Designing & Construction of a Motorbike by using HEV Technology

Transcription

1 Designing & Construction of a Motorbike by using HEV Technology M. Zeeshan Shahid, Waleed Abbas, Farid Ahmad Khan Sherwani, M. Bilal Latif, Mariyam Arif Faculty of Engineering and Technology Superior University Lahore, Pakistan Abstract Efforts a re being done in order to make vehicles fuel efficient and less pollutant. Electric vehicles were an uprising so lution but problem was their pro lo nged charging time. Hybrid Electric Vehicle technology became rather popular because such vehicles are capable of giving fuel economy, causing less pollutio n and pro viding bo th speed and power upon need, without any kind of charging limitations. Hybrid technology preferred cars over motorbikes, resulting in their increased cost, by which they have failed to facilitate common consumer. This paper discusses designing and modeling of a motorbike by using HEV (hybrid electric vehicle) technology. A comparison of two HEV configurations has been conducted and discussed. A model of hybrid electric motorbike (HEM) made on ICS (Iso lated Charging System) configuration is discussed and elaborated. The ICS appro ach includes a gasoline engine working as a generato r fo r battery charging and an electrical po wertrain including a motor to power the rear wheel of the bike; together they give fuel economy and less emission. Moreover, the ro le of o ther valuable means such as Regenerative Braking, Solar and Wind is also discussed, which leads to improvement in current design. Index Terms Hybrid Electric Vehicles, Motorbike Modeling, Isolated Charging System. INTRODUCTION (HEADING 1) In today s modern era, scientists are striving to cope up with the increasing demand of fossil fuels and their limited resources. These fuels are being used for generation of electricity, in households, and majorly for transportation. Continuous reduction in these assets has created an alarming situation in the whole world. This situation has arisen at two frontiers; one is the common one, the need for fuel for many applications of life and second is the impact of using fossil fuel on our home, the earth. Use of these fossil fuels contributes to the production of green house gases, hazardous emissions causing pollution and depletion of the ozone causing harmful sun rays to reach the earth surface producing ailments like skin cancer [1]. Electric vehicles were introduced as a solution to the above stated problems but they failed to achieve much popularity among people due to several reasons. Firstly it was due to their prolonged charging time and limited distance coverage per charge. Secondly there comes a social barrier among people regarding buying a vehicle of less power and more limitations, specially the youth prefers power over economy due to their brought up and some natural reasons. In Pakistan, people due to lower living standard, make use of vehicles for many applications rather than mere transportation; as commonly seen with bikes, especially that they are being used for delivering milk, eatables to shops and even for toeing purposes. These all reasons combine and pose rejection to the use of electric vehicles which have limited capabilities. In this paper, with regard to the problems, and the reasons for these problems, a hybrid electric vehicle approach is brought forward. This paper targets the use of this approach on bikes instead of cars. The reason is to facilitate the lower level consumer with a below normal living standard and less buying power; although many hybrid electric cars have been made but they fail to facilitate common population of the country as they are out of reach. HEV APPRO ACH IN BIKES A lot of work is done on the HEV (Hybrid Electric Approach) in the field of automobiles. Many cars are made on hybrid technology but they fail to facilitate the low level consumer due to their higher cost. Hybrid bicycles have also been made which work in combination with the rider's paddle power and electric power of the motor, supplied from the battery. This way these bicycles assist the rider. But this also fails to provide solution to the problems above stated, as they are uncommon and are not much popular especially among Pakistanis. There originates a need for such a vehicle which can deliver economy as well as power, when required. To fulfill this need a new approach of hybrid electric motorbike (HEM) is introduced. Like hybrid cars, hybrid bikes are capable of working on both gasoline engine and electric motor, providing both power and economy. Integration of an electrical drivertrain and powertrain of a gasoline engine is to be done in an effective manner to achieve a good fuel economy at less expense of power and at a decreased cost. There are two separate configurations to interface gasoline powertrain and electrical powertrain; each of which has their own advantages and disadvantages. First configuration is a dual source configuration in which power at wheels can be directly delivered from an electrical powertrain or a gasoline powertrain or by both. This configuration can be termed as a Parallel Hybrid (PH) configuration, as both sources can be utilized in a parallel manner, fig.1 shows this configuration for a hybrid vehicle [2].

2 Figure 1: Parallel Hybrid Configuration Second configuration involves the use of a gasoline powertrain in series with the electrical powertrain, which assists the electrical powertrain. Gasoline powertrain has no direct coupling with the wheels and power supplied to wheels solely by electric powertrain. This configuration has both sources in series which are assisting each other, so this configuration can be termed as a Series Hybrid (SH) configuration, Fig.2 shows this configuration for a hybrid vehicle [2]. On the basis of the behavior and function of electrical powertrain in both PH and SH configurations, the electrical systems involved in both of these configurations can be termed as Regenerative Electrical System (RES) and Isolated Charging System (ICS). Target is to improve the overall efficiency of the system by making improvements in the electrical portion of the system. Regenerative Electrical System In this system configuration a DC motor is coupled with front or rear wheel in such a way that when bike s speed is from zero to forty kilometers per hour or any threshold defined, only electrical motor works, engine stays off and bike runs on battery[2]. In this operation mode, engine is turned off and bike is in neutral. As soon as the bike speed crosses a defined threshold (say it achieves a speed of 41km/h) a control system comes into operation, it engages the clutch, gears the bike to a gear corresponding to speed (say 3 rd gear for 41km/h). Now user can use the bike as a normal gasoline bike. This mode is suitable for high speed & power applications where economy is not preferred. User has the choice to chose between Automatic (Hybrid Configuration) or Manual modes (Complete Electric or Complete Gasoline) as per requirement. If the user continues to use the Automatic mode, as soon as the bike slows down and reaches a predefined threshold, the control system operates and engages the clutch, gearing control activates to take the bike to neutral, after that electric motor is given signal to operate. The regenerative part in this solution is the unique ability of the system [2]. Whenever the user is in gasoline mode or speeding, the motor will start working as a generator and will charge the battery. In this system the clutch and gearing control system can be made simpler by only using the clutch and holding it until the motor operates and then releasing the clutch when motor disengages. This way the need for automatic gearing can be overcome. Figure 3 shows that bike wheels can get power from both gasoline engine and DC motor but only by one at a time. Figure 2: Series Hybrid Configuration During engine operation, power from wheels is also fed to the same dc motor working as a DC generator this time. Advantages Less weight of system because no separate generator is required. Same motor works as generator. Less space required in the bike due to absence of a separate generator. Space can be reduced even more by using a hub motor instead of a mounted one. Identical mechanical design requiring less mechanical alteration in a regular gasoline bike as no changing is required in the current chain drive mechanism. Speed and Power available on demand. If one requires more power during a climb up, one can switch to gasoline engine and obtain power directly from it. Backup available. If during a journey one source malfunctions (say engine), one can still switch to battery power. Similarly if electrical powertrain malfunctions, petrol engine is still available. Less powerful motor is required due to presence of an engine. Disadvantages Less generator efficiency due to variable wheel RPMs [2]. Excessive load on engine to run the generator as well as bike on Gasoline. Bigger engine required for the application (100cc or greater) results in less fuel economy. Isolated Charging System It is comparatively a much simpler system. As seen from its name, it has an isolated charging system for the battery and all the power supplied to wheels is by means of a DC motor. Figure 3: Regenerative Electrical System

3 In this configuration, bike thoroughly runs on electric power just like an electric motorbike in which a battery is charged and then battery supplies power to the DC motor which in turns power up the wheels. The reason this system is different from a regular electric motorbike is that a regular electric motorbike runs on battery and requires plug in charging for 2 to 3 hours on a speed charger and 5 to 6 hours on a regular low current charger [8]. This is a major flaw due to which sale of electric vehicles is not much impressive. The isolated charging system (ICS) is a solution to this flaw. In Figure 4 it can be clearly seen that Isolated Charging System is a cyclic process. In this process bike solely runs on electric power by a DC motor which is being supplied power through battery just like a simple electric bike, but when battery charge drops from a certain level, (say less than 70% or defined by user) controller starts the engine and in turn generator starts converting mechanical energy to electrical energy and starts storing it in the battery. It also provides enough power to keep the motor running. As soon as a required charge level is reached, controller cut offs the engine and bike again continues to run on battery solely. In this way engine s energy never gets wasted and results in better fuel economy. Use of engine can then be further minimized by using alternative electric power sources like plug-in charging option, regenerative approaches and by integration of renewable energy sources to the bike. Advantages Less Pollution. System is able to store mechanical energy of the engine even when bike is at rest. In this way even when bike is at a traffic signal, engine s energy is still being stored, whereas ordinary gasoline bikes are wasting fuel at that time, giving rise to pollution. More Fuel Economy. As maximum energy from fuel is stored in the battery without waste, by which engine never runs in vain and its utilization is less. Smaller engine (50cc) can do the same job as there is no bike load on engine and it has to run the generator only. More efficient due to absence of chain drive and transfer of power to rear wheel in electrical form. Fuel economy can be increased even more by plug in charging whenever available. Bike can work solely as an electric bike although some charging and distance limitations are present. Disadvantages More weight due to a separate generator [2]. Sole dependency on motor, if motor malfunctions, no backup is available. More powerful motor is required due to overall dependency on it. Maximum speed and power is compromised due to motor limitations. More changes are to be made in mechanical design as chain drive is to be removed and generator is to be coupled with engine. Figure 4: Isolated Charging System DESIGNING HEM BY ICS CONFIGURATION Despite of some disadvantages like excessive weight, and power limitations, ICS configuration is more acceptable to RES. This is because of the fact that in isolated charging system configuration, engine s output power never gets wasted during idling and is stored in the battery pack. Infrastructure Isolated charging system is deployed in such a way that the DC power stream is maintained at a constant voltage level of 80 Volts, the output from all the sources is brought up to the DC mainstream level and is fed to the stream. Mainstream behaves like a bus bar, on which both load and sources are coupled. A mainstream controller oversees the behavior of all the sources and loads connected to the power bus; it also maintains DC levels by controlling the power from source to load. A block diagram of schematic power bus is shown in Fig. 3 Electric Motor A Permanent Magnet DC motor is selected. The reason for its selection is its high efficiency up to 95% [3].A 1000 Watt DC motor is specified for the current design. A hub motor, replacing the rear wheel and chain drive is used. Motor power was computed by formula: s : a = = : ( ) : is the power required in horsepower. is the force required to push the bike, given in Pounds per foot. S is the required speed of the bike. Terminal voltage is kept 72V in order to reduce the current drawn by motor, which results in a smaller winding size of the motor and cheaper equipment. A Shunt DC Hub motor is used in order to save space and extra weight; moreover it does not require any separate mechanical coupling mechanism. Motor speed is controlled by armature resistance control method because of its simplicity, controllability, and easy deployment [4]. Battery A 72volt 20 ampere-hour capacity LiFePo 4 (Lithium-Iron Phosphate) battery pack is used. Li-Ion battery is preferred because of their higher charge concentration, less weight, long

4 life (greater than 1200 charge & discharge cycles), environment friendliness and thermal stability [5]. These batteries are capable of delivering higher charge and discharge rates, which conveniently suits the current requirement of 1C charge rate in order to charge the battery with one hour of engine operation. Battery pack is preferred on sealed boxed type battery, in order to utilize the space in the bike frame in best possible way by altering the shape of the battery pack as per requirement. Charging time of battery was computed as follows: ( h) o w =? o? ( ) Where ( is the Charging time of the battery in hours. For at least two hour of operation the battery capacity is found out by: u = c Where t is the capacity of the battery in ampere-hours. e is the ampere drawn by the motor and is the time for which the motor is to operated. Electric Generator An Alternator is used instead of using a PMDC (Permanent Magnet DC Generator) because of less cost, flexibility of rewinding and achieving any required output voltage and current. Moreover, due to its AC construction, not only an alternator weighs less, and is smaller as compared to a PMDC generator, but also subjects less load on the engine after modification. Alternator is driven by the engine by a belt drive. An alternator is rewound in order to get an output of 80 Volts and 20 Amperes. Voltage level is kept higher than the terminal voltage of the battery, in order to provide effective charging even after going through all the conversions. 20 Ampere current was selected in order to charge a 20Ah Li-ion battery at 1C charge rate, so that battery gets fully charge in an hour, which means less engine operation and maximized economy. Figure 5: Control Infrastructure Engine A four stroke CDI engine with a 50CC Head is used to reduce the fuel usage. Engine is completely automatic, with self start feature, automatic twin gear transmission, and automatic clutch. The reason for including these features is because an independent operation is required by the engine. Engine is to be controlled by a main controller which gives a signal to engine when battery goes below a threshold and then engine starts; afterwards, when battery reaches a threshold, engine goes off again. Chassis A common 70cc bike chassis is altered in order to mount all the components and make space for the battery bank. Vehicle aerodynamics and outlook is considered during modifications, so that bike may not lose the attention of the market. OPTIMIZATIO N A MAT LAB simulation done for a similar series hybrid configuration of a bike using an HCCI engine is showed an improvement of 132 % in the bike economy and the fuel consumption improved fuel economy form Km/liter to Km/liter [6]. Which justifies that implementation of series hybrid system on bikes is a successful approach. To further optimize the efficiency of the motorbike it is required to keep the engine OFF as long as possible. This can be done by deploying alternative power sources on the bike. The best replacement for these alternative sources is the renewable and regenerative resources. Bike is exposed atmosphere in a direct manner, so renewable energy sources like Solar Photovoltaic Cells and Miniature wind turbines can be deployed to improve the overall performance. Another option is to provide a plug in power jack in the bike. At any long stay, bike can be plugged to a wall socket for charging. Solar Power Deployment of solar panels requires a large surface area. To reserve such area on a bike is quite difficult if the panel to be deployed is in one piece. The area requirement is fulfilled by modifying the panel shape, which is done by cutting the panels or by buying solar modules of a required size. Modules are required to coupe up with the installation of solar panels on less surface area of the bike. These modules can be pasted on curved surfaces of the bike, like upon the fuel tank, on mudguards and on front hood in required quantity, in such a way that the resultant voltage of all the modules reaches the voltage level of the power bus of the bike. This will ensure that same voltage level is available throughout the power bus for battery charging and motor operation. Power Jacket A new approach introduced for deployment of solar modules is in the form of a solar jacket. It is a jacket which is to be worn by the rider. Jacket will have a top layer of solar module. Rider will wear the jacket and when rider sits on the bike, the jacket can then be interfaced to the bike s power bus by means of a jack. This jacket will then contribute to the power stream by providing solar power. Also this power jacket

5 will include jacks inside the pockets for charging cell phones etc. A conceptual design of a solar jacket is shown in Fig. 4. Wind Power: A bike is effectively exposed to high speed wind on the way. This wind potential can be utilized by deploying miniature wind turbine (MWT) on the bike. Just like the solar module, the MWT installed will have the same voltage profile as of the whole system and will produce current according to capacity. This will aid to maintain the overall voltage and will contribute to the power bus of the bike. Installing site for turbine may include front hood fiber body manufactured in such a way that it covers the turbine and provides an air intake for it. Regenerative Sources Regenerative technologies like Regenerative Braking System (RBS) can be effectively utilized to capture energy fro m the traction during braking[d]. RBS will not only store the energy that will be wasted when motor draws high current during start and stop operation but it will also add up to the braking power by electronic brakes. RBS is proved to increase the range of an electric vehicle up to 15% [7]. A motor controller with MOSFET based regenerative system will be used to extract power from the hub motor. RBS will also save energy during idle operation of the bike on a slope. REFERENC ES 1. M. Norval, The human health effects of ozone depletion and interaction with climate change, University of Edinbergh Medical School, EH8 9AG, Carriere. W. M. The future potential of electric and hybrid vehicles, Washington D.C. : Congress of the United States, Office of Technology Assessment, 1982, pp Groen and Benjamin Carson, Investigation of DC motors for electric and hybrid electric vehicles using an infin itely variable transmission, Brigham Young University, 2010, pp Chapman. Electric Machinery Fundamentals. 4 th ed., McGraw-Hill, 2003, p Thorat and Indrajeet Vilasrao. Understanding performance limiting mechanisms in Li-Ion batteries for high rate applications, Brigham Young University, 2011, pp Yuh-Yih Wu1, Chen Duan, Kai-Xian Hong1, Hsien-Chi T sai1 and Craig J Hoff, Design Modeling and Development of a serial hybrid motorcycle with HCCI Engine Advances in Automobile Engineering, Iqbal Husain. Electric and Hybrid Vehicles: Design Fundamentals. New York: CRC Press, C. Ellers, Electric Vehicle Conversion Manual, CONCLUSION By implementing electric hybrid technology on vehicles, their fuel economy and efficiency can be increased effectively. Series hybrid configuration with an isolated charging mechanism is better as compared to parallel hybrid configuration on the basis of fuel economy. Parallel hybrid configuration is useful when power and economy are required as demanded by the user. Usage of regenerative approach like Regenerative Braking System and Renewable Energies like photovoltaic cells and miniature wind turbines can effectively improve the efficiency and distance coverage range of hybrid electric vehicles. Figure 4: Conceptual design of a Power Jacket