Finding Ultimate Limits of Performance for Hybrid Electric Vehicles

<div class="section abstract"><div class="htmlview paragraph">Increasingly stringent regulations in the field of pollutant are forcing engine manufacturers to adopt new solutions to contain exhaust emissions, such as Hybrid Electric Vehicles (HEV) or Full Electric Vehicles (FEV).</div><div class="htmlview paragraph">Still far from the wide diffusion of FEV limited from electrochemical storage systems together with the difficulty of creating adequate infrastructure distributed throughout the territory to recharging batteries, the HEV seems to be actually a better solution. The hybrid vehicle is already able to guarantee satisfactory autonomy and low pollution levels by combining the advantages offered by the two technologies of thermal and electric propulsion.</div><div class="htmlview paragraph">Currently on the market there are several types of hybrid vehicles, with different degree of hybridization (electric motor power versus propulsion total power), capacity to store electricity and type of scheme constructive adopted for the integration between the thermal engine and the electric machine.</div><div class="htmlview paragraph">A particular interest is getting the mild-hybrid (or light hybridization) and the micro-hybrid (or minimum hybridization) with 48V electrical system added to the classic 12V one.</div><div class="htmlview paragraph">A possible solution could be the electric turbo-compounding system where a turbine coupled to a generator (turbo-generator) uses the exhaust gas flow of a reciprocating engine to harvest waste heat energy and convert it into electrical power. In this way, the power generated from the system can be used to feed local electrical loads such as engine auxiliaries, increasing the whole system efficiency.</div><div class="htmlview paragraph">The present study deals with the simulation of a spark ignition engine, present in a test room of Istituto Motori (CNR), including a turbo-generator at the exhaust to evaluate the advantages in terms of overall efficiency. The internal combustion engine model was developed by using a 1D code (GT-Power software), while the turbo-generator and the electric system are described in the Matlab/Simulink environment.</div><div class="htmlview paragraph">The results obtained showed an appreciable increase in the overall efficiency.</div></div>

<div class="section abstract"><div class="htmlview paragraph">In recent years, global warming, depletion of fossil fuels, and reducing pollution have become increasingly prominent issues, resulting in demand for environmentally-friendly two-wheeled vehicles capable of reducing CO2 emissions. However, it remains necessary to meet customers’ expectations by providing smaller drivetrains, lighter vehicles, and support for long-distance riding, among other characteristics. In the face of this situation, hybrid electric vehicle (HEV) systems are considered to be the most realistic method for creating environmentally-friendly powertrains and are widely used.</div><div class="htmlview paragraph">This research introduces a hybrid electric two-wheeled vehicle fitted with an electrical variable transmission (EVT) system, a completely new type of electrical transmission that meets the aforementioned needs, achieving enhanced fuel efficiency with a compact drivetrain. The EVT system comprises double rotors installed inside the stator. The hybrid electric two-wheeled vehicle equipped with the EVT system has the electric drive and regenerative braking functions of a fully electric vehicle, internal combustion start and power generation functions as an engine generator, and hybrid power generation functions, including combined power generation and drive through integrated control. The EVT system also provides boost acceleration functions and direct double rotor connection functions, offering wide-ranging advantages compared to conventional motorcycles and enabling the provision of new types of distinctive value.</div><div class="htmlview paragraph">The authors developed a prototype hybrid electric two-wheeled vehicle fitted with this unique EVT electrical transmission.</div><div class="htmlview paragraph">This article considers its qualities compared to other two-wheeled vehicles and describes the hybrid topology, the various functions of the EVT, the working principle of the EVT, the EVT configuration and the two-wheeled vehicle configuration, the prototype EVT machine, the EVT powertrain hybrid control strategy, the hybrid powertrain development environment, the results of hybrid electric two-wheeled vehicle performance measurements and the possibilities presented by hybrid electric two-wheeled vehicles.</div></div>

<div class="htmlview paragraph">An electro-mechanical variable speed transmission (eVT) is proposed for hybrid electric vehicles. The transmission is comprised of a pair of planetary gear trains interconnected with two electric machines and clutches. With on-board energy storage devices, the transmission combines, in a compact unit, independent speed-ratio control and power regulation between the engine and drive wheels. It offers a highly integrated, efficient and low cost solution to hybrid electric vehicles.</div> <div class="htmlview paragraph">Operating principles of the transmission were outlined. Virtual transmission and vehicle prototypes were built with EASY5. Simulations were conducted to evaluate its performance in context of a hybrid electric vehicle. Comparisons were made against non-hybrid vehicles equipped respectively with eVT and four-speed automatic transmission, and against the production hybrid vehicle Prius.</div> <div class="htmlview paragraph">Results showed superior performance of the proposed eVT in hybrid vehicle. It improved vehicle acceleration and significantly reduced fuel consumptions comparing to the non-hybrid vehicles. The fuel economy improvements were 158% for FTP cycle and 92% for HWFET cycle over the non-hybrid vehicle with four speed automatic transmission.</div> <div class="htmlview paragraph">Simulation indicated that the hybrid vehicle with eVT offers considerable technical advantages over Prius. It improved fuel economy and substantially decreased the power and torque demands on electric machines.</div> <div class="htmlview paragraph">The peak torque of the electric machines for eVT was about 1/3 of the Prius, and peak power was about 2/3 of the Prius over various drive cycles.</div>

<div class="section abstract"><div class="htmlview paragraph">The recent advance in the development of various hybrid vehicle technologies comes along with the need of establishing optimal energy management strategies, in order to minimize both fuel economy and pollutant emissions, while taking into account an increasing number of state and control variables, depending on the adopted hybrid architecture.</div><div class="htmlview paragraph">One of the objectives of this research was to establish benchmarking performance, in terms of fuel economy, for real time on-board management strategies, such as ECMS (Equivalent Consumption Minimization Strategy), whose structure has been implemented in a SIMULINK model for different hybrid vehicle concepts. The results obtained from these simulations have then been compared with those derived from a general purpose, off-line optimization technique, based on deterministic DP (Dynamic Programming), and capable of finding the numerical global optimum and of generating the optimal cycle-based control trajectory over a discretized multidimensional grid of the selected state and control variables. The paper investigates the structure of the DP problem and its interactions with the specific hybrid architecture, especially in terms of the most appropriate selection of state and control variables. The implications of the chosen modeling approach are also critically evaluated, searching for the best compromise between accurate simulation results and reliable comparisons between off-line and on-line optimization results.</div><div class="htmlview paragraph">One of the outcomes is that the system model should be designed in order to be compatible with efficient DP techniques implementation, with the objective of obtaining robust optimal control policies while achieving acceptable computational costs.</div><div class="htmlview paragraph">The concepts that have been analyzed in this work are the following two parallel hybrid architectures: HEV (Hybrid Electric Vehicle), normally applied in current hybrid vehicles production, and HSF-HV (High Speed Flywheel Hybrid Vehicle), an interesting and promising hybrid mechanical solution. An example of the influence of the selected gear has also been investigated by implementing a multi-dimensional DP optimization routine. In order to perform this analysis, a general purpose DP MATLAB function, including specifically designed algorithms to avoid numerical interpolation issues that typically occur in constrained problems, has been modified to run any SIMULINK-based engine-vehicle model.</div></div>

<div class="htmlview paragraph">A great deal of interest has been expressed recently in hybrid electric vehicles, both for their potential for reduced environmental impacts as well as their increased range over electric-only vehicles. Several organizations have initiated programs to design and evaluate a specific type of hybrid vehicle, the Range Extender Vehicle (REV). Based upon this industry activity, the U.S. Department of Energy's Electric and Hybrid Propulsion Division commissioned the two-phase study which serves as the basis of this paper.</div> <div class="htmlview paragraph">A range extender vehicle is a hybrid vehicle, where a small engine generator (a “genset”) is added to a basic electric vehicle design. This genset “sustains” vehicle operation beyond the range provided by the batteries. The additional weight of the genset and fuel is balanced by the removal of some of the vehicle's batteries. Such a concept may be useful in the near term, when commercially available batteries are not expected to have adequate specific energy to provide the range necessary for market acceptability.</div> <div class="htmlview paragraph">In Phase I, the range extender designs were based on existing, well-characterized electric vehicle designs. Established driving cycles were used to define the basic energy and power needs of the vehicle systems. The emphasis during this initial effort was placed on near-term designs. These designs were based on the use of existing vehicle platforms (Ford Taurus, Dodge Caravan, and Chevrolet C1500 pickup), available lead acid batteries, and primarily small, off-the-sheff engine generator systems.</div> <div class="htmlview paragraph">The primary performance requirement for Phase I was a minimum generator-set-only top speed of 25 mph (40 km/h). This was done for two reasons. First, it followed the rationale used by several organizations, which indicated that a 6 to 10 kWe generator set would be appropriate for the REV configuration. Second, it provided a useful starting point for REV analysis, yielding a lower bound for potential performance.</div> <div class="htmlview paragraph">The Phase II analysis, which is the basis for this paper, evaluated higher performance REV conceptual designs. National Highway Traffic Safety Administration (NHTSA) standards for electric vehicles as well as development requirements for the Ford ETX-II and Modular Electric Vehicle Programs were used to provide the basis for comparison. These included acceleration, speed at grade, and minimum top speed requirements. In all cases, these desired levels of performance indicated that significantly larger generator sets would be required, estimated to be in the 25-50 kWe range. These requirements dictated the use of more advanced engine technologies. A number of engine types and sizes were examined for application to the REV, including advanced four-stroke, two-stroke, gas turbine, rotary, Stirling, and compression ignition engines. The engines selected for analysis ranged from 24 kWe to nearly 63 kWe, at the operating points selected.</div> <div class="htmlview paragraph">Overall, the Phase II analysis demonstrated that higher-performance REVS could be developed, using more advanced heat engine/generator configurations. This higher performance should appeal to a broader range of potential users (than the Phase I design), increasing the REV's potential market penetration.</div>

<div class="htmlview paragraph">Alternative powertrain configurations such as hybrid electric vehicles and fuel cell vehicles seem to be the best response to the need of reduced pollutant emissions, especially in urban areas, and to meet future emission limits, that appear to be very severe targets for traditional technologies.</div> <div class="htmlview paragraph">In hybrid electric vehicles (HEVs) an internal combustion engine is combined with one or more electric machines, with the aim of extending the range of the electric and making the entire vehicle more energy–efficient. The architecture of a hybrid drive train is complex, comprising at least two different energy conversion devices (i.e. internal combustion engine and electric machine) drawing energy from at least two different energy storage devices (i.e. fuel tank and battery). Moreover, complex control strategies must be defined in order to properly control the division of load between the thermal engine and the electric machines.</div> <div class="htmlview paragraph">To meet increasing global competition, which means reducing lead-time and costs for hybrid vehicles design, it is necessary to develop methods that wouldquickly evaluate various design concepts. Even if many computational models are available to simulate the performances of HEVs, there’s still a lack of generalized mathematical analyses.</div> <div class="htmlview paragraph">An analytical model has been developed in order to study power flows in hybrid vehicle drive trains. The mathematical formulation allows a quick analysis of the complete energy cascade from fuel energy to tractive power, comprising electricity generation and consumption and energy recovery from braking. As a result a general formulation of the total tractive energy and of the global efficiency of hybrid electric vehicles in function of the main characteristics of its components is provided.</div> <div class="htmlview paragraph">The goal of the analytical model is to enable a quick exploration of design possibilities of hybrid powertrains. Some results are presented in order to show how the present model allows a quick insight into the effects of the main system characteristics on the power flows and the corresponding component losses of the drive train.</div>

<div class="htmlview paragraph">Electric hybrid vehicles, because of their multiple energy sources and large varieties of propulsive configurations and control schemes, present a special problem in the development of formalized Environmental Protection Agency (EPA) test procedures. The Jet Propulsion Laboratory (JPL) is undertaking a task under the Department of Energy (DOE) Hybrid Commercialization Project to develop a draft test procedure with supporting actual test data that will assist the government in the development of a formal EPA test procedure for emissions certification and equivalent fuel economy determination for the possible inclusion of electric hybrid vehicles (EHVS) in corporate average fuel economy (CAFE) allowances.</div> <div class="htmlview paragraph">The procedures are being developed by an iterative review process with the interested and effected government agencies and industrial organizations. Data obtained from testing an EHV at JPL and from the General Electric Near-term Hybrid Vehicle program will be used to support the development and verify the procedure.</div> <div class="htmlview paragraph">This paper summarizes the procedure development plan and discusses the impacts and complexities of a variety of factors. A straw-man test procedure is developed and discussed.</div> <div class="htmlview paragraph">The paper emphasizes the need for interaction and input into the development process by all interested parties. While absolute concensus is not realistic, at least the final procedure must be considered “reasonable” and be understood by all the affected interests.</div>

<div class="section abstract"><div class="htmlview paragraph">One of the main advantage of a hybrid thermal-electric vehicle is that the internal combustion engine (ICE) can be shut down when not needed anymore (Stop&Start system, propulsion with full-electric mode), thus reducing fuel consumption. But this use of the ICE impacts its thermal behavior because of a lack of heat source and thermal losses. Furthermore, the ICE is sometimes used with higher load in order to charge the batteries that increases the total heating power produced by the combustion. Therefore, the simulation of hybrid vehicles becomes really interesting to evaluate the effect of different control strategies (energy repartition between the engine and the electric motor) on the fuel consumption. However, in most of actual hybrid vehicles simulation tools, for calculation speed reasons, the thermal phenomena are either not taken into account, or their calculation is not based on physical equations (empirical formulas). Their predictive capability is then limited.</div><div class="htmlview paragraph">The global aim of this study is the development of a simulation tool (using the Amesim® software) for hybrid electric vehicle which takes into account most of the thermal phenomena occurring in the various components and between them without increasing the calculation time. In this paper, we first focus on thermal phenomena occurring in the spark ignition ICE. The coupling of a combustion model with a thermal model of the engine cooling system and its metal parts allows a simulation of its warm-up after a cold start. The thermal transfers between the different thermal inertia are computed and their dependence with different parameters like speed or load is evaluated. Research about the heating speed of the cooling water and the lubricating oil (due to the viscous friction and dependent of the global thermal state of the ICE) are interesting in order to find the best use of the ICE and therefore reducing the fuel consumption. Finally, the model of the engine including the thermal transfers is integrated in a simulation of the whole vehicle.</div><div class="htmlview paragraph">The thermal behavior of two vehicles (a conventional and a parallel hybrid electric) using the same spark ignition engine is finally presented. The first results show that the thermal phenomena have a significant impact on the final consumption of the vehicles.</div></div>

<div class="htmlview paragraph">Hybrid vehicles have been in the news quite a bit of late given the commercial introduction of a number of hybrid vehicles that sport significant improvements in fuel economy. The improved fuel efficiency of these vehicles can be directly attributable to the hybridized power train on board these internal combustion engine vehicles.</div> <div class="htmlview paragraph">Similarly, hybridization of fuel cell vehicles not only helps improve fuel economy but can also help overcome other technical barriers (start up delays, transients). For fuel cell vehicles, hybridization of on-board fuel cell systems is expected to have the potential to improve the vehicle efficiency largely due to the ability to recover braking energy and via flexibility in designing the system controls. However, the advantages can be offset by the tradeoffs due to added energy losses associated with the DC/DC converter and the battery pack itself. Additional tradeoffs not explicitly addressed in this study include added overall complexity, additional packaging constraints, and potentially higher overall cost.</div> <div class="htmlview paragraph">This report will focus on a quantitative analysis of the performance of the indirect-hydrocarbon (IH, onboard fuel processor using gasoline type fuel), hybrid and load-following fuel cell vehicles (FCVs) from the viewpoint of the energy use throughout the system. Specifically, the vehicle energy use and efficiency will be compared between the load following (non-hybrid) and hybrid vehicle platforms.</div> <div class="htmlview paragraph">Several hybrid component configurations were studied and two representative configurations were investigated in depth. The first (Configuration 1), in which the DC/DC converter is placed in the path of the fuel cell stack current, there does appear to be some benefit, in terms of energy usage, in hybridizing the IH fuel cell vehicle.</div> <div class="htmlview paragraph">Specifically, on the US EPA cycles, the hybrid vehicle outperformed the load following vehicle on the FUDS</div> <div class="htmlview paragraph">sequence but the load following vehicle had slightly better results on the HIWAY cycle. However, if the DC/DC converter is placed in the battery current path only, with the fuel cell stack directly connected to the electric drive train (Configuration 2), the benefits in terms of improved fuel economy are larger than in the first configuration. The results corresponding to both these configurations will be analyzed and discussed in this paper.</div> <div class="htmlview paragraph">Overall, three main factors affect these vehicle results, all of which will be explicitly examined in this study.</div> <div class="htmlview paragraph">These factors are: vehicle weight, fuel cell system efficiency (including the battery), and regenerative braking capabilities. Specifically, the hybrid vehicle fuel economy can be reduced due to a ∼10% heavier vehicle, and a lower overall fuel cell system efficiency (when including the battery and DC/DC converter losses). One important factor is clearly the regenerative braking capability; but the other factor is associated with the ability to improve the efficiency of the fuel cell system itself by taking advantage of the flexibility offered energy storage sub-system and adopting better control strategies.. The real question however is whether these gains outweigh the losses introduced by the additional components needed to hybridize the vehicle.</div>

<div class="htmlview paragraph">During last four years the authors were involved in the simulation and investigation of combustion and ionization in the cylinder of gasoline and natural gas Spark Ignition (SI) engine. Two-zone model of combustion and chemical non-equilibrium ionization and results of the numerous numerical investigation were presented by the authors at SAE 2002 and SAE 2003 World Congresses. This model and numerical results provided an important insight into combustion products behavior and gave the chance to find correlation between chemical and thermal ionization of combustion products and SI engine performances.</div> <div class="htmlview paragraph">In order to provide better correspondence of the numerical data to the experimental results in the wide range of operational parameters for different geometry of engines a new three-zone model was developed and successfully tested. In comparison with previous one new model includes the additional third zone, which simulates the processes in the small volume of flame kernel inside the gap between spark plug electrodes.</div> <div class="htmlview paragraph">Following processes in the flame kernel are taken into account:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">detailed mechanism of chemical interaction including chemical and thermal ionization;</div> </li> <li class="list-item"><div class="htmlview paragraph">heat exchange between combustion products and electrodes;</div> </li> <li class="list-item"><div class="htmlview paragraph">mass exchange between third zone and combustion products in the cylinder.</div> </li> </ul> </div> <div class="htmlview paragraph">The comparison of numerical and experimental results showed more accurate correlation between measured and calculated values of pressure and ion current. The concentration of electrons in the gap between spark plug electrodes corresponds better to the experimental data for gasoline engines in comparison with two-zone model. Three-zone model became a new generation among the models for the investigation of in-cylinder combustion products ionization and simulation of operational and ecological performances of SI engine.</div>

<div class="htmlview paragraph">An inlet system can be selected by experiments or numerical analysis. Physical and mathematical models of filling a four-stroke, spark ignition engine with air are discussed in this article. Based on these models software enabling geometrical parameters to be chosen was elaborated.</div> <div class="htmlview paragraph">The main hypothesis is that for initial numerical choice of an inlet system, theoretical analysis can be limited to dynamic phenomena in this inlet system and the process of load charge, compression and decompression.</div> <div class="htmlview paragraph">Model verification was carried out by engine experiments. Modelling and experiments were performed for a four-stroke two cylinder engine with a carburettor which was adopted to an MPI system. For the adaption an inlet system with separate pipes was made. The results obtained show the real advantages of the dynamic charge in terms of performance. Experiments and modelling were limited to the length of pipes.</div> <div class="htmlview paragraph">The physical model of the process was based on the following points:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1</span> <div class="htmlview paragraph">The air in both inlet system and cylinder is treated as a semi-ideal gas.</div> </li> <li class="list-item"> <span class="li-label">2</span> <div class="htmlview paragraph">The air motion is a one-dimensional wave flow.</div> <div class="htmlview paragraph">The mathematical model was formulated using:</div> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">the law of mass conservation</div></li> <li class="list-item"><div class="htmlview paragraph">the law of momentum conservation</div></li> <li class="list-item"><div class="htmlview paragraph">the law of energy conservation</div></li> </ul> </li> <li class="list-item"> <span class="li-label">3</span> <div class="htmlview paragraph">The first law of thermodynamics was used to describe the phenomena in the engine cylinder.</div> </li> </ol> </div> <div class="htmlview paragraph">As a result, the mathematical model consists of differential equations which describe phenomena in both inlet system and cylinder as well as several additional relations.</div> <div class="htmlview paragraph">The following conclusions were made:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1</span> <div class="htmlview paragraph">Length of inlet system influences maximum torque and rev. speed.</div> </li> <li class="list-item"> <span class="li-label">2</span> <div class="htmlview paragraph">The longer the inlet system the higher the torque and the smaller the rev. speed.</div> </li> <li class="list-item"> <span class="li-label">3</span> <div class="htmlview paragraph">The main hypothesis was proved. Using the model and software the initial choice of the inlet system can be made both for newly designed engine as well as for a modified engine.</div> </li> </ol> </div>

<div class="htmlview paragraph">NVH refinement is an important aspect of the powertrain development and vehicle integration process. The depletion of fossil-based fuels and increase in price of gasoline have prompted most vehicle manufacturers to embrace propulsion technologies with varying degrees and types of hybridization. Many different hybrid vehicle systems are either on the market, or under development, even up to all-electric vehicles. Each hybrid vehicle configuration brings unique NVH challenges that result from a variety of sources. This paper begins with an introductory discussion of hybrid propulsion technologies and associated unique vehicle NVH challenges inherent in the operation of such hybrid vehicles.</div> <div class="htmlview paragraph">Following this, the paper outlines a two-dimensional landscape of typical customer vehicle maneuvers mapped against hybrid electric vehicle (HEV) operational modes. Overlaid on this map are NVH issues such as those associated with global powertrain vibration, driveline vibration, HEV component-specific noise, motor/generator whine, accessory noise, gear rattle, and noise pattern changes. The remainder of the paper focuses on specific examples from case studies illustrating key HEV NVH issues such as engine start/stop behavior, motor/generator whine, and influence of electric machines on powerplant integration issues. The use of advanced time-domain methods such as vehicle interior noise simulation (VINS) to understand and optimize HEV vehicle NVH behavior is shown. Finally, the findings from the discussed studies are summarized and appropriate conclusions are drawn with respect to understanding, characterizing, and solving unique hybrid vehicle NVH issues.</div>

<div class="htmlview paragraph">In the “scenario” of increasing concerns for environmental pollution, hybrid vehicles will play a significant role in the near future. Compared to electric vehicles, the hybrid ones have an unrestricted driving range, higher performance and transport capability, still fulfilling ZEV emission regulation.</div> <div class="htmlview paragraph">The hybrid vehicle features a power train that integrates a thermal engine with an electric motor. Among the several possible configurations for hybrid vehicle, the parallel hybrid one has been chosen for the FIAT MULTIPLA, for the following reasons:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">lower weight and volume of the electric unit to obtain the same driving mission;</div> </li> <li class="list-item"><div class="htmlview paragraph">higher global efficiency of the system, due to direct thermal to mechanical energy conversion;</div> </li> <li class="list-item"><div class="htmlview paragraph">a better vehicle performance (acceleration and max speed), thanks to the contribution of both motors to traction.</div> </li> </ul> </div> <div class="htmlview paragraph">In the development of a hybrid parallel concept, the critical aspects to be overcome are related to the system mechanical complexity and the simultaneous control of the two motors.</div> <div class="htmlview paragraph">In this paper the Fiat Auto and Elasis approach to the hybrid vehicle is presented with particular reference to the powertrain unit and its control strategies.</div>

<div class="section abstract"><div class="htmlview paragraph">Hybrid and electric vehicles present a promising trade-off between the necessary reductions in emissions and fuel consumption, the improvement in driving pleasure and performance of today's and tomorrow's vehicles. These hybrid vehicles rely primarily on electronics for the control and the coordination of the different sub-systems or components. The number and complexity of the functions distributed over many control units is increasing in these vehicles. Functional safety, defined as absence of unacceptable risk due to the hazards caused by mal-function in the electric or electronic systems is becoming a key factor in the development of modern vehicles such as electric and hybrid vehicles. This important increase in functional safety-related issues has raised the need for the automotive industry to develop its own functional safety standard, ISO 26262.</div><div class="htmlview paragraph">The aim of the paper is to briefly introduce the ISO 26262 standard and the specific hazards associated with hybrid and electric vehicles. The paper will highlight how the risk-based approach of ISO 26262 can influence the safety integrity level of some safety related functions specific to hybrid and electric vehicles. It will also highlight how well established safety related functions, such as torque monitoring of a conventional internal combustion engine can be influenced through vehicle hybridization. A vehicle safety concept for the torque monitoring of an electric vehicle will then be presented. The results of the implementation of this functional safety concept in an electric vehicle developed by the company FEV GmbH will be shown as example. The first measurements made in the vehicle show that the monitoring concept fulfills the reaction time requirement to ensure that unintended torque increase do not lead to uncontrollable vehicle acceleration.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Solid particle emissions from a modern gasoline hybrid electrical vehicle (HEV) and a conventional gasoline vehicle were studied under diverse transient drive cycles on a chassis dynamometer.</div><div class="htmlview paragraph">It is found that solid particle emissions from the conventional gasoline vehicle which has a 3.8-liter engine are sensitive to vehicle temperatures. Over 90% of solid particles are emitted during the first 250 seconds of transient cycles. Spikes for solid particle emissions from the HEV during a transient cycle are mainly caused by engine starts, hard accelerations after engine starts, and the engine running harder at high vehicle speeds. The engine and vehicle temperature status on the HEV doesn't show a strong correlation to the solid particle emission.</div><div class="htmlview paragraph">While the conventional gasoline vehicle is cold, it emits over 2 times less solid particles than the HEV although it is larger and has heavier curb weight; and, while it is fully warmed up, it emits over 30 times less solid particles than the HEV. It is likely that frequent engine starts and a relatively higher percentage of maximum engine torque and power caused by engine downsize are contributing factors to increasing solid particle emissions from the HEV.</div></div>