M. Gordić i dr. Prepravak u električno vozilo: optimizacija parametara u procesu konstruiranja ISSN 1330-3651 (Print), ISSN 1848-6339 (Online) https://doi.org/10.17559/TV-20160613131757 ELECTRIC VEHICLE CONVERSION: OPTIMISATION OF PARAMETERS IN THE DESIGN PROCESS Mirko Gordić, Dragan Stamenković, Vladimir Popović, Slavko Muždeka, Aleksandar Mićović Preliminary communication One of the directions for making cleaner and more economic vehicles is to adopt electric vehicle concept. The paper shows current design concepts for electric vehicles worldwide, as well as current sources for supplying vehicles with electric energy. It describes a conversion of one vehicle so that it can be powered by electric motor. The results of tractive and dynamic characteristics calculation and vehicle stability simulation, before and after the conversion, are shown. Obtained results and influential factors are analysed so they can be optimised in order to influence the final characteristics of the converted vehicle. The conclusion is that the complete optimisation process should be performed before the beginning of vehicle conversion in order to avoid undesirable effects, i.e. undesirable characteristics of converted vehicle and high conversion costs. Keywords: conversion; electric vehicle; vehicle dynamics Prepravak u električno vozilo: optimizacija parametara u procesu konstruiranja Prethodno priopćenje Jedan od pravaca ka stvaranju čistijih i ekonomičnijih vozila jeste prihvatanje koncepta električnog vozila. Rad predstavlja suvremene koncepte konstrukcije električnih vozila širom svijeta, kao i načine snabdjevanja vozila energijom. Opisan je prepravak vozila kako bi ga se moglo pogoniti elektro- motorom. Prikazani su rezultati vučno-dinamičkog proračuna i simulacije stabilnosti prije i poslije prepravka. Analizirani su dobiveni rezultati i utjecajni čimbenici radi optimiziranja u cilju utjecaja na karakteristike prepravljenog vozila. Zaključeno je da je proces optimizacije neophodno provesti prije početka prepravka kako bi se izbjegle neželjene posljedice, tj. neželjene karakteristike prepravljenog vozila i visoki troškovi prepravka. Ključne riječi: dinamika vozila; električno vozilo; prepravak 1 Introduction aspect of optimising vehicle parameters when making decisions regarding production, i.e. conversion into a At the mention of global warming, the first thing that completely electric vehicle. comes to mind is an increasing number of vehicles in traffic, as well as exhaust gases these vehicles emit. 2 Electric vehicle drive Analyses show that, from 1880 to 2012, average temperature on the surface of the Earth has increased by One or more electric motors are used to propel an 0,85 °C [1], and it is anticipated that by the end of the 21st electric vehicle. Electric motors can significantly differ in century this value will reach 3,7 °C [2]. In the meantime, construction, working principle, mass and dimensions – concentration of carbon dioxide (CO2) in the air has which are all parameters that need to be considered in the increased by 40 % compared to preindustrial period [2]. It design process. However, the types of electric motors is expected that climate changes will have direct effect on used in vehicles will not be discussed in this paper, but flora and fauna of the planet [ 3]. only the concepts for their installation. It is estimated that 26,33 % of greenhouse gases Over the time, four basic concepts have become emitted in 2011 in the US are caused by transportation dominant in terms of the number and position of electric (41,2 % of which by passengers cars) [4]. motors [7, 8]: European Environment Agency estimates that 24 % • Centrally positioned motor which transmits its power of greenhouse gases emitted in European Union are and torque through reduction drives, differentials and caused by transportation, with road transportation taking drive shafts to the wheels; part with 19 % in total greenhouse gas emission [5]. • Wheel-hub drive or in-wheel drive is a concept where At the Paris Climate Change Conference held in a motor without the reduction drive is placed directly November 2015, the parties adopted the agreement on on the driven wheel; There are no losses in power limiting the global warming. The climate agreement transmission system here, but since there is no anticipates that, by the end of the century, the increase in reduction drive, the motor works most of the time in global average temperatures will be limited below 2 °C insufficiently efficient mode with low RPM and high compared to preindustrial period [6]. torque; There is a long-time tendency within automotive • Wheel-hub with reduction drive – this solution industry to build vehicles with as low CO2 emission as eliminates the issue of insufficient efficiency by possible. Large vehicle manufacturers make enormous installing additional reduction drive; There are also investments in the development of hybrid drive vehicles, no losses in power transmission system in this case; fuel cell powered vehicles and electric vehicles. However, the main disadvantage of this and the This paper describes a modification procedure for a previous concept is the increase in vehicle unsprung specific vehicle and a comparative calculation of tractive mass which affects vehicle manoeuvrability and and dynamic characteristics. In the conclusion, the increases vibration; importance of shown analyses is emphasised from the Tehnički vjesnik 24, 4(2017), 1213-1219 1213 Electric vehicle conversion: optimisation of parameters in the design process M. Gordić et al. • Close-wheel drive is a drive where motor and infrastructure. However, the advantages of BEVs reduction drive are integrated into a single assembly. outweigh the problems mentioned. However, unlike previous two concepts, power and For hybrid vehicles, the issues are dependence on torque are transmitted to the driven wheels through petroleum derivatives, complex systems, energy source drive shafts; This way, there is no increase in vehicle management and dependence on driving style. unsprung mass; This concept was applied to There is a small number of FCEVs on the market, and Mercedes-Benz SLS AMG E-CELL vehicle. these vehicles are usually built in small series (Honda FCX Clarity, Toyota Mirai, Mercedes-Benz F-CELL…). If we add gearboxes to these four concepts, we could Basic issues are manufacturing, hydrogen storage and generally make a total of six typical configurations that transport, high costs and infrastructure. could be divided into two groups, depending on the The vehicle analysed in this paper uses lithium-ion number of installed electric motors: batteries as energy source (BEV). • One-motor drive: - Motor, gearbox, differential, drive shafts, wheels; 4 Description of the conversion - Motor, constant gear ratio reduction drive, differential, drive shafts, wheels; The converted vehicle is FIAT PUNTO MkII 1.9 - Motor and reduction drive integrated into single JTD, production year 2001. Schematic view of the assembly, differential, drive shafts, wheels. converted vehicle is shown in Fig. 1. • Two-motor drive: Technical characteristics of the original vehicle: - Motor and reduction drive integrated into a single • Vehicle category: M1 assembly, drive shafts, wheels, no differential; • Maximum engine power: 59 kW @ 3000 RPM - Electric motor with integrated reduction drive in • Maximum engine torque: 196 Nm @ 1500 RPM 3 wheel (so-called wheel-hub with reduction drive); • Engine displacement: 1910 cm - Wheel-hub (in-wheel). • Working principle: Compression engine • Vehicle mass in running order: 1170 kg The vehicle analysed in this paper was modified by • Number of seats: 5 installing one electric motor and it has a gearbox, a differential and a drive shaft. Technical characteristics of the converted vehicle: • Vehicle category: N1 3 Electric energy supply • Maximum engine power: 41,51 kW @ 3700 RPM • Maximum engine torque: 128 Nm @ 1500 RPM The previous part of the paper presented basic • Working principle: Electric motor concepts of electric vehicle design regarding their drive. • Vehicle mass in running order: 1215 kg However, in order to use these vehicles, we need to • Number of seats: 2 provide them with such power sources that will enable easy transport, low price and satisfactory vehicle autonomy. That is, in fact, the biggest problem the electric vehicle manufacturers are faced with. Nowadays, we expect the best results from the development of the following three basic concepts for supplying the electric motors with energy [9÷12]: • Battery electric vehicles (BEV) – they have a set of rechargeable batteries permanently installed onto the vehicle; • Hybrid electric vehicles (HEV); • Fuel cell electric vehicles (FCEV). Figure 1 Schematic view of the positions of the elements installed onto the converted vehicle (EM - electric motor, EMC - electric motor For vehicles powered by batteries (BEV) and fuel controller, G - gearbox, BAT - batteries) cells (FCEV), it is necessary to provide completely new infrastructure. Hybrid electric vehicles (HEV) can use The choice of the electric motor and the batteries was existing infrastructure since they use internal combustion made in such a way as to result in the lowest possible engine as a power source. difference in the mass of uninstalled and newly installed BEVs and FCEVs are characterised by zero exhaust elements, while retaining (as much as possible) the emission, independence on petroleum products and high original mass distribution between the axles. This could efficiency of