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Simulation and Modelling

by Bohar Singh
Type: NoteInstitute: Punjab Technical University Course: B.Tech Specialization: Computer Science EngineeringOffline Downloads: 104Views: 6465Uploaded: 5 months agoAdd to Favourite

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Discrete Event System Simulation

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Bohar Singh
Bohar Singh
System Simulation and Modelling INTRODUCTION TO SIMULATION      SIMULATION is the imitation of the operation of a real-world process or system over time. Purpose : researchers, analyst, professors, so that they can infer something. Can simulate globe, planetarium, bank or online sale transactions, study of aerodynamics. The behavior of a system as it evolves over time is studied by developing a SIMULATION MODEL. SIMULATION-GENERATED DATA is used to estimate the measures of performance of the system. WHEN SIMULATION IS THE APPROPRIATE TOOL Simulation can be used for the following purposes: 1. Simulation enables the study of, and experimentation with, the internal interactions of a complex system or of a subsystem within a complex system. 2. Informational, organizational, and environmental changes can be simulated, and the effect of these alterations on the model's behavior can be observed. 3. The knowledge gained in designing a simulation model may be of great value toward suggesting improvement in the system under investigation. 4. By changing simulation inputs and observing the resulting outputs, valuable insight may be obtained into which variables are most important and how variables interact. 5. Simulation can be used as a pedagogical device to reinforce analytic solution methodologies. 6. Simulation can be used to experiment with new designs or policies prior to implementation, so as to prepare for what may happen. 7. Simulation can be used to verify analytic solutions. 8. By simulating different capabilities for a machine, requirements can be determined. 9. Simulation models designed for training allow learning without the cost and disruption of on-the-job learning. 10. Animation shows a system in simulated operation so that the plan can be visualized. 11. The modern system (factory, wafer fabrication plant, service organization, etc.) is so complex that the interactions can be treated only through simulation. 1
WHEN SIMULATION IS NOT APPROPRIATE Ten rules when simulation should not be used: 1. When problem can be solved by common sense. 2. When problem can be solved analytically. 3. When it is easier to perform direct experiments. 4. If the costs exceeds the savings. 5. When resources are not available. 6. When time is not available. 7. If data is not available. Since simulation uses lots of data. 8. If there is no enough time or personnel are not available. It is concerned with verification and validation of the model. 9. When managers have unreasonable expectations, asking for too much too soon, power of simulation is over estimated, simulation is not appropriate. 10. System behavior is complex. ADVANTAGES OF SIMULATION 1. New policies, operating procedures, decision rules, information flows, organizational procedures, and so on can be explored without disrupting ongoing operations of the real system. 2. New hardware designs, physical layouts, transportation systems, and so on, can be tested without committing resources for their acquisition. 3. Hypotheses about how or why certain phenomena occur can be tested for feasibility. 4. Time can be compressed or expanded allowing for a speedup or slowdown of the phenomena under investigation. 5. Insight can be obtained about the interaction of variables. 6. Insight can be obtained about the importance of variables to the performance of the system. 7. Bottleneck analysis can be performed indicating where work-in-process, information, materials, and so on are being excessively delayed. 8. A simulation study can help in understanding how the system operates rather than how individuals think the system operates. 9. What-if. questions can be answered. DISADVANTAGES 1. Model building requires special training. 2. Simulator results can be difficult to interpret. 3. Simulation modeling can be time consuming and expensive. 4. Simulation is used in some cases when an analytical solution is possible, or even preferable. In defense of simulation, the disadvantages are: 1. Simulation packages being developed contain models that need only input data for their opeƌatioŶ. “uĐh ŵodels haǀe the geŶeƌiĐ tag ͞siŵulatoƌ͟ oƌ ͞teŵplate.͟ 2. Simulation software vendors have developed output analysis capabilities within their packages for performing very thorough analysis. 2
3. Simulation performs faster which permit rapid running of scenarios. 4. Closed form models are not able to analyze most of the complex systems that are encountered in practice. 3
AREAS OF APPLICATION The Winter Simulation Conference (WSC) helps us to learn more about the latest in simulations application and theory. It is sponsored by six technical societies and NIST (National Institute of Standards and Technology). 1. Manufacturing Applications :  Dynamic modeling of continuous manufacturing systems, using analogies to electrical systems.  Benchmarking of a stochastic production planning model in a simulation test bed.  Paint line color change reduction in automobile assembly.  Modeling for quality and productivity in steel cord manufacturing.  Shared resource capacity analysis in biotech manufacturing.  Neutral information model for simulating machine shop operations. 2. Semiconductor Manufacturing  Constant time interval production planning with application to work-in-progress control.  Accelerating products under due-date oriented dispatching rules.  Design framework for automated material handling systems in 300-mm water fabrication factories.  Making optimal design decisions for next generation dispensing tools.  Resident entity based simulation of batch chamber tools in 30-mm semiconductor manufacturing. 3. Construction Engineering and Project Management  Impact of multitasking and merge bias on procurement of complex equipment.  Application of lean concepts and simulation for drainage operation maintanence crews.  Building a virtual shop model for steel fabrication.  Simulation of the residential lumber supply chain. 4. Military Applications  Frequency based design for terminating simulations: A peace enforcement example.  A multibased framework for supporting military based interactive simulations in 3D environments.  Specifying the behaviour of computer generated forces without programming.  Fedelity and validity: Issues of human behavioral representation.  Assessing technology effects on human performance through trade-space development and evaluation.  Impact of an automatic logistics system on the sortie-generation process.  Research plan development for modeling and simulation of military operations in urban terrain. 5. Logistics, Supply chain and Distribution Applications 4

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