SIMULATION STUDY ON ACTIVE AMBULANCE STRETCHER...

SIMULATION STUDY ON ACTIVE AMBULANCE STRETCHER

ADNAN BIN HASSAN

This report is presented in

Partial fulfillment of the requirements for the

Degree of Bachelor of Mechanical Engineering (Automotive)

Faculty of Mechanical Engineering

Universiti Teknikal Malaysia Melaka

MAY 2010

ii

I have read this thesis

and from my opinion this thesis

is sufficient in aspects of scope and quality for awarding

Bachelor of Mechanical Engineering (Automotive)

Signature : …………………….

Name of Supervisor I : …………………….

Date : …………………….

Signature : …………………….

Name of Supervisor II : …………………….

Date : …………………….

iii

“I declare this report is on my own work except for summary and quotes that I have

mentioned its sources”

Signature :

Name of Author :

Date :

iv

To my beloved family

v

ACKNOWLEDGEMENT

I am greatly to ALLAH SWT on His blessing for making this research

successful.

I am sincerely appreciative to my lecturer, Mr. Mohd. Hanif Bin Harun for

serving as my supervisor and for providing guidance while conducting the research and

the writing of this Projek Sarjana Muda (PSM).

I would like to thank everyone who involved directly and indirectly in this

project. The sacrifice and commitment given towards me earning my bachelor’s degree

are indescribable and without them, this PSM thesis would have been impossible.

Finally, thank you my colleagues at the Faculty of Mechanical Engineering,

UTeM for providing an enjoyable research environment.

vi

ABSTRACT

The aims of this research are to establish to non-linear mathematical model and

active control technique of the hydraulically actuated active suspension system for a full

stretcher ambulance ride model. It is characterized by a special-purpose 3-degree of

freedom parallel structure. This compact mechanical architecture is able to compensate

the shocks caused by road unevenness while performing pitch and roll rotations during

accelerating, braking and curving phases. Stretcher loading and unloading operations

have been considered. Direct and inverse kinematics and control strategy are discussed,

and the system effectiveness is shown by simulation results. A simulation study is

performed to proof the effectiveness and active control approach. The result thus

compared with the passive suspension system. The simulation will be performed in

MATLAB Simulink. The purpose of this research is not to create a better suspension, but

to investigate how active control can improve ambulance stretcher ride and also to

reduce this undesirable effect of the input vibration from road and driving behavior. A

theoretical model of two-dimensional active control for ambulance stretcher suspension

is proposed. Numerical calculations are carried out to examine the effectiveness of

active control strategy, which is synthesized to minimize the mean square vertical and

pitching response whilst considering the relative displacement of stretcher suspension. It

shows that the active control with disturbance feed forwarded provides significant

reduction of vertical and pitch angular acceleration of stretcher compared with the

passive stretcher suspension. The relative displacement and resonance peak values of

vibration components in the sensitive frequency range of human body are effectively

suppressed in comparison with the passive stretcher.

vii

ABSTRAK

Kajian ini bertujuan mengetengahkan model matemetik tak linear dan teknik

kawalan aktif dalam pemodelan dan kawalan ke atas gantungan aktif dengan dinamik

hiraulik untuk model pengusung ambulan. Ianya berpandukan ciri-ciri yang digunakkan

pada 3-darjah kebebasan rangka selari. Melalui senibina mekanikal kompleks, gegaran

yang terhasil daripada ketidakrataan permukaan jalan raya ketika berlakunya situasi

kecondongan, kegolekkan semasa memecut, membrek dan pada tahap kelengkungan.

Proses menurunkan dan menaikkan beban pada usungan ambulan. Perulangbalikan

kinematik dan strategi kawalan dibincangkan, dan sistem keberkesanan ditunjukkan

dalam keputusan simulasi. Kajian simulasi dilakukan untuk membuktikan keberkesanan

dan perkaitan sistem kawalan aktif. Hasil kajian kemudiannya dibandingkan dengan

sistem kawalan pasif. Simulasi akan dijalankan mengunakan (Matlab Simulink). Tujuan

kajian ini dijalankan bukannya untuk membina suatu sistem gantungan yang baik, tetapi

menyiasat bagaimana kawalan aktif ini dapat meningkatkan pemanduan pada usungan

ambulan serta mengurangkan kesan yang tidak diinginkan daripada gegaran dari

keadaan jalan dan tingkah laku permanduan. Model teori dua-dimensi dicadangkan bagi

sistem gantungan gantungan pada usungan ambulan. Pembentukan persamaan saringan

berkadar dengan masa dikembangkan bagi melangkapkan anggaran kepada ganguan

dinamik. Pekiranan nombor di bawa keluar untuk menyelidiki keberkesanan strategi

kawalan akif, yang mana dapat mengurangkan purata seimbang pada keadaan lurus dan

kecondongan semasa mempertimbangkan sesaran relatif penggantungan usungan. Ia

menunjukkan yang kawalan aktif dengan suapan gangguan dihantar bagi menyediakan

pengurangan signifikasi tegak dan pecutan sudut kecondongan usungan berbanding

dengan usungan gantungan pasif. Sesaran relatif dan nilai-nilai puncak gema bahagian-

bahagian getaran dalam julat frekuensi sensitif badan manusia adalah berkesan dalam

perbandingan dengan usungan pasif.

viii

CONTENTS

CHAPTER TITLE PAGE NUMBER

CONFESSION ii

DECLARATION iii

DEDICATION iv

ACKNOWLEDGEMENT v

ABSTRACT vi

CONTENTS viii

LIST OF FIGURES xi

LIST OF TABLES xiii

LIST OF SYMBOLS xiv

CHAPTER I INTRODUCTION

1.1 Background study 1

1.2 Project Scope 2

1.3 Researcher Objectives 2

1.4 Problem Statement 2

ix

1.5 Structure and Layout of

Report

1.6 Gantt Chart

3

4

CHAPTER II LITERATURE REVIEW

2.0 Introduction 6

2.1 Suspension System 7

2.1.1 The passive

suspension system

8

2.1.2 Semi-Active

Suspension System

9

2.1.3 Active Suspension

System

10

2.2 Pervious Study of Active

Control System

12

2.3 Modeling with Simulink 18

2.4 PI Control 19

CHAPTER III METHODOLOGY

3.1 Introduction 20

3.2 Flow Chart 20

3.3 Equation of Motion

Modeling using MATLAB

23

3.3.1 Ambulance

Stretcher Ride Model

23

3.3.2 Theoretical

Calculation

24

x

3.3.3 Equation balance

unsprung mass

24

3.3.4 Full ride Model

Integrated control (3

DOF)

26

3.3.5 Equation of

Decoupling

Transformation

28

3.3.6 Reference Data 29

3.4 Ambulance stretcher

concept design

30

3.4.1 Controller Design 30

3.4.2 Ziegler-Nicholas

Method

35

3.5 Simulink Modeling 36

3.5.1 Design of Active

suspension system

39

CHAPTER IV RESULTS & DISCUSSION 42

CHAPTER V CONCLUSION AND

SUGGESTION

53

REFERENCE 57

BIBLIOGRAPHY

60

APPENDIX 61

xi

LIST OF FIGURES

No. TITLE PAGE

2.1 Ambulance stretcher 6

2.2 The passive suspension system 8

2.3 Semi-Active Suspension System 9

2.4 A Skyhook Damper 10

2.5 A low bandwidth or soft active suspension system 11

2.6 A high bandwidth or stiff active suspension system 11

2.7 Matlab Simulink 18

3.1 Project Process Flow Chart 22

3.2 Stretcher Ride Model for Passive System 23

3.3 Sprung Mass Free Body Diagram 24

3.4 Free body diagram of pitching 25

3.5 Free body diagram of rolling 25

3.6 Schematic diagrams for ride model active suspension system 26

3.7 Pitching of ambulance stretcher 27

3.8 Rolling of ambulance stretcher 27

3.9 Ambulance Stretcher 30

3.10 Plan view of ambulance stretcher 30

xii

No. TITLE PAGE

3.11 Side view of ambulance stretcher 31

3.12 Side front view of ambulance stretcher 31

3.13 Tray height of ambulance stretcher 32

3.14 Active control suspension ambulance stretchers 32

3.15 A block diagram of a PID controller 33

3.16 Ziegler–Nichols Tuning Rule 35

3.17 Example of trajectory compensation 36

3.18 Design of Simulink by using Matlab Simulink 37

3.19 Ride model schematic for passive stretcher system 38

3.20 Ride model schematic for Active stretcher system 39

3.21 Active Ambulance Stretcher Subsystem 40

4.1 The vertical body displacements of passive and active (case1) 43

4.2 The vertical body acceleration of passive and active (case1) 44

4.3 The pitching acceleration of passive and active (case1) 44

4.4 The vertical body displacements of passive and active (case 2) 46

4.5 The Body Acceleration of passive and active (case 2) 47

4.6 The Roll angle of passive and active ambulance stretcher (case2) 47

4.7 The vertical body displacements of passive and active (case 3) 47

4.8 The vertical body acceleration of passive and active (case 3) 50

4.9 The roll angle of passive and active (case 3) 50

xiii

No. TITLE PAGE

4.10 The vertical displacements of passive and active (case 4) 52



xiv

LIST OF TABLE

No. TITLE PAGE

1 List of parameters 30

2 Reduction in Peak Value in deferent parameters (case 1) 45




xv

LIST OF SYMBOLS

a = Distance of sprung mass C.G. from front axle

b = Distance of sprung mass C.G. from rear axle

= Front left suspension damping coefficient

= Front right suspension damping coefficient

= Rear left suspension damping coefficient

= Rear right suspension damping coefficient

= Front left suspension force

= Front right suspension force

= Rear left suspension force

= Rear right suspension force

= Front left spring force

= Front right spring force

= Rear left spring force

= Rear right spring force

= Front left damper force

= Front right damper force

xv

= Rear left damper force

= Rear right damper force

h = Height of vehicle C.G.

= Pitch moment of inertia

= Roll moment of inertia

= Front left suspension stiffness

= Front left suspension stiffness

= Rear left suspension stiffness

= Rear right suspension stiffness

= Front left tire stiffness

= Front right tire stiffness

= Rear left tire stiffness

= Rear right tire stiffness

= Distance of vehicle C.G. from front axle

= Distance of vehicle C.G. from rear axle

= Sprung mass

= Front left unsprung mass

= Front right unsprung mass

= Rear left unsprung mass

= Rear right unsprung mass

w = Track width

xvi

= Front left road profile

= Front right road profile

= Rear left road profile

= Rear right road profile

= Sprung mass vertical acceleration at body C.G.

= Front left sprung mass displacement

= Front left sprung mass velocity

= Front right sprung mass displacement

= Front right sprung mass velocity

= Rear left sprung mass displacement

= Rear left sprung mass velocity

= Rear right sprung mass displacement

= Rear right sprung mass velocity

= Rear left sprung mass displacement

= Front left unsprung mass vertical displacement

= Front left unsprung mass vertical velocity

= Front left unsprung mass vertical acceleration

= Front right unsprung mass vertical displacement

= Front right unsprung mass vertical velocity

= Front right unsprung mass vertical acceleration

xvii

= Rear left unsprung mass vertical displacement

= Rear left unsprung mass vertical velocity

= Rear left unsprung mass vertical acceleration

= Rear right unsprung mass vertical displacement

= Rear right unsprung mass vertical velocity

= Rear right unsprung mass vertical acceleration

= Pitch angle at the body C.G.

= Pitch rate at the body C.G.

= Pitch acceleration at the body C.G.

= Roll angle at the body C.G.

= Roll rate at the body C.G.

= Roll acceleration at the body C.G.

1

CHAPTER I

INTRODUCTION

1.1 Project Background

For seriously injured patients the ambulance transport is often very dangerous.

During about 10% of journeys some patient deterioration occurs. In order to avoid this

risk, it’s often necessary to remarkably reduce the ambulance speed, but obviously this

also may be dangerous. The most harmful vibrations to patients lying down are between

about 2 and 8 Hz, close to the natural frequency of the human body. The vibrations

caused by the road unevenness and transmitted through the vehicle suspensions are quite

strong in this frequency range; the use of a device to isolate the patient can bring

important benefits. Moreover, also the accelerations due to the ambulance trajectory

(curves and speed variations) are harmful to patients (Source L.E. Bruzzone and R.M.

Molfino, 2003).

For this project I am using Matlab SIMULINK to design mechanism of the

active ambulance stretcher of ambulance for full car model. The block diagrams are

drawn in Matlab Simulink based on the full car model according to the parameters. The

block diagrams will drawn from the car model which was consider on body, damper,

spring, actuator and wheel and describes of the Active Ambulance Stretcher, including

2

control system design and performance evaluation. From the results of driving

experiments and simulation, it shows that the Active Ambulance Stretcher is able to

reduce the vibration acting on a patient.

1.2 Scope

The objective of this project is to propose control mechanism of the active

ambulance stretcher for ambulance in Malaysia.

1.3 Research Objective

MATLAB Simulink Software will be chosen as a computer design tools used to

simulate the dynamics behavior and evaluate the performance of the control structure.

The research methodology implemented in this project takes the following steps of

works: literature review on related fields, study some previous works and the latest

development on active ambulance stretcher, development of equation of motion,

simulation and comparison with the passive system.

The Active Suspension System is divided into three main categories:

• Study about software called SIMULINK

• To study about passive suspension system in full stretcher ambulance ride model.

• To study about active suspension system in full stretcher ambulance ride model.

• To do the comparative study between passive suspension and active suspension.

• To simulate the system using software called SIMULINK.

1.4 Problem Statement

An ambulance transfer service is required to take a patient to hospital as quickly and

safely as possible. However, it is difficult to meet this requirement since there is

3

essentially a trade-off between quickness and safety, quick transportation exposes a

patient to large vibration acceleration or inertial acceleration, which causes strong pain,

feeling of discomfort or sometimes critical damage for seriously injured persons. It is

possible to reduce the acceleration by driving an ambulance carefully, but it usually

results in a longer delay until hospital arrival.

Passive control method has a disadvantage of disturbance rejecting when used to control

suspension system. Active control is believed can give a better control for active

suspension system in term of maintaining a smooth drives for the drivers. The pneumatic

tire is the first line of defenses and is the most important of all the suspension mediums.

1.5 Structure and Layout of Report

This project work towards developing active suspension and passive suspension

for quarter car, using Matlab Simulink is presented in five chapters. As the development

progress can be divided in to 5 main categories.

The first chapter introduces the active suspension system and details the problem

statement and objective of this project.

The second chapter reports on the review of literature on passive and active

suspension system that inspires the scope of the present report.

Chapter three proposes a method of design of the system in software by using

Matlab Simulink software.

Chapter four, deals with result and discussion of active suspension system’s

operation and design. Application of this suspension is also discussed. A compressive

summary of the project efforts and the conclusions derived from this project work is

presented in chapter five. Constraints and future research potential of the passive and

active suspension system are also presented.

4

Gantt chart for PSM I

NO.

TASK

WEEK

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1 Confirming title

2 Literature review

3 Collect The Data

From Previous Study

4 Solving problems

7 Collecting raw data

from the actual

ambulance stretcher

8 Preparation of

progress report

9

Develop

mathematical

equation

10 Ambulance

stretcher concept

design

11 Preparation on

technical report

12 Edit technical report

13 Submission of

technical report

5

Gantt chart for PSM II

NO.

TASK

WEEK

1 2 3 4 5 6 7 8 9 10 11 12 13 14

1 Survey form/questionnaire

2 Simulation passive and active

suspension

3 Comparison results

4 Discussion of comparison results

5 Validation results

6 Preparation on technical repot

7 Submission of technical repot

6

CHAPTER II

LITERATURE REVIEW

2.0 Introduction

Basicaly the ambulance stretcher is very basic stracture to carry out the patient. It

may be dangerous trauma to the patient with the accelerations due to a fast ambulance

journey. A special active control system, interposed between the ambulance frame and the

stretcher, and a possible control strategy have been designed in order to compensate the

road profile and the accelerations due to the ambulance trajectory. In order to avoid this

risk, it’s often necessary to remarkably reduce the ambulance speed, but obviously this

also may be dangerous.

SIMULATION STUDY ON ACTIVE AMBULANCE STRETCHER...

Documents

Transcript of SIMULATION STUDY ON ACTIVE AMBULANCE STRETCHER...