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IET 525 System Analysis and Simulation
• Instructor: William J. Bender, Ph.D., PE,
• Office phone: 963-3543, Home # 509 933-3583 E-mail: [email protected] please call or write
• Web Page www.cwu.edu/~benderw/benderw.html this page has syllabi, exams, and handouts
• Teaching Philosophy this is a graduate course students do a lot of reading and learning on our own. Class is for reviewing concepts, discussion, and group exercises. Labs are performed on students time “doesn’t have to be Wed night”
• Syllabi
IntroductionChapt 1
• Need for Modeling & Simulation• Terminology• Model Building• Simulation
– Simulation Modeling & Analysis McGraw-Hill, by Law & Kelton– Discrete -Event Simulation Prentice Hall, by Banks, Carson, & Nelson
• Simulation of a Bank Teller• Data Collection/ Statistics• Apply what you know pg 17
Needfor Modeling & Simulation
• Chemicals, Pharmaceuticals, hospitals, shipping, retail, defense, electronics, construction, manufacturing, shipping, communications
• …all industries need a method to “try something out” before building or changing a process/ manufacturing line.
• Bottom line helps decision makers solve complex problems by providing a systematic process to develop data, experiment and see what happens
Simulation
• “Building logical & mathematical models of real or proposed systems & use PCs to experiment with the parameters/ resources of the system.
• We will simulate systems via a simulation language called Visual SLAM…very user friendly
• AweSim is a program that runs the simulation & animates Visual SLAM … very user friendly
• one of many…I learned Extend a graphical simulation package that my dissertation was formed around
System
• We will perform “Systems Analysis” by modeling and simulation systems & see what happens
• A system is “Interdependent items that describe the area of interest or perform a specific function”
• And is defined by the SCOPE of the problem we are trying to solve
Construction System
Trades, Equip, Material, Processes, etc
Design
Weather
Rules
Suppliers
System
• External forces may effect system– Include– Ignored– Treated as inputs
Construction System
Trades, Equip, Material, Processes, etc
Design
Weather
Rules
Suppliers
Models
• Models are the description of systems/ abstract of the system– Physical ie WSU hydraulic lab
– Math ie Differential equations, logical (CPM)
– Graphical ie visual computer displays
• First models are built…then simulated to understand interactions of elements
Model Building
• Key is defining the elements of the model/ system & how they interact with each other– Problem statement or Goal
– Established boundaries
– Performance measures/ Design alternatives
• Takes an iterative process
System Goal
Boundaries
Performance
Model Simulate &
Solve Problem
Simulation
• Build Models and experiment with it on a computer• Benefits
– Work out bugs before built if proposed ie hospital/ man line
– W/O disturbing operating systems
– NTD
Model Design
Parameters
Performance
Simulate Solve Problem
Simulation States Discrete or Continuous
• Continuous = constantly changing ie weather, waves, auto pilot
• Discrete Event = Small incremental steps ie construction, bank teller, manufacture line, etc– Deterministic ie 10 minutes or 2 days
– Stochastic ie normally distributed, mean =10, std =2
Simulation of Bank Teller
• An example to show where we are going…• Want to model the operations of a bank determine how
long a person waits in line and % of time a teller is idle• Model is:
Wait for tellerCustomer Arrives
Served by teller
Exit bank
How Long? % of time idle?
Simulation of Bank TellerConcepts
• At any instant model is in a particular state• As events occur, state changes• Events define the model
Wait for tellerCustomer Arrives
Served by teller
Exit bank
How Long? % of time idle?
Simulation of Bank TellerCustomer
#ArrivalTime
Service time
1 3.2 3.82 10.9 3.53 13.2 4.2
Cus # Arrtime
Sertime
StartDeptime
Timein line
Timeinbank
(1) (2) (3) (4) (3)-(2) (4)-(2)
1 3.2 3.2 7.0 0 3.82 10.9 10.9 14.4 0 3.5
3 13.2 14.4 18.6 1.2 5.4Pg 8& 9
Simulation of Bank TellerEvent oriented Description
TimeEvent
Cus#
Event # inline
# inbank
Teller Idletime
0.0 1 St 0 0 Idle3.2 1 Arr 0 1 Busy 3.2
7.0 2 Dep 0 0 Idle
To track customers in line & teller busy or idle at discrete points in time
Time
# in line
Pg 10 & 11
Simulation of Bank TellerEvent oriented Description
Time
Busy
•Need Data
•At any point in time the model is in a particular state
•Need “Book keeping” function to track changes
•Two perspectives 1)Customer 2)Teller
Idle
Teller Status
Data Collection & Analysis
• Use existing Data or Collect Data• Existing data, ie census, cost data, government…may be
easily obtained but typically very broad• Surveys especially for qualitative material..Delphi• Field Studies/ experimenting, expensive but best type• Descriptive Statistics
Data Collection & Analysis Descriptive Statistics
• Grouping Data• Group Data into cells for Frequency Distribution or
Cumulative Frequency• Displayed graphically as Histogram
# of People
Ave wait time
Data Collection & Analysis Descriptive Statistics
• Parameter Estimation• Population = All possible observation• Sample = only part of population
• Can estimate Population with mean = and
variance = 2
• From a sample can find mean & variance to describe a population
Data Collection & Analysis Descriptive Statistics
• Distribution Estimation• Use a know statistical distribution to estimate a
population, ie normal, beta, exponential, weibel
Chapt 1 Summary
• Build Model based on goal, parameters, design, performance
• Simulate to experiment with model and solve problem• Can use statistical estimation for data
Chapt 1 Exercises
• # 1-2 pg 18 Build a model for the MSET program from the students point of view similar to Figure 1-1
• # 1-6 Describe/ draw the functional/mechanical operation of a car using boxes connected with arrows, use chassie, engine, transmission, wheels …by developing a model. How can this be simulated to understand the performance characteristics of Speed, MPG, cargo capacity, cost, performance ie 0-60mph time
Chapt 1 ExercisesSolution
• # MSET program model similar to Figure 1-1
MSET
Course Interest
Project interestAdvisor/ Committee
Financial
Rules/ degree requirements
Available Classes
Others?
Chapt 1 ExercisesSolution
• # 1-6 Describe/ draw the functional/mechanical operation of a car using boxes connected by arrows, use chassie, engine, transmission, wheels …by developing a model. How can this be simulated to understand the performance characteristics of Speed, MPG, cargo capacity, cost, performance ie 0-60mph time
Chassie engine Trany Wheels
Simulate by changing:weight, wheel base, engine size, engine turbo, engine gas/ diesel, trany gears, wheel size and out put performance of speed, MPH, HP, Size, Cost…others
Chapter 2 Simulation Modeling Perspectives
• Modeling World Views• Discrete Simulations• Continuous Simulations• Visual SLAM
Simulation World Views
• The functional relationship of how a system is perceived and described
• Either:
• Discrete – Dependent variables change at specific points in simulated time
• Continuous– Dependent variables continuously change in simulated time
Discrete
• Discrete = Dependent variables change at specific points in simulated time– Construction of a road, Dependent Variable = % complete, specific lane openings – Window assembly line, Dependent Variable = people idle/busy, machine
idle/busy– Bank Teller Dependent Variable = # of customers, teller idle busy
Event Times
Dependent Variable
Continuous
• Continuous = Dependent variables continuously change in simulated time– Sine wave approximation of an ocean wave Dependent variable is the height
of the wave– Position of a space craft Dependent variable is exact location in orbit– Auto pilot of an aircraft, Dependent variables are speed, bearing, attitude, etc
Time
Dependent Variable
Combined
• Both discrete and continuous• Some activity develops slowly over time and at a specific
event the state changes• Chemical process, slowly reaches a certain concentration
then a catalyst is added an an explosion occurs
Event Times
Dependent Variable
Discrete Simulation Modeling
• Goal = Reproduce the activities the entities are engaged in to learn about the behavior of the system.– Entities = Objects within the boundaries of discrete system ie people, machines, $,
resources
– Activities = discrete function, unit of work
– Event = Start or stop of an activity
– Process = sequence of events that includes several activities
Discrete Simulation Modeling
Discrete Sim formulated by 3 methods:• Event Orientation = Define changes in the state at each event time (Busy/Idle)• Activity Scanning Orientation = Describe the activities which entities engage
in (system state based on activities condition)• Process Interaction orientation = Describe process which activities flow
(CPM)
Discrete Simulation Modeling Event Orientation
• Define changes in the state at each event time (Busy/Idle)• Done by: Determine the events that can change the state of the system & use logic to
model the system• ie Bank System
– Status of teller
– # of customers
• Performed by maintaining a calendar of events and cause their execution simulated time
Discrete Simulation Modeling Activity Scanning Orientation
• Describe the activities which entities engage in (system state based on activities condition).
• Done by: describing activities & prescribe conditions which cause an activity to start or end
• Not used much (must scan all activities) except when an activity is indefinite or determined by a prescribed condition
Discrete Simulation Modeling Process Interaction Orientation
• Describe process which activities flow (CPM)• Simulation that includes elements that occur in defined
patterns• Manufacturing/ construction/ where you want to
understand the entire process
Discrete Simulation Modeling Process Interaction Orientation
Model the flow of entities thru a system & define a sequence of events that are executed by the simulation
Continuous Simulation Modeling
• Dependent Variables change continuously over time• Models are frequently written as derivatives….or
differential equations• State variable SS (wave height/ speed) over time T want to
determine the response of the variable over time
2 2 t t)(s dt
ds(t)
•Or integrate ds/dt over time using numerical integration methods using simulation
Visual SLAMAweSim
• Visual SLAM is the computer language that is specifically written for simulation
• AweSim is the software product that combines language with modern window, graphics…makes SLAM user friendly
• Visual SLAM able to do discrete simulations as event or process orientations or both. Also does continuous and combined continuous/discrete.
Visual SLAMAweSim
• Consists of nodes and branches to model queues, servers, machines and decision points.
• DE modeler defines the events and the changes to the system when events occur
• Continuous model is represented by diff eq that describe the dynamic behavior of of the state variables
Modeling Perspectives Summary
• Discrete Simulations...three orientation mostly use– Event – Process
• Continuous Simulations– Defined by diff eq for constant changes
• Visual SLAM/ AweSim– Computer Language that performs simulation
• Will become clearer when we work with a simulation
Modeling Perspectives Exercises
• Page 32• # 2-3 Paint shop describe system using event orientation
and process orientation• #2-4 Describe HVAC control in terms of state variables,
time events and state events
Modeling Perspectives Exercises Solutions
• # 2-3 Paint shop – event orientation 4 events, 1) arrive to prep area, 2) complete prep, 3) arrive at spray machine, 4) end spray/take
out – process orientation essentially visualize an entity going thru the following sequence waiting for prep, prep,
travel to spray, wait for spray, spraying
• #2-4 Describe HVAC control – state variable = temperature– time events = reset thermostat, turn on heat or cool, breakdown, lose power– state events temperature crosses the thermostatic setting….moisture content to turn on/off humidifier