FYP_Report_Faraz_Ahmad_12029180_Final

Faraz Ahmad UB: 12029180 Supervisor:Dr.H.S.Qi
MODELLING AND SIMULATION OF A VEHICLE WITH A
CONTROLLED DUAL CLUTCH TRANSMISSION
BEng Dissertation
FARAZ AHMAD
(12029180)
Project report submitted for the Degree of Bachelor of Engineering (Honours)
in Mechanical Engineering
Supervisor: Dr. Hong Sheng Qi
University of Bradford
School of Engineering, Design and Technology
April 2015

DECLARATION OF AUTHORSHIP
I fully understand that the contents of this report must reflect my own work. Any material that I have
usedfrom third party sources such as web journals and technical papers must be accounted for, in the
form of references. I understand this report must be written in my own words apart from any quoted
material which should be clearly identified. I realize that the work which I shall submit for this project
must be work carried out by myself only during the project period (September 2014 - April 2015), and
not that whichhas beendone previously.Iunderstandthataviolationof these conditions may result in
mark of zero for the particular section(s) of assessed work.
PrintName:FARAZAHMAD Signature:fahmad
UB Number:12029180
Course:BEng Mechanical Engineering(Hons.) Date: 22/11/2014

ACKNOWLEDGEMENT
I would like to express my gratitude to my supervisor, Dr. Hong Sheng Qi, for his counseling and
guidance towardshelpingme undertake thisproject.Iwould also like to thank him for being so patient
and having a strong belief in my ability, for the resources and the expert advice that he gave me. At
times I thought that this project would be too much for me to handle, but Dr. Qi constantly motivated
me and made me believe that I could do it.

ABSTRACT
The transmission is one of the most functionally significant components of a vehicle's powertrain,
withoutitthere would be no way for the engine torque to reach the wheels. The transmission system
ensures that engine power is transferred to the wheels as efficiently as possible, and resultantly
determinesthe behaviorand fuel economy of the vehicle. Gear efficiency, noise and shift time have a
huge impacton the performance of a vehicle'stransmission, theseparametersdetermine how much of
the power produced by the engine is actually transmitted to the wheels.
A dual clutchtransmissiondue toitsdouble clutchstructure,doesn'tneedatorque converter,the result
isimprovedfuel efficiency (most automatics lose their power and efficiency in the torque converter).
Using two clutches, one each for the odd and even gear sets means that the next gear is always
preselected, thus shifting time is reduced. The double clutch structure also means that engine power
flowtothe wheelsisuninterrupted, therefore overall powerloss is reduced to about 15%, compared to
nearly 22% for automatics.These reasonshave triggeredthe rapidgrowthandpopularityof DCT's in the
automobile market worldwide, especially the sport/performance vehicles division.
This BEng project dissertation shall aim to study the performance of a vehicle with a dual clutch
transmission,withspecial emphasisonthe gearshiftingprocessandthe role of the transmissioncontrol
module.A detaileddescriptionof the DCTtechnology, its main functional components and principle of
operation is included. This project entails the simulation of a DCT vehicle model developed using
Simulink®,effortshave been made to make this as realistic as possible. The model works properly and
the results indicate a good agreement with the literature. The results successfully demonstrate the
benefits and performance improvements brought about by using a DCT, as compared to the
conventional manual/automatic.

TABLE OF CONTENTS
CHAPTER 1 - INTRODUCTION........................................................................................................................................1
1.1.0 PROJECT BACKGROUND...................................................................................................................................1
1.2.0 AIM AND OBJECTIVES........................................................................................................................................6
1.3.0 REPORT STRUCTURE OUTLINE...................................................................................................................7
CHAPTER 2 - LITERATURE REVIEW AND BASIC THEORY .......................................................................10
2.1.0 DCT OVERVIEW...................................................................................................................................................10
2.2.0 HISTORY AND DEVELOPMENT.................................................................................................................13
2.3.0 CONSTRUCTION & LAYOUT ........................................................................................................................16
2.4.0 MAIN FUNCTIONAL COMPONENTS .......................................................................................................18
2.5.0 PRINCIPLE OF OPERATION .........................................................................................................................26
2.6.0 ADVANCED CONTROL STRATEGIES ......................................................................................................31
2.6.1 INTRODUCTION .............................................................................................................................................31
2.6.2 OVERVIEW OF CONTROL THEORY....................................................................................................31
2.6.3 MAIN CONTROL TECHNIQUES..............................................................................................................32
2.6.4 TRANSMISSION CONTROL ......................................................................................................................33
2.7.0 CHAPTER SUMMARY.......................................................................................................................................35
CHAPTER 3 - METHODOLOGY ....................................................................................................................................37
3.1.0 PROBLEM STATEMENT .................................................................................................................................37
3.2.0 SYSTEM DEVELOPMENT...............................................................................................................................37
3.3.0 LIMITATIONS........................................................................................................................................................38
3.4.0 EXPECTED RESULTS........................................................................................................................................38
3.5.0 GEARBOX AND ENGINE DATA...................................................................................................................39
CHAPTER 4 - MODELLING THE POWERTRAIN................................................................................................41
4.1.0 INTRODUCTION ..................................................................................................................................................41
4.2.0 VEHICLE DYNAMICS........................................................................................................................................42
4.3.0 ENGINE.....................................................................................................................................................................43

4.3.1 ENGINE CONTROL UNIT................................................................................................................................45
4.4.0 SHAFTS.....................................................................................................................................................................46
4.5.0 TRANSMISSION...................................................................................................................................................48
4.5.0 WHEELS & TIRES...............................................................................................................................................51
CHAPTER 5 - TRANSMISSION CONTROL MODULE DESIGN ....................................................................53
5.1.0 INTRODUCTION ..................................................................................................................................................53
5.1.1 HOW IT WORKS..............................................................................................................................................54
5.2.0 SHIFT STATE.........................................................................................................................................................55
5.3.0 GEAR SHIFT DEMANDS..................................................................................................................................56
5.4.0 COMPLETE VEHICLE MODEL.....................................................................................................................57
CHAPTER 6 - TESTING, RESULTS AND DISCUSSION ....................................................................................59
6.1.0 SIMULATION CONDITIONS..........................................................................................................................59
6.2.0 SIMULATION RESULTS...................................................................................................................................60
6.3.0 DISCUSSION OF RESULTS.............................................................................................................................63
CHAPTER 7 - CONCLUSIONS........................................................................................................................................66
7.1.0 CONCLUSION.........................................................................................................................................................66
7.2.0 RECOMMENDATIONS FOR FUTURE IMPROVEMENT.................................................................67
7.3.0 SAFETY AND SUSTAINBILITY ....................................................................................................................68
7.4.0 ETHICS......................................................................................................................................................................69
REFERENCES..........................................................................................................................................................................71
APPENDICES...........................................................................................................................................................................75
APPENDIX A - MINUTES OF MEETINGS...........................................................................................................75
APPENDIX B - PROJECT ACTION PLAN ............................................................................................................79

LIST OF FIGURES
Figure 1 Average emissions for period 1998-2013 (Cooke, 2014) ................................................. 1
Figure 2 7-speed dual clutch transmission schematic (Edwards, 2008)......................................... 2
Figure 3 7- speed DSG odd gears and clutch K1 (Edwards, 2008) .................................................. 3
Figure 4 7-speed DSG even gears and clutch K2 (Edwards, 2008) ................................................. 3
Figure 5 Advantages of DCT (http://www.zf.com/media/media/en/img_1.jpg)........................... 4
Figure 6 Volkswagen 6-speed DSG (Self-Study Programme 308, 2003) ......................................... 5
Figure 7 Sectional view of the VW Group Dual Clutch DSG (Self-Study Programme 308, 2003) . 11
Figure 8 Kegresse dual clutch gearbox proposal (Wenbourne, 2006).......................................... 13
Figure 9 Sectional view of DSG including differential and idler shaft (Wenbourne, 2006).......... 16
Figure 10 Basic layout for a typical five-speed DCT. (Harris, 2006).............................................. 17
Figure 11 Basic multi-plate wet clutch design (Harris, 2006)....................................................... 18
Figure 12 Basic multi-plate wet clutch design (Harris, 2006)....................................................... 19
Figure 13 Input shafts (Self-Study Programme 308, 2003)........................................................... 20
Figure 14 Input shaft 2 (Self-Study Programme 308, 2003) ......................................................... 20
Figure 15 Input shaft 1 (Self-Study Programme 308, 2003) ......................................................... 21
Figure 16 Front and side angle views of output shaft 1 (Self-Study Programme 308, 2003)....... 21
Figure 17 Front and side angle views of output shaft 2 (Self-Study Programme 308, 2003)....... 22
Figure 18 Front and side angle views of reverse shaft (Self-Study Programme 308, 2003) ........ 23
Figure 19 Single-taper synchronizer ZF-B (Lechner, Naunheimer and Ryborz, 1999).................. 24
Figure 20 Diagram showing the principle of operation (Self-Study Programme 308, 2003) ....... 26
Figure 21 Audi DSG gear/clutch schematic and operating principle (Audi, 2006) ....................... 27
Figure 22 Torque transmission 1st gear (Self-Study Programme 308, 2003)............................... 28
Figure 23 Torque transmission 2nd gear (Self-Study Programme 308, 2003) ............................. 28
Figure 24 Torque transmission 3rd gear (Self-Study Programme 308, 2003) .............................. 28
Figure 25 Torque transmission 4th gear (Self-Study Programme 308, 2003) .............................. 29
Figure 28 Torque transmission Reverse gear (Self-Study Programme 308, 2003)....................... 30
Figure 29 Typical single-input single-output control system (Control theory, 2008)................... 31
Figure 30 Electronically controlled AWD system (Volvo S60, 2010) ............................................ 33
Figure 31 Electronic control unit (Self-Study Programme 308, 2003).......................................... 34
Figure 32 Modern vehicle powertrain (Akehurst, 2007) .............................................................. 41
Figure 33 Vehicle body block on Simulink .................................................................................... 42
Figure 34 Engine subsystem closed view on Simulink .................................................................. 43
Figure 35 Engine subsystem expanded view on Simulink ............................................................ 43
Figure 36 Engine control unit expanded view on Simulink .......................................................... 45

Figure 37 Input shaft expanded view on Simulink........................................................................ 46
Figure 38 Output shaft expanded view on Simulink..................................................................... 47
Figure 39 Transmission subsystem expanded view on Simulink .................................................. 48
Figure 40 DCT odd gears expanded view on Simulink.................................................................. 49
Figure 41 DCT even gears expanded view on Simulink ................................................................ 50
Figure 42 Wheels & tires expanded view on Simulink ................................................................. 51
Figure 43 TCM expanded view on Simulink.................................................................................. 53
Figure 44 TCM shift state expanded view on Simulink................................................................. 55
Figure 45 TCM gear shift demands expanded view on Simulink .................................................. 56
Figure 46 Complete vehicle model closed view on Simulink........................................................ 57
Figure 47 Sim1 Engine power graph (HP) ..................................................................................... 60
Figure 48 Sim1 Engine speed graph (RPM)................................................................................... 61
Figure 49 Sim1 Vehicle speed graph (mph) .................................................................................. 61
Figure 50 Sim1 Gear state graph................................................................................................... 61
Figure 51 Sim1 Normalized throttle graph ................................................................................... 62
Figure 52 Sim1 Demanded & achieved torques graph (Nm) ........................................................ 62

LIST OF TABLES
Table 1 VW DSG® Life cycle assessment (The DSG Dual-Clutch Gearbox, 2008) ......................... 35
Table 2 Vehicle data (Kulkarni, Shim and Zhang, 2007) .............................................................. 39
Table 3 Vehicle body block parameters........................................................................................ 42
Table 4 Generic engine block parameters .................................................................................... 44
Table 5 Input shaft subsystem block parameters ......................................................................... 46
Table 6 Output shaft subsystem block parameters ...................................................................... 47
Table 7 Clutches K1 and K2 parameters ....................................................................................... 49
Table 8 DCT gear ratios including final drive ratio and losses ...................................................... 50
Table 9 Dog clutch parameters ..................................................................................................... 50
Table 10 Wheels & tires parameters ............................................................................................ 51
Table 11 Minutes of meetings ...................................................................................................... 78

LIST OF ABBREVIATIONS
DCT Dual Clutch Transmission
DSG Direct Shift Gearbox
CVT Continuously Variable Transmission
VW Volkswagen
PDK Porsche Dual Klutch
TDI Turbocharged Direct Injection
FL Fuzzy Logic
SMG Sequential Manual Gearbox
FDR Final Drive Ratio
TCM Transmission Control Module
GDEM Gear Demand
TDEM Torque Demand
AI Artificial Intelligence
MPC Model Predictive Control
LQG Linear-Quadratic-Gaussian control
ASIS Adaptive Shift Strategy
PID Proportional Integral Derivative

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CHAPTER 1 - INTRODUCTION
1.1.0 PROJECT BACKGROUND
In today'sworld,withnatural resources such as oil and gas set to run out in the near future, petrol and
diesel priceshave beenskyrocketing. Therefore, it is becoming increasingly important for automobile
manufacturers to make cars that deliver good fuel economy. Powertrain engineering and in particular
transmission systems, are facing very difficult and diverse challenges nowadays compared to the
decadesbefore.Thesechallengesare triggered mainly by international legislation, which is tightening
the regulationson emissionsandfuel consumption all around the globe. According to (Matthes, 2005),
in Europe the carbon dioxide emissions have been reduced by 10% from 1995 to 2003. We can see, in
the figure below; the trends in average emissions from light-duty vehicles over the past decade.
Figure 1 Average emissions for period 1998-2013 (Cooke, 2014)
Automatic transmissions have been a staple for the past decade or two as they offer more comfort to
the driverthana traditional manual, especiallywhendrivingthroughcities and on congested roads. But
thiscomesat the costof a lowerfuel economyas plentyof poweris lost in the torque converter, which
is a fluid coupling that is used to transfer rotating power from the engine to the transmission. The
conventional manual transmissionhasbeenlosingpopularity inrecenttimes, due the drivingdiscomfort
associated with them; things such as "torque interrupt" which occurs when gears are shifted makes it
difficultforanunskilleddrivertodrive amanual car. This has compelledautomakerstothinkabout Dual
Clutch Transmission systems, and quite a few have already implemented this technology in some of
theirproductionvehicles.Dual clutchtransmissions(DCTs) provideboth, the sportyand responsive feel

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of a manual and the full shift comfort of conventional automatics with improved performance and
betteroverall efficiencies. Additional advantages of DCTs include higher top speeds, better and more
dynamic accelerations compared to planetary-ATs and CVTs. (Matthes, 2005).
A dual clutchtransmissionisanewkindof semi-automatictransmission system which utilizes a double
clutchstructure,comprisingof twoindependentclutches,one eachfor the odd and even gear sets. The
dual clutch transmissionisbasedlargely on a conventional manual gearbox, it can be described as two
separate manual gearboxessharingthe same housing,each consisting of a gear set (odd or even) and a
respective clutch.However,unlikethe manual transmission;the twoclutches in a DCT are linked to two
inputshafts,the shiftandclutchactuationis controlledbythe transmission control module also known
as the mechatronics module, and there is no physical clutch pedal for a driver. In most modern cars
equipped with a DCT, the driver can initiate the gear change either manually using a paddle shift or
buttons, or by keeping the shift-stick in the fully automatic 'D' or 'S' modes. (Matthes, 2005).
Figure 2 7-speed dual clutch transmission schematic (Edwards, 2008)
According to (Razzacki, 2009), the basic gear train architecture utilized here comprises of two or three
output shafts carrying the output speed gears and synchronizers, and two concentric input shafts
carrying the input gears, with a launch clutch mounted on the front end of each. This parallel shaft
arrangementwithsynchronizersallowssmoothgeartransition,withanuninterrupted power flow from
the engine to the transmission, delivering much higher fuel efficiency.

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The Figures 3 and 4 below illustrate how a typical 7-speed DCT with a direct shift gearbox works; the
system is configured in such a way that both clutches (K1 and K2) are disengaged when the engine is
idle. When the engine is running, one clutch is always engaged, this way there is continuous
transmissionbyone gearset.The nextgearis alreadypreselected by the other gear set whose clutch is
still disengaged.Whengearsare changed,one clutch is disengaged whilst the other one gets engaged.
(Edwards, 2008).
Figure 3 7- speed DSG odd gears and clutch K1 (Edwards, 2008)
Figure 4 7-speed DSG even gears and clutch K2 (Edwards, 2008)

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Dual clutch transmissions generally come in two distinctive types, one variant uses single-plate dry
clutches whereas the other uses wet multi-plate clutches. The latter is the one that is used more
commonlyinproductionvehiclesworldwide. Single-plate dryclutchesdeliver higher efficiency as there
are no drag losses in the transmission fluid, but are less resistant to wear and suited for smaller cars.
Wet clutches, on the other hand, can deliver much higher torque outputs than their dry counterparts,
they are less efficient though as power is lost in the transmission fluid. (Matthes, 2005).
The Figure 5 belowshows how a DCT betters the acceleration and fuel consumption of a conventional
6-speed manual:
Figure 5 Advantages of DCT (http://www.zf.com/media/media/en/img_1.jpg)
Gettingback to the DCT technology,numerous automobile manufacturing companies across the globe
have startedincorporatingDCTsintosome of theirmodels to transmit power to the wheels efficiently,
with big names like VW and AUDI leading the pack. DCTs carry broad development prospects as they
consolidate the advantagesof existingtransmission systems in several ways such as: driver experience
and better fuel economy. (Xuexun, Chang, Fei, Yun, Zheng, 2007).
Volkswagenwasthe firstautomobile manufacturing company to use a dual clutch transmission (Direct
ShiftGearbox) ina passenger car, which was the Golf R32 in 2003. Improved fuel economy and the fact
that DCTs are significantlysmootherthan single clutch units, with gearshifts taking mere milliseconds,
has prompted big companies like Ferrari and BMW to make a switch. (Haj-Assaad, 2012).
RichardTruett fromFord explainedwhatthe future holdsfor their DCT. “We are continually working to
refine andimprove the dual clutch transmission, so that when it changes gears the sensation won’t be
any different from a traditional hydraulic step-gear transmission,” he said, acknowledging past
criticisms. (Haj-Assaad, 2012).
Accordingto (Haj-Assaad,2012), Volkswagen is quite upbeat though. Mark Gillies, manager of product
and technologycommunicationsforVW says, “The future looks good for DSG, because it combines the
ease and convenience of an automatic transmission with the fun-to-drive element of a manual and
because it doesn’t have an energy-sapping torque converter, it usually gets better gas mileage than a
conventional automatic. He also adds, “We are very happy with the technology and feel it gives us a

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unique sellingproposition,particularlyonourTDIand sportyvehicles.”Todate,Volkswagenhassold3.5
million cars with their dual clutch transmissions.
Figure 6 Volkswagen 6-speed DSG (Self-Study Programme 308, 2003)
Despite offeringafarbetterdrivingexperience thanthe conventional stickshiftorautomaticandhaving
a brightfuture,DCTs have beenencounteringafew drawbacks.Some drivershave saidthatgearshifting
isnot as smoothas theyexpected,whileothershave pointed out slowness in the selection of the next
gear,especiallywhentryingtoaccelerate atlow speeds. These little drawbacks are minor compared to
the benefitsof DCTsandcompaniesare workingon trying to improve this technology, adaptive control
is something that could help, there has been ongoing research on this. (Haj-Assaad, 2012).
Thisprojectshall aimat the developmentandtestingof asimulationmodelfora vehicle with a 5-speed
dual clutch transmission using MATLAB™/Simulink®.

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1.2.0 AIM AND OBJECTIVES
AIM:
Modeling, simulation and analysis of a vehicle with a controlled 5-speed dual clutch
transmission (DCT) using MATLAB™/Simulink®.
OBJECTIVES:
1. Modelling the individual components of the vehicle power-train in the form of subsystems
(Engine,ECU,vehicle body,DCT,shaftsandwheels)using Simulink® and SimDriveline® blocks.
2. Designingacontroller(TCM) forthe DCT basedontraditional control theories, toensure timely
gearshifts, smooth vehicle speed and reduced shifting times.
3. Linking the power-train components (subsystems) with the control system (TCM) into a
complete and working vehicle model.
4. Testingthe vehicle model bysimulatingitinthe Simulink®environmentforafixed time period.
5. Displaying simulation results in the form of graphs for: engine power & rpm, vehicle speed,
gearshifts, normalized throttle and demanded & achieved torques.
6. Evaluationanddiscussionof results, demonstrating the performance advantages of DCTs over
other transmissions.

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1.3.0 REPORT STRUCTURE OUTLINE
Thisreporthas beendividedintothe followingchapters:
CHAPTER 1: INTRODUCTION
This chapter sheds a little light on Dual Clutch Transmission systems along with an overview of the
technology and provides a background of fuzzy logic and its applications in today's world. The chapter
also contains the project scope, plan of action and lists the aim and objectives of this report.
CHAPTER 2: LITERATURE REVIEW & BASIC THEORY
Chapter 2 presents an overview of the DCT technology along with its development events. The
construction of a DSG gearbox and the basic theory behind the principle of its operation is discussed
here in detail. The theoretical data is based on the "Direct Shift Gearbox 02E" by Volkswagen and has
been obtained from their "Self-study programme 308".
CHAPTER 3: METHODOLOGY
Thischapter restates the problemandagivesa descriptionof how the projectwill be completed, ittalks
abouthow the aimshall be metand the objectivesachieved.The limitationsto the scope of this project
have been discussed in this chapter along with any assumptions that have been made to design the
simulation model. Lastly, the expected outcome or result of this project has been stated.
CHAPTER 4: MODELLING THE POWERTRAIN
This chapter demonstrates how the following components (subsystems) of the vehicle model were
created in Simulink®: Engine, ECU, vehicle body, transmission (DCT), shafts, wheels & tires. It also
includesall the parametersusedforthese componentsandimagesof what every individual subsystem
looks like.
CHAPTER 5: TRANSMISSION CONTROLLER DESIGN
Chapter5 focusesonthe designof the mostimportantfunctional elementof the vehiclemodel,whichis
the transmission controller. Every subsystem within the controller is analyzed and its functions are
explained. The gearshifting procedure is demonstrated and how this is controlled.

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CHAPTER 6: TESTING & DISCUSSION OF RESULTS
Thischapter dealswiththe mostimportantaspect,whichisthe testing(simulation)of the vehiclemodel
inthe Simulinkenvironment. The results, in the form of graphs produced at the end of the simulation,
are discussed and then verified by performing certain calculations.
CHAPTER 7: CONCLUSION
The final chapterof thisreportprovides a synopsis of the objectives which were successfully achieved
along with recommendations for future work.

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CHAPTER 2 - LITERATURE REVIEW AND BASIC THEORY
2.1.0 DCT OVERVIEW
Most people are aware that in today's time, motor vehicles come with two basic types of power
transmission.Theseare namely;manuals,whichallow the driver to shift gears by using a stick shift and
depressingthe clutchpedal,andautomaticswhichcarry outgear shiftingautomaticallybasedonvehicle
speed using clutches, a torque converter and a set of planetary gears. There is a new type of
transmission that has become increasingly popular over the last decade, this is called the dual clutch
transmissionandisalsoknownasthe double clutchtransmission,semi-automatic transmission and the
automatedmanual transmission.The dual clutchtransmissionfallssomewhereinbetweenmanuals and
automatics, offering the best of both worlds. (Harris, 2006).
Semi-automatictransmissionssuchasthe sequential manual gearbox (SMG) and continuously variable
transmissions(CVTs) have beenprevalentinthe worldof performance andracingautomobilesforyears.
ApproximatelyfortyyearsafterDCTswere inventedby the automotive pioneer Adolphe Kegresse, the
firstracecar equippedwithaDCT;the Porsche PDKwas launched.However,in the world of commercial
production vehicles, it's a fairly new technology, one that is being defined by a very specific design
knownas the dual-clutch or direct-shift gearbox. There has been vast research and development with
regardsto thisoverrecenttimesas thistechnologyhasproventoreduce fuel consumption and provide
dynamic accelerations and better overall efficiencies. (Harris, 2006).
A dual clutch transmission essentially comprises of two manual gearboxes operating independently
containedwithinone housing.Tobe able tounderstandhow it works, it would essential to first review
howa traditional manual gearbox works.Whilst drivingastandardmanual car, whenthe driverwantsto
shiftfromone gear to the next,he or she firstdepressesthe clutch pedal. This operates a single clutch,
which disconnects the engine from the gearbox and interrupts power flow to the transmission. The
driver, then shifts the stick to the desired gear position, this selects a new gear. Devices
calledsynchronizersmatchthe gearsbefore theyare engagedtopreventgrinding.Once the new gear is
engaged, the driver releases the clutch pedal, which re-connects the engine to the gearbox and
transmits power to the wheels.
Conventional manual transmissions are victims of a phenomenon called "shift shock" or "torque
interrupt". This happens as a result of interruptions in power flow from the engine to the wheels as
powerdeliveryswitchesoff during the gearshift period. There are certain driving techniques that help
minimize shift shock, but for an unskilled driver, torque interrupt causes passengers to be thrown
forward and backward as gears are changed. (Harris, 2006).
While driving a manual, the driver has to depress the clutch pedal and then select a new gear. On the
contrary, a dual-clutch or direct-shift gearbox uses two clutches but without the need for a physical
clutch pedal, as the term "direct-shift" implies. In terms of principle, a DCT runs similar to a manual
transmission;the gears,synchronizersandclutchare housedbythe inputandauxiliaryshafts.However,
the process of depressing the clutch pedal at the right time whilst driving a stick-shift, is emulated in

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DCTs by sophisticated electronics and hydraulics. Computers, solenoids and hydraulics carry out the
actual shiftingjustasitisin a standard automatic. DCTs are operate automatically but to an extent; the
drivercan still tell the computerized system when to take action using paddles, buttons or a gearshift.
The same is not possible in automatic transmissions, where gearshifts are fully automatic based
primarily on vehicle speed.
In a vehicle witha6-speedDCT,however, the clutches operate independently. One clutch controls the
odd gears (first, third, fifth and reverse), while the other controls the even gears (second, fourth and
sixth).Usingthisarrangement, gears can be changed at lightning fast speeds, without interrupting the
power delivery from the engine to the transmission. (Harris, 2006).
Figure 7 Sectional view of the VW Group Dual Clutch DSG (Self-Study Programme 308, 2003)
Figure 7 above showsa part-cutawayview of the Volkswagen six-speed DSG 02E. The concentric multi-
plate clutches and the mechatronics module (TCM) have been sectioned. (Self-Study Programme 308,
2003)
Clutch Types
Fundamentally,there are twotypesof clutchesusedindual-clutch transmissions which are either; two
wetmulti-plateclutches lubricated in oil (cooling purposes), or two dry single-plate clutches. The wet
clutchdesignsuitsmore powerful enginesgeneratingtorquesof 350 Nm and is used in the VW 6-speed
DSG 02E. (The DSG Dual-ClutchGearbox,2008). Wet clutchesrequire alarge amountof lubricatingoil to
operate, the oil needs to be evenly spread on the clutch plates to allow the energy generated during

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shifting to be dissipated. (Audi, 2006). Wet clutches hold certain benefits over their dry counterparts,
such as lowwearand hightorque output. The wet multi-plate clutch used in the Bugatti Veyron's DCT,
for instance,isdesignedtocope withtorques as high as 1,250 Nm, but at the cost of a lower efficiency.
On the otherhand, the single-plate dry clutches are aimed at the lower end of the market with torque
outputs up to 250 Nm maximum, and these were used in the VW 7-speed DSG DQ200. These clutches
usuallyoperate adjacenttoeachother,witheachtransferring torque to one gear-train half and usually
have an extrashaftfor reverse gear.Furthermore,dryclutchvariantsdo holda compellingadvantage,in
that theyofferanincrease infuel efficiency,asthere are nopumping losses of transmission fluid in the
clutch housing. (Self-Study Programme 390, 1995) and (The DSG Dual-Clutch Gearbox, 2008).
Clutch Installation (Lechner, Naunheimer and Ryborz, 1999)
There are nowthree differentwaysinwhichclutchesare installed nowadays, lets shed light on each of
these briefly:
 The first or original design had a concentric arrangement, where both clutches were on the
same plane perpendicular to the transmission input. Both clutches were installed along the
same centre line asthe engine crankshaft;whenviewedhead on along the input shaft, thereby
making one clutch noticeably larger than the other.
 The secondvariationmade the use of two single-plate clutches, also sharing the centre line of
the crankshaft, arranged side by side, when viewed from the perpendicular angle.
 The latestimplementationutilizedtwoseparate butidentically sized clutches, in a side by side
arrangement when viewed head on, and also share the same perpendicular plane.
Pros and Cons of DCTs (Harris, 2006)
I. Improved fuel economy is probably the most significant benefit of using a dual clutch
transmissions. As discussed earlier, during gearshifts power delivery from the engine to the
transmissionisuninterruptedandthereforefuelefficiency increases dramatically. A number of
experts believe that a six-speed DCT such as VW's (DSG 02E) can produce up to a ten percent
increase in relative fuel economy when compared to a conventional five-speed automatic.
II. The option of choosing between automatic shifting done by the computer or manually
controllingit,is a compelling advantage that DCTs bring. As there is no clutch pedal, the driver
can shiftgearsveryconvenientlyandquickly(upshiftstakingupto8milliseconds), resulting in a
very dynamic and smooth acceleration.
III. Anotheradvantage of DCTsis the elimination of shift shock/torque interrupt that is associated
with manual transmissions. This makes driving fairly easier for unskilled drivers.
IV. Certain automakers are worried about the costs associated with modifying production and
assembly lines to accommodate a new type of transmission. This will initially increase the
market prices of cars equipped with DCTS and therefore put off for some consumers.
V. There have been complaints about cars with DCTs (VW Golf) failing to change gears at high
engine speeds, due to possible faults in the mechatronics module. These are being resolved.

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2.2.0 HISTORY AND DEVELOPMENT
The invention of the dual-clutch gearbox, which was by a man who was a pioneer in automotive
engineering,datesbackseveralyearstoas earlyas1939. This man,Adolphe Kégresse is well known for
developingthe half-track,atype of vehicle equippedwith endlessrubbertreadsallowing it to drive off-
road overvariousformsof terrain.In 1939, Mr. Kégresse came upwiththe ideaof a dual clutch gearbox,
which he hoped to equip the legendary Citroën "Traction" vehicle. Due to adverse business
circumstances and France being a state of war at the time, there was no further development to his
idea. (Harris, 2006) and (Wenbourne, 2006).
Figure 8 Kegresse dual clutch gearbox proposal (Wenbourne, 2006)
Quite a few years later, the German automakers Audi and Porsche picked up on the dual-clutch
technology,however its use was limited only to racecars at the time. In 1985, Audi made history when
theirSportQuattro S1 rallycar equippedwithaDCT wonthe "PikesPeakhill climb",whichwasa race up
the 4,300 meter high mountain in the United States. The 956 and 962C racecars manufactured by
Porsche included the "Porsche Dual Klutch" transmission, or PDK. The Porsche 962 model won the
"Monza 1000 KilometerWorldSportsPrototype Championshiprace" in 1986, this was the first ever win
for a car equipped with the PDK semi-automatic paddle shifted transmission. (Harris, 2006).

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Due to lack of manufacturing facilities and high initial costs, it has not been feasible to commercialize
the dual clutch transmissionuntilrecently.DCTshave gainedpopularityinrecentyears,especiallyin the
European markets, possibly due to the hike in fuel prices and the need for optimized performance.
VolkswagenhasbeenamajorpioneerinDCTsduringthe pastdecade or more,theyhave licensed Borg-
Warner's "DualTronic" technology which is being used in numerous modern VW vehicles. In today's
world, several European automobiles are equipped with DCTs such as:
 VW - Golf, Jetta and Beetle models
 Audi - TT and the A3
 Skoda - Octavia and Superb
 Seat - Leon and Toledo
(Harris, 2006).
The fastestDCTs inthe worldtoday(speedsupto8ms) are producedbythe Volkswagengroup,withthe
Direct Shift Gearbox (DSG) name which is derived from the German words: "Direkt-Schalt-Getriebe".
(Self-Study Programme 308, 2003). The DSG gearbox is used in all of their mainstream marquees,
including VW Passenger Cars, Audi, SEAT, Skoda, and VW Commercial Vehicles, and also its top-tier
marque Bugatti. Audi which is a part of the Volkswagen group also used the Direct Shift Gearbox term
initially, but now has given a new name to their DCTs, "S tronic". (Audi, 2006).
The firsteverworldwide series production of a transmission of this type was the VW Group DQ250 six-
speed dual-clutch transmission, comprising dual concentric wet multi-plate clutches. It was
manufactured at the Group's Kassel plant under exclusive license from Borg-Warner for use in
transverse power-traininstallations,of eitherfront-wheel drive orfour-wheel drive (4WD) layouts. This
DQ250 variant is used in a wide range of models: VW Passenger Cars (Polo, Golf/Rabbit/Golf Plus,
Sirocco,Jetta,Eos, Passatand Touran);Audi cars (A3,and TT); SEAT cars (Ibiza, León, Altea and Toledo);
Škodacars (OctaviaandSuperb);andVWCommercial Vehicles(CaddyandT5 Transporter). (Volkswagen
Group extends reach of dual clutch transmissions, 2009).
In 2008, another variant of the Direct-Shift Gearbox (DSG) went into series production, the DQ200,
consistingof sevenforwardratios.Thisvariantusestwodrysingle-plateclutchesas opposed to the wet
ones used in the DQ250. These two dry clutches are arranged in a tandem design, as opposed to
concentrically, and are similar in size to the wet multi-plate clutches. The DQ200 variant just like the
original DQ250, is designed for use in transverse powertrain installations. However this variant is
intended for equipping smaller cars, with smaller displacement engines that deliver relatively lower
torque outputs. When installed in the latest Golf model with the 90 kilowatts (122 PS; 121 hp) engine,
thisnew7-speed DSG uses roughly 6% less fuel than the same engine with a manual transmission and
up to 20% lessthan a conventional automatictransmission (5.9l/100 km for the 7-speed DSG compared
to 6.3l/100 km with the 6-speed manual gearbox). (Volkswagen Group extends reach of dual clutch
transmissions, 2009).

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AfterVolkswagen,Fordisthe second major automobile manufacturer to make a commitment towards
dual-clutch transmissions. Their DCTs are made by Ford of Europe on a fifty-fifty joint venture with
transmissionmanufacturer,GETRAG-Ford.The "PowerShift"systemwhich is the name given to the six-
speed DCT manufactured by GETRAG-Ford, was demonstrated at the 2005 Frankfurt International
Motor Show. However, the production of commercial vehicles equipped with the first generation
"PowerShiftSystem"beganafternearlytwoyears,due tobusinessrestraints and lack of manufacturing
facilities at the time. (Harris, 2006).
Ford released their first wet clutch "PowerShift" dual clutch transmission on the 2008 Ford Focus and
the C-MAX. This DCT was designed by gearbox specialist GETRAG under the joint venture with Ford
which was founded in 2001, the "PowerShift" system is expected to feature in other motor vehicle
models by Ford and Volvo in the future. (Ford starts production of six-speed dual clutch PowerShift
transmission, 2010).
Japanese automakerssuchasHonda have alsomade a commitmenttowards dual-clutch transmissions,
however in a slightly different manner. Honda have implemented a technology which has grown
increasinglycommoninautomobiles over the past few years, in their sculpted VFR1200F sport-touring
motorcycle which was launched in October 2009. This was the first time that someone has used this
type of transmission on a two wheeler. (Schwartzapfel, 2010).
The Mitsubishi FusoTruckand Bus Corporation have designed a brand new double-clutch transmission
for theirheavyvehicles.Thisisthe firsttime that a transmission of this sort has been manufactured for
heavy vehicles. The new six-speed M038S6 "Duonic transmission" features wet clutches and
incorporates the ability to creep in traffic, resulting in a more efficient operation. Although Duonic-
equipped trucks will probably be driven mostly in fully automatic mode, the transmission can also be
manually shifted. (First double-clutch transmission in a truck, 2010).
The Korean automobile manufacturers Kia, have recently entered the fray as well after developing a
new seven-speed dual clutch transmission using dry clutches. This will be a potentially strong
replacementforitscurrentsix-speedautomatic.The new transmissionshall be introduced in global Kia
modelsstartingsometime in2015, althoughthe exactmodelshaven't been specified yet. Compared to
the six-speed DCT currently used in the Europe market, the new transmission is expected to deliver a
fuel-economy improvement of 7 % and a 5 % improvement in 0–62 mph acceleration times.

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2.3.0 CONSTRUCTION & LAYOUT
The directshiftgearbox,usedinDCT's underdifferentnamescomprisesin essence of two transmission
units constructed the same way as a manual gearbox, which are independent of each other, but work
side by side. A wet multi-plate clutch is assigned to each transmission unit, namely K1 and K2, as the
name suggeststhese clutchesare wet and work in DSG oil. The VW mechatronics system emulates the
functionof a TCM by controllingthe opening,closingandshiftingof the twoclutches,depending on the
gear to be selected. (Self-Study Programme 308, 2003).
Transmission unit 1 consists of the 1st, 3rd, 5th and reverse gears which are selected via multi-plate
clutchK1. The secondtransmissionunitcomprises of the 2nd, 4th and 6th gears and these are selected
viamulti-plate clutchK2.Everysingle gearisallocatedasynchronizationandselectorelement,similarto
the one usedinconventional manual gearboxes.Usingthisarrangementmeanswhilstone transmission
unitisin gear,the other transmissionunitcanhave the nextgearpre-selectedbutwithclutchstill in the
open position. (Self-Study Programme 308, 2003).
Figure 9 Sectional view of DSG including differential and idler shaft (Wenbourne, 2006)

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The torque is transmittedtothe relevantclutchthroughthe outerplate carrier.When the clutch closes,
the torque is transmitted further to the inner plate carrier and then to the relevant input shaft. One
multi-plate clutch is always engaged. (Self-Study Programme 308, 2003).
As showninFigure 10, the inputshaftappears to be single shaft comprising of two parts, with gears on
eitherside.Asdiscussedearlier,DCT'sconsistof twotransmissionunits which are independent of each
other,these two units require an input shaft each. Instead of using two separate input shafts, the DCT
splits up odd and even gears on two concentric input shafts. This is made possible by hollowing the
outer shaft out, making room for the inner shaft which is nested inside. (Harris, 2006).
Figure 10 below shows the arrangement for a typical five-speed dual clutch transmission, the
transmissionmodelcreatedinthisproject will be very similar to this. We can see that clutch 1 which is
labelledingreencontrolsthe greengears(2nd and 4th) and the clutch 2 controls the red gears (1st, 3rd
and 5th). This arrangement ensures constant and uninterrupted power delivery to the wheels and
lightning quick gear shifts. The same is not possible via a manual transmission, because manual
gearboxes use a single input shaft and a single clutch for all odd and even gears. (Harris, 2006).
Figure 10 Basic layout for a typical five-speed DCT. (Harris, 2006)

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2.4.0 MAIN FUNCTIONAL COMPONENTS
Multi-plate clutches
A dual clutchtransmissionisquite similartothe conventionalautomatic,the main difference being the
double clutchstructure compared to the single automatic clutch used in automatics. Automatics make
the use of a torque converter to transfer engine torque from the engine to the transmission, DCTs on
the otherhand don'trequire torque converters. DCTs present in the market today use wet multi-plate
clutchestofulfill the same purpose.A "wet" clutch is a type of clutch whose components are bathed in
lubricating fluid, with the purpose of reducing friction and limiting the production of heat energy.
Manual transmissionsare generallyequipped with dry clutches and some DCT manufacturers are using
these too, however, all production vehicles today which are equipped with DCTs use the wet version.
(Harris, 2006).
Figure 11 Basic multi-plate wet clutch design (Harris, 2006)
These wet multi-plate clutches are similar, in terms of principle of operation to torque converters, in
that theyalsouse hydraulicpressure todrive the gears.AsseeninFigure 11, the lubricatingfluiddoes it
workinside the clutchpiston.Whenthe clutchisengaged,hydraulic pressure inside the piston forces a
set of coil springs apart, this in turn pushes a series of stacked clutch plates and friction discs against a
fixedpressure plate.The frictiondiscsshown in Figure 11 have got teeth on the inside, these teeth are
shapedandsizedinsuch a way that they can mesh with splines on the clutch drum. This clutch drum is
connectedto the gear-set which will receive the transfer force. The wet multi-plate clutches in Audi's

Page | 19
DCTs comprise of both a small coil spring and a large diaphragm spring. To disengage the clutch, fluid
pressure inside the piston is reduced. This allows the piston springs to relax, which eases pressure on
the clutch pack and pressure plate. These wet clutches engage and disengage based purely on fluid
pressure whichiscontrolledbythe transmissioncontrol module (TCM), or the mechatronics module as
VW like to call it. (Harris, 2006) and (Audi, 2006).
Figure 12 below shows the basic wet clutch design, when clutch 1 is engaged, clutch 2 is disengaged:
Figure 12 Basic multi-plate wet clutch design (Harris, 2006)
The main advantage that wet multi-plate clutches hold over single-plate dry clutches is that they can
produce highertorque outputsandshow a betterresistance towear.The bathingfluid used such as the
DSG oil usedby VWhelpstoreduce friction,andinturn dissipatesthe heat energy generated. The only
real issue withwetmulti-plateclutchesislowerefficiency as compared to their dry counterparts, there
is on-going research and development with regards to this. (The DSG Dual-Clutch Gearbox, 2008).

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Input shafts
The main rotary elements of the DSG gearbox are the two input shafts which house the odd and even
gear sets.These inputshaftsare concentric,andare coaxiallyembeddedtogetherasdisplayed in Figure
13. The Input shaft 1receives power via clutch K1 and input shaft 2 receives power through clutch K2.
(Self-Study Programme 308, 2003).
Figure 13 Input shafts (Self-Study Programme 308, 2003)
Inputshaft2
In the figure below, Inputshaft2isshownin relationtothe installationposition of inputshaft1.
Figure 14 Input shaft 2 (Self-Study Programme 308, 2003)
InputShaft 2
InputShaft 1
6th/4th gear
2nd gear
Pulse wheel

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Inputshaft2 is connectedto the multi-plate clutchK2viasplines,ithasa hollow constructioninorderto
allowinputshaft1 to be nestedinside.A commongear wheel is used for the 4th & 6th gears, whilst for
the rest; helical gear wheels on input shaft 2 are used. (Self-Study Programme 308, 2003).
InputShaft1
Figure 15 Input shaft 1 (Self-Study Programme 308, 2003)
We can see fromFigure 13 that inputshaft1 the longerone of the two,rotatesinside the hollowinput
shaft2, andis joinedtoclutchK1 throughsplines.Locatedoninputshaft1 are helical gearwheelsfor
5th gear and a commongear wheel forreverse gear.(Self-StudyProgramme 308,2003).
Output shafts
In line with the two input shafts, the direct shift gearbox also features two output shafts.
Output shaft 1
Figure 16 Front and side angle views of output shaft 1 (Self-Study Programme 308, 2003)
3rd gear
1st/reverse gear5th gear
Pulse wheel
1st gear
3rd gear
4th gear 2nd gear
Outputshaftgear
Inputshafts
Installationposition
ingearbox
Lockingcollar

Page | 22
Located on input shaft 1 are:
 Three-fold synchronized selector gears for 1st, 2nd, 3rd gears
 Single synchronized selector gear for 4th gear
 Output shaft gear for meshing into the differential
The output shaft meshes into the final drive gear wheel of the differential. (Self-Study
Programme 308, 2003).
Output shaft 2
Figure 17 Front and side angle views of output shaft 2 (Self-Study Programme 308, 2003)
Located on input shaft 2 are:
 Selector gears for the 5th, 6th and reverse gears
 Pulse wheel for gearbox output speed
 The output shaft gear for meshing into the differential
Both output shafts transmit the torque further to the differential via their output shaft gears.
Installationpositioningearbox
5th gear 1st gearReverse gear6th gear

Page | 23
Reverse shaft
The functionof the reverse shaftisswitchingthe directionof rotationof outputshaft2and therefore
the directionof rotationof the final drive inthe differential aswell. Itengagesinthe commongear
wheel for1st gearand reverse gearoninput shaft1 and the selectorgearforreverse gear onoutput
shaft2. (Self-StudyProgramme 308,2003).
Figure 18 Front and side angle views of reverse shaft (Self-Study Programme 308, 2003)
Installationpositioningearbox
Gear wheel for1st and
reverse gear
Reverse shaft

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Synchronizer
The most significantinternal shifting component in a DSG gearbox is the transmission synchronizer, as
the name suggests,itsfunctionis to synchronize or balance the different gear speeds. A synchronizing
mechanism is therefore required to match the circumferential speeds of the parts to be connected in
0.1 to 0.3 seconds with the application of a minimum of force in order to avoid premature locking.
Manual transmissions also contain a synchromesh unit within the gearbox, but there is power
interruptioninbetweengearshiftswhenthe clutch is engaged/disengaged. In contrast, DSG gearboxes
shift without power interruption due to the double clutch structure. In 1993 approximately 60% of
commercial vehicleswere fittedwithsynchromeshgearboxes,inorderto improve road safety and ease
of use. Road safety is improved as synchromesh gearboxes allow gears to be shifted at any time and
they are easier to use than traditional manuals as there is no physical clutch pedal. (Lechner,
Naunheimer and Ryborz, 1999).
Accordingto (Lechner,Naunheimerand Ryborz,1999), gear wheel transmissionwithmulti gearsmaybe
synchronized in the following ways:
 synchronizing mechanism for each individual gear
 central synchronizer for the whole transmission
 speed synchronization by the prime mover
Figure 19 Single-taper synchronizer ZF-B (Lechner, Naunheimer and Ryborz, 1999)
1) Idler gear with needle roller
bearings
2) Synchronizerhubwith selector
teeth and friction cone
3) Synchronizerring with counter-
cone and locking toothing
4) Synchronizerbodywith internal
toothing for positive locking with
the transmission shaft and
external dog gearing for the
gearshift sleeve;
5) Gearshift sleeve with internal
dog gearing and ring groove
6) Transmission shaft

Page | 25
A mechanical synchromesh unit such as the one shown above in Figure 19 frictionally matches the
different speeds of the transmission shaft (and the gearshift sleeve rotationally fixed to it) and of the
idler gear to be shifted. When their speeds have been synchronized, the elements are positively
engaged.The synchromeshunitincorporatesafrictionallyengaged clutch and a positive locking clutch.
(Lechner, Naunheimer and Ryborz, 1999).

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2.5.0 PRINCIPLE OF OPERATION
DCT's as the name suggests,workonthe basisof two clutchesworkinginconjunctiontocontrol the odd
and evengear-sets.Thisresultsinenhancedshiftresponse andreducedshifttimes(typically0.3to 0.4
seconds),bringingaboutamore dynamicperformance andimprovedoverallefficiency.During
operation,whilstanoddnumberedgearratioisbeingdrivenbyone clutch(K1),an evennumberedgear
ratiocan be pre-selectedandmade readyforengagementbyswitchingtothe secondclutch(K2).Using
thisprinciple ensurescontinuouspowerflow duringgearshiftsthatare quickerthata manual and
smootherthanthe conventional automatic. (Wenbourne,2006).
Figure 20 Diagram showing the principle of operation (Self-Study Programme 308, 2003)
Synchronization principle
To engage a certain gear, the locking collar has to be pushed onto the teeth of the selector gear,
synchronizationisthe processof balancingthe speedof the engaginggearwheelsandthe lockingcollar,
using molybdenum coated brass synchro-rings. 1st, 2nd and 3rd gears are equipped with three-fold
synchronization as the balancing of the large speed differences in the lower gears is slightly slower.
The 4th, 5th and 6th gears are synchronized using the simple cone system, there are smaller speed
differenceswhenthese gearsare selected.Asaconsequence,the balancingof speedsisfasterwithlittle
effortbeingrequiredforsynchronization.The reverse gear is equipped with dual cone synchronization
due to a significant differences in selector gear speeds. (Self-Study Programme 308, 2003).
Transmissionunit2
Multi-plate clutchK1
Engine torque
Transmissionunit1
Multi-plate clutchK2

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Figure 21 showsoperationof the DSGwhilstthe vehicle isaccelerating in first gear, we can see that the
next gear which is 2nd in this case is preselected, waiting for clutch 2 to be engaged. (Audi, 2006).
Figure 21 Audi DSG gear/clutch schematic and operating principle (Audi, 2006)
Torque transmission
The torque in the gearbox istransmittedeitherviathe outerclutchK1 or the innerclutchK2. Each clutch
drives an input shaft, with input shafts 1 (inner) and 2 (outer) being driven by clutches K1 and K2
respectively.
Power is transmitted further to the differential via output shaft 1 for the 1st, 2nd, 3rd, 4th gears and
output shaft 2 for the 5th, 6th and reverse gears. (Self-Study Programme 308, 2003).
Figures 22 to 28 (Self-Study Programme 308, 2003) show torque transmission in each gear for the DSG
02E:

Page | 28
Figure 22 Torque transmission 1st gear (Self-Study Programme 308, 2003)
Figure 23 Torque transmission 2nd gear (Self-Study Programme 308, 2003)
Figure 24 Torque transmission 3rd gear (Self-Study Programme 308, 2003)
1st gear
ClutchK1
Inputshaft1
Outputshaft1
Differential
2nd gear
ClutchK2
Inputshaft2
Outputshaft1
Differential
3rd gear
ClutchK1
Inputshaft1
Outputshaft1
Differential

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Figure 25 Torque transmission4thgear(Self-StudyProgramme308, 2003)
Figure 26 Torque transmission 5th gear (Self-Study Programme 308, 2003)
Figure 27 Torque transmission6thgear(Self-StudyProgramme308, 2003)
6th gear
ClutchK2
Inputshaft2
Outputshaft2
Differential
4th gear
ClutchK2
Inputshaft2
Outputshaft1
Differential

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Figure 28 Torque transmission Reverse gear (Self-Study Programme 308, 2003)
Reverse
ClutchK1
Inputshaft1
Reverse shaft
Outputshaft2
Differential
The change indirectionof rotationfor
reverse geariscarriedout viathe
reverse shaft.

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2.6.0 ADVANCED CONTROL STRATEGIES
2.6.1 INTRODUCTION
From the previous sections it can be concluded that a dual or double clutch transmission is basically a
automaticallycontrolledmanual transmission,comprisingof twoindependent clutches. The manual bit
of this type of transmission is that it provides the driver the option of shifting gears using paddles or
buttons,the automaticside beingthatthere is no clutch pedal needed and the driver can choose to let
the transmission control module do all the work.
A DCT is a fairlycomplicatedmechanical system andcontrollingitcanbe verychallenging.Sophisticated
electronicsandhydraulicsare atthe heart of the transmissioncontrol module fora DCT. The sections to
followshall brieflyexplore variouscontrol strategies andshedsome lightuponhow these are applied to
DCTs by automakers today.
2.6.2 OVERVIEW OF CONTROL THEORY
A control theory can be defined as a set of principles which deal with influencing the behaviour of
dynamic systems. It is an interdisciplinary subfield of science which originated in engineering and
mathematics, and now has evolved into various fields. Control systems comprise of five functional
elements: detector, transducer, transmitter, controller and final control element. Their job is to carry
out a seriesof functionswhichare;measure,compare,computeandcorrect. The function of measuring
is carried out by the detector, transducer and transmitter which are all contained within one unit. The
2nd and the 3rd functionsare carriedoutby the controller electronically, examples are; PID controller,
programmable logiccontrolleretc.The correctionfunction,iscompletedbythe final control element,by
modifying input/output in the control system that affects the manipulated or controlled variable.
(Simrock, 2010).
Figure 29 Typical single-input single-output control system (Control theory, 2008)
Besides the TCMof a dual clutch transmission, another example of a sophisticated control system is a
car's cruise control,whichisa device designedtokeep the vehicle'sspeedata constantvalue chosen by
the driver.Inthisexample,the caristhe system, the controlleristhe cruise control,the outputisvehicle
speedandwhat'sbeingcontrolledisthe engine'sthrottle positionwhichdetermineshow much poweris
delivered by the engine.

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2.6.3 MAIN CONTROL TECHNIQUES
There are variouscontrol strategiesusedinthe worldof engineering today depending on the nature of
the system.Closed-loopcontrol isthe preferredtypeof control nowadaysasitallowsfeedback,inother
words, it allows the measurement of the system's output to be used to alter the control. The main
control techniques are summarized below:
 Adaptive control - Uses on-line identification of the process parameters, or modification of
controller gains. Was applied for the first time in the aerospace industry in the 1950s.
 Hierarchical control - Includesaseriesof devicesandcontrolling software in a hierarchical tree.
 Intelligent control - This type of control uses artificial intelligence (AI) methods such as: fuzzy
logic, bayesian probability, genetic algorithms and evolutionary computation.
 Optimal control - Consists of two main design methods namely; "Model Predictive Control"
(MPC) and "Linear-Quadratic-Gaussiancontrol"(LQG).Alongwith PID controllers, MPC systems
are the most commonly used control procedure in process control.
 Robust control - Deals with uncertainty in an explicit manner during controller design. Robust
control systems can normally cope with small differences between the true system and the
nominal model used for design.
 Stochastic control - If there is a degree of uncertainty in the model to be controlled, then this
type of control is effective as it takes random deviations/changes into account.
 Energy-shapingcontrol - A type of controllerdesign methodology that achieves stabilization of
mechanical systems,providingthe closed-loopwithaLangrangianorHamiltonianstructure with
a desired energy function.
 Self-organized criticality control - This method attempts to interfere in the self-organized
system's power distribution.
(Killian, 2005).

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2.6.4 TRANSMISSION CONTROL
A vehicle'stransmissionisacomplex mechanical systemwhichiscontrolledby the transmission control
module. The TCM utilizes a series of driver-selected and automatic adaptive strategies to control
transmissionoperationandmaintainvehiclesafety.The waythatit implementssafetyisthatitprevents
the driver from doing things that would damage the transmission such as: the reverse gear being
engagedathighforwardspeeds,manual downshiftingatexcessiveengine speeds. (Curriculum Training
Automatic Transmission G457059, 2005).
The "ZF 6HP26" transmission control system, which has been used in numerous production vehicles
including: BMW 3 and 5 series, Jaguar XK and XF, Rolls Royce Phantom and others, employs the newly
developed"AdaptiveShiftStrategy" (ASIS). In this system, the TCMinteracts with vehicle components
and obtains data regarding vehicle status, driver demands and operating conditions. According to
(Curriculum Training Automatic Transmission G457059, 2005), signals received by the TCMfrom other
systems include:
 Engine rpm and torque
 Engine oil temperature
 Accelerator pedal position
 Wheel speed
 Longitudinal and lateral acceleration
Detailedevaluationandprocessingof the signals above allows refined adaptive control of the system,
the TCM can respond to various driving situations by transmitting the refined shift strategy to the
hydraulic unit. This way the control system adapts to numerous variations in driving style and
conditions. (Curriculum Training Automatic Transmission G457059, 2005).
Figure 30 Electronically controlled AWD system (Volvo S60, 2010)

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VW DSG 02E - Mechatronics Module
Volkswagen's direct-shift gearbox 02E, looked at in detail in previous sections, uses a mechatronics
module as a transmission controller, comprising of an electronic control unit and an electro-hydraulic
control unit.All signalsfromothercontrol unitsinthe vehicle meetatthe mechatronics module, and all
processes are initiated and monitored from here. (Self-Study Programme 308, 2003)
The gear actuators are regulated via hydraulic means using pressure modulation valves, by the
mechatronics system. It also controls the flow of cooling oil from both the clutches, K1 and K2. The
mechatronicscontrol unitisa closed-loopsystem;whichusesadaptivecontrol to monitor the positions
of the clutches, main pressure and the positions of the actuators when a gear is engaged. (Self-Study
Programme 308, 2003)
Figure 31 Electronic control unit (Self-Study Programme 308, 2003)
The advantages of using a single compact control unit are:
 Most sensors are integrated within the module
 Electric actuators are located directly in the mechatronics module
 Electrical interfaces required are merged at one central connector
Due to the above measures,the mechatronics module is very compact with a lower weight and higher
electrical efficiency as the amount of wiring has been cut down. It performs a huge range of complex
functions,consideringhowsmall insizeitphysicallyis. Eventhoughthe system has been designed well
to cope well withdeviationssuchaschangingdrivingconditions,there have been a few reported faults
at high engine speeds. These are being looked into and the adaptive control strategies are be ing
improved. (Self-Study Programme 308, 2003)

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2.7.0 CHAPTER SUMMARY
Thischapter providesanindepthreview of some of the existentliteratureondual clutch transmissions,
including the history and development of the technology so far, and a detailed examination of its
operational theories. The main aim of this project is to design and test a controlled DCT model, and
therefore thischapteralso sheds some light upon control theories and transmission control strategies
used in the modern day. Volkswagen's Direct-Shift Gearbox 02E has been discussed in detail in the
previoussectionsof thischapter,it'sconstruction,functionalelements and principle of operation have
been explored. The environmental profile of these gearboxes over the entire life cycle is generally
enhanced, comparedwith automatictransmissions,due tohigherefficiency, reducedconsumption and
reduced emissions. Below is some quoted life cycle assessment data from VW's environmental
commendation (The DSG Dual-Clutch Gearbox Environmental Commendation, 2008), this shows the
benefits of using the DSG over the conventional automatic:
Factors in reduced fuel consumption:
a. use of dual clutch
b. intelligent transmission control
c. high efficiency
Significantly reduced fuel consumption:
a. 0.3 l/100 km less with 6-speed DSG
b. 0.8 l/100 km less with 7-speed DSG
Lower greenhouse effect over the entire life cycle:
a. reduction of 1.2 metric tons in carbon dioxide emissions with 6-speed DSG
b. reduction of 3.5 metric tons in carbon dioxide emissions with 7-speed DSG
Enhanced environmental protection and resource conservation:
a. 71 percent less oil required (7-speed DSG) – lower contributions to summer smog and
acidification
Torque convertertransmission 6-speedDSG® 7-speedDSG®
Numberof gears 6 6 7
Max. torque 320 Nm 350 Nm 250 Nm
Clutch - Wet Dry
Transmissionoil volume 5.8 l 6.5 l 1.7 l
Weight 85 kg 93 kg 77 kg
Consumptionadvantage Reference -0.3 l/100 km -0.8 l/100 km
Efficiency 83% 85% 91%
Table 1 VW DSG® Life cycle assessment (The DSG Dual-Clutch Gearbox, 2008)

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[ BLANK PAGE ]

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CHAPTER 3 - METHODOLOGY
3.1.0 PROBLEM STATEMENT
The purpose of this dissertation is to study the operational principles and analyze the performance
benefits of a dual clutch transmission system. The aim of this project is modeling, simulation and
analysis of a vehicle with a controlled 5-speed dual clutch transmission (DCT) using
MATLAB™/Simulink®. The resources that shall be used for the research and literature review of this
project will be SAE technical papers, relevant textbooks and authentic articles on the internet. The
methodology used to fulfill the purpose of this project, or in other words, the practical work shall be
carried out using the mathematical computing software "MATLAB™" by MathWorks® and its add-ons.
These add-ons which are namely: Simulink® and SimDriveline® shall be used in conjunction to design
and simulate the DCT vehicle model.
3.2.0 SYSTEM DEVELOPMENT
A lot of research was carried out initially, to determine the choice of software to achieve the desired
results afterthe projecttheme hadbeenselected.A combination of 3D modelling software Solid Edge
ST6™ and Msc Adams® was considered and looked into, so was a combination of Msc Adams® and
MATLAB™.Afterdeepconjecture,MATLAB™/Simulink® alongwithadditionalSimDriveline® components
was selected as the choice of software, to try and achieve the objectives of this project.
SimDriveline® is an add-on to the MATLAB™/Simulink® package which is designed for automotive
power-train applications. This package contains built-in blocks that represent vehicle driveline
componentssuchas:genericengine,vehiclebody,wheels& tiresandothermechanical elements.Using
this package provides access to vehicle component blocks, some of which can be very challenging to
create from commonSimulink® blocks. Beingable topurchase anduse this add-on also means, that the
DCT vehicle model couldbe made fairlyadvanced,one thatcandeliverresultswhich really reflect some
of the performance advantages that DCTs offer today.
Fuzzy logic had been the first choice of control strategies to implement for the design of the TCM, but
due to the intricacy of the model and time constraints the idea was dropped. Traditional control was
then applied to design the TCM, comprising a set of sensors and actuators to control the two clutches,
this is further elaborated in chapter 5.

Page | 38
3.3.0 LIMITATIONS
As Simulink® is a tool that I haven't ever used before, it would be a challenge for me to develop a
thorough understanding of this and learn how to use it to achieve the desired results within the short
span of time. Asa drive-trainof avehicle isverycomplex consistingof various components, it would be
difficult to make a model of this with the main focus being on the dual clutch transmission.
There isa riskof makingthe model toocomplicatedwhichwouldconsequently cause problems such as
drifting away from the main aim of the project and not being able to finish the work on time. On the
other hand, certain components have to be included for the model to work properly and deliver the
expectedresults. Thismodelwillbe based primarily on the VW Golf R32 DSG. However, due to the lack
of certaindata(parameters) andthe challengesfaceddue tocomplexityindesign,itwouldbe extremely
difficult to simulate the performance of the actual vehicle, exactly how it is in real life.
3.4.0 EXPECTED RESULTS
1) A fully working model of a vehicle with a 5-speed DCT, based on conventional control.
2) A smooth gear shifting process and reduced shifting times with the aid of the TCM.
3) A reductioninthe time delayduringgearselection anduninterruptedpowerflow from the engine to
the wheels, resulting in a smooth vehicle speed.
4) Graphs producedforvaluessuchas engine power,rpm, vehicle speed, currentgear state, torque and
throttle; on running the simulation for a fixed time period.

Page | 39
3.5.0 GEARBOX AND ENGINE DATA
VW Golf R32 DSG
Parameter Value
Engine size 3.0 L V6
Maximum power 184000 W
Speed at maximum power 6300 RPM
Vehicle mass 1538 kg
Frontal area 2.22 m2
Coefficient of drag 0.320
Tire radius 0.312 m
Effective tire rolling radius 0.308 m
Final drive gear ratio 3.07
Final drive gear's moment of inertia/side shaft
inertia
0.0002 kg.m2
Transmission gear ratios First-3.14, second-1.98, third-1.37, fourth-1.00,
fifth-0.76
Odd gear's moment of inertia 0.0023 kg.m2
Even gear's moment of inertia 0.0009 kg.m2
Intermediate shaft moment of inertia 0.008 kg.m2
Engine moment of inertia 2.7 kg.m2
Input shaft moment of inertia 0.004 kg.m2
Solid/output shaft moment of inertia 0.002 kg.m2
Hollow shaft moment of inertia 0.001 kg.m2
Table 2 Vehicle data (Kulkarni, Shim and Zhang, 2007)

Page | 40
[ BLANK PAGE ]

Page | 41
CHAPTER 4 - MODELLING THE POWERTRAIN
4.1.0 INTRODUCTION
The powertrain for my DCT vehicle model has been created using SimDriveline® blocks within the
MATLAB™ Simulink® environment. The powertrain consists of functional components in the form of
blocks (subsystems) such as: vehicle body, engine, engine control unit, input and output shafts,
transmission (DCT), TCM, wheels & tires. The engine data, vehicle dynamics, shaft inertias and
transmission ratios are based on the VW Golf R32 DSG 3.0 L V6 model, obtained from (Kulkarni, Shim
and Zhang, 2007).
Figure 32 Modern vehicle powertrain (Akehurst, 2007)
The powertrain in a modern vehicle consists primarily of:
– The Engine (showninorange),typicallydieselorgasoline,but other combustion concepts exist or
are on the horizon.
– The Transmission (shown in green), either a manual, automatic, continuously/infinitely variable
transmission, DCT, or a hybrid powertrain with additional electrical components.
– After-treatment Systems such as catalysts or particulate traps (shown in blue).
– Electronic Control Unit (ECU) and control software.
Quoted material: (Akehurst, 2007).

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4.2.0 VEHICLE DYNAMICS
For thiscomponent,the standardvehiclebodyblockfoundunderSimDrivelineinthe Simulink Library is
used:
Figure 33 Vehicle body block on Simulink
Vehicle Data - VW Golf R32 DSG
Parameters Value Units
Mass 1538 kg
Number of wheels per axle 2 -
Horizontal distance from CG to
front axle
1.533 m
Horizontal distance from CG to
rear axle
1.515 m
CG height above ground 0.73 m
Frontal area 2.22 m^2
Drag coefficient 0.320 -
Initial velocity 0 m/s
Table 3 Vehicle body block parameters
The valuesinthe table above are basedon real vehicle parametersandhave beenobtainedfromthe
VW Golf R32 DSG performance review andTable 2.

Page | 43
4.3.0 ENGINE
The engine subsystem consists of the generic engine block found under SimDriveline and a range of
sensors built using common Simulink® blocks.
Figure 34 Engine subsystem closed view on Simulink
The SPS converter block converts a unit-less Simulink input signal to a physical signal. The PS2S
converterblockconverts the physical inputsignal to a Simulink output signal which is displayed on the
scope as engine power in the units of HP.
Figure 35 Engine subsystem expanded view on Simulink

Page | 44
Engine Data - VW Golf R32 DSG
Parameters Value Units
Engine Torque
Model parameterization Normalized3rd-orderpolynomial matched to peak power -
Engine type Spark-ignition -
Maximum power 184000 W
Speedat maximum power 6300 rpm
Maximum speed 7000 rpm
Stall speed 200 rpm
Dynamics
Inertia 2.7 kg*m^2
Initial velocity rpm0 rpm
Engine time constant 0.2 s
Initial normalized throttle 0 -
Limits
Speed threshold 20 rpm
Fuel Consumption
Fuel consumption model Constant per revolution -
Fuel consumption per rev. 25 mg/rev
Table 4 Generic engine block parameters
The valuesinthe table above have been obtained from the VW Golf R32 DSG performance review and
Table 2.

Page | 45
4.3.1 ENGINE CONTROL UNIT
The ECU controls the engine rpm and throttle. This subsystem was built using a series of common
Simulink blocks such as "gain" and a switch that inhibits the engine's idle speed controller when the
normalizedthrottledemandexceeds0.02.The maincomponentof thissubsystemisthe "InverseEngine
Map", this converts measured speed and demanded torque into normalized throttle demand.
The block parameters for the inverse engine map are:
Engine maximum power (W) - 184000
Engine speed at maximum power (rpm) - 6300
The "Goto" block in red sends a signal to a scope which displays the engine's normalized throttle.
Figure 36 Engine control unit expanded view on Simulink

Page | 46
4.4.0 SHAFTS
InputShaft
The inputshaftprovidesmeasuredtorque tothe transmission.Thissubsystemconsistsof a"Rotational
Damper"and a "Rotational Spring", these provide torque whichismeasuredbythe "Ideal Torque
Sensor".The SPSblockconvertsthe physical inputsignal fromthe torque sensorintoaSimulinkoutput
inthe unitsof Nmwhichis displayedasmeasuredtorqueonthe scope.The inputshaftinertiaisevenly
splitbetweenJ1and J2, the value of thisinertiahasbeenobtainedfrom Table 2.
Figure 37 Input shaft expanded view on Simulink
Input Shaft Data
Block Parameter Value Units
Rotational Spring Spring rate 3000 N*m/rad
Rotational Damper Damping coefficient 10 N*m/(rad/s)
Inertia Inertia 0.004 kg*m^2
Table 5 Input shaft subsystem block parameters
The valuesforthe springrate and dampingcoefficientare pre-definedandbuiltin parametersby
Simulink®,nochangestothese have beenmade.

Page | 47
Output Shaft
The outputshaft delivers torque fromthe transmission tothe wheels.Thissubsystemconsistsof a
"Rotational Damper"anda "Rotational Spring" whichare connectedparalleltoeachotherwithinertia
on eitherside. The outputshaftinertiaisevenlysplitbetween the twoinertiablocks andthe value of
thisinertiahasbeenobtainedfromTable 2.
Figure 38 Output shaft expanded view on Simulink
OutputShaftData
Block Parameter Value Units
Rotational Spring Spring rate 10000 N*m/rad
Rotational Damper Damping coefficient 20 N*m/(rad/s)
Inertia Inertia 0.002 kg*m^2
Table 6 Output shaft subsystem block parameters
The values forthe springrate and dampingcoefficientare pre-definedandbuiltinparametersby
Simulink®,nochangestothese have beenmade.
Side Shafts
The side shaftsare modelled inthe formof an inertiablockconnectedtothe Wheels&Tiresblock.The
value of thisinertiais0.0002 kg*m^2 and this has beenobtainedfromTable 2.

Page | 48
4.5.0 TRANSMISSION
The transmissionsubsystemis the focal point of the powertrain model, this is a five speed dual clutch
transmissioncomprisingof two sets of gears (odd and even) controlled by the two clutches (K1 and K2
respectively)andcorrespondingslipsensors (slipsensor1and slipsensor2).The SPSconverter converts
the unit-less input pressure signal to a physical signal for the clutch.
The shaft inertias are as follows:
Shaft 1 inertia - 0.0023 kg*m^2
Shaft 2 inertia - 0.0009 kg*m^2
Intermediate shaft moment of inertia - 0.008 kg*m^2
Figure 39 Transmission subsystem expanded view on Simulink
All different values of inertia are real and have been obtained from Table 2.

Page | 49
Clutches K1 and K2 parameters (built in and pre-defined by Simulink®)
Parameter Value Units
Geometry
Effective torque radius 130 mm
Numberof frictionsurfaces 4 -
Engagementpistonarea 0.001 m^2
Friction
Kineticfrictioncoefficient 0.3 -
Staticfrictioncoefficient 0.31 -
De-ratingfactor 1 -
Clutchvelocitytolerance 0.001 rad/s
Engagementthresholdpressure 1 Pa
Table 7 Clutches K1 and K2 parameters
Oddgears
The odd gear momentof inertiais0.0023 kg*m^2. A busselectorisusedtolinkthe odd& evengearsets
Figure 40 DCT odd gears expanded view on Simulink

Page | 50
Even gears - Even gears moment of inertia is 0.0009 kg*m^2, obtained from Table 2.
Figure 41 DCT even gears expanded view on Simulink
Gear ratios used (based on Table 2)
Gear Follower (F) to base (B) teeth ratio (NF/NB)
1 3.14
2 1.98
3 1.37
4 1.00
5 0.76
FDR & losses 3.07
Table 8 DCT gear ratios including final drive ratio and losses
Dog clutchdata (pre-defined Simulink® values)
For dog clutches 1-5
Maximumtransmittedtorque 1000 N*m
Clutchteethmeanradius 50 mm
Table 9 Dog clutch parameters

Page | 51
4.5.0 WHEELS & TIRES
The wheelsandtiresof the vehicle are modelledusingthe standard"Tire (MagicFormula)"SimDriveline
blockfromthe Simulinklibrary.The twoblockslabelled"S"connectedtothe frontand rear tires are slip
sensors which obtain the front and rear wheel slip readings, which are then displayed on scopes.
Figure 42 Wheels & tires expanded view on Simulink
Tires data (dimensions and dynamics pre-defined by Simulink®)
Tire magic formula coefficients are load dependent and are calculated automatically by Simulink
Tire nominal vertical load 4000 N
Rolling radius 0.308 m
Tire inertia 0.5 kg*m^2
Coefficient of rolling resistance 0.015 -
Velocity threshold 1e-3 m/s
Table 10 Wheels & tires parameters

Page | 52
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Page | 53
CHAPTER 5 - TRANSMISSION CONTROL MODULE DESIGN
5.1.0 INTRODUCTION
Thiswas the final stage andarguablythe most challengingdesignphase of mySimulink® vehicle model.
There are several reasons behind this but mainly due the technical difficulties experienced whilst
programming,asa result of the complex structure of the DCT. The engagement and disengagement of
the clutches K1 and K2 and the gear shifting process needs to controlled, in order to deliver realistic
results for engine power, torque, throttle and vehicle speed. Various control mechanisms were
explored, and in the end I decided to use traditional control comprising common mathematical
functions used in Simulink® block methods.
Figure 43 TCMexpanded view on Simulink

Page | 54
5.1.1 HOW IT WORKS
The "shiftstate"and "gearshiftdemands"subsystemssendsignals(gear state, next gear, P1, P2) to the
clutch control blocks. These control blocks in turn, send torque and clutch pressure demand signals
(Tdem& Pdemrespectively) tothe clutchesK1 and K2, which then engage or disengage to perform the
required gearshift.
If gear state is 1st, 3rd or 5th, the clutch K1 will be locked and K2 opened. If gear state is 2nd or 4th,
then clutch K2 will be locked and K1 opened.
If an up-shift is required and U/D is 1.5 or 3.5 (1st to 2nd gear or 3rd to 4th gear respectively), or if a
down-shiftisrequiredandU/Dis 2.5 or 4.5 (3rd to 2nd gear or 5th to 4th gear respectively), then clutch
K1 will be shifted to K2.
If a down-shiftisrequired and U/D is 1.5 or 3.5 (2nd to 1st gear or 4th to 3rd gear respectively), or if an
up-shiftisrequiredandU/D is 2.5 or 4.5 (2nd to 3rd gear or 4th to 5th gear respectively), then clutch K2
will be shifted to K1.

Page | 55
5.2.0 SHIFT STATE
The "shift state" subsystem is the most functionally significant element of the TCM, and all the other
subsystems within the controller are connected to it as displayed in Figure 43. This subsystem
demonstrates or rather carries out the controlled gear shifting process based on vehicle speed, clutch
pressure andengine rpm.All the possible up-shifts and down-shifts are modelled in the form of block
subsystemsas shown in Figure 44, with G1->G2 being an up-shift from 1st gear to 2nd gear and G2->G1
being a down-shift from 2nd gear to 1st gear, and so on. The blocks representing up-shifts consist of
masked subsystems which calculate the vehicle speeds at which the gear changes should take place.
Input U/D is positive if shifting up, and negative if shifting down. Input C goes high when a shift takes
place. Hence E goes from zero to 0.5 when a shift to a higher gear is completed, and from zero to -0.5
whena shifttoa lowergear completed. Shifts between gears are denoted by G (U/D) taking fractional
values,forexample whenshifting up from 1st to 2nd gear, G is 1.5 and when shifting down from 5th to
4th gear, G is 4.5.
Figure 44 TCMshift state expanded view on Simulink

Page | 56
5.3.0 GEAR SHIFT DEMANDS
The "gear shiftdemands"subsystem receives gearstate andpressure signalsforthe engagement of the
clutches(P1 and P2 for clutches K1 and K2 respectively). It also receives an input signal from the "shift
state"subsystemforthe nextgear number.If nextgearnumberchangesandclutch K1 is not engaged, a
pulse iscreatedandtransmittedtoeither Actuator 1, 3 or 5 depending on whether the next gear is 1st,
3rd or 5th respectively. If nextgearnumberchangesandclutchK2 isnot engaged,apulse iscreated and
transmitted to either Actuator 2 or 4 depending on whether the next gear is 2nd or 4th respectively.
The bus creator (boldvertical rectangle) hasgot five inputs in the form of actuator demands (U1-U5), it
createsand transmitsa single output bus signal "Gdem" which denotes 'gear demand' to the DCT. Two
bus selectors are used in the DCT, one each for the odd and even gear sets (as displayed in figures 4-9
and 4-10). These accept the signal "Gdem" from the bus creator as input and send output signals (U1-
U5) to the respective actuators, which in turn engage the required gear.
Figure 45 TCMgear shift demands expanded view on Simulink

Page | 57
5.4.0 COMPLETE VEHICLE MODEL
The transmission control module has been connected to the rest of the elements of the vehicle
powertrain,and the completed vehicle model is shown in Figure 46 below. We shall find out whether
thismodel worksproperlyornotand discussresultsduringthe testingstage. The simulationcannow be
run usingthe variable-stepode23t(mod.stiff/Trapezoidal) solver,thisshall be done in the next chapter
(testing & results).
Figure 46 Complete vehicle model closed view on Simulink

Page | 58
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Page | 59
CHAPTER 6 - TESTING, RESULTS AND DISCUSSION
6.1.0 SIMULATION CONDITIONS
The DCT vehicle model shall nowbe simulatedinthe Simulink®environment, driving on a level road. In
order to demonstrate all the possible lower to higher gearshifts and the vehicle acceleration, the
simulations will be run for a time period of 100 seconds, this will allow ample time for the vehicle to
reach 5th gear. The simulationresultsshall be displayed onthe scopes, in the form of individual graphs
for the following values:
 Engine power (W)
 Engine speed (RPM)
 Vehicle speed (mph)
 Normalized throttle
 Gear shifting process
 Demanded & achieved torques (Nm)
 Gearbox shaft slip (RPM)
 Tire slip
The model configurationparametersonSimulink® are summarized below, these can be accessed from
the main taskbar under "Simulation".
Simulation time (s)
Start time: 0.0 Stop time: 100.0
Solver settings
Solver: ode23t (mod. stiff/Trapezoidal)
Type: Variable-step
Max step size: 0.1
Min step size: auto
Initial step size: auto
Relative tolerance: 1e-3
Absolute tolerance: auto
Data refine factor: 5

Page | 60
6.2.0 SIMULATION RESULTS
The vehicle model shallnowbe simulateddrivingonalevel road,the simulationresultsare displayed in
the graphs below, where the value being measured is plotted against time.
Figure 47 Sim1 Engine power graph (HP)

Page | 61
Figure 48 Sim1 Engine speed graph (RPM)
Figure 49 Sim1 Vehicle speed graph (mph)
Figure 50 Sim1 Gear state graph

Page | 62
Figure 51 Sim1 Normalized throttle graph
Figure 52 Sim1 Demanded & achieved torques graph (Nm)

Page | 63
6.3.0 DISCUSSION OF RESULTS
Engine power (HP)
From the engine powergraph(Figure 47),we can see that during the simulation period of 100 seconds,
the engine produces a maximum of approximately 37.55 hp or 28 kW. This is one-fifth of the engine's
maximumpower,the losseswillbe minimalasthere isnotorque converterandhence,better efficiency.
The smoothline inthe engine power(HP) graphsuggestsuninterrupted power flow from the engine to
the transmission whichresultsinamore uniform accelerationascomparedtoa conventional automatic.
As discussedearlier,thisisone of the mainadvantagesof DCT'sovertraditional manual/automatic cars.
N.B.For a vehicle withaconventional manualtransmission,the engine power graph would look similar
to the engine RPMgraph due to interruptionsinengine powertransmissionwhile the clutch is engaged
and gears are shifted.
Engine speed (rpm)
In the engine rpmgraph (Figure 48),we can see thatthe engine reachesamaximumspeedof just under
4500 RPM. At t=0, a high throttle is applied by the driver and the engine responds by increasing its
speed.Asthe vehicle then accelerates quickly, the engine gains speed reaching nearly 4000 RPMuntil
about t=5, at which an up-shift from 1st to 2nd gear occurs. Characteristically, the engine speed
suddenlydrops,itthenincreasesagainandreaches itsmaximum (approx. 4500 RPM) at t=13 where the
2-3 up-shift occurs. Once again, as the transmission has shifted to a higher gear (3rd), engine speed
drops suddenly and then increases. At t=24, another gear change takes place (3-4), the engine again
losesspeedandthenacceleratesagain,ataslowerrate thistime.The final up-shifttakesplace atnearly
t=54, where the engine drops speed (a smaller decrease this time to just under 3500 RPM), and then
stays almost constant as the vehicle stays in top gear.
Vehicle speed (mph)
From Figure 49, we can see that the vehicle speed reaches a maximum of nearly 67 mph in the time
periodof 100 seconds.The velocitycurve isquite smooth,thisdemonstratesreducedshiftingtime anda
more dynamic acceleration, which is the main purpose of using a DCT.
A speed-time graph demonstrating the acceleration of a conventional manual for a fixed time period,
will displaysuddendropsandincreasesinvehicleaccelerationatshiftpoints.The shiftpointiswhere an
up or downshiftoccurs, and thisiswhere engine powerdeliveryisinterruptedforashort periodof time
whichis known as the shifting time. For skilled drivers this can be between 0.3-0.5 s, which is why the
velocity curve for a manual vehicle would not be a smooth one.
A DCT such as the one developedinthismodel,candelivershifttimesof 0.1sand under,and this can be
depictedfromthe nearuniformacceleration displayed in Figure 6-3. The model can be simulated for a
much longerperiodof time, to determine at what instance the vehicle reaches its top speed of nearly
186 mph (calculated using vehicle and engine data for this model).

Page | 64
Gear state
The gear state graph in Figure 50 displays the gearshiftingsequence asthe vehicle acceleratesfrom 0 to
67 mph, the vehicle reaches 5th gear after 55 seconds and remains in this gear until the end of the
simulation. We can see thatthe shifttimesare verysmall (fractionsof a second), whereas for a vehicle
witha manual transmissionthe linesjoining the gear numbers would be sloped; demonstrating longer
shiftingtimes. The gearstate graphfurtherverifies and validates the results obtained from the vehicle
speed graph.
Normalizedthrottle
At t=0, the driverstepstoa throttle of justover0.25, the engine respondsimmediately by increasing its
speed to nearly 800 RPM. The throttle then drops to just under 0.25 and then stays nearly constant
around the 0.23 mark, this demonstrates a near uniform acceleration which is also portrayed in the
vehicle speed graph.

Page | 65
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Page | 66
CHAPTER 7 - CONCLUSIONS
7.1.0 CONCLUSION
Dual clutch transmissions provide the comfort and convenience of an automatic, they are the first
automatics with up to 10% better fuel economy and improved performance than a conventional
manual.The dual clutch transmissionisalsothe onlyautomatictransmissionwellsuitedforhighrevving
standard engines, gasoline and diesel alike, and carries wide development prospects. Considering all
these benefits, we can expect DCTs to rapidly gain market share and evolve into a mainstream
transmission in the near future. (Matthes, 2005).
From the results inthe previouschapter,itcanbe seen that the model is behaving like an actual motor
vehicle equippedwithaDCT.The transmissioncontroller,withthe aidof the "shiftstate"and"gear shift
demands" subsystems, carries out its job of engaging/disengaging the clutches K1 and K2 at the right
time resulting in controlled and timely gearshifts. The simulation results; the gear state graph in
particular,indicatesthatthe TCMdesigned forthismodel reflectsthe dynamic shifting characteristic of
DCTs.
Most importantly, DCT model developed in this project clearly fulfils its main purpose of delivering
uninterrupted power flow from the engine to the wheels, resulting in a reduced shifting time.
Furthermore,the vehicle speedissmoothandstable,andthe accelerationquite dynamic. This is clearly
proven by the engine power, gear state and vehicle speed graphs in the previous chapter.
Belowisa brief summaryof the objectives that were defined at the start of this project and how these
have been achieved.
1. Models of the individual components of the vehicle power-train in the form of subsystems
(Engine, ECU, vehicle body, DCT, shafts and wheels) have been created using Simulink® and
SimDriveline® blocks.
2. The transmissioncontrol module hasbeendesignedsuccessfully resultinginasmooth gearshift
and reduced shifting times.
3. The power-traincomponents(subsystems) have been assembled into a complete and working
vehicle model.
4. The vehicle model has been simulated in the Simulink® environment for a fixed time period.
5. Simulationresultshave beendisplayedinthe form of graphs for engine speed, engine power,
vehicle speed, gear state, normalized throttle, demanded & achieved torques,
6. The results have been evaluated and discussed .

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