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'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)