PEMODELAN DAN SIMULASIINTRODUCTION TO SIMULATION

ekofajarcahyadi@ittelkom-pwt.ac.id

PREVIEW

1. When the simulation is the appropriate tool

2. When the simulation is not appropriate

3. Advantages and disadvantages of simulation

4. System and system environment

5. Component of a system

6. Discrete and continuous system

7. Model of a system

8. Type of models

9. Discrete-event system simulation

10. Steps in a simulation study

WHEN THE SIMULATION IS APPROPRIATE

WHEN THE SIMULATION IS NOT APPROPRIATE

WHEN THE SIMULATION IS NOT APPROPRIATE

ADVANTAGES OF SIMULATION

DISADVANTAGES OF SIMULATION

1. Model building requires special training. It is an art that is learned over time and through experience. Furthermore, if two models are constructed by different competent individuals, they might have similarities, but its highly unlikely that they will be the same.

2. Simulation results can be difficult to interrupt. Most simulation outputs are essentially random variables (they are usually based on random inputs), so it can be hard to distinguish whether an observation is a result of system interrelationships or of randomness.

3. Simulation modeling and analysis can be time consuming and expensive.

SYSTEM AND SYSTEM ENVIRONMENT

COMPONENTS OF A SYSTEM

Entity, is an object of interest in the system.

Attribute, is a property of an entity.

Activity, represents a time period of specified length.

Object studies Bank. Customers might be one of the entities, the balance in their checking accounts might be an attribute, and making deposits might be an activity.

State of a system is defined to be that collection of variables necessary to describe the system at any time, relative to the objectives of the study. State Ex: The number of busy tellers, the number of customers waiting in line or being served, and the arrival time of the next customer.

COMPONENTS OF A SYSTEM

Event, defined as an instantaneous occurrence that might change the state of the system. Endogenous is used to describe activities and events occurring within a system. Exogenous is used to describe activities and events in the environment that affect the system.

Object studies Bank. The arrival of a customer is an exogenous event, and the completion of service of a customer is an endogenous event.

KOMPONEN SISTEM

System Entities Attributes Activities Events State variables

Banking Customers Checking-account

balance

Making deposits Arrival; departure Number of busy

tellers; number of

customers waiting

Rapid rail Riders Origination;

destination

Traveling Arrival at station;

arrival at

destination

Number of riders

waiting at each

station; number of

riders in transit

Production Machines Speed; capacity;

breakdown rate

Welding; stamping Breakdown Status of machines

(busy, idle, or down)

Communications Messages Length; destination Transmitting Arrival at

destination

Number waiting to

be transmitted

Inventory Warehouse Capacity Withdrawing Demand Levels of inventory;

backlogged

demands

Examples of Systems and Components

SISTEM DISKRIT (DISCRETE) DAN KONTINYU(CONTINUOUS)

Sistem Diskrit

Diskrit merupakan jenis sistem dimana variabel keadaan hanya berubah pada set titik waktu yang diskrit.

Contoh: Jumlah customer yang menunggu di antrian

“A discrete system is one in which the state variable(s) change only at a discrete set of

points in time”

SISTEM DISKRIT (DISCRETE) DAN KONTINYU(CONTINUOUS)

Sistem Kontinyu

Variabel-variabel berubah secara kontinyu seiring waktu.

Contoh: arus listrik

“A continuous system is one in which the state variable(s) change continuously over time”

MODEL OF A SYSTEM

TYPE OF MODELS

TYPE OF MODELS

DISCRETE-EVENT SYSTEM SIMULATION

Merupakan suatu pemodelan sistem dimana variabel keadaan berubah pada set waktu yang diskrit.

Model simulasi dianalisis menggunakan metode Numerik, bukan Analitik.

Numerik : Metode yang menggunakan prosedur komputasi untuk menyelesaikan suatu model matematis.

Analitik : Menggunakan alasan deduktif dari matematika untuk menyelesaikan suatu model.

DISCRETE-EVENT SYSTEM SIMULATION

Problem formulation

Setting of objectives and overall project plan

Model conceptualization Data collection

Model translation

Verified?

Validated?

Experimental design

Production runs and analysis

More runs?

Documentation

and reporting

Imple

ment

ation

Yes Yes

No No

No

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STEPS IN A SIMULATION STUDY

Formulasi Masalah (Problem Formulation)Mengidentifikasikan masalah yang akan diselesaikanMendeskripsikan operasi sistem dalam term-term objek dan aktivitas

STEPS IN A SIMULATION STUDY

Penetapan Tujuan dan Rencana Proyek (Setting of Objectives and Overall Project Plan)Pendekatan yang digunakan untuk menyelesaikan masalah

Konseptualisasi Model (Model Conceptualization) Membangun model yang masuk akal

“A good model is a judicious tradeoff between realism and simplicity.

On the one hand, a model should be a close approximation to the real

system and incorporate most of its salient features. On the other hand,

it should not be so complex that it is impossible to understand and

experiment with it.”

STEPS IN A SIMULATION STUDY

Pengumpulan Data (Data Collection)Mengumpulkan data yang diperlukan untuk running simulasi (seperti laju ketibaan, proses ketibaan, disiplin layanan, laju pelayanan, tsb).

Penerjemahan Model (Model Translation)Konversi model suatu Bahasa pemrograman.

Verifikasi (Verification)Verifikasi model melalui pengecekan apakah program bekerja dengan baik.

STEPS IN A SIMULATION STUDY

Validasi (Validation)Cek kembali apakah system merepresentasikan system riil secara akurat.

Desain Eksperimen (Experimental Design)Berapa lama waktu simulasi?

Menjalankan Simulasi dan Analisis (Production Runs and Analysis)Running simulasi secara aktual dan menganalisis hasil keluaran.

Jalankan lagi? (More Runs?)Menjalankan simulasi lagi jika perlu.

STEPS IN A SIMULATION STUDY

Dokumentasi dan PelaporanDokumen dan laporan hasil

Implementasi

STEPS IN A SIMULATION STUDY

STEPS IN A SIMULATION STUDY

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