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INTRODUCTION TO MODELING AND SIMULATION

HOW IS SIMULATION USED?

simulation model

Is a descriptive model of a process or system, and includes parameters that allow the model to be configurable,(represent a number of somewhat different system or process configurations).

As a descriptive model, can use to

compare

Experiment

Evaluate

any number of system alternatives

WHEN SHOULD SIMULATION BE USED

Simulation is most useful when:

There is no simple analytic model that is accurate to analyze the situation.

The real system is regularized

The real system has some level of complexity, interaction or interdependence between various components

Are designing a new system, considering major changes in physical layout or operating rules in an existing system

Are considering a large investment in a new or existing system, and it represents a system modification

Need a tool where all the people involved can agree on a set of assumptions

Simulation with animation is an excellent training and educational device, for

ADVANTAGES

Allows the identification of problems

managers

supervisors

engineers

Allows comparison of many alternative designs and rules of operation.

Allows study of the dynamics of a system

A simulation model provides about the only method to study new, non-existent complex dynamic systems for which analytic or static provide at best a low fidelity model with correspondingly low accuracy.

VALUE OF SIMULATION

DISADVANTAGES

Is too costly

In some situations may mislead decision makers into premature conclusions based on insufficient evidence.

are time-consuming, data is not available or costly to obtain

SIMULATION TEAM

almost always conducted by a team that include

The customer’s executives and managers( the decision-makers)

The customer’s engineers, (will live with implemented solutions)

In-house or outside systems designers,( designing a new system or changes)

The simulation analyst.

The Simulation Analyst

practice and- Good communication skills

Models should be developed in a suitable, commercially available and supported simulation package.

STEPS IN A SOUND SIMULATION STUDY

Project Initiation

Problem Formulation and Setting of Objectives

Overall Project Plan

Conceptual Model and Assumptions Document

Project Work

Model Development

Data Collection, Cleansing and Analysis

Model Verification and Validation

Model Verification

Model Validation

Experimentation, Analysis and Reporting

Experimental Design

Experimentation

Analysis

Reporting

MANAGING A SIMULATION PROJECT

should follow these guidelines and watch for a number of potential pitfalls

Have clearly defined and achievable goals.

Allocate adequate resources.

Get upper management support and buy-in.

Have periodic review meetings with all key people present.

Don’t be afraid to ask obvious or “stupid” questions.

Assume nothing. Confirm everything.

Documents assumptions and all changes to assumptions.

Potential pitfalls and causes of project failure

Scope creep

Time slippage/project overrun

Too much detail

Wrong skill sets

DEFINITIONS AND CONCEPTS

simulation model

Is a representation that incorporates time and the changes that occur over time.

discrete model

is one whose state changes only at discrete points in time, not continuously.

discrete-event model

is one whose state changes only at discrete times called event times.

An event

is an instantaneous occurrence that changes the model’s state.

An activity

is a duration of time

the science portion, programming, modeling, and a working knowledge of probability and statistics