Understanding Simulation: Modeling Real Systems with Arena, 3rd Ed., Study notes of Engineering

Download Understanding Simulation: Modeling Real Systems with Arena, 3rd Ed. and more Study notes Engineering in PDF only on Docsity! Chapt. 1 -- Handout 1 Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 1 of 22 Chapter 1 By Lian Qi What is Simulation? Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 2 of 22 Simulation Is … • Simulation – very broad term – methods and applications to imitate or mimic real systems, usually via computer • Applies in many fields and industries • Very popular and powerful method • This course covers simulation in general and the Arena simulation software in particular Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 3 of 22 Systems • System – facility or process, actual or planned, big or small Examples abound … – Manufacturing facility – Bank operation – Airport operations (passengers, security, planes, crews, baggage) – Transportation/logistics/distribution operation – Hospital facilities (emergency room, operating room, admissions) – Computer network – Freeway system – Business process (insurance office) – Criminal justice system – Chemical plant – Fast-food restaurant – Supermarket – Theme park – Emergency-response system Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 4 of 22 Work With the System? • Study the system – measure, improve, design, control Maybe just play with the actual system – Advantage — unquestionably looking at the right thing But it’s often impossible to do so in reality with the actual system – System doesn’t exist – Would be disruptive, expensive, or dangerous Chapt. 1 -- Handout 2 Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 5 of 22 Models • Model – set of assumptions/approximations about how the system works Study the model instead of the real system … usually much easier, faster, cheaper, safer Can try wide-ranging ideas with the model – Make your mistakes on the computer where they don’t count, rather than for real where they do count Model validity (any kind of model … not just simulation) – Care in building to mimic reality faithfully – Level of detail – Get same conclusions from the model as you would from system Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 6 of 22 Types of Models • Physical (iconic) models Flight simulators • Logical (mathematical) models Approximations and assumptions about a system’s operation Often represented via computer program in appropriate software Exercise the program to try things, get results, learn about model behavior Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 7 of 22 Studying Logical Models • If model is simple enough, use traditional mathematical analysis … get exact results, lots of insight into model Queueing theory Linear/non-linear programming • But complex systems can seldom be validly represented by a simple analytic model • Often, a complex system requires a complex model, and analytical methods don’t apply … what to do? Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 8 of 22 By Simulation! • Can be used to study simple models but should not use it if an analytical solution is available • Real power of simulation is in studying complex models • Simulation can tolerate complex models since we don’t even aspire to an analytical solution Chapt. 1 -- Handout 5 Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 17 of 22 Using Computers to Simulate • General-purpose languages (FORTRAN) Tedious, low-level, error-prone But, almost complete flexibility • Simulation languages GPSS, SIMSCRIPT, SLAM, SIMAN (on which Arena is based, and is included in Arena) Popular, still in use • High-level simulators Very easy, graphical interface Domain-restricted (manufacturing, communications) Limited flexibility — model validity? Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 18 of 22 Where Arena Fits In • Hierarchical structure Multiple levels of modeling Can mix different modeling levels together in the same model Often, start high then go lower as needed • Get ease-of-use advantage of simulators without sacrificing modeling flexibility Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 19 of 22 When Simulations are Used • Uses of simulation have evolved with hardware, software • The early years (1950s-1960s) Very expensive, specialized tool to use Required big computers, special training Mostly in FORTRAN (or even Assembler) Processing cost as high as $1000/hour for a sub-286 level machine Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 20 of 22 When Simulations are Used (cont’d.) • The formative years (1970s-early 1980s) Computers got faster, cheaper Value of simulation more widely recognized Simulation software improved, but they were still languages to be learned, typed, batch processed Often used to clean up “disasters” in auto, aerospace industries – Car plant; heavy demand for certain model – Line underperforming – Simulated, problem identified – But demand had dried up — simulation was too late Chapt. 1 -- Handout 6 Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 21 of 22 When Simulations are Used (cont’d.) • The recent past (late 1980s-1990s) Microcomputer power Software expanded into GUIs, animation Wider acceptance across more areas – Traditional manufacturing applications – Services – Health care – “Business processes” Still mostly in large firms Simulation with Arena, 3rd ed. Chapter 1 – What Is Simulation? Slide 22 of 22 When Simulations are Used (cont’d.) • The present Proliferating into smaller firms Becoming a standard tool Being used earlier in design phase Real-time control • The future Exploiting interoperability of operating systems Specialized “templates” for industries, firms Automated statistical design, analysis Networked sharing of data in real time Integration with other applications Distributed model building, execution