Chapt 3 Modeling & Simulation Processes

• Intro/ steps in the process– Formulate problem– Specify the model– Build model– Simulate model– Use model– Support decision making

• AweSim & Visual Slam

Modeling & Simulation Processes

• Use an iterative process where relationships & parameters are continually redefined & improved.

Formulate Problem

Specify Model

Build Model

Simulate Model

Use Model

Support Decision Making

Formulate the Problem

Focuses the modeling/ simulation efforts

1) Identify the Goal

2) Specify the system performance measures

3) Set objectives

4)Completely define the systems to be modeled

Formulate the Problem• Goals

– specify what is to be achieved ie lower cycle time by capital investing

• Performance measures– Measurable outputs ie profits/costs, inventory levels, speed, % waiting time

• Objectives– More specific, ie reduce queue/bottle neck for process or provide redundant machine for maintenance/

redundancy

• Complete definition – Scope and boundary definitions

Specify Model

• Define system but w/o unnecessary detail• Easily understood but realistic • Reasonable simplifying assumptions• Include interactions of activities• Conceptualize data requirements

– collected– use statistical methods

Build Model

• Develop Simulation model– Interactive & Iterative- continually redefined, updated, modified & extended

• Collect data– Time studies, accessing data bases, statistical

• Define Experimental Controls– Number of sim runs, report types/ plots/ histograms, status of specific variables ie idle/busy

• All steps are interdependent

Simulate Model

• Run Model– Simulation advances time in accordance with the movement of entities thru nodes and activities

• Verify Model– Does the model behave as expected ie correct CPM Does the model work right?

• Validate the Model– Reasonable representation of the system, does the model truly represent reality?

• Steps are interdependent/ have interactions

Use Model

• Make the sim runs and interpretation of the data outputs – Make make several runs to find optimal solution– ie try run with one manufacturing set up - find output, tweak manufacturing

set up - find out put, continue to tweak…– Evaluate alternatives…one bottle neck solved look for others that may crop up

• Interactions….may need to rebuild model once see output

Support Decision Making

• Presentation and documentation of the results/ outputs of the simulations

• Graphical is best

AweSim Visual SLAM• Open architecture to databases, MS office, C/C++, Windows based• Project Structure builds scenarios to investigate alternate designs

to improve a system• Build networks (models), perform simulations runs, view

animations

AweSim Visual SLAM

AweSim Visual SLAM

Modeling & Simulation Process Exercises

• # 3-2 Discuss the use of statistics and graphics in each of the steps of a modeling/ sim process – see fig 3-1 pg 36

• #3-4 Using the steps in the modeling/ sim process build an explanatory model of the university system to obtain an MSET – see fig 3-1 pg 36

Chapt 4 Application of Simulation

• Intro/ steps in the process

• Performance measures

• Examples– Capital Expenditures in the steel industry– Risk analysis of Pipeline const– MOB using Extend

Application of SimulationIntroduction

• Widely used by industrial engineering, management, by service industry, industrial products and government.– Manufacturing-plant layout, efficiencies, lean production– Project Controls-cost estimation, risk analysis, planning– Health care, transportation, communications, space

flight, etc

• Provided examples are only one solution… typically many and may take several iterations

Performance Measures

• Performance of a systems is measured by the efficiency is achieving its objectives

• Objectives vary dependent on type of system involved ie car production vs plant construction… general info provided by looking a manufacturing system

Performance Measuresfor Manufacturing Terms

• System performance is combined with cost to establish profitability….Sim focuses on performance

• Throughput= production rate output/time

• Capacity=max throughput

• Flow time= amount of time a job spends in the system…want to min this

• Resources=people, mtls,equip, machines, etc want to max their utilization=time productive

Performance Measuresfor Manufacturing Terms

• WIP= Work In Progress…unfinished units awaiting parts, mtl etc = want to min this

Capital Expenditure in the Steel Industry

• Improve ops involving melting scarp & desulfuring metal by determining # of submarines that cost $1M

Basic Oxygen furnace Shop

Dumping Area

Proposed Desulfurization Area

Proposed Scrap Melter

Blast Furnace Area

C F g H J

Capital Expenditure in the Steel Industry • Model scheduling rules, add rule to dump hot metal if submarine is

not available to accommodate blast furnace..sim save buying another sub

Basic Oxygen furnace Shop

Dumping Area

Proposed Desulfurization Area

Proposed Scrap Melter

Blast Furnace Area

C F g H J

Risk Analysis of Pipeline const

• Problem formulation= complete project by specific due dates• Sim construction activities based on weather and inputs to resources (people, equip, etc)

Prep trench Lay Pipe Weld pipe Cover & finish

Use of Models

• Modeling & Sim used to enhance system performance or solve problems, Also for:– Explanatory to understand a problem– Communication to describe– Training– Analysis– Review design alts

Application of SimulationExercises

• Using a block wiring diagram, develop a model for repairing/replace a building foundation

• Want most efficient use of recourses • Activities are:

– lift up on jacks/ supports– remove existing foundation– Form/ pour new concrete foundation– Remove form/ lower building

• Write what variables to Sim to create most efficient system

Application of SimulationMOB