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VOL. 7, ISSUE 2, APR - JUNE 2014
POWERTRAIN
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History of Powertrain
Basics of Transmission
Hydraulic Hybrid
Hybrid Powertrain: Revolo
Alternate Fuel Powertrain
Powertrain Components: Variable Valve LiftSensors in Powertrain
Safety Features in Powertrain
Selecting Powertrain Technologies for the Future
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Colophon
TechTalk@KPIT is a quarterly journal of
Science and Technology published by
KPIT Technologies Limited, Pune, India.
Dr. Vinay G. Vaidya
CTO,
KPIT Technologies Limited,
Pune, [email protected]
Kanchan Chivate
Reenakumari Behera
Kailash Shrinivasan
Smita Nair
Mindsye Communication, Pune, India
Contact : 9673005089
The individual authors are solely responsible
for infringement, if any.
All views expressed in the articles are those
of the individual authors and neither the company
nor the editorial board either agree or disagree.
The information presented here is only for giving an
overview of the topic.
For Private Circulation Only
TechTalk@KPIT
Guest Editorial
Chief Editor
Editorial and Review Committee
Designed and Published by
Suggestions and Feedback
Disclaimer
Anup Sable
Senior VP -
Automotive and Engineering,
KPIT Technologies Ltd.
Pune, India
Pranjali Modak
Priti Ranadive
Aditi Sahasrabudhe
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Editorial
Scientist Profiles
Book Review
Articles
Guest Editorial 2
Anup SableEditorial 3
Dr. Vinay Vaidya
'Karl Benz' - 49
Smita Nair
Where Good Ideas Come From 37
The natural history of innovation
Steven JohnsonPriti Ranadive
4
Mayurika Chatterjee
10
Sushant Hingane
16Kailash Srinivasan and Milind Potdar
20
Sachin P. Pandit and Nandulal Kushabhau Gavali
26
Samir Sattigeri and Kiran Dakle
32
Subodh Pachghare
38
Shweta Kabade
44
Priyank Vijapur and Santosh Nalanagula
Ravi Ranjan and Naveen Manuel
History of Powertrain
Basics of Transmission
Hydraulic Hybrid
Hybrid Powertrain: Revolo
Alternate Fuel Powertrain
Powertrain Components: Variable Valve Lift
Sensors in Powertrain
Safety Features in Powertrain
Selecting Powertrain Technologies for the Future 50
Contents
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Guest Editorial
It is indeed a great pleasure for me to get this opportunity to write an editorial on Powertrain.
Powertrain as a domain is very close to my heart since childhood days. Memories are still fresh of
discovering an ethanol engine in the scraps market and struggling to get it to work while in
secondary school and then meeting another teenager who had created steam engine at home
using pressure cooker as the boiler to generate the steam.
No one can question the impact that the invention of powertrain has had on humanity. From the
initial steam powered vehicles to the modern gasoline and diesel powered engines, human beings
owe a lot to the power of this technology towards bringing us a better quality of life.
In the last 125 plus years, powertrains have made a progress from purely mechanical system to an
electronically assisted mechanical system (mechatronics), to very complex software driven
electronic systems. Today, thousands of parameters are internally computed using software in real
time to measure and then deliver accurately the fuel to the engine so that the engine delivers us the
best (or more appropriately the optimum) fuel efficiency bundled with performance and emissions.
Today more and more innovation is happening in connecting the powertrain via telematics to
external world to bring in even more fuel efficiency, safety and emission control.
While there has been a tremendous impact of powertrain on our lives in a positive way, it has also
now brought in a set of issues. Modern cities are plagued with traffic problems and as a result the
vehicles are spewing harmful gases and particulates while they stall in the traffic or move at a snail's
pace. This throws up challenges for innovators and we all know that cleaner options like the electric
vehicles are making slow but steady progress to replace the conventional powertrain and solve this
pollution problem.
While the electric vehicles offer a solution to the environmental issues, today the commercial
viability of the electric vehicles is questionable, largely due to the cost of the batteries. There have
been, some evidence of success in pockets that indicate that electric technology is here to stay and
shape the future of the mankind.
To supplement the electric powertrain there needs to be a lot of innovation going into the generation
of electricity in cleaner ways. On the horizon we have other technologies like fuel cells which are
commercially unviable now but present a great future for cleaner transportation.
Overall, faster transportation is here to stay.So, go ahead and enjoy this issue of TechTalk, where
you can explore this history of powertrain and also take a look at what future has in store for us.
Senior VP -Automotive and Engineering,KPIT Technologies LtdPune, India.
Anup Sable
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Dr. Vinay G. VaidyaCTOKPIT Technologies Limited,Pune, India
Editorial
Please send yourfeedback to :[email protected]
TechTalk@KPIT, Volume 7, Issue 2, 2014
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Eric Morris, a grad student at UCLA in 2007, in his well-known master's thesis, wrote about the state of New York
and London during the late 1800s. One of his articles on the subject is aptly titled, 'From Horse Power to
Horsepower'. In the article, he mentions the top problem discussed in the international town planning conference
in 1898 in New York. To our surprise, that problem was getting rid of horse manure. One can only imagine the
euphoric feeling of many when Karl Benz invented an internal combustion (IC) engine in 1879, which led to thefirst automobile. Ironically, the invention of the automobile was thought to have solved the problem of pollution,
since automobiles would eliminate horse manure. Karl Benz was granted a patent on automobile in 1886. Benz
truly revolutionized transportation for masses.
In less than two decades after the grant of the first patent on automobile, came the flying machine at Kitty Hawk in
December 1903. This was another major event that revolutionized transportation around the globe. It is quite
interesting to compare the history of advancements in automobiles with those in aircrafts over the last century.
Advancements in automobile came from different directions. It included increase in horsepower, manufacturing
processes, mass production methods, auto transmission, tires, shock absorbers, comfort, communication, GPS,
as well as infotainment. From combustion side, we have come a long way to completely electronic ignition as well
as improving efficiency all the way to mid-30 percent. Starting with a speed of 4 km/h, we have now reached wellover 400 km/h.
Aircrafts have also made lot of progress. Starting with propellers, airplanes moved on to using jet engines. This
change led to breaking the sound barrier. From propellers to jets to supersonics is one way to look at it. The other
is to see increase in size and capacity to carry load. As technology advances, we lose the charm of new
technology and we start accepting it as the only way of life. Out of that acceptance, mental limits and boundaries
are built. This is where innovation stops.
Let us dream of a completely new era with new designs and no baggage of technology barriers.
The first dream is about an automobile. Let us come up with the following specifications for this dream car. It
should have an IC engine with more than 60% efficiency. It should have a range of 1500 km. It should cost lessthan 2 cents per km. The expectation for the top speed is 100 kmph. It should be 50% better for the environment
than present day cars.
The second dream is about an aircraft. We are going to be equally hard on the specifications. The first barrier that
we want to break is that of needing a runway to takeoff. Thus, the specifications would be as follows. It should be
able to takeoff without a runway. It should be able to carry 10000 kg of load. It should be able to carry 50
passengers. It should be able to stay up in the air without refueling for more than 3 weeks. Top speed should be
160kmph. It should be 70 % more environmentally better than a cargo airplane.
Which one of these would you say is impossible? Chances are good that you would say that the second dream is
less likely to come true. However, the good news is that second dream has come true. On Feb. 28, 2014, this
aircraft was unveiled by Hybrid Air Vehicles Ltd. This aircraft is 300ft long and is 60ft longer than the biggestairliners.
If the impossible is possible, how about taking the challenge of the first dream and making it a reality? We have not
seen much in the past 125 plus years in terms of radical breakthrough in the IC engine design. Isn't it time that we
make a major impact on IC engine efficiency and go beyond 60? Any takers for the challenge? Where have all the
innovators gone?
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Journey of thePowertrain Technology
Mayurika Chatterjee
Automotive, Allied Engg.CREST,KPIT Technologies LimitedPune, India
Areas of Interest
Mechatronics & Control Systems
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Figure 1: Today's 'Wheeled Motor Vehicle' [Ref.1]
The central character of this article is a'wheeled motor vehicle' [Fig.1], which is self-propelled and carries passengers. This articlecovers the journey of this character. Theinteresting part is that ever since the 'wheeledmotor vehicle' is conceptualized, it hasevolved through decades. It took almost100,000 patents around the world to create
the modern automobile that we see around ustoday.
Going through the history, it can be said thatthere are major three aspects which broughtabout the evolution in the powertraintechnology, viz. government policies, publicdemands and the technology advancements.
I. Introduction
The concept of mobility is very important partin human evolution. During earlier times,people used animal carts as a means oftransport that was later replaced by the steamengine automobile. With passage of time andother technological advancements, mankind
demanded new and improved means ofmobility. Now, just traversing the distance wasnot the only intent but other factors such as thetravel cost, environmental impact, etc. wererequired to be considered. This resulted innew expectations from various domains of theautomotive industry.
One of the most important aspects of thesesystems was to connect a power source to thewheels of the carriage that carried people.This, as the name indicates, is basically thepowertrain system of a vehicle, a system that
powers the wheels. It consists of the parts thatproduce energy (then horse, now engine),some part that converts the energy to torque(then linkages, now transmission gears) andlastly, the part that sends that energy to theelement (drive shaft/mechanical linkages towheels) which ultimately propels the vehicle.
This article covers the evolution of thepowertrain systems including how and whythe powertrain technology has changed overtimes. Multiple scenarios and renewedexpectations discussed in the subsequentsections of the article led various technologies
to come together to make these changeshappen.
II. Let's move!
The story begins in 1769, with the advent ofsteam engine automobiles. In the early 19th
century, a variety of vehicles powered bysteam were on road, such as steam cars,buses and steam rollers [3]. It was a simplemechanical technique which did not need anysort of transmission mechanism. However, the
Figure 2:Cugnot's Steam Locomotive, 1769 [Ref. 2]
steam engine vehicles did not take off well.The design did not prove to be an ideal choicefor a road vehicle due to its high maintenancecost and its requirement for greater space.Other impact factor was the labor costs forcoal handling. The 'technology' did not helpmuch either with below par machiningtechniques. Its high power to weight ratio andthe slow start process (since steam needed tobe pressurized up to a certain amount for avehicle to start)were not suitable features for a
road vehicle. Cugnot built the first steam-powered self-propelled tricycle in the year1770. Next, a French inventor improvedCugnot's design and is also known to be thefirst one to invent differential gear [4]. In 1789,Oliver Evans was granted the first U.S. Patentfor a steam powered automobile [4].
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Other aspects that affected the usage ofsteam engine were the 'government policies'and the 'public demands'. People experiencedthat the steam engines caused road damage,scared the horses (Yes! Pretty much a big dealat that time), blocked narrow lanes anddisturbed the locals at night due to their loudnoise. Hence, due to public demands and
other safety concerns, 'The Locomotive Act'(1865), famously known as the 'Red Flag Act'was passed. This included maintaining aspeed limit of 4mph (2mph in towns), apartfrom the compulsory presence of a man onfoot who led the vehicles by swaying a red flagand blowing a horn. This, along with thetechnological limitations discouraged itsusage in road transport.
However, until the early 20th century, thesteam-powered automobiles were beingcontinually developed in different parts of the
world. Between the years 1873 to 1883,Amedee Bollee Sr. designed and built manyadvanced steam cars which included basictransmission units such as shaft drive to thedifferential [4]. In the late 19th century, anothertechnology, the powerful petrol engines cameinto being. This was the last straw in thealready limping steam technology whichultimately ended the steam engine era.
A n o t h e r a s p e c t o f ' T e c h n o l o g yadvancements', plays an important role in thissect ion . I t i s these techno log ica ladvancements that helped make internalcombustion engine (ICE) technology assuccessful as it is today. From a labexperimental set-up to its vast usage in majorapplications (including in automotive), it hasset a strong foot-hold in the market.Experiments during the early 19th centurywere not successful due to lack of suitablefuels. In 1807, Swiss inventor, Francois Isaacde Rivaz invented an ICE using mixture ofhydrogen and oxygen as fuel and with electric
ignition. He patented it in 1807 and in 1808 hecreated the 'world's first internal combustionpowered automobile' [5]. But his design wasunsuccessful. However, the experiments tocreate successful ICE design continued. JeanJoseph tienne Lenoir patented a double-acting, electric spark-ignition internal
III. Rise of a long shadow
combustion engine fueled by coal gas in theyear 1860 [5].Subsequently, in the year 1863,Jean Joseph tienne Lenoir improved hisengine design by using petroleum as fuel andadding a primitive carburetor. This vehiclecreated history by completing a fifty-mile roadtrip [5].This design and de Rochas' designs ofa four stroke engine was improved by the
German engineers, Eugen Langen andNikolaus August Otto in the year 1866.
A decade later, Otto patented a four-strokeengine, popularly known as the "Otto cycle".Taking it one step further, in 1885, the duo ofGottlieb Daimler and Wilhelm Maybachdesigned a small, fast and light weight enginewith a carburetor through which gasoline gotinjected into a vertical cylinder [5]. Later, as it isgenerally known, Karl Benz was granted apatent on his design of a gas-fueled car in theyear of 1886. Several types of engines were
being developed and improved, like the two-stroke, four stroke, etc. This basically madethe system compact which resulted in a lowweight to power ratio. The commercial viabilityalso helped in its popularity. Also, dieselpowered engine was in development and inthe year 1893, Rudolf Diesel received a patentfor his engine design based on compressedignition.
Still, the powertrain technology had a long wayto go to be called as a successful technology.It had its own problem of inefficient engine
power transmission and thus the transmissionsystem (gears, clutches etc.) was invented [6].The transmission system allowed transferringthe engine power efficiently to the wheels, asper the requirement. The first one was manualtransmission, where the gears are changedmanually by the driver, as per the powerdemand. The first transmission invented by W.H. James in 1832 was a three-speedtransmission [7]. The modern transmission isattributed to the French inventors, Levassorand Panhard, who fitted their design to thePanhard motor car in 1895. The semi-
automatic type transmission becameavailable since 1937 and where known as 'theAutomatic Safety Transmission'. Thisfacilitated easy shifting of gears and hence aneasier driving. This system included the usageof planetary gears and conventional frictionclutch [8].
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Figure 3 : Transmission system [Ref.9]
In parallel, in the electronics domain,technologies such as solid-state electronicsand the control theory were advancing. Thesetransitions allowed the usage of refinedelectronic systems to be used in solvingautomotive control and instrumentationchallenges. Until today, large scale applicationof control theory and modeling is observed inthe development of powertrain system whichstarted during the 1980s. The transmissionsystem also gained with such technologicaladvancements. For example, the automatictransmissions became a reality. The first true
automatic transmission developed by GMengineer was included in the 1948 Oldsmobileand subsequently, Ford installed theautomatic transmission design by BorgWarner in the 1950[8]. Today, the transmissionsystem is also electronically controlled and it isstill evolving.
For a very long time, IC engines ruled theindustry and many technologies were lost in itsshadow. But, change is inevitable. Increasingpollution and global warming was a majorconcern and people demanded better and
cleaner technologies. IC/diesel engineshandled significant changes to regulateemissions, but this did not stop the automotiveindustry to call upon a long lost technology-The Electric car.
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IV. Revenge of an Electric car
For many, it might be a surprise that electricca rs we re ac t ua l l y bu i l t o r evenconceptualized before 21st century. In theyear 1837, Robert Davidson invented galvaniccell powered electric vehicle.
Plante. This led to further developments inelectric vehicle design as the rechargeablebattery allowed electricity storage on board.Andreas Flocken invented the first electric carin 1888, popularly known as the 'FlockenElektrowagen'. It was quite popular betweenlate 1800s and early 1900s, since it providedease of operation and comfort as opposed to
the gasoline cars available at that time.But, as mentioned earlier, 'technologicaladvancements' in the IC engine techniques,soon took over the electric car. The petroleumindustry too prospered during that time andbecame almost a monopoly in the market.Also, petrol vehicles could be quickly refueledand were cheaper as compared to the electriccar. These factors ultimately did not let electricpropelled vehicles sustain and they were lostin the dark.
In the late 1990s, the electric vehicle came into
the picture again when GM introduced anelectric vehicle known as the EV1. Thisbecame hugely popular due to its reasonableprice and performance. Later, 'The CaliforniaAir Resources' passed a mandate for theautomotive manufacturers directing them toproduce a fixed amount of electric vehicle peryear [10]. But this was short-lived due to somenegative publicity and pressure from large oilcorporations (which saw electric vehicle as athreat). Thus, the electric vehicles werescrapped and again lost its place. In themeantime, research on hydrogen car
technology began hoping to find another cleanalternative fuel technology. The technologyhas feasibility issues and currently extensiveresearch is going on to make it a commercialreality.
But, as fate would have it, the electric vehiclescame back with vengeance. The veryadvantages of the petrol engines were now itsmain handicaps. The fuel prices peaked andother governmental concerns caused a rise inthe degree of excitement towards electricvehicle. Innovators and entrepreneurs all
around the world now started to invest andexplore the electric vehicle technology. Theadvancements in the battery systems,electrical machines and control techniqueshelped in the renewal of the electric vehicles.There are many versions of electrified
There was a significant development inrechargeable battery technology in 1859 bythe invention of lead-acid battery by Gaston
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vehicles available in the market today- Hybridvehicle, Plug-in hybrid, full electric vehicle andso on. The electric transmission technologyfurther increases the controllability andefficiency of the system. Research is alsobeing conducted for the In-Wheel motor typeelectric vehicles which further improves thevehicle stability.
Even though the electric vehicle is expensivethan the conventional system, technologistaround the world are making constantprogress in every aspect to make itcommercially viable for the common man.
Our central character of the article, 'wheeledmotor vehicle', has come a long way and asbeing predicted, still has a longer way to go.There will always be the three aspects-government policies, public demands and
V. Conclusion
technological advancements- which will pavethe way for a better future. There is also achance that other new aspects, such asavailabil ity of resources, unforeseendevelopments and concerns, might appear onthe scene which would decide the course ofevolution of the powertrain. Today, with launchof every new vehicle, powertrain capability
plays a major role. All the aspects and thecharacters described may eventually lead usto an electric Nano (low cost and environmentfriendly) with equally great high-tech featuresthat we have in today's conventional high endvehicle. May be, even our first ever vehicle,the steam powered automobile, may rise fromits ashes and advance to overtake theconventional and existing technologies, whoknows!
Bibliography
1. Image source available at ' http://expertshub.org/training-programs/advanced-ic-engine-technology/'
2. Carl Burgess Glasscock, Car History - A Vision Becomes Reality , an article available at
'http://www.americanautohistory.com/Articles/Article001.htm'
3. History of the automobile,Wikipedia, available athttp://en.wikipedia.org/wiki/History_of_the_automobile
4. The History of the Automobile available at http://inventors.about.com/library/weekly/aacarssteama.htm
5. Automobile History : History of Cars and Engines available at
http://inventors.about.com/od/cstartinventions/a/Car_History_2.htm
6. Chao-Hsu Yao, Automotive Transmissions: Efficiently Transferring Power from Engine to Wheels, Article in
Discovery Guides
7. Automobile History : History of Cars and Engines available at
http://inventors.about.com/od/cstartinventions/a/Car_History_2.htm
8. History of Automotive Transmission available at
http://www.diablotransmissions.com/history_automatic_transmission.html
9. Image from How Manual Transmissions Work, HowStuffWorks, Inc. available
athttp://auto.howstuffworks.com/transmission.htm
10.Andrew Xia,The Death and Re-birth of the Electric Car available athttp://www.theyoungwanderer.com/the
death-and-re-birth-of-the-electric-car-andrew-xia/
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'From Manual to Automatic'
Area of interestsMathematical Modelling andSimulation, Control System.
Sushant HinganeAutomotive, Allied Engg.
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Planet carrieris lockedin place
Outer planetgears turnring gear
Input fromtorque
converter
Small sun gearturns inner
planet gears
Inner planetgears mesh
with, and turnouter planet
gears
Large sun gear'freewheels'
I.Introduction: Trans-missionImpossible!Imagine yourself in a dirt track racing or in arace on a terrain that has steep slopes andsharp turns. Would you let your car decidewhat wheel torque to select? On the otherhand, consider yourself in bumper-to-bumpertraffic condition on a city road where there are
several traffic junctions and cross sections. Doyou want to keep on shifting the gears everytime you slow down or put the pedal to themetal? Or you want a car that is smart enoughto select the gear according to the acceleratorpedal position? The easiest type that will cometo you depends on which side of the Atlanticyou are. Around 80% of the car users in theUnited States prefer automatic gear shift overmanual, whereas 80% of the European carusers prefer manual transmission overautomatic [1]. But that doesn't meanautomatic transmission vehicles are not liked
in Europe. In fact, they are. Even in a growingautomobile market in India, the automatic geartechnology is much appreciated and is indemand these days. Ok, so moving further,let's gear up now, shall we?
In this article, we will discuss some of the typesof the vehicle transmissions and then you canmake a reasonable choice for yourself. We willsee the advantages and the drawbacks ofeach of the transmission technologies. Thecomponents that go into each type and theirfunctionalities are also covered in the article.
II. Manual transmission: Swaggerwith a stick
Before getting into manual transmission, let'sbegin with transmission. What exactly is atransmission system? The job of a vehicletransmission [2] [3] [4] is to take the torquepower coming from the engine and transfer itto the wheels, through various componentassemblies. Now, it is not just the 'transfer' ofthe torque, but it is also 'multiplication' orimprovement of the engine torque through the
gear set assembly. Lower gears provide high
Figure 1: Manual transmission system overview
torque but less speed, whereas higher gearsprovide less torque but high speed. Thus, for adriver, it becomes obvious that he needs hightorque power (i.e. lower gears) while movingthe vehicle from the rest, or to climb a hill, or incase if the vehicle is heavily loaded. Inordinary driving conditions, when the vehicleis already in motion and has acquired a
significant speed, the driver can shift to highergears to multiply the rotational speed comingfrom the engine, of course at the cost of thetorque power.
Manual transmission, sometimes referred toas Standard, is the simplest form of thevehicle transmission so far. In this system, theinterlocking gear wheels are so arranged that,by operating the selector lever, a driver canselect one of the several speed ratios betweeninput shaft and output shaft. And to allowsmooth shifting from one gear to another, aclutch is provided to disengage the engine
from the transmission. Figure 1 shows a blockdiagram overview of manual transmission.
A. ClutchThe first stage in the transmission of a car with
manual gearbox is a clutch. This concept is an
excellent solution for changing the gears while
the vehicle is moving. The job of a clutch is to
engage or disengage two rotating shafts, one
driven by the engine and other driving the
wheels. Purpose is to prevent the stalling of
the engine when vehicle has come to halt.
Most of the clutches work on the principle of
friction. When the clutch pedal is pressed, a
cable or a hydraulic piston pushes the frictiondisk from the gear side to get disengaged with
the disk from the engine side. This is the time
when the gear is to be shifted. Since the clutch
action is based on the friction, it is always
recommended to gradually press the clutch to
achieve a smooth transition.
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Planet carrieris lockedin place
Outer planetgears turnring gear
Input fromtorque
converter
Small sun gear
turns innerplanet gears
Innergear
with, aouter
ge
Large sun ge'freewheels
Figure 2: Simple gear mechanism [Ref. 6]
Figure 2 shows a five speed transmission on astandard transmission vehicle. In this, themovement of the three collars (shown in pink)is controlled through the gear selector fork andin turn the gear selector lever [5].
III. Semi-automatic transmission-Manumatic or Autoual?
The transmission technique that isintermediate between manual and automatictransmission is semi-automatic or also knownas clutch less manual transmission or dual-clutch transmission. In this, the transmissiondoes not change the gear automatically, but iteliminates the need of a clutch for the geartransition.
In a semi-automatic transmission there aretwo clutches (so is called 'dual clutchtransmission'), but no clutch pedal. So, unlikethe manual transmission, where the driverpresses the clutch pedal and changes thegear with the selector lever, the clutches arecontrolled through electronic or hydrauliccontrols [6]. One clutch controls evennumbered gears and the other clutch controlsthe odd numbered gears, as shown in Figure3.
Figure 3: Dual clutch assembly [Ref. 7]
IV. Automatic transmission- Juststep on the gas!
The period from 1940 to 1960 was when thebiggies in the American automobile industry,like General Motors, Ford, and Chryslerstarted to adopt the automatic transmissionsystem (or simply automatics) and asignificant number of automatic vehicles
started to run on the roads. The automatictransmission can switch to the optimum gearwithout driver's intervention, except forstarting the vehicle and going into the reverse.For a person behind the wheel, the maindifferences in driving an automatictransmission are:
- There is no clutch pedal.
- There is no gear selector lever.
So, when a user has selected the 'Drive'mode, the gear changes automatically.
The Figure 4 shows a schematic overview ofthe automatic transmission line.
B. Gears
Manual transmission has relatively simplegear mechanism as compared to automatic.The gear shift procedure is to press the clutchpedal gradually, move the gear selector leverin the appropriate gear position and thenrelease the clutch pedal.
Figure 4: Automatic transmission system overview
A. Torque Converter
Unlike the manual transmission, there is no
clutch (and of course a clutch pedal) in an
automatic transmission. So, there is no
mechanism that will disengage the gearbox
input shaft and the engine crankshaft while in
a gear transition. If the engine crankshaft and
the gearbox input shaft are always connected,
the engine will stop as soon as the vehicle
comes at rest. To solve this problem, the
torque converter is used [7].
This device not only provides a mechanicaldecoupling of the input shaft (turbine output
shaft in Figure 5) and the engine crankshaft,
but also multiplies the engine torque up to the
ratio 3:1 with the help of fluid coupling.
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Planet carrieris lockedin place
Outer planetgears turnring gear
Input fromtorque
converter
Small sun gearturns inner
planet gears
Inner planetgears mesh
with, and turnouter planet
gears
Large sun gear'freewheels'
Figure 5: Torque converter [Ref. 8]
As can be seen in Figure 5, the torqueconverter casing is filled with the transmissionfluid which takes the kinetic energy from thevanes of the rotating pump (impeller)connected to engine and transfers it to theturbine which drives the output shaft.
There is a high torque requirement when thevehicle has to start from the resting position.This initial push is provided by a small
component called a stator. The returning fluidfrom the turbine vanes to the impeller isredirected by the stator so that it aids therotation of the impeller, instead of impeding it.This action results in the increase in theturbine output torque and reduction in the heatloss in the fluid.
One more feature of the torque converter is anelectronically operated lock-up clutch. Whenthe vehicle reaches a high speed, the lock-upclutch gets activated to mechanically connectthe flywheel from the engine side and the
output shaft turbine. This brings thetransmission fluid temperature down byreducing the load on circulating the fluid. Inthis condition, the total engine speed istransferred to the planetary gearbox.
The planetary gear set or epicyclic gearsystem, consists of one or more sets of acentrally pivoted sun gear, a ring gear (orannulus) and several planet gears whichrotate between these. Similar to the solar-planetary system, the planet gears rotate
around the sun gear.
B. Planetary Gear Set
The vehicle can have more than one planetarygear set. By controlling the clutches and thebrake bands, one can prevent certaincomponents from moving. In doing so, theinputs and the outputs of the system can bealtered, thus, a change in overall gear ratio isachieved. The final gear ratio depends onwhich component is fixed, which component isdriving and which one is being driven. Thesimple planetary gear operation is explainedin Table 1.
These gears are automatically changed byusing hydraulics or solenoid techniques whichare discussed in a further section.
Table 1: Simple planetarygear operation [Ref. 9]
Sun gear
Planet carrier
Ring gear
Carrier
Sun gear
Ring gear
Stationary Power Input Power Output Rotational Rotational
directionSpeed Torque
Ring gear
Sun gear
Planet carrier
Same directionas drivemember
Same directionas drivemember
Opposite directionas drivemember
Planet carrier
Sun gear
Planet carrier
Ring gear
Ring gear
Sun gear
Reduced
Increased
Reduced
Increased
Reduced
Increased
Increased
Reduced
Increased
Reduced
Increased
Reduced
C. Transmission control unit.
The automatic transmission system iscont ro l led using the computer ized'Transmission Control Unit' ECU [10], whichperforms the following functions:
- Monitor the torque converter parameterssuch as transmission fluid temperature, slipratio, output shaft torque, etc.
- Monitor the wheel speed, engine speed,
engine torque, etc.- With the measured parameters of the vehiclespeed and engine speed, calculate the mostsuitable gear ratio for the transmission.
- Control the clutches and brakes in the gearsets to automatically shift the gears in order tomeet the prior calculated gear ratio.
Gear shift using electric solenoids.
The shifting of the gears in automatic is merelycontrolling the clutches and the brake bands inthe gear set. One of the ways to control them isusing electrical solenoids, a device that willconvert the electrical signal into a translationalmotion of a needle. This needle, when pushed
on the clutch band, will engage the gear.Gear shift using pressure solenoids.
For some transmission controls, the gearclutches and bands are hydraulicallycontrolled using hydraulic pressure actuatingsolenoids. These are the solenoids in whichthe translational movement of the needle iscontrolled through hydraulic pressure.
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Planet carrieris lockedin place
Outer planetgears turnring gear
Input fromtorque
converter
Small sun gear
turns innerplanet gears
Innergear
with, aouter
ge
Large sun ge'freewheels
V. Automatic transmission: DrivingmodesEven though there is no 'gear selector' lever infully automatic vehicles, the drivers areprovided with various drive mode optionswhich even include the manual gear shiftmode. Some of the vehicles have a modeselector lever while some of the vehicles havea rotary knob. Mentioned below are someofthe important drive modes [10].
Park (P).This mode prevents the vehicle frommoving by locking the transmission. The parkmode engages the teeth on the notch providedin the parking brake to hold the vehicle still.Since it only locks the transmission, when inPark mode, the driven and non-driven wheelscan still rotate freely. That's why it is alwaysrecommended to use hand brake whenparked.
Neutral (N).In this mode, by disengaging allgear trains within the transmission, no torqueis transferred to the drive wheels. This modecan be selected just before a driver stops theengine.
Drive (D). This posit ion allows thetransmission to use all forward gears (totally 4to 8 depending on the vehicle) in high or lowrange.
Reverse (R).This mode can only be selectedwhen the vehicle is stationary and engine is atidle, allowing a vehicle to be drivenbackwards. Reverse is very similar to the firstgear as far as the gear ratio is concerned.
Overdrive (OD). In this mode, the torqueconverter lock-up clutch engages the flywheelas discussed before, to maximize the output
speed. Transmission will automatically selectthe gear according to the vehicle speed andthe throttle pedal position.
Sport (S). This mode, similar to the Drivemode, uses all the forward gears, but up shiftsand holds the gears at higher engine speed,thus, improving the acceleration. This mode isespecially used in the off-road conditions.
Manual (Steptronic) (+/-). Manual modeallows the transmission to operate in semi-automatics steptronic mode. The driver canshift gears up and down with the freedom of
manual transmission.Winter (W).This mode engages second gearinstead of first, while driving off from thestationary position, in order to avoid the loss oftraction due to wheel spin on snow or ice.
Brake (B). This mode works as an enginebrake while the vehicle is descending a hill by
slowing down the engine with the help of afriction-based retarder. This is a way ofslowing down the car without downshifting oreven without pressing the brake pedal.
VI. Conclusion Trans-mission
accomplished!
A brief comparison between manual andautomatic transmission is provided below.
Looks cooler and feels sporty. You need
manual transmission vehicle to win a
race.
Parameter Manual Automatic
Driver'sComfort
FuelEconomy
Control
Panache
Cost
Automatics win the race of
technology, but it is still not
something what the James Bondwould drive.
Costs less as compared to the
automatics.
Speaking in general, manual
transmissions are less convenient than
automatic. But again, it depends on how
comfortable/conversant the driver is with
the gear stick.
More fuel efficient.
Manual wins here. For a person who
wants a complete control over the wheel
torques, manual transmission provides a
level of flexibility to set the gear ratio
which is favourable in situations like
racing, off-road terrains, etc.
Costs more but some might feel
it worthy to pay more.
When it comes to the driver's
comfort, all the extra money that
is spent on the automatic
vehicles starts paying off.
Consumes more fuel than
manual.
The vehicle intelligence sets the
gear ratio, based on the
selection of various drive modes
by the driver.
Manual transmission is the old school methodwhere the (smart and skilful) drivers can enjoythe complete control over the power deliveredto the wheels. But they are not made foreveryone. While, the automatic transmissionsapplies so much advancement and ingenuityinto the computerized control that it brings outan excellent driving experience as the yearsgo by. So, the drivers who like to havecomplete control of their vehicle can go for themanual transmission, while those who preferan intelligent vehicle that drives itself can gofor an automatic transmission- pick yourchoice and set the wheels in motion.
Referencesth
[1] Blog: Automatic versus manual cars, by Tim Barnes-Clay, May 28 2013.th
[2] BOSCH Automotive Handbook, 8 edition- May 2011, Wiley, Chapter Drivetrainth
[3] William B. Ribbens, Understanding automotive electronics, 7 edition 2013,
chapter Digital Powertrain control systems[4] Davy Geuns, Description: Automatic gearbox, June 2003[5] A real transmission, part of How manual transmission works.
Available:http://auto.howstuffworks.com/transmission4.htm[6] Dual-clutch transmission, Wikipedia.[7] Inside a torque converter, part of How torque converter works.
Available:http://auto.howstuffworks.com/auto-parts/towing/towing
capacity/information/torque-converter2.htm[8] The transmission bible
Available: http://www.carbibles.com/transmission_bible_pg2.html[9]Automatic transmission- course 262 section 3, TOYOTA technical training
Available: http://www.autoshop101.com/forms/AT03.pdf[10] Automatic transmission, Wikipedia
Available: http://en.wikipedia.org/wiki/Automatic_transmission
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Hydraulic Hybrid
Milind Potdar
Kailash SrinivasanCorporate Marketing
Areas of InterestContent, Marketing Communications,New Media, Digital Marketing.
Areas of Interest
Embeded System,Hardware & S/W Design, RTOS.
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I. Introduction
II. Hydraulic Hybrid Systems
As the number of vehicles has increased onroad, so have the ill-effects on theenvironment. Vehicle manufacturers havecome to realize this and have been constantlyworking towards reducing the vehicularemissions without compromising on theperformance of the vehicle. These pursuits
lead to having electronic controls in engine fordiesel, petrol, and gasoline engines. However,it was found that having only an internalcombustion engine with electric power wasn'tgoing to be sufficient for reducing emissions.As a next step, the battery-operated electricvehicles were launched. But they were notfeasible for long drives as the battery was theonly source of power and the battery neededto be recharged frequently. This limitation ofthe electric vehicles gave birth to the idea of'hybrid vehicles'.
The hybrid vehicles use two or more
propulsion systems; integrating an internal
combustion engine with some second power
source. Hybrid vehicles utilize two sources of
power and energy to achieve optimal
propulsion and efficiency for a vehicle. One
type of hybrid is the motor and battery-
operated hybrids. These hybrids offer several
benefits, such as fuel efficiency, good mileage,
fewer emissions etc. The other hybrid sources
for powering a vehicle include gaseous fuels
like hydrogen, CNG, LPG, ethanol, hydraulics,etc. In this article, we will explore the hydraulic
hybrid vehicle system. A hydraulic hybrid
system uses pumps or motors to store energy
in hydraulic accumulators. Hydraulic hybrid
systems works well for heavy duty vehicles
and off-road vehicles, as they require large
space for the pumps/motors and the
accumulators.
Hydraulic systems are similar to conventional
hybrid electric vehicles in the sense that they
both improve fuel economy by utilizing the
energy generated every time a driver brakes,
also known as regenerative braking. However,
instead of storing energy in a lithium-ion
battery (like in battery-operated hybrids), the
hydraulic systems uses a hydraulic pump-
motor, reservoir, and accumulator with an
internal combustion engine. The energy is
used to move fluids from a reservoir into the
accumulator. As the fluid enters the chamber
there is a build-up of pressure, which turns into
compressed energy helping to launch the
vehicle.
The hydraulic hybrid systems are cheap and
fuel efficient as they can store energy quickly,
allowing them to capture more energy from the
braking. Hydraulic hybrid recovers up to 75%
of the vehicle's kinetic energy compared to the
25% for the electric hybrids. Hydraulic hybrids
are more effective and efficient for vehicles
that need to start and stop frequently. Hence, itbenefits commercial and heavy duty vehicle,
like garbage trucks, delivery trucks, and city
buses, as these vehicles need to start and
stop a lot while on their way.
III. Working Principle
As shown in Figure 1, hydraulic hybrid vehiclesystem consists of four main components [1]:
1. The working fluid
2. Reservoir, pump/motor (in parallel hybrid
system) or in-wheel motors3. Pumps (in series hybrid system)
4. Accumulator
ICE
Pow
ertra
in
split
Tran
smission
HYDMOTO
R
Fluid Gas
Fluid Gas
HYD
PUMP
Reservoir
Accumulator
Figure1: Block diagram of Hydraulic Powertrain
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Like the motor and battery operated hybrids,the hydraulic systems are also configured asthe parallel hydraulic hybrid and the serieshydraulic hybrid. In a parallel hydraulic hybrid,the hybrid components (reservoir, pump andaccumulator) are attached to the conventionaltransmission and the driveshaft which drivesthe wheels. So, it is an add-on to the existing
drive train. The engine provides power to thewheels through the conventional transmissionsystem. This configuration allows thehydraulic system to assist the engine instopping and accelerating the vehicle. Thekinetic energy lost during braking is stored inthe hydraulic accumulators.
In a series hydraulic hybrid there is noconventional transmission and driveshaft. Theengine is not connected to the wheels and thepower is directly delivered to the wheels. Thepump acts as a motor and uses the high
pressure fluids from the accumulator to propelthe vehicle. As the hydraulic system itselfdrives the wheels, the gasoline engine can beshut off, unlike in the parallel hydraulichybrids, providing more fuel savings. Both, theparallel and the series configuration lead toimprovements in fuel economy, brake life,acceleration and emissions.
Figure 2 shows the actual hydraulic system invehicle developed by Peugeot and BOSCH.
Figure 2: Actual working model (Ref. 3)
IV. Conclusion
Hydraulic hybrid systems are lighter and
cheaper than the electric systems of similarpower. High power hydraulic systems arerobust systems. Hydraulic systems are perfectfor all the heavy-duty vehicles such as trucks,busses, military vehicles, etc. as they need tostart and stop frequently. The hydraulic hybridsystems can operate over a range of climatic
conditions when the right kind of oils is utilized.Hydraulic hybrid systems are fuel neutral -they can be applied to vehicles using differenttypes of fuel, like diesel, CNG, LPG, etc.Hydraulic hybrid technology offers improvedacceleration and reduced fuel consumption,brake wear and emissions [5].
Although the hydraulic hybrids are now findinga place in the market, adapting hydraulicsystems for commuter cars will prove to be abig challenge. The reasons are plenty.Small/passenger cars do not have thenecessary space to accommodate the bulkyair storage tanks that are found in largervehicles. Add to that the industrial-qualitynoise, which will also have to be drasticallyreduced to suit smaller cars. So, the wayforward will be to find a way to power to allelectrical systems in a vehicle, such as windshields, headlights etc., without relying on a
battery. Several companies are working on orhave plans to work on the hydraulic hybridvehicles. If their technology is successful, itcould prompt many manufacturers to go forhydraulic hybrids and it may potentiallychange the market for the commuter vehicles.
References
1. Hydraulic HybridsAvailable online at:https://en.wikipedia.org/wiki/Hydraulic_hybrid
2. How hydraulic hybrids worksAvailable online at: http://auto.howstuffworks.com/hydraulic-hybrid2.htm
3. Hydraulic Hybrid system, by BoschAvailable online at:http://www.bosch.fr/en/fr/newsroom_7/news_7/news-detail-page_12864.php
4. Improving the fuel economy by using Hydraulic HybridPowertrain in passenger cars by SakotaZeljko (Machines,Technologies, Materials: ISSN 1313-0226. ISSUE 4/2013)
5. Presentation, Hydraulic Hybrid Vehicle Technologies, byMichael Conrad, September 9, 2008.
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Hybrid Powertrain: 'Revolo'
Sachin P. PanditRevolo Hybrid Program
Areas of interestSystem Engineering,Control Logic Development,& Performance Optimization of HEV
Nandulal Kushabhau GavaliHybrid Solution
Area of InterestsMotor Control,ECU Designs for Powertrain,& Automotive Embedded Applications
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I. IntroductionThe current global warming, pollution, priceinflation and depletion of natural resourceshave led to a need for development of greentechnologies. The amount of pollution causedby vehicles and continued increase ingasoline price has resulted in a need forsearching alternate fuel options. Researchhas been ongoing since the time of conception
of the vehicle, to make it more efficient in termsof fuel usage and to make it moreenvironmental friendly. This has given rise toalternative technologies to the conventionalinternal combustion engines. One suchalternative developed is the hybrid vehicletechnology. A hybrid vehicle is the one in whichthe engine is acting as one power sourcewhereas the battery or fuel cell is acting asanother power source.
It is well known that hybridization of the vehiclereduces the total emissions caused by the
vehicle in its entire life. Hence, the hybridvehicle systems are useful to reducegreenhouse gases. 'Revolo', is one suchaffordable and innovative plug-in hybridelectric vehicle technology developed by KPITTechnologies. This plug-in, parallel hybridsolution transforms vehicles, enables motorand engine to work seamlessly for a fuelefficient, green vehicle. 'Revolo' maybe usedas a retro-fit solution and hence provides theadvantage of converting the existing on-roadvehicles into a plug-in hybrid. The productonce fitted will help improve fuel efficiency of
over 35%, reduce CO2 Emissions by over30% and resulting in net energy savings ofover 25%. The solution is applicable to a largerange of vehicles from a small 800cc gasolinehatchback to 3000cc diesel light commercialvehicle OR school bus. Given the way it isdesigned and engineered, Revolo is the mostfrugal plug-in hybrid solution available. Nowonder that KPIT Technologies has won manyprestigious awards for this innovativetechnology. Some of the awards include: WallStreet Journal's Technology Innovation Awardin 2011, and 'Best Implemented Sustainability
Innovation of the Year 2011' award at GlobalKnowledge @ Whar ton Innovat ionTournament.
The broader scope of the article is to study thedifferent types of hybrid powertrains availablein industry as well as the different componentsincluded in such powertrains. We also present
a case study on the innovative and patentedelectric-hybrid vehicle system, 'Revolo'. It isinvented, designed, developed, andmanufactured by KPIT Technologies.
Hybrid vehicles operate on a dual mode,wherein the power is provided by both, anengine and a motor. The motor is used to drivethe partial load which is carried by the engine.The motor is directly connected to engineeither through a belt-pulley drive or through agearbox assembly. In some designs, the
motor is placed on the shaft where it connectsto a differential gear box of the vehicle.Different types of motor technologies arebeing deployed into the hybrid vehicle system.
The batteries used as the second powersource for supplying power to the motor areLead Acid, Ni-MH (Nickel-Metal hydride), andLi-Ion (Lithium-ion) types. The ValveRegulated Lead Acid(VRLA) batteries are themost commonly used in industry. Good thingabout the VRLA batteries is that it can berecycled. Hence, the emission or waste
created due to these batteries is very low andcan be advantageous when compared toGasoline/Diesel/CNG engines. Li-Ion has avery good energy to weight ratio. It also has agood life over the lead acid batteries. Li-Ionbatteries have to be protected against the highrate of charge, high discharge, and hightemperature so as to use them into a safeoperational zone.
Today different types of hybrid configurations
are employed in vehicles. The majordifference is based on how the engine and themotor assist each other in the total operationof the vehicle. There are also differencesbased on the how much hybridization hasbeen used in the vehicle. These differences,based on the level of hybridization, arecovered
II. Scope of the Article
III. Background
IV.Different types of HybridPowertrain
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in detail in the subsequent sections.
A Parallel Hybrid Topology
The parallel hybrid topology is shown inFigure1 [1]. In this topology, the motor isdirectly coupled to the engine through acoupling or a pulley-belt arrangement. Apower-electronic converter is the 3-phaseinverter, along with intelligence of applyingdifferent amount of torque based on thespeed-load condition of the vehicle. Theengine RPM is measured using an enginecrank-speed sensor. The vehicle speed ismeasured using a speed sensor. Thedifference in speeds always gives the gearposition in which the vehicle is running. This isthe indirect load measurement on the engine.The motor revolutions per minute (RPM) canbe varied and based on the speed of the motor
V. The different hybrid topologiesare as follows:
MotorController
3 phaseMotor
Wheel
IC Engine
Coupling
Figure 1: Typical Parallel Hybrid topology in a vehicle
torque applied can be controlled. The vehicle
can be tuned on chassis dynamometer for
various torque-speed operating points. The
speed differential created between the engine
RPM and the motor RPM will determine the
actual assistance applied.
B. Series Hybrid Topology
The typical series hybrid topology is as shown
in Figure 2 [1]. The engine is used to charge
the batteries in a running condition. The main
advantage of this system is higher efficiency.
The engine can be run at a constant speed or a
variable speed based on the charging current
required. Hence, it can be ensured that the
engine will always run at the highest possible
efficiency.
MotorController
3 phaseMotor
Charger
GeneratorEngine
Wheel
Figure 2: Typical Series Hybrid topology in a Vehicle
The vehicle will always run as an electricvehicle while the engine, generator, charger,and battery will be acting as a fuel cell. Themain limitation of this topology is that theaftermarket system assembly becomesdifficult. So, it can be advantageous if this hasbeen fitted by the OEM into the vehicle.
C. Series-Parallel Hybrid Topology
As name suggests, it is the mixed series andparallel hybrid topology. It is also known asPower-Split hybrid topology. The engine isdirectly coupled to the motor as well asgenerator for battery charging. Hence, thecapacity of engine will be higher thanwhatever is used in the Series-Hybridtopology.
A. Micro-hybrid
In micro-hybrid type vehicle, the engine will bestopped during high idle time and theregenerative braking is used to stop theengine instantaneously. The vehicle will startsimply by pressing the clutch paddle or anyother means. This will be advantageous interms of fuel economy and the reduction ofvehicle emission.
B. Mild-hybrid
The mild hybrid type vehicle is similar to amicro-hybrid with addition to torqueassistance to the engine. A typical example ofa mild-hybrid is the Honda Civic.
C. Strong hybrid
The strong hybrid consists of the mild hybridcomponents plus an electric launch. It meansthat the vehicle can launch in an electricalmode. The battery used is smaller than PHEVtype and generally it is less than 2KWhr rating.
Due to the smaller battery used the totalelectric range is less. A good example of astrong hybrid is the Toyota Prius.
VI. Level of Vehicle Electrification
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D. Plug-in Hybrid Electric Vehicle (PHEV):
In this type of electrification, the strong hybridtype is added with a plugging feature. Theplugging feature means an external chargingfacility is made available. Higher capacitybatteries are used (> 2KWhr) in this type ofhybrid so that longer electrical range isachieved. A good example of a PHEV is the
KPIT 'Revolo'.E. Electric VehicleIn pure electric vehicle, there will be no engineavailable. The only source of power is theelectrical motor which generates the energyrequired to drive the vehicle. Higher capacitybatteries are used so as to achieve longerelectrical range.
A. Introduction of Revolo Hybrid System
'Revolo' hybrid is a plug-in parallel electric
hybrid powertrain developed by KPIT. Thispowertrain allows the engine and an electricmotor to supply torque to the wheels. Revolopowertrain can be adapted to either gasolineor diesel engine vehicles which can either beretrofit or be integral to the on-road vehicles.
The objectives of Revolo Powertrain are toincrease the fuel economy, reduce theexhaust emissions and to recover the brakingenergy.
The block diagram arrangement of the major
Revolo powertrain components is shown inthe Figure 3. It consists of the followingcomponents:
V I I . K P I T R e v o l o H y b r i dSystem[3][4][5]
Battery
Pack
Vehicle
Battery
Pack Engin
e
MC
U
DC-
DC
HCU
Charge
r
Motor
Figure 3: Block Diagram arrangement ofRevolo Powertrain System
I. Electric Motor:A compact size caged rotorinduction motor provides torque up to 25% ofthe vehicle engine rating.
II. MCU:Also referred to as the inverter whichprecisely controls the torque of the electricmotor as decided by the control algorithm.
III. HCU: Control logic for the completeoperation of Revolo powertrain resides in theKPIT designed Hybrid control unit (HCU).
IV. Traction Battery Pack: 48V DC batterypack provides the electrical energy sufficientto achieve the decided/predetermined hybridrange.
V. Traction Battery Charger: Chargerensures the charging of the hybrid batterypack with a predefined charging profile tomaximize the life of hybrid battery pack. Thischarger works with domestic power outlet.
VI. DC to DC Charger:48V DC to 12V DCconverter fulfills the load requirement of thevehicle's electrical system. This converter isrequired in those Revolo powertrainconfigurations where the 12V alternator isremoved from the vehicle.
B. Working Principle
There are certain operating zones of theengine where the exhaust emissions are veryhigh. The carbon content in the gases from theexhaust indicates the fuel economy of a
vehicle. Higher the carbon content, lower isthe fuel economy of the vehicle. Engine torquesharing at these high emission operatingzones results into lowering of the amount ofexhaust emissions which further leads to anincreased fuel economy.
Revolo powertrain works on the torquesharing principle. Electric motor provides thetorque assistance to the engine where theexhaust emissions are very high. Emissionsimulation tuning approach helps indetermining the low emission operating points
and the amount of motor torque beingprovided to the engine [2].
Revolo powertrain continuously operates inthe following modes:Hybrid traction, Enginealone and Regeneration.
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ECM
Engine
HCU
MCU
Vehicle Sensors and
Switches
Motor
Battery
Pack
Figure 4: Overall Control Scheme of Revolo Powertrain
The control algorithm residing in the HCUdecides the mode of operation and thecorresponding amount of positive, zero ornegative torque command considering thedriving conditions. Driving conditions aresensed by the sensors and the switcheslocated in the vehicle. HCU communicatesthis torque command to the MCU which furthercontrols the operation of the motor,accordingly. Figure 4 shows the overall controlscheme of the Revolo powertrain.
C. Dynamometer Testing Results
With an optimized HEV control algorithm, theoveral l system ef f ic iency improvessignificantly. Figure 5 illustrates the change incarbon dioxide emissions because of motorassist on a particular zone of a drive cycle.Primary axis indicates the vehicle speed andsecondary axis indicates the carbon dioxideemissions. It can be observed that with theRevolo hybrid technology, the emissions arereduced almost by 40% in this operating zone.
Figure 5: CO2 emissions with Revolo and without Revolo
VIII. ConclusionThere are different types of hybrid topologiesthat have been experimented with. Also, thereare different amount of electrificationsavailable in the vehicle, from micro-hybrid to acomplete electric vehicle. KPIT 'Revolo' is oneof the PHEV types of hybrid system. It isdesigned such that, as a retro-fit application, it
will take minimum amount of time to install intoa vehicle. Revolo performance statistics areillustrated in Figure 6.
Figure 6: Revolo performance statistics
Emission reduction30%+
Fuelefficiency
improvement35%+
Cost of traveldecreases by
25%+
In Revolo, the torque assisting is designed insuch a way that the above parameters can bematched. Apart from the targeted parameters,the safety issues are also considered into thedesign and the selection of differentcomponents into hybrid system. Revolo is anentirely new and novel approach tohybridization. Till date, 14+ patents have beenfiled for the 'Revolo' technology across variouscountries. The patents are for both, noveldesigns at component level as well as at the
system level. The patent applications cover awider variety of novel ideas related to themotor, motor control, energy storage systems,and hybrid systems with lower powerrequirement for vehicle. Furthermore, theproduct is independent of the degree ofelectronic control of the base vehicle and canalso be installed in vehicles with a puremechanical powertrain.
D. Safety Considerations
Various safety considerations that are takencare of in the Revolo powertrain include overtemperature, over voltage, over current, undervoltage, short circuit, EMI/EMC compliance,vehicle ignition interlock and emergencymanual cutoff.
References1. Available online,
http://en.wikipedia.org/wiki/Hybrid_vehicle_drivetrain
2. U.S Patent no. 8,560,156, titled 'Power assisting
system'
3. U.S Patent no. 8,596,391, titled 'Method of
converting vehicle into hybrid vehicle'
4. U.S Patent no. 8,423,214, titled 'Motor assistance
for a hybrid vehicle'
5. U.S Patent no. 8,606,443, titled 'Motor assistance
for a hybrid vehicle based on user input'
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Alternate Fuel Powertrain
Samir SattigeriHybrid Revolo
Areas of InterestAlternate Fuel &Advanced Technology inPowertrain Development
Kiran DakleHybrid Revolo
Areas of InterestVehicle/Component Homologation& Testing
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StepperMotor
Pressure
Regulator
Gear Box Engine
CNG ECU
CNG FuelLine
CNG Tank
Refillingvalve
I. Introduction
II. Gaseous Fuel
Powertrain is the heart of an automotivedesign. Engine and transmission are the maincomponents of a vehicle powertrain. Enginegenerates power required to drive the vehicleby combustion of the fuel. This power is thenapplied to the drive the vehicle through thetransmission. Broadly, the two types of fuelsthat are used in the vehicle are gaseous fuelsand liquid fuels. Out of these, diesel andgasoline are the conventional fuels used in avehicle.
Energy, security, environmental effects andpollution, CO2 reduction, etc. are the keydrivers that are causing automotivemanufacturers to conduct research onexploring use of alternate fuels for driving thevehicles. The alternate fuels that can be usedto drive a vehicle can be broadly classified intotwo groups:
1. Gaseous Fuel 2. Liquid Fuels
In this article, we will take a detailed look atsome of the gaseous fuels, their powertrainmodifications, the technology roadmap andapplication, the pros and cons and thechallenges. This is followed by a brief look atthe liquid fuels and the hybrid and electricvehicles.
Now-a-days increasing numbers of vehiclesare seen running on gaseous fuels like CNG(Compressed Natural Gas), Propane / LPG(Liquefied Petroleum Gas), hydrogen, etc.Amongst them, CNG and LPG fuels are beingused widely [1].
A. Changes Needed in Base Vehicle
(Powertrain)Technically, vehicles running on eithergasoline or diesel can be retrofitted to run onthe dual or dedicated fuel mode. It is possibleto retrofit a vehicle that is already in use andnow automakers are also coming up with
factory fitted CNG / LPGv e h i c l e s . I n c a s e o f
CNG/LPG, accommodatingan add-on fuel mode in agasoline vehicle is easiercompared to the dieselvehicle. Retro-fitting an add-on fuel mode in a dieselengine vehicle need
modification of the engine from CI(Compression Ignition) to SI (Spark Ignition).This modification includes changes in thecylinder head, the piston, the cylinder, theignition system, the cooling system, etc [3].
Figure 1 below shows the basic layout of aCNG enabled vehicle.
StepperMotor
PressureRegulator
Gear Box Engine
CNG ECU
CNG FuelLine
CNG Tank
Refillingvalve
Figure 1: Basic Layout of a CNG Enabled Vehicle
Running a gasoline vehicle on hydrogenneeds a number of changes/modification inthe base powertrain like the valves,connecting rod, spark plug, ignition coil andintake manifold, etc. One example ofmodification is there placement of the normalspark plug with non-platinum tip plugs. Themodification costs would be about 1.5 times of
the current cost of the gasoline engine [2].
B. Technology Road Map
i. In Vehicle Technology: For CNG / LPGvehicles, it primarily started with the 'OpenLoop' system (without feedback) integrationwith carbureted vehicles. As time passed,stringent emission norms forced thistechnology to evade and then the 'Close Loop'system took the lead in market from 1998 to2010. Currently, the third generation systemcalled 'Sequential System' (Injection system)is becoming more popular due to its reliability
and at par performance with gasolinetechnology. Use of hydrogen as a fuel to runthe vehicle started with the supply of hydrogenthat was stored on-board to the engine. Then,considering the passenger safety (as on-board stored hydrogen is risky), the nextphase evolved which is enrichment of base
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StepperMotor
Pressure
Regulato
Gear Box Engine
CNG ECU
CNG FuelLine
CNG Tank
Refillingvalve
fuel with onboard generated hydrogen.Currently, automotive industry is working onusing hydrogen fuel cell to run the vehicleswhich is safer and also helps keep theenvironment clean [3].
ii. Infrastructure Technology: Instead ofhaving one mother station and multipleoutlets, government should emphasis onhaving multiple mother station as retail outlets.This will increase fuel availability with correctpressure (in case of CNG) and will encouragepeople to go these greener alternate fuelvehicles.
C. Technology Selection and Application
Alternate fuels being a source of cleaner andeconomical fuel, they are now getting hugetraction in market. Automotive market ismainly divided in two streams i.e. passengervehicles and commercial vehicles. Alternatefuels like CNG, LPG and Hydrogen (in someextent) are seen being popular in thepassenger vehicle segment. Option to choosebetween the dual fuel and the dedicated fuelmode are available for the customers.However, commercial vehicles mostly run ondedicated fuel mode only [3].
D. Pros and Cons:
Alternate fuels are cleaner than theconventional fuels which help to protect theenvironment. Due to the complete combustionof the alternate fuels, we save energycompared to gasoline and diesel. Theoperating costs are lower than its conventionalcounter parts. As the end consumer isbenefited in monitory terms, the usage ofalternate fuels has been increasing. Thedrawback of alternate gaseous fuels is that thestorage of such high pressure fuel in vehicle isrisky. However, mandate of exercising safetycode of conduct lowers the risk to minimum.Also, installing the alternate fuel system on thevehicle requires high initial cost.
E. Rules & Regulations
Some government rules are already in placeto regularize the use of alternate fuels invehicles either by retrofit solutions for theexisting vehicles or by use of factoryfitted/installed alternate fuel kits on vehicle.
F. Challenges: Consumer Acceptance
Step wise action plan needs to be executed to
make alternative fuel as a first choice for thetransportation industry. Multiple studiessuggest that the considerations mentionedbelow will largely contribute in boosting thealternative fuel usage [4]:I .Government po l i c ies to p romotedevelopment and usage of alternate fuelsII. Facilitate local manufacturers to developtechnology in order to boost economyIII. Infrastructure development: Refillingstations, fuel pipe line density, etc.IV. Mandate to automakers for manufacturingalternate fuel vehicles.V. Tax incentives for vehicles enabled withalternate fuelVI. Individual contribution to protect theenvironment and conserve energy
Under the liquid alternate fuels, we will brieflylook at bio-diesel, LNG, ethanol and methanol.
A. Bio DieselBio diesel is domestically produced, non-toxic,biodegradable and a renewable fuel. It can bemanufactured from vegetable oils, animal fats,or recycled restaurant grease. It burns cleaneras compared to the petroleum diesel fuel.
Bio diesel is different from the vegetable andwaste oils that are used in fuel converteddiesel engines. Biodiesel is to be used in thestandard diesel engines. Biodiesel is adomestically produced. It burns clean and is arenewable substitute for petroleum diesel.
When biodiesel is used as a vehicle fuel, itincreases energy security, improves publichealth and provides a cleaner environment.
Biodiesel can be used alone or may beblended with petro diesel in any proportions.Blends of biodiesel and conventionalhydrocarbon-based diesel are mostcommonly distributed in the retail diesel fuelmarketplace. A system known as the "B" factoris used to state the amount of biodiesel in any
III. Liquid Fuels
fuel mix. For example, 100%biodiesel is referred to as B100,20% biodiesel, 80% diesel islabeled B20, 5% biodiesel, 95%diesel is labeled B5, and so on.Blends of 20% biodiesel andlower can be used in dieselequipment with no or only someminor modifications to the
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StepperMotor
Pressure
Regulator
Gear Box Engine
CNG ECU
CNG FuelLine
CNG Tank
Refillingvalve
Biodiesel can be handled, stored andtransported without any risk.
B. LNG (Liquefied Natural Gas)
In a gaseous state, liquefied natural gasoccupies about 1/600th volume of naturalgas.LNG is odorless, colorless, non-toxic andnon-corrosive.LNG is flammable after itvaporizes into a gaseous state. The/volumetric/ energy density of LNG is 2.4 timesgreater than that of CNG or 60 percent of thatof diesel fuel.LNG achieves a higher reductionin volume as compressed to natural gas(CNG). Due to this, it is efficient to transportLNG over long distances, where there are nopipelines. Cryogenic sea vessels or cryogenicroad tankers are specially designed carriersfor transporting LNG [5] [8].
LNG is used to transport the natural gas to themarkets. It is then re-gasified and distributedas pipeline natural gas. LNG maybe used innatural gas vehicles. However, generally,vehicles are designed to use the compressednatural gas. The relatively high cost ofproduction and the need to store the gas inexpensive cryogenic tanks has hindered thewidespread commercial use of LNG.
C. Ethanol
Ethanol (CH3CH2OH) is a clear, colorlessliquid and a renewable fuel. It is made fromvarious plant materials collectively known as"biomass." It is also known as ethyl alcohol.Ethanol in a low-level blend is used tooxygenate the fuel and reduce the air pollutionin more than 95% of the U.S. gasoline. Ethanolis also available as E85, or high-level ethanolblends. The flexible fuel vehicles are the onesthat can run on high-level ethanol blends,gasoline, or any blend of these. The blender orthe fuel supplier mixed the Ethanol with thegasoline before distributing it to the fuelingstations [5].
Due to the higher octane number that Ethanolhas as compared to gasoline, it providespremium blending properties. Low-octanegasoline is blended with 10% ethanol to attainthe standard 87 octane requirement. Ethanolcontains about 30% less energy thangasoline. E85 contains about 25% less energythan gasoline. High-level ethanol blendscontain less energy per gallon than doesgasoline, to varying degrees, depending on
is spills on the surface orwhen released into theenvironment. It is safer thanpetroleum diesel because itis lower combustion point.The flashpoint for biodiesel ishigher than 130C, whereasit is about 52C for petroleumdiesel.
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powertrain [5] [6].
As compared to petroleum diesel, use ofbiodiesel in a conventional petroleum dieselengine substantially reduces tailpipeemissions of unburned hydrocarbons (HC),carbon monoxide (CO), sulfates, polycyclicaromatic hydrocarbons, nitrated polycyclicaromatic hydrocarbons, and particulatematter (PM). All the engines that aremanufactured in 2010 and later are required tomeet the emission standards irrespective ofwhether they are running on biodiesel, diesel,or even natural gas. Selective catalyticreduction (SCR) technology, which reducesnitrogen oxide (NOx) emissions to near zerolevels, makes this possible. For these newtechnology engines, the emissions from dieselfuel are comparable to those from biodieseland are extremely low. These new technologyengines are some of the cleanest engines on
road. B100 provides the most reduction inemissions, but lower-level blends also providesome benefits. B20 has been shown to reducePM emissions 10%, CO 11%, and unburnedHC 21% in older engines. Greenhouse gasand air-quality benefits of biodiesel areroughly commensurate with the blend. B20use provides about 20% of the benefit of B100use [5] [7].
Biodiesel improves fuel lubricity and raises theCetane number (measure of combustionquality) of the fuel. The lubricity of the fuel
prevents the moving parts of the diesel enginefrom wearing out prematurely. The lubricity ofdiesel fuels can be increased by use ofbiodiesel at blend levels as low as1%.However, before using biodiesel be sureto check your engine warranty to ensure thathigher-level blends of this alternative fuel donot void or affect your engine.As biodiesel is nontoxic, it causes lessdamage as compared to petroleum diesel if it
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StepperMotor
Pressure
Regulato
Gear Box Engine
CNG ECU
CNG FuelLine
CNG Tank
Refillingvalve
the volume percentage of ethanol in the high-level blend. A lower octane number preventsengine knocking, thus, ensuring drivability [5].
D. Methanol
Methanol (CH3OH) is also known as woodalcohol. As an engine fuel, methanol haschemical and physical fuel properties similarto ethanol. Methanol maybe one of thealternatives to the conventional transportationfuels. Methanol is cheaper to produce ascompared to the other alternative fuels.Methanol has a lower risk of flammabilitycompared to gasoline. Methanol also offersimportant emission benefits as compared togasoline. It can reduce hydrocarbonemissions by 30 to 40 percent with M85 and upto 80 percent with M100 fuels. Since the early1990s, the use of Methanol in vehicles hasdeclined drastically. Automakers are no longer
interested in manufacturing methanol vehicles[5] [9].
Under the Energy Policy Act of 1992,electricity is considered an alternative fuel.Electricity can be produced from variousprimary energy sources. Plug-in vehicles arecapable of drawing electricity from off-boardelectrical power sources (generally theelectricity grid) and store it in batteries.Though not yet widely available, fuel cellvehicles use hydrogen to generate electricityin a clean manner onboard the vehicle.
In a plug-in electric vehicle, energy is stored inthe onboard rechargeable batteries. Thisenergy is used to power the electric motor.Although vehicles that run only on electricityproduce no tailpipe emissions, there areemissions associated with the production ofelectricity itself. Fueling plug-in vehicles withelectricity is currently cost effective comparedto gasoline, especially, if drivers takeadvantage of off-peak rates offered by theutilities.
Many plug-in vehicle owners prefer chargingtheir vehicles at home (or at fleet facilities, inthe case of fleets). Some employers offeraccess to charging at the workplace. At someplaces, plug-in vehicles have the facility toaccess public charging stations at libraries,shopping centers, hospitals, and businesses.
IV. Electric & Hybrid Vehicle
However, charging infrastructure has beenimproving recently. The advancement in thesecharging facilities is making chargingconvenient and allowing the driver to coverlonger distance ranges. This is giving thedrivers confidence to meet their needs by useof the plug-in vehicles [10].
Vehicles that run on alternate fuels can costless, reduce emissions, and reducedependence on foreign fuels. Alternate fuelssuch as Natural Gas, Ethanol, Petroleum Gasand Bio-diesel have a very bright future in thewake of growing concern over the health of ourenvironment. The technologies like electricand hybrid vehicle have been in the market fora while now. However, to make them moresustainable additional research is required onbattery technology since they are costly andneed frequent charging.
V. Conclusion
References
1. Semin, Rosli Abu Bakar, A Technical Review of Compressed Natural Gas as an Alternative
Fuel for Internal Combustion Engines, American J. of Engineering and Applied Sciences 1 (4):
302-311, 2008, ISSN 1941-7020
2. Alternative Fuels: An Energy Technology Perspective, IEA/ATO working paper, Paris:
International Energy Agency, 2010.
3. Ross Braun, Doug Karlen and Dewayne Johnson, Sustainable Alternative Fuel Feedstock
Opportunities, Challenges and Roadmaps for Six U.S. Regoins, Soil and Water Conservation
Society, September 2010.
4. Clean Cities Program of U.S dept. of Energy.
Available online at: http://www1.eere.energy.gov/cleancities/
5. Department of Energy
Available online at: http://www.energy.gov/
6. Alternative Fuels Data Centre
Available online at: http://www.afdc.energy.gov/fuels/biodiesel_basics.html
7. Biodiesel, Wikipedia
8. Liquefied Natural Gas, Wikipedia
9. Methanol, Wikipedia
10. Heejay Kang, An Analysis of Hybrid-Electric Vehicles as the Car of the Future,
Dept. of Science, MIT, June 2007
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Powertrain Component:Variable Valve Lift
Subodh PachghareCRESTKPIT Technologies LimitedPune, India
Areas of InterestHigh Performance Computing,Parallel Programming,Operating System Internals & Automotive
,
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I. Introduction
Today's modern car engines are the bestexamples of precision control systems, andform a crucial part of powertrain, comprisingtransmission, drive shafts, differentials andfinal drive system. In this article, we will focuson micro-components of the engine,especially the parts that help the engine to
breathe. Inlet and outlet valves are the onesthat allow the engine to inhale air-fuel mixtureand exhale burnt gases respectively, thus, inturn producing rotational power by means ofexpanding gases.
Figure 1: Basic Engine Assembly (Ref. 1)
II. What are Engine Valves?
III. How Variable Valve Timing
Works?
To understand what exactly valves do, we willtake a look at Figure 1. Valves are controlledby camshafts having lobes designedspecifically to tap the valves that are reversetensioned by springs. This peculiar tapping bylobe opens the valves inside the cylinder up toa particular depth defined by the geometry ofthe lobe. As soon as this lobe rotates, the
springs cause the valve return to its originalposition. Both intake and exhaust cams areoperated by timing belts, which are againdriven by the engine power produced in thelast cycle. Each camshaft rotates once forevery two rotations of the crankshaft.
As explained earlier, today's engines canregulate opening of valves. As explained inSection II, all valves open at the same timewhen the lobe rotation hits each valve. Now, ifyou want to specifically control the timing anddelay the opening of valves of the exhaust,you will need a separate control mechanism
on exhaust camshaft. Variable valve timing isachieved by cam phasing or by using multiplecamshafts. Both the systems employ heavyamount of sensors to detect optimal timingsand act accordingly.
Based on the crank-shaft rotational speedsensor and ECU (Electronic Control Unit), thecar decides the timeframe for which to openthe exhaust valves and the intake valves. Cam
phasing takes input from the crankshaftpositional sensor, which in turn retards thetiming of the camshaft, thus, causing morepotent explosion of air-fuel mixture. Thisresults in high torque in the given RPM(revolution per minute) bracket. Cam phasingonly works on the concept cam phase angle.However, during recent times, cam phasing isknown to have some limitations. Variablelobes cannot be used in cam phasing due tothe oscillating angle position of the cam shaft.Early opening of valves (advance stage) canbe done by rotating the cam angle in the clock-wise direction while delayed opening of valves
(retard stage) can be done by rotating the camangle in a counter-clock wise direction [2].
IV. Disadvantages of Pure Vvt
Systems, Need for Variable Valve
Lift & Design
Only advancing and retarding of a valvedoesn't result into optimum torque delivery inhigh/low rpm range. Design of lobe can bealtered to enable change in lift height of thevalves, thus, creating overlapping regions ofperiod of intake valve openings as well asexhaust valve openings. So VVT system
underwent design revisions to change thecam dynamically. Lobe structure is given inFigure 2.
The flank of the lobe determines the lift of thevalve i.e. height of the valve opening. Theduration of the lobe also alters the time forwhich the valve remains open. On onecamshaft rod you can have multiple lobesspaced; ECU can shift the camshaft axially toengage different lobes based on the need andfeature tuning done by the car driver.Hydraulic actuators can be used to shift thecamshaft. At higher engine speeds, most of
VVTL systems shift to higher lift and higherduration lobes. Higher lift causes more air tobe pumped into the cylinder. Engines revvingat high speeds, for example 5000 rpm, cangenerate enough air momentum to shut thevalves from inside of the cylinder. Hence,special attention has to be paid whileopening/closing of the valves.
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Figure 2: Camshaft Lobe Cross Section (Ref. 3)
If the engine is naturally-aspirated non-turbocharged