'30000002161854*

U N I V E R S I T I T U N H U S S E I N O.N'N M A L A Y S I A

PENGESAHAN STATUS TESIS

I M P R O V E M E N T O F S C R E W P R E S S P R O D U C T I O N IN P A L M O I L M I L L USING F U Z Z Y L O G I C S Y S T E M

SESI P E N G A J I A N : 2008/2009

Saya WAN ZUI.KAKNAIiN BIN OTIIMAN mcngaku mcmbcnarkan Tcsis Sarjana ini D I M N I P . m <li Perpustakaan dengan syarat-syarat kegunaan seperti beriknt:

1. Tcsis adalali hakmilik Universiti Tun I lussein Onn Malaysia. 2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tcsis ini sebagai balian pertukaran antara iiistilusi

pengajian tinggi. 4. ** Silatandakan(V)

SULIT (Mengandungi maklumat yang bcrdarjab kcselamatan atau kepentingan Malaysia seperti yang tcrmaktub di dalam AKTA RAIISIA RASMI 1972)

• T E R H A D

TIDAK. T E R H A D

(Mengandungi maklumat TERHAD yang telah ditcntukan oleh organisasi/badan di mana penyelidikan dijalankan)

Disahkan Oleh

( T A N D A T A N G A N PENULIS)

A l a m a t T c t a p : 11051

Taman Sri Jaya 3, Gong Pauh, 24000 Chukai Kcmanan, Tcrcngganu

PROF. DR M A N BIN HASSAN

Tarikh

Tarikh : 'Jo/c

CATATAN: Jika tcsis sarjana ini SULIT atau TERHAD, sila lampirkan sura! danpada pilink berkuasa'organisasi berkenaan dengan mcnyatakan sckah ^cb.sb d.:r, tcmpoh tesis ini pcrlu di kclaskan sebagai SULIT atau TERHAD.

"I hereby declare that I have read this thesis and in my opinion this thesis in terms of content and quality requirements fulfills the purpose for the award of

the Degree of Master of Mechanical Engineering"

IMPROVEMENT OF SCREW PRESS PRODUCTION IN

PALM OIL MILL USING FUZZY LOGIC SYSTEM

W A N ZULKARNAIN BIN O T H M A N

A thesis submitted in

fulfillment of the requirement for the award of the

Degree of Master of Mechanical Engineering

Faculty of Mechanical and Manufacturing Engineering

Universiti Tun Hussein Onn Malaysia

JUNE, 2008

I hereby declare that the works in this thesis is my own except for quotations

summaries which have been duly acknowledged.

Signature

Name of Author

Date

J^k&H W A N ZULKARNAIN..BIN O T H M A N

iii

Dedicated to

my beloved wile and children

iv

ACKNOWLEDGMENT

Bismillaahirrahmaanirrahiim...

Praise be all to Allah SWT, the Most Gracious, the Most Merciful. Shalawat

and salam be to Rasulullah Muhammad saw. By the grace of Allah SWT, this thesis is

finally completed and submitted to Faculty o f Mechanical and Manufacturing

Engineering, Universiti Tun Hussein Onn Malaysia, to full fill the requirements for the

Degree of Master o f Mechanical Engineering.

I would like to take this great opportunity to express my warmest gratitude to

my supervisor Professor Dr. Sulaiman bin Hassan and co-supervisor Assoc. Professor

Dr. Mohd Nor bin Mohd Than for their guidance, concern and strong support

throughout the completion of this thesis. Their enthusiasm has been a great source of

inspiration to me and it gives me a great sense of honour to be under their wings.

Great thanks to my friends who have assisted in making this thesis a wonderful

one and finally to those who have contributed to the success of this thesis, especially

Kumpulan Kilang Sawit RISDA Bhd. Without them this thesis would not have been

possible.

V

ABSTRACT

A screw press machine is used to compress the fruit mash between the main screw and

the travelling cones to extract the palm oil. The position of the cones against the

discharge end o f the press cage determines the pressure. The pressure controller is an

important factor in determining the oil loss and nut breakages. A conventional control

system which is the band control system, uses a kilowatt meter as a controller in

adjusting the press cage pressure. However, the screw press machine can be improved

in order to reduce the oil loss and nut breakages. Not much researches has been

conducted on reducing the nut breakages as well as oil loss. Therefore, the objective of

this study is to minimise the oil loss and broken nuts. The objective can be achieved

through upgrading the screw press machine and the use of fuzzy control system. During

the course of this research project, the hydraulic system of the screw press machine was

upgraded by utilising the proportional pressure relief valve. A current transducer was

used to measure the motor current load. A ladder diagram program and fuzzy logic

algorithm were written and downloaded into the programmable logic control to regulate

the press cage pressure. For comparison purposes, a band control system and fuzzy

control system were implemented in the control environment. The performances of both

systems were compared in a number of tests. The first test was the oscillation of motor

current load with the performance of fuzzy control system that was stabilised at

8.33mA. This is due to the reaction o f fuzzy pressure controller in regulating the

proportional pressure relief valve. The fuzzy control system is able to reduce 1.20% of

oil loss compared to tiie band control system. The percentage o f the broken nuts of the

fuzzy control system was reduced by 3.55%. This implies that the objective to reduce

the breakages is achieved. Thus, the screw press machine with a fuzzy control system is

found to be significantly more efficient than the band control system.

vi

ABSTRAK

Mesin penekan skru digunakan untuk memampatkan lecekan buah antara skru utama

dan kon penggerak bagi tujuan mengekstrak minyak sawit. Kedudukan kon di hujung

keluaran sangkar pemerah menghasilkan tekanan. Pengawal tekanan merupakan satu

faktor yang utama terhadap kehilangan minyak dan biji pecah. Sistem kawalan lazim

yang sedia ada iaitu sistem kawalan jalur, menggunakan kilowatt meter sebagai

pengawal bagi tujuan melaras tekanan di dalam sangkar pemerah. Oleh yang demikian,

prestasi pemprosesan mesin pemerah skru ini, beipotensi untuk dimajukan bagi

mengurangkan lagi kehilangan minyak dan biji pecah. Tidak banyak penyelidikan yang

telah dijalankan dalam mengurangkan kehilangan minyak dan biji pecah. Oleh itu,

objektif kajian ini adalah untuk mengurangkan kehilangan minyak dan biji pecah.

Objektif kajian ini boleh dicapai dengan menaik taraf mesin penekan skru dan

penggunaan sistem kawalan kabur. Sepanjang projek penyelidikan ini, sistem hidraulik

mesin penekan skru telah dinaik taraf dengan menggunakan injap pelega tekanan

berkadar. Pencerap arus elektrik telah digunakan untuk mengukur muatan arus elektrik

motor. Aturcara PLC dan algoritma logik kabur telah ditulis dan di muat turun ke PLC

bertujuan untuk mengawal tekanan sangkar pemerah. Perbandingan antara sistem

kawalan jalur dan sistem kawalan kabur telah dilaksanakan dengan mengadakan

beberapa ujian. Ujian pertama adalah ayunan muatan arus elektrik motor dan didapati

prestasi sistem kawalan kabur adalah stabil pada 8.33mA. Ini adalah disebabkan oleh

tindakan pengawal tekanan kabur dalam mengatur injap pelega tekanan berkadar.

Sistem kawalan kabur didapati mampu mengurangkan 1.20% kehilangan minyak

berbandingan sistem kawalan jalur dan peratusan biji pecah sistem kawalan kabur

adalah lebih baik dengan perbezaan sebanyak 3.55%. Ini menunjukkan, objektif kajian

iaitu untuk mengurangkan kehilangan minyak dan biji pecah telah dicapai. Oleh itu,

mesin penekan skru dengan sistem kawalan kabur adalah lebih baik berbanding dengan

sistem kawalan jalur.

TABLE OF CONTENTS

CHAPTER TITLE PAGE

TESTIMONIAL ii

DEDICATION iii

ACKNOWLEDGMENT iv

ABSTRACT V

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLE xi

LIST OF FIGURE xii

NOMENCLATURE xiv

ABBREVIATIONS XV

LIST OF APPENDIX xv i

I PALM OIL SCREW PRESS

1.1 Introduction 1

1.2 State of The Art in Palm Oil Mill

Screw Press 3

1.3 Problem Statement 4

1.4 Objectives 5

1.5 Thesis Outline 5

viii

II LITERATURE REVIEW

2.1 Introduction 6

2.2 History o f Palm Oil Extraction 7

2.3 Screw Press Power Consumption 8

2.4 Basic Principles of the Screw Press 9

2.5 Screw Press Conventional Control

System 10

2.5.1 Band Control System II

2.5.2 Proportional Control System 11

2.6 Comparison of the Performance

between the Band and the Proportional

Controller 12

2.7 Fuzzy Control 14

2.7.1 Fuzzy Sets 15

2.7.2 Fuzzy Set Membership

Functions 16

2.7.3 Fuzzy Set Operations 17

2.7.4 Union or Max 17

2.7.5 Intersection or Min 17

2.7.6 Fuzzy Logic Controller 18

2.7.7 Knowledge Base IS

2.7.8 Fuzzy Set Variables 19

2.7.9 Inference Rules 19

2.7.10 Fuzzification 20

2.7.11 Defuzzification 21

2.8 Reviews o f Fuzzy Logic Controller

Application 23

2.9 Application of Fuzzy Logic in PLC 25

2.10 Conclusion 28

ix

III SCREW PRESS FUZZY LOGIC

CONTROLLER DESIGN

3.1 Introduction 30

3.2 Screw Press System Development 31

3.3 Fuzzy Logic Control System

Development 35

3.3.1 Fuzzy Pressure Controller 37

3.4 Fuzzy Pressure Controller Development 38

3.5 Fuzzy Logic PLC Programming

Development 48

3.5.1 Assigning of Inputs and

Outputs 49

3.6 PLC Program 50

3.7 Conclusion 50

IV EQUIPMENT SETUP

4.1 Introduction 51

4.2 Current Transducer (CT) 55

4.3 Proportional Pressure Relief Valve

(PPRV) 56

4.4 Fuzzy Logic PLC 57

4.5 Complete Equipment Setup 60

4.6 Conclusion 61

V EXPERIMENTAL RESULTS

5.1 Introduction 62

5.2 Oil Loss and Broken Nuts versus PPRV

Command Value 63

5.3 Regression Analysis of Screw Press

X

Motor Current Load 64

5.4 Simulation Studies 65

5.5 The Performance of the Fuzzy Pressure

Controller 68

5.6 Comparison of Oscillation Current Load 70

5.7 Comparison of Power Consumption 71

5.8 Process Performance 72

5.9 Financial Implication of Oil and Free

Kernel Loss 75

5.10 Conclusion 76

VI CONCLUSION AND SUGGESTION

6.1 Conclusion 77

6.2 Contribution and Future Research 78

REFERENCES 80

APPENDIXES 85

X I

LIST OF TABLE

TABLE TITLE PAGE

2.1 Comparative press trial between the band

control and proportional control system

(Ongand Yong, 1987) 13

2.2 Example of rule matrix for two input and single

output system 20

2.3 Inferred fuzzy output sets 21

3.1 The linguistic variable and the magnitude of

input error 39

3.2 Fuzzy rules 42

3.3 Fuzzy rules application 46

3.4 Fuzzy control output 47

3.5 I/O words 49

3.6 I/O bit 49

5.1 Summary of press cake results 73

5.2 Financial implication of oil and free kernel loss 75

xii

LIST OF FIGURE

FIGURE TITLE PAGE

1.1 Palm oil processing 1

1.2 The operation of screw press 2

1.3 Schematic diagram of the hydraulic system for

the hand control system (Bosh Rexroth,2000) 4

2.1 Relative distance of the travelling cone, d, 8

2.2 Reaction of the travelling cone at variance with

the force 9

2.3 Fuzzy membership 16

2.4 Block diagram of a fuzzy logic controller 18

2.5 Fuzzy input membership 19

2.6 Fuzzy input sets 20

2.7 Fuzzy output sets 22

3.1 Overview screw press fuzzy logic controller

design work flow 31

3.2 Screw press system schematic diagram 32

3.3 Parts of screw press system: (a) press

mechanism; (b) hydraulic system; and (c) fuzzy

logic control system 33

3.4 The structure of a fuzzy logic control system 35

3.5 The structure of a fuzzy pressure controller 37

3.6 Input membership functions for current

error (ie) and current error variance (Az'e) 40

3.7 Fuzzy output membership function 41

3.8 The degree of membership function for ie

and Me 45

3.9 Fuzzy output control surface 47

3.10 Control flow of pressure control 48

Band control system setup

Fuzzy logic control system setup

Fuzzy logic control system configuration

Wiring connection

Current transducer (CT)

The installed proportional pressure relief valve

(PPRV) on the hydraulic system

Detailed schematic of the proportional pressure

relief valve (PPRV), (Bosch Rexroth, 2002)

Programmable logic controller (PLC) with

fuzzy logic unit

Overall schematic of the implementation

equipment setup

Linear analogue output characteristic of the

analogue output unit

Complete equipment setup for the screw press

fuzzy control system

The effect of PPRV command value to the oil

loss and broken nut

Command values and current load data fitted to

a regression model

Fuzzy logic control system

The increment and decrement of hydraulic

cylinder pressure were determined by fuzzy

output variable, u

Current error (ie) performance test

Current error variance (A/e) performance test

Fuzzy output (M) performance test

Comparison of signal level between band

control system and fuzzy control system

Power consumption between band control system and fuzzy control system

NOMENCLATURE

SYMBOL DESCRIPTION

A Ampere

Ai Rod side piston area

A2 Piston surface area

d Relative distance

F Force

'a Actual current

ie Current error

ir Desired current load

mA Milliampere

Pi Pressure acting on the rod side of the hydraulic piston

Pi Pressure acting on hydraulic piston surface

Ppc Press cage pressure

Pr Hydraulic pressure

11 Output of Fuzzy Controller

Ale Current error change

APf Fuzzy output variable

Apr Hydraulic pressure output variable

Membership grade of the j th

Membership grade of the / th

ABBREVIATIONS

AID Analogue to Digital

AC Alternate Current

COG Centre of Gravity

CPU Central Processing Unit CT Current Transducer

D/A Digital to Analogue

DC Direct Current

DM Data Memory

FFB Fresh Fruit Bunch

FSS Fuzzy Support Software

HMPB Harrisons Malaysian Plantations Berhad

I/O Input/Output

IR Internal Relay

KW Kilowatt

MPD Mass Passing to Digester

NL Negative Large

NM Negative Medium

NS Negative Small

PD Proportional-Derivative

PI Proportional-Intergral

PID Proportional, integral and derivative

PL Positive Large

PLC Programmable Logic Controller

PM Positive Medium

PPRV Proportional Pressure Relief Valve

PS Positive Small

rpm revolutions per minute

SBB Binary Subtraction

ZR Zero

xvi

LIST OF APPENDIX

APPENDIX TITLE PAGE

A Flow Chart 86

B PLC Ladder Diagram 100

C The Operation of PLC Program 10 8

D Simulation of Screw Press Fuzzy Logic Controller 112

CHAPTERI

PALM OIL SCREW PRESS

1.1 Introduction

The palm oil mill processes is shown in Figure 1.1. On the arrival of the fresh

fruit bunch (FFB), the FFB are steam sterilised where the fruits soften and easily

detached from the stalk. These detached fruits are further softened with steam in

digesters. The digester mash is then passed to the screw press where the oil and the nut

are extracted.

Find Shift Eflfesnt p l t

Figure 1.1: Palm oil processing

2

There are various types of screw presses used for the extraction of palm oil. The earliest was introduced to the palm oil industry in the early 1960's. This type of machine had been developed for a multitude of applications, both for extraction and extruding (Sivalingam, 1999).

The concept of the screw press is to compress the fruit mash between the main

screw and the travelling cones to extract the palm oil. The position of the cones, as

shown in Figure 1.2, against the discharge end of the press cage determines the pressure

maintained on the mash i.e. smaller slot between cone and press cage will result in

higher pressure and vice versa.

Figure 1.2: The operation of screw press

In the screw press, the stability of the press cage pressure is an important factor

in determining the oil loss and nut breakage in the press cake. A high pressure causes a

better recovery of the oil but unfortunately produce a higher nut breakage.

The effectiveness of the screw press is very critical in optimising the oil

extraction. Ineffective press will result in oil loss and nut breakage and also high

maintenance cost of the machine. Engineers and researches have always tried to

optimise the oil press operation and this research is studying one method of achieving

this. Therefore a fuzzy logic system has been chosen in this research to stabilise the

pressure in the press cage.

3

Fuzzy logic system has been successfully used for a wide number of

applications dealing with complex and non-linear processes, wherein they are proved to

be robust and less sensitive to parametric variations and noise than conventional

controllers (Roger Jang and Gulley, 1997). In addition, fuzzy logic system has been

proven to reduce the oscillations, smoothing the output as far as the error decreases.

This nonlinear characteristic of the controller is a great advantage and was not possible

by a linear Proportional-Derivative (PD) controller (Corbet and Lawrence, 1996).

1.2 State of The Art in Palm Oil Mill Screw Press

The screw press system is one of the least understood processes in a palm oil

mill even though it is one of the most important. Hence, very little progress in the

quantitative understanding of screw presses has been achieved even though they have

been used in palm oil mills for the past fifty years. In view of the oil losses

improvement, the extraction method has gone through some evolution in term of

method of extraction, design and control (Sivasothy, 1993).

One method of controlling the press cone is utilising kilowatt set point. The

press cone movement depends on the kilowatt set point. When the measurement is less

than set point, the press cone will move in and vice-versa (Yee, et. al., 1987). These

conventional pressure control systems are used extensively in the palm oil industry.

This controller is sometime referred to as band control system. However, these

controllers do not take the interaction effect into consideration and the design and

adjustment are difficult despite of their high performance (Burhan Sidek, 1988).

The pressure inside the cage must be measured accurately to ensure effective

control. Thus the method of measuring the pressure is therefore very important.

Pressure can be measured indirectly by the measurement of the power consumed by the

screw press. In general, the pressure can be controlled and it relies on the precision of

the instrument and the screw press condition (Sivasothy, 1993).

4

To summarise, an extensive review of the literature have shown that there are

limited number of published papers on the topic of palm oil mill screw press control

system. As such, that this will remains as an area in which substantive research needs

to be conducted. This research project will attempt to introduce another mean of

controlling pressure in the palm oil mill screw press.

1.3 Problem Statement

In conventional screw press control system, as shown in Figure 1.3, the press

cage pressure is measured via the screw press motor current load by using the current

transducer. If the level is rises, the travelling cone will move away from the press cage

opening. By doing this, the pressure inside the press cage will be reduced. However

the regulating pressure in the press cage efficiency is relatively poor and produces a

fluctuation pressure. The fluctuation press cage pressure cause the increment of oil

losses and nut breakage.

Figure 1.3: Schematic diagram of the hydraulic system for the band

control system (Bosch Rexroth, 2000)