algorithm is studied.

Performance evaluation of ABR flow-control protocols in a wireless ATM network

Using an object-oriented simulation model of a basic client-server scenario in a wireless ATM network, we study the impact of handover and error-control protocols on the performance of high-speed data communication by the ABR service class. We present performance results of the ABR flow-control protocols ERICA and ERICA+ and discuss some implications for the protocol design.

Optimum Design and Operation of Airport Passenger Terminal Buildings

The standard procedures for the design and operation of airport passenger terminal buildings (PTBs) often lead to either high operating and maintenance costs or passenger dissatisfaction. A new philosophy of planning, design, and operation that is based on optimum resource utilization and passenger flow management and control was initiated. An optimum resource utilization model was developed on the basis of important issues such as an early association of physical and operational plans, the stochastic nature of airport demand, the long-term costs of over- and undersupply of PTB facilities, performance measures, and utilization of scarce resources. Three submodels were developed as part of the optimum resource utilization model, that is, the simulation, optimization, and flow management and control models. An object-oriented simulation model, which consists of a set of simple submodels and nodes, was developed to perform as a real-world airport terminal. The optimization model will provide a list of optimum required resources for all predefined segments of the PTB. A real-time flow management and control model was developed, in which the PTB operator would be able to respond to preplanned or spontaneous events.

3616 ホロニック生産システムにおけるリアルタイムスケジューリング

This paper deals with a real-time scheduling system for holonic manufacturing systems. An object-oriented simulation model is adopted to develop a simulation model of a holonic machining system. A mechanism is implemented to the simulation system in order to carry holonic out real-time scheduling for the holonic machining system.

Using Object-Oriented Simulation to Explore Substitution Between Technologies: An Application to the UK Mobile Telecommunications Industry

This paper discusses how an object-oriented simulation model can explore substitution processes in a competitive market. We show how a conceptual model of the UK mobile telecommunications industry, based on entities and their relationships, can be translated into a dynamic simulation model. The model focuses on two conflicting pressures, namely, the need to migrate customers from the analogue to the digital network versus the need to invest in expanding coverage and capacity of the digital network. The model allows an exploration of determinants of customer choice and how these can be affected by the strategies followed. Thus, management decision variables are endogenous to the model and there are feedback mechanisms between decisions and the migration speed. We examine different strategies for migrating customers from analogue to digital mobile networks and discuss the benefit of using such models.