“Eliica” – the 370Km/H Maximum Speed Electric Vehicle
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TRANSPORTATION AND SAFETY IN JAPAN “ELIICA” - THE 370KM/H MAXIMUM SPEED ELECTRIC VEHICLE Hiroichi YOSHIDA Hiroshi SHIMIZU Professor, Graduate School of Media and Governance Professor, Faculty of Environmental Information Keio University Keio University 1. INTRODUCTION development target, basic technol- the wheel can be dispersed. Global warming is caused by ogy and development processes of The purpose of developing excessive emission of carbon diox- Eliica. Eliica was to realize an electric ve- ide into the atmosphere and the hicle with versatility, practicability rate of this emission due to ve- 2. DEVELOPMENT TARGET and usefulness as an embodiment hicles is shown to be 20% of the OF ELIICA of automobile engineering through total. Our goal is to develop an elec- applying the compactly wrapped Therefore, there have been tric vehicle that will eventually settle up integrated platform concept to many projects aimed at replacing down in society as a down-to-earth a passenger vehicle. conventional internal combustion vehicle. We believe that society In line with this purpose, engine vehicles. would not accept any new product Eliica was developed in two types; Among these, the motor without new features. one named “high speed type” de- driven cars using a secondary bat- In order to create such new signed to make higher maximum tery as the power source have been features, we recognized that the speed available by adopting smaller called “electric vehicles.” Although vehicle body structure should be gear ratio on the built-in motor; the these vehicles have a long history different from that of conventional other type with larger gear ratio of development, there has not been internal combustion engine vehicles. putting more emphasis on the ac- any electric vehicle that has been Finally we arrived at the concept of celeration. put on the market widely. However, integrated platform. As shown in From the standpoint of ve- a large size Lithium-ion battery Figure 1, this concept consists of hicle practicability, the high-ac- was successfully developed. Since the following components; (1) in- celeration type is more useful. We this new battery is promising for wheel motor, or the motor housed thought, however, that development electric vehicles, the potential of the in the wheel; (2) component-built- of high-speed type is also important electric vehicles has been enhanced in frame that is comprised of a hol- because it facilitates evaluation of again. low frame structure under the floor safety as well as expression of its The author and his team have with the batteries and other major capability in a straightforward been convinced that the Li-ion bat- components housed therein, and fashion. tery powered electric vehicle is ex- (3) tandem wheel suspension Concerning the style of ve- tremely feasible, not only because which replaces a large wheel with hicle, Eliica was defined as a ve- of its minimum burden on the en- two smaller wheels so that the hicle that has features of both a vironment but also because it en- force from the ground acting on sports car and a passenger sedan. ables the addition of new features to electric vehicles. In an attempt to In-wheel motor prove this, a prototype, named Motor is mounted in each wheel Eliica was developed. This name is • High efficiency • Lighter weight an acronym of “Electric Lithium- • Expanded effective space Tandem wheel suspension Ion Battery Car”, which represents Spring systems of two wheels are connected by hydraulic piping. a new image of the electric vehicle • Improved ride comfort • Improved cornering speed having completely different func- • Expanded effective space tions than conventional electric ve- Component built-in frame hicles. Batteries, inverters and controllers are mounted under floor The Eliica Project was a col- • Lighter weight laborative project by 35 participat- • Lower center of gravity ing companies . • Expanded effective space This paper introduces the Fig. 1 Vehicle body with new concept of the integrated platform 74 • IATSS RESEARCH Vol.29 No.2, 2005 With internal combustion en- Manganate for the plate. For each shown in Table 2. Since this in- gines, these different usage types of the two Eliica prototypes, differ- verter needs to be installed in a can not help having contradicting ent battery specifications are used; limited space of the component features, like horse power and ride, a power intensive battery for high built-in frame, it was specially de- either of which needs to be sacri- speed type and energy intensive signed to have sufficient capabil- ficed to place emphasis on the other. type for the high acceleration type. ity of supplying power while it is On the other hand, the con- Table 1 summarizes the basic prop- constructed within the size limita- cept of an integrated platform al- erties of these batteries. tions, or height, width and length, lows the car to have wider floor In this project, 80 cells are as shown in Table 2. space as well as huge driving connected in series to form a bat- power from the eight motors and tery stack. (3) Motor batteries under the floor. Also, the Each Eliica carries 4 battery The electric motor selected is component built-in frame enables stacks, each providing a power a synchronous motor using a Nd- to lower the center of gravity, source for two motors. With this Fe type permanent magnet. The which is effective for improving power arrangement, the vehicle number of extremes and poles are ride and stability of the car body. would not stall instantly even when 8 and 12, respectively. On top of these, eight wheels of the one battery or motor fails, resulting The rotor is an inner rotor tandem wheel suspension remark- in improved fail-safe capability. type with its surface lined with ably improves ride on a rough road firmly fixed magnets. The rotor di- as well as increases the tire adhe- (2) Inverter mensions are 114mm dia. and sion during negotiation curve. The inverter employed is a 86mm long and the permissible me- Thus, the use of the inte- PWM controlled type with IGBT chanical rotational speed is 14,400 grated platform can provide wide as the switching element. The ba- rpm. space and ride comfort required for sic specifications of the inverter are sedans and can also realize high maneuverability and driving per- Table 1 Specifications of lithium-ion battery on Eliica formance required for sports cars. Prototype No.1 Prototype No.2 Thanks to these characteris- Total length, mm 170 170 tics, Eliica is supposed to be either Total width, mm 47 47 a sedan that outperforms a sport Total height, mm 133 133 car, or a sports car that offers space Weight, kg 2.1 2.1 and ride comfort equivalent to or Nominal energy density, Wh/kg 41 72 better than a sedan. In other words, Nominal power density, W/kg More than 1,500 More than 700 the project ambitiously aimed at a vehicle combining features of both Table 2 Specifications of inverter a sports car and a sedan, which is referred to as a “cross-over vehicle”. Prototype No.1 Prototype No.2 Total length, mm 380 380 Total width, mm 300 300 3. BASIC TECHNOLOGY OF Total height, mm 150 150 ELIICA Weight, kg 17 17 3.1 Elemental technology Maximum output capacity, kW 80 60 (1) Battery Maximum input voltage, V 360 360 The battery used is a Lithium- Maximum current, Arms 459 459 ion battery employing Lithium Carrier frequency, Hz 12 12 IATSS RESEARCH Vol.29 No.2, 2005 • 75 Table 3 Specifications of motor Prototype No.1 Prototype No.2 Total length, mm 195 195 Diameter, mm 214 214 Weight, kg 20 20 Maximum torque, Nm 100 100 Maximum rotational speed, rpm 12,500 12,500 frame is comprised of the central Fig. 4 Integrated platform block where the batteries are stored and the side blocks where the in- verters are housed. Besides, a rect- angular protrusion is provided on both sides of the central block to accommodate suspensions and other components. The battery storing block and Fig. 2 Appearance of in-wheel motor the rectangular protruding portion are formed with thin, hollow struc- Fig. 5 Photo of Eliica tural members of extruded alumi- num. With four such members 3.2Vehicle body construction being welded together. Figure 3 spindle sensor attached to the technology shows a section of the frame. steering distributor. (1) In-Wheel Motor The vehicle body design of The motor is integrated with (3) Tandem Wheel Suspension Eliica was built up on the basis of a planetary gear for speed reduc- In Eliica, the two front wheels the body construction technology tion, outer ring rotating wheel hub are located forward of the front described above, to which added bearing and disc brake unit, and wheel with narrow spacing. the suspension structure, upper inserted into the wheel as a pack- The front two axels are steered frame, upper body, and finally the age. The gear ratio for the plan- by a system wherein the turning interior. etary gear is 3.257 for No.1 vehicle force on the steering column is dis- Figure 4 shows a photograph and 6.923 for No. 2. tributed to the first and second of the integrated platform with sus- The disc brake adopts a float- axels through different gear ratios. pension mounted viewed from the ing type, and on the rear side of this This mechanism for distribution of rear of the vehicle. brake is mounted a parking brake. steering effort is called a steering The appearance of the com- Figure 2 shows the overall distributor in this paper. For each plete car body is shown in Figure view of the in-wheel motor.