In troductio n of Hybrid Electric VehicleAbstract: As the environmental pollution and energy crises are getting more and more remarkable, hybrid electric vehicles (HEVs) have taken on an accelerated pace in the world. In this paper, we will see the types of HEV, and introduce somefamous HEVs in Chi na and all around the world.Key words: HEV, automobile, Classification, development.In 1997, Toyota Motor Corporation released the hybrid electric vehicle ( HEV in the world, which was n amed "Prius".Firstly, what is a hybrid electric vehicle? Broadly speaking, a hybrid electric vehicle has two power sources at least, no matter fossil fuel, nuclear energy, solar en ergy or electric en ergy and so on, but in real life, most hybrid cars use the traditional internal combustion engine and electric motor as a power source.Why hybrid electric vehicle feel valued by many coun tries rece nt years? As weknow that, oil is not in resources,a lot of information indicate that if miningspeed rema in at curre nt level, proved oil reserves could merely use fifty to sixty years, so, en ergy supply becomes a tough questi on. And also by the reas on of more and more serious en vir onmen tal polluti on, hybrid electric vehicles have to be pushed onto the stage of history.And what is the adva ntage of hybrid electric vehicles whe n compared to blade electric vehicles(BEV) or conventional vehicles? The characteristic of the electric motor is, when compared to internal combustion engine, more quiet, efficie ncy and cleaner, i n the same time, speed-torque con trol features is more flexible. When at low rotate speed, electric motor has a constant torque, when at high rotate speed, it has a constant power. Hybrid electric vehicles combine electric drive with traditional internal combustion engine drive, give full play to the adva ntages of both. Mean while, it can effect a perma nent cure to the problem of blade electric vehicles(BEV)'s weak dyn amic performa nee and short cruis ing distanee. In summary, as a appropriate transitional product, hybrid electric vehicle is a good choice in this time that energy crises are getting more and more remarkable and the development of new energy automobile is still in a primary.Compare to conventional vehicle, HEV can save fuel for the following reasons.(1) HEV can store part of the vehicle ' s kinetic energy in battery while brakingor dow nslope in which otherwise is bur nt in the brake drums in the form of heatin conven ti onal vehicle.(2) The ICE in an HEV can be designed with a smaller displacement withoutcompromis ing the performa nee of vehicle. [1](3) HEV can make ICE operate at maximum efficiency point or optimal operating lineby regulating the output power of battery to satisfy the required power of vehicle.(4) HEV is a multiple en ergy system; the main issue of HEV is how to optimize thepower flow to obtain best fuel economyor low emission at lower cost, which is often referred to as the en ergy man ageme nt (EM) problem. The issue will be discussed innext section in detail. [2]Classificatio nHybrid electric vehicles can be classified accord ing to the way in which power is supplied to the drivetra in. So, it has three types.The first one is called the series hybrid, picture 1.1 [3] shows the simple structure of this type. Series hybrid is the simplest of three types. The mechanical en ergy made by in ternal combusti on engine tran sformmed into electricity through generator, then one part of the electricity is used to propel the wheels through electric motor and transmission, and the other part of the electricity is used to recharge the storage battery, when the vehicle is accelerating or on other workingcondition, this part can be used. They also usually have a larger battery pack than parallel hybrids, making them more expensive. Oncethe batteries are low, the small combustio n engine can gen erate power at its optimum setti ngs at all times, mak ing them more efficie nt in exte nsive city driv ing. Compared to conven ti onal internal combustio n engine vehicle, it is a electrombile with a assista nt engine, in order to in crease the trip dista nee of a vehicle. There is no clutch in the mecha ni cal connection device of engine and electric motor, so it has Someflexibility. Although the transmission structure is simple, it still need three driveparts,engine, gen erator and electric motor. If in con siderati on of large climbi ng gradie nt and frequent acceleration, the maximumpower should be supplied, the three drive partsn eed higher quality. This type of structure is widely used on urba n buses, rarely used on salo on cars. [4]The second one is called the parallel hybrid, picture 1.2 [3] shows the simplestructure of this type. What this type differe nt from the series hybrid is that it propels the vehicle by two independent drive system of engine and electric motor. Engine and electric motor usually drive wheels through different clutches, it can adapts three different work pattern:single engine drive, single electric drive andhybrid drive, this system is suitable for a wide variety of driving conditions, especially for complex road. On the contrary, it is a engine with a electric motor, in order to reduce emissions and fuel consumption. Whenthe power provided by engine exceed what the vehicle n eed or on rege nerative brak ing, electric motor work ing at a stage of a gen erator, charge the excess en ergy into the storage battery.Compared to the series hybrid, the patten of parallel hybrid only need two drive part of engine and electric motor, in addition, before the storage battery is discharged, its power requireme nt of engine and electric is lower. [4]The third one is called the power-split hybrids, picture 1.3 [3] shows the simple structure of this type. This type combines the features of the parallel hybrid and the series hybrid. Compared to the series hybrid, it has added the tran smissi on line of power mach in ery; Whe n compared to the parallel hybrid, it has added the tran smitt ing way of electric en ergy. Thus, power-split hybrids have the ben efits of a comb in ati on of series and parallel characteristics But on the other han d, it also causes the shortage of structural complexity and high cost. [4]According to the motor output power accounted for the percentage of total output power in the whole system, hybrid systems can be divided into the follow ing fourcategories, it also can be described as the degree of hybridization.The first one is called the micro hybrid. In this hybrid electric system, a belt-alter nator startergen erator is moun ted at the start motor of conven ti onal in ternal combusti on engin e.This electric motor con trols the start and shutoff of the engine in the same time, thus, it has can celled idli ng worki ng con diti on and cut dow n the fuel con sumpti on and exhaust emissi on. From the strict sen se, micro hybrid is not really a hybrid electric system, because its electric motor by no mea ns provides the vehicle a con ti nu ous power.The second one is the light hybrid. This hybrid system adopts a integrated startergenerator(ISG),in comparison with the previous one, it can start or stop the engineby a dynamo, it also can achieve some other functions, for instant, when at the operation condition of decelerating or braking, it can absorb a portion of the en ergy, and whe n driv ing the vehicle, engine operates at a con sta nt speed, the en ergy produced by engine can be divided to driv ing the wheels or to charge the battery reas on ably. The mixed ness degree of this system usually below twenty percents. General Motors Corporation's hybrid electric pickup trucks use this the hybrid system.The third one is namely the mild hybrid. It also has a integrated starter generator, whilst what different from the light hybrid system is that it adopts a high tension dynamo. In additi on, whe n vehicle is accelerat ing or at high load con diti on, the electric motor gives a assist to the engine to propel the vehicle, in order to make up the lack of power of the engine, con seque ntly impro ving the property of thevehicle. The mixed ness of this system is con siderable high, reach ing a value of 30%about, the mature tech no logies makeit widely used. As compared to full hybrids, mild hybrids have smaller batteries and a smaller, weaker motor/ge nerator, which allows manu facturers to reduce cost and weight. Hon da's early hybrids in cludi ng the first gen erati on In sight used this desig n, [26]leveragi ng their reputati on for desig n of small, efficie nt gasoli ne engin es; their system is dubbed In tegrated Motor Assist (IMA). Starting with the 2006 Civic Hybrid, the IMA system now can propel the vehicle solely on electric power duri ng medium speed cruisi ng. [5][6] The last one is called the full hybrid, sometimes also called a strong hybrid,is a vehicle that can run on just the engine, just the batteries, or a comb in ati on of both. This system adopts a high tension electric motor from 272 to 650V. Compared to the mild hybrid system, the mixedness even reach at a value of 50%. Ford's hybrid system, Toyota's Hybrid Synergy Drive and General Motors/Chrysler's Two-Mode Hybridtech no logies are full hybrid systems. Ford's hybrid system, Toyota's HybridSyn ergy Drive and Gen eral Motors/Chrysler's Two-Mode Hybridtech no logies are full hybrid systems.[26] The Toyota Prius, Ford Escape Hybrid, and Ford Fusi on Hybrid are examples of full hybrids, as these cars can be moved forward on battery power alo ne.A large, high-capacity battery pack is n eeded for battery-only operati on.These vehicles have a split power path allowing greater flexibility in the drivetra in by in terc onverting mecha ni cal and electrical power, at some cost in complexity. The full hybrid system will gradually become the main developme ntdirect ion with the tech no logy develop ing. [5][6]A new type HEV is called plug-i n hybrid electric vehicle (PHEV), also known asa plug-in hybrid, is a hybrid electric vehicle with rechargeable batteries thatcan be restored to full charge by connecting a plug to an external electric powersource. A PHEV shares the characteristics of both a conven ti onal hybrid electric vehicle, hav ing an electric motor and an in ternal combustio n engine; and of an all-electric vehicle, also hav ing a plug to connect to the electrical grid.PHEVs have a much larger all-electric range as compared to conventional gasoline-electric hybrids, and also eliminate the "range anxiety" associated with all-electric vehicles, because the combusti on engine works as a backup whe n the batteries are depleted. ⑹[7][8] Developme nt in the worldIn HEV's domain, Japan, Germany and America are the main countries, they grasp many tech no logies of hybrid, and they also own many famous HEV products. [9][10] Buick Regal EcoHybrid madeby General Motors Corporation, it adopts the BSGhybrid pattern, fuel consumption per hundred kilometers has lifted from 9.8 to 8.3 litersBMW X5 HEV is the first vehicle that adopts BMW ActiveHybrid system, its hybrid pattern is ISG with AT.[11]Civic Hybrid madeby Honda Motor Corporation adopts a hybrid pattern of ISG withCVT, it is a new gen erati on.Some other hybrid electric vehicles such as S400 BlueHybrid madeby Daimler-Benz Motors Company,Cadillac Escalade, Chevrolet Volt etc, are someoutstanding hybrid electric vehicles. Around the world, Japan is one of the few countries in the fastest rate ofdevelopme nt of electric vehicle tech no logy, especially in terms of the developme nt of hybrid vehicles, Japa n is a world leader. Only two Japa nese car compa nies have the capacity of bulk sales of hybrid vehicles in the world.Recent years, China has put a high value to the research and development of hybrid electric vehicle, colleges, scientific research institutions and companies have be en couraged by gover nment to exploit the way of HEV develop ing. un der such circumsta nces, sig ni fica nt developme nts have bee n made on HEV.Changan Jiex un HEV is the first mild hybrid motorcycle type with in depe ndentresearch in China, and it is mass produced, thereout, Changan Motor Corporationhas set up the Chin a's first product ion line of HEWy totally in depe ndent research and developme nt.Benteng B70 made by First Auto Work is another HEV, it has two electric motor,and is the type of full hybrid. However the manu facturi ng costs is eve n tripleto the same vehicle type of in ternal combusti on engine.Some other hybrid electric vehicles such as Rongwei 750 HEVmadeby Shanghai Motor Corporati on, A3ISG and A5BSG made by Chery Automobile Co, EQ7200 HEV made by Dongfeng Motor Corporati on, F6DM made by BYD Motor Corporati on etc, also playi ng a role in a China's HEV market.Particularly worth mentioning is the BYDMotor Corporation, its "Two-ModeHybrid" is much more advaneed than other companies's. At the Beijing Auto Show in 2012, BYD Motor Corporati on laun ehed their brand new HEV vehicle type which is n amely "Qin g", with the 0-100km/h spri nt completed in 5.9s sec onds it stunned many car enthusiasts. Qing adopts BYD's second generation two-mode hybrid, and it is a parallel hybrid, it came into existe nce marked that Chi na's hybrid tech no logies has reached at a new stage. Just also at the Beiji ng Auto Show in 2014 a few days ago, BYDgave us anther surprise, BYDTang appeared, it's a SUV, the 0-100km/h sprintcompleted in 4.9s seconds stunned us once again. However, comprehensively, hybrid tech no logies in China is mainly focus on light and mild hybrid, lags beh ind developed coun tries.summaryHEVs have many advantages ,however, PEV is not widely used currently. Expensive price keeps people from it. But we can believe that with the tech no logy develop ing, the cost of HEVwill be muchlower, and the reliability will be more better by that moment, HEVs will become mainstream of automobile market, and be loved by people.[1] A. Sciarretta and L. Guzzella, “ Control of hybrid electric vehicles, ” IEEE Control Systems Magazine, vol. 27, no. 2, pp. 60 - 70, 2007. View at Publisher • View at Google Scholar[2] I nternatio nal Journal of Vehicular Techn ology Volume 2011 (2011), Article ID571683, 7 pages[4] Hybridce . 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