Development of Mount for Electric Powertrains - A Multi Degree of Freedom Optimization Approach

<div class="htmlview paragraph">As the community is becoming more and more aware and conscious of the pollution problems caused by the internal combustion engine and its use in transportation, we are now seeing the first projects and prototypes regarding hybrid and electrically-powered vehicles.</div> <div class="htmlview paragraph">One of the main problems witnessed by engineers has been that of the relatively low operating range provided by the storage batteries available on the market today, and so, recovering the energy that is inevitably lost during braking is of primary importance.</div> <div class="htmlview paragraph">The concept of regenerative braking is fairly simple as it consists in making the electric motors function as generators.</div> <div class="htmlview paragraph">In many of today's applications we find two indipendent controls for the operation of the hydraulic brake and for the activation of regenerative braking. The choice on which braking mode to use, or in which sequence the two modes are to be used is left to the driver who, at the onset of braking, is forced to make mental considerations in order to activate the two braking modes in the right sequence. Furthermore, the driver must not forget to disable the regenerative function at the end of each stop.</div> <div class="htmlview paragraph">BREMBO has designed a braking system in which a single control, that is, the brake pedal, activates and disables in the right sequence the two different braking modes, thus allowing:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"> <div class="htmlview paragraph">to maximize energy recovery by the electric motors each time the driver steps on the brake pedal;</div> </li> <li class="list-item"> <div class="htmlview paragraph">the hydraulic brake to be used in addition to regenerative braking when the latter is not enough to produce the required deceleration.</div> </li> </ul> </div> <div class="htmlview paragraph">The proposed braking system is lightweight and versatile. It can be adapted to the different powertrain configurations seen on various electric vehicles.</div>

<div class="htmlview paragraph">The Idaho National Engineering Laboratory (INEL) evaluates EV propulsion systems and components for the U. S. Department of Energy (DOE) Electric and Hybrid Vehicle (EHV) Program. This paper describes an INEL study which compares the exterior and interior acoustic noise levels of an electric vehicle to its internal combustion engine (ICE) counterpart base vehicle, under various operating conditions.</div> <div class="htmlview paragraph">The electric vehicle was a converted 1988 Ford Escort station wagon, retrofitted with a DC electric powertrain developed by Soleq Corporation. A comparably-equipped gasoline-fueled ICE-powered Ford Escort station wagon provided the baseline acoustic noise levels with which to compare the electric vehicle. Measurements of the interior and exterior noise levels were obtained using a Bruel and Kjaer (B&K) Type 2231 Modular Precision Sound Level Meter. The tests were conducted in accordance with applicable Society of Automotive Engineer's (SAE) standard practices (<span class="xref">1</span>, <span class="xref">2</span>, <span class="xref">3</span>, <span class="xref">4</span>, <span class="xref">5</span>, <span class="xref">6</span>, <span class="xref">7</span> and <span class="xref">8</span>)<span class="xref">*</span> at Chrysler's Arizona Proving Grounds in Wittmann, Arizona.</div> <div class="htmlview paragraph">The results indicate that radiated interior and exterior acoustic noise levels of the electric vehicle were noticeably quieter under acceleration and idle conditions. However, under constant speed operation the electric and the ICE exhibited essentially equivalent interior and exterior noise levels.</div>

<div class="section abstract"><div class="htmlview paragraph">Electric Vehicles is the new trend in automotive industry and differentiator is electric motors which are taking over a conventional internal combustion engine. One of the major challenges with electric vehicles is the efficiency of E-drives, which is mainly affected by motor operating temperatures. Temperature affects the motor characteristics (torque vs speed), which could result in motor underperform or even fail to perform. Hence, it is critical to develop and design a methodology which can accurately predict the electric motor thermal behaviour in advance or try different iterations before getting in to a detailed and extensive analysis. The correct identification of temperatures inside the motor at different drive cycles, has always been a challenge. Experimental validation of motors gives accurate temperature measurements, but it has dependencies on prototypes which costs heavily, and feedback is not available at design stage. Another way is to have detailed 3D Simulations at early stage of design, but it is time consuming for model building and solving which delays the design phase. To solve this, a combined hybrid method of 1D Lumped Parameter Thermal Network (LPTN) approach and 3D Conjugate heat transfer (CHT) approach is proposed. In the proposed approach, detailed multidisciplinary discretized 1D LPTN model method is developed to predict temperature distribution for input drive cycles. 1D LPTN model has fidelity to analyse any drive cycle and incorporate electromagnetic, mechanical and friction generated heat losses which gives reasonably accurate temperature identification at faster solving rates. After identifying the worst cases based on 1D analysis, detailed 3D CHT finite element analysis is used to understand the temperature sweeps, rises and hot spots on the motor components at shortlisted drive cycle cases. This hybrid (1D LPTN and 3D CHT) approach, will help in early design stage by predicting motor temperatures quickly and efficiently, which saves product development time. In this Hybrid approach, the 1D and 3D thermal models are optimised and then validated with test data to establish the method.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Electric vehicles (EVs) present a distinct set of challenges in noise, vibration, and harshness (NVH) compared to traditional internal combustion engine (ICE) vehicles. As EVs operate with significantly reduced engine noise, other sources of noise, such as motor whine, power electronics, and road and wind noise, become more noticeable. This review paper explores the key NVH issues faced by EVs, including high-frequency tonal noise from electric motors, gear meshing, and vibrations. Additionally, it examines recent advancements and trends in NVH mitigation techniques, such as active noise control, improved material insulation, and advanced vibration isolation systems. Furthermore, this paper discusses the role of computational tools, simulation technologies, and testing methodologies in predicting and addressing NVH concerns in EVs. By providing an in-depth analysis of the challenges and the latest innovations, this review aims to contribute to the ongoing development of quieter and more refined EVs.</div><div class="htmlview paragraph">EVs pose unique challenges in the realm of noise, vibration, and harshness (NVH) that differ from those encountered in traditional internal combustion engine (ICE) vehicles. With the significant reduction in engine noise in EVs, other noise sources—such as motor whine, power electronics, and road and wind noise—become more prominent. This review paper delves into the primary NVH challenges associated with EVs, including the high-frequency tonal noise produced by electric motors, gear meshing, and vibration issues. It also explores the latest advancements and trends in NVH mitigation techniques, such as active noise control, enhanced material insulation, and advanced vibration isolation systems. Additionally, the paper highlights the role of computational tools, simulation technologies, and testing methodologies in predicting and addressing NVH challenges in EVs. Through a comprehensive analysis of these challenges and innovations, this review aims to support the ongoing efforts to develop quieter and more refined EVs</div></div>

<div class="section abstract"><div class="htmlview paragraph">In the pursuit of carbon emission reduction, hybridization has emerged as a significant trend in powertrain electrification. As a crucial aspect of hybrid powertrain system development, achieving high brake thermal efficiency (BTE) and a wide operating range with high efficiency are essential for hybrid engines to effectively integrate with the hybrid system.</div><div class="htmlview paragraph">When developing dedicated hybrid engines (DHE), several design considerations come into play. First, in order to make efficient use of available resources and enable engine production on the same assembly line as conventional engines, it is crucial to maintain consistency in key design parameters of the cylinder head and block, thus extending the platform-based design approach. Among the key measures to achieve high BTE, cooled exhaust gas recirculation (EGR) has been extensively explored and proven effective in improving efficiency by mitigating knocking and reducing engine cooling heat loss. Fast combustion, acting as a facilitator, becomes crucial for the system to handle high EGR rates. Therefore, a high-tumble combustion system design is required as an integral part of the hybrid engine to promote rapid combustion.</div><div class="htmlview paragraph">Optimizing the gas exchange system is another crucial aspect in achieving high brake thermal efficiency. Investigation results indicate that through system optimization and trade-offs, optimal matches can be found among EGR rate, cam duration, and compression ratio for a hybrid engine. Furthermore, by optimizing energy management strategy with the hybrid system, the engine operates under high-efficiency regions for the majority of the WLTC test cycle, resulting in reduced fuel consumption.</div><div class="htmlview paragraph">This paper describes the evolution of combustion system design from conventional engines to DHE at SAIC Motor, and presents investigations into the impact of key technical measures on brake thermal efficiency. It also explores the optimization of energy management strategies and their effect on engine operating conditions and fuel consumption of the hybrid vehicle in the WLTC cycle.</div></div>

<div class="section abstract"><div class="htmlview paragraph">One of the practical consequences of the development of low CO₂ emission cars is that many of the traditional NVH sound engineering processes no longer apply and must be revisited.</div><div class="htmlview paragraph">Different and new sound sources, new constraints on vehicle body design (e.g., due to weight) and new sound perception characteristics make that the NVH knowledge built on generations of internal combustion-powered vehicles cannot be simply transferred to Hybrid and Electric Vehicles (HEV). Hence, the applicability of tools must be reviewed and extensions need to be developed where necessary.</div><div class="htmlview paragraph">This paper focuses on sound synthesis tools as developed for ICE-powered vehicles. Because of the missing masking effect and the missing intake and exhaust noise of the Internal Combustion Engine (ICE) in electric vehicles, on one hand electric vehicles are quieter than traditional vehicles. On the other hand, other components such as HVAC system, alternator, vacuum pump, power-steering pump, cooling systems, transmission systems, inverter noise, etc., become more important and generate new complex sound signatures. Typically, their interior noise is well-defined by high-frequency noise components which can be subjectively experienced as annoying, hence the increased importance put to sound quality aspects and perceptual-relevant NVH studies.</div><div class="htmlview paragraph">In the paper, a Virtual Car Sound (VCS) synthesis technique for HEV is designed. This approach turns out to be a very helpful engineering tool to design a brand specific sound and allows reproducing typical sound features of HEV during real-time driving simulation based on a Sound Quality Equivalent Model (SQE). Several SQE models were constructed for different powertrains of HEV in various engine conditions. Finally, the results of the sound metrics and listening tests indicate a comparison between the synthesized sounds and the original sound recordings.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The means of vehicle propulsion - sources of mechanical work - comprise Otto or Diesel cycle engines. However, in hybrid or purely electric vehicles, the arrangements of powertrain can be configured in a whole range of new possibilities. The demands of working arrangements and specific performance in automotive applications are now imposed on the electric motorization. The electrical energy storage has been of interest for science and technology due to the multiplicity of solutions that rely on this function. The theoretical principles have evolved, as well the technological resources and the knowledge of materials. This exploratory study investigates the national objectives for electric and hybrid vehicles in Japan and South Korea regarding types of light-duty urban vehicles under development and their main characteristics in terms of vehicle propulsion seeking to present the progress achieved by companies that already sell some models, including Hyundai, KIA, Nissan and Toyota. Secondary data were collected from specific literature and technical publications. In addition, we considered the public policies adopted in Japan and South Korea at different stages and specificities of the value chain of electric and hybrid cars. With this study, we expect contribute to mapping the possibilities and alternatives for a sustainable development of the emerging industry of electric and hybrid vehicles in Brazil.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Conventional charging systems for electric and plug-in hybrid vehicles currently use cables to connect to the grid. This methodology creates several disadvantages, including tampering, risk, depreciation and non-value added user efforts. Loose or faulty cables may also create a safety issue. Wireless charging for electric vehicles delivers both a simple, reliable and safe charging process. The system enhances consumer adoption and promotes the integration of electric vehicles into the automotive market. Increased access to the grid enables a higher level of flexibility for storage management, increasing battery longevity.</div><div class="htmlview paragraph">The power class of 3.7kW or less is an optimal choice for global standardization and implementation, due to the readily available power installations for potential customers throughout the world. One of the key features for wireless battery chargers are the inexpensive system costs, reduced content and light weight, easing vehicle integration.</div><div class="htmlview paragraph">This paper demonstrates a wireless charging design with minimal component content. It includes a car pickup coil with 300 mm side length and low volume and mass 1.5 dm<sup>3</sup> power interface electronics. After an overview of its hardware requirements, power transfer and efficiency benefits are presented, providing the anticipated horizontal and lateral deviations.</div><div class="htmlview paragraph">An intense magnetic field is required to transfer the target power at low volumes between the transfer units. This field heats up any metal object over the transfer coil, similar to an induction oven. Consequently, the system should be powered down whenever a metal object is detected in this area. A Foreign Object Detection (FOD) design has been developed to continuously monitor the critical high field area. Device testing results are also provided.</div><div class="htmlview paragraph">Field characteristics are verified alongside the vehicle, ensuring system safety for living beings; compliant with all applicable standards reference limits which is more challenging than the basic limits [<span class="xref">13</span>].</div></div>

<div class="htmlview paragraph">Controlled Auto-Ignition (CAI) combustion, also known as HCCI or PCCI, has recently emerged as a viable alternative combustion process to the conventional spark ignition (SI) or compression ignition (CI) process for internal combustion (IC) engines, owing to its potential for high efficiency and extremely low emissions. One of the most effective and practical means of achieving CAI combustion in an engine is to retain or recycle the burnt gases. In order to understand better the effects of recycled burnt gases on CAI combustion, detailed analytical and experimental studies have been carried out. The analytical studies were performed using an engine simulation model with detailed chemical kinetics.</div> <div class="htmlview paragraph">The five effects of the recycled burned gases studied include:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">(1.)</span><div class="htmlview paragraph">Charge heating effect: higher intake charge temperature due to hot burned gases;</div></li> <li class="list-item"><span class="li-label">(2.)</span><div class="htmlview paragraph">Dilution effect: the reduction of oxygen due to the presence of the burned gases;</div></li> <li class="list-item"><span class="li-label">(3.)</span><div class="htmlview paragraph">Heat capacity effect: due to higher specific heat capacity of burned gases;</div></li> <li class="list-item"><span class="li-label">(4.)</span><div class="htmlview paragraph">Chemical effect: chemical reactions involving CO<sub>2</sub> and H<sub>2</sub>O in the burned gases</div></li> <li class="list-item"><span class="li-label">(5.)</span><div class="htmlview paragraph">Stratification effect: recycled burned gases are stratified from the fuel/air mixture.</div></li> </ol> </div> <div class="htmlview paragraph">And the main conclusions are:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">(1.)</span><div class="htmlview paragraph">The charge heating effect is mainly responsible for the advanced AI timing due to hot burned gases. It increases the heat release rate and shortens the combustion duration.</div></li> <li class="list-item"><span class="li-label">(2.)</span><div class="htmlview paragraph">The dilution effect does not affect AI timing, but it extends combustion duration. Its slows down the heat release rate only when large amount of burned gases is present.</div></li> <li class="list-item"><span class="li-label">(3.)</span><div class="htmlview paragraph">The heat capacity effect is mainly responsible for the reduction in the heat release rate, and it has a similar effect to extend the combustion duration as the dilution effect.</div></li> <li class="list-item"><span class="li-label">(4.)</span><div class="htmlview paragraph">The chemical effect does not affect AI timing and heat release rate. It reduces the combustion duration slightly at high concentrations of burned gases.</div></li> <li class="list-item"><span class="li-label">(5.)</span><div class="htmlview paragraph">The stratified burned gases facilitate the CAI combustion due to the presence of higher temperature region at the boundary between of the hot burned gases and combustible charge.</div></li> </ol> </div>

<div class="section abstract"><div class="htmlview paragraph">Global CO<sub>2</sub> reduction by 2021, according to some projections, will be comprised of multiple vehicle technologies with 7% represented by hybrid and electric vehicles (2% in 2014) [<span class="xref">1</span>]. Other low cost hybrid methods are necessary in order to achieve widespread CO<sub>2</sub> reduction. One such method is engine-off coasting and regenerative braking (or recuperation) using a conventional internal combustion engine (ICE).</div><div class="htmlview paragraph">This paper will show that a 48V power system, compared to a 12V system with energy storage module for vehicle segments B, D and E during WLTP and NEDC, is much more efficient at reducing CO<sub>2</sub>. Passive engine-off coasting using 12V energy storage shows a CO<sub>2</sub> benefit for practical real world driving, but, during NEDC, multiple sources of friction slow the vehicle down to the extent that the maximum benefit is not achieved. By adding active engine-off coasting at the 48V level the CO<sub>2</sub> emissions for NEDC are improved by decreasing the rate of deceleration with a 48V electric motor for propulsion. Also important, which will be explored in more detail, are the necessary power dimensions for the major components for different electrical load profiles.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Globally all OEMs are moving towards electric vehicle to reduce emission and fuel cost. Customers expect highest level of refinement and sophistication in electric vehicle. At present, the customers are sensitive to high pitched tonal noise produced by electric powertrain which gives a lot of challenges to NVH engineers to arrive at a cost-effective solution in less span of time.</div><div class="htmlview paragraph">Higher structure borne tonal noise is perceived in electric vehicle at the vehicle speeds of ~ 28 kmph, 45 kmph and 85 kmph. The test vehicle is front wheel drive compact SUV powered by motor in the front. The electric drive unit is connected to cradle and subframe with help of three mounts. Transfer path analysis (TPA) using blocked forces method is carried out to identify the exact forces of the electric drive unit entering the mounts. Powertrain mount is characterized by applying the predicted forces and dynamic stiffness at problematic frequency is measured. By reducing the dynamic stiffness of powertrain mounts, the noise levels are reduced by ~ 5 dB (A). The dynamic stiffness at powertrain mount connection point on cradle and subframe is increased by ~ 2 times which reduced noise by ~ 3 dB (A). With all the modifications, noise levels are considerably reduced by ~ 10 dB (A). NVH criteria which should be considered to avoid the structure borne tonal noise is also elaborated.</div></div>

<div class="htmlview paragraph">Hybrid and Electric Vehicles offer the possibility of fuel saving by regenerative braking, where the electric motor is used as a generator which converts the kinetic energy of the moving vehicle into electric energy when decelerating the vehicle. Special brake systems are needed to entirely exploit the regenerative capability of these vehicles. The brake systems command the two brake actuators (electric generator and brake pressure) and are capable of regenerative blending between them.</div> <div class="htmlview paragraph">This article describes the design of the specific regenerative brake system (RBS) developed by Continental for different hybrid vehicles which went into series production in summer 2008 in the US. The system layout and the components are shown. Specific emphasis is put on general issues involved with regenerative brakes and on the control and failsafe of the specific system. Experimental data from the vehicles brought into series production prove the performance of the system.</div>

<div class="htmlview paragraph">Hybrid electric vehicles (HEV) and other advanced propulsion technologies offer greater fuel economy and lower pollutant and tailpipe emissions. Some experts regard the HEV technology as a practical, attractive solution to social concerns about fuel economy (and related fossil fuel conservation) and vehicle emissions. [<span class="xref">Maples 98</span>] The technology is practical; however, an HEV is more expensive to produce than a conventional internal combustion engine (ICE). In a world of limited resources and many petroleum users and emissions sources, the policy question is whether the best use of resources is to build HEV, to improve the fuel economy and lower emissions from other sources, or to devote the resources to other environmental projects.</div> <div class="htmlview paragraph">We compare the second generation (designed for the United States) Toyota Prius, to the conventional internal combustion engine Toyota Corolla. We examine both private (vehicle purchase price, maintenance, and fuel) and social (the pollutant [non-methane organic gases, carbon monoxide, nitrogen oxides] and carbon dioxide emissions) costs. For each of the vehicles, we evaluate lifetime vehicle exhaust emissions as well as upstream emissions from producing the fuel.</div> <div class="htmlview paragraph">We find that the second generation Prius is still not cost-effective in improving fuel-economy and lowering emissions. For the Prius to be attractive to U.S. consumers, the price of gasoline would have to be more than three times greater than the present level. To be attractive to regulators, the social value of abating tailpipe emissions would have to be 14 times greater than conventional values. Alternatively, the value of abating greenhouse gas emissions would have to be at least $220 per ton. We judge that any HEV would have a difficult time competing with the Corolla because of the Corolla's already high fuel economy and low pollutant emissions.</div> <div class="htmlview paragraph">We also examine the costs and benefits of making a GM Silverado pickup truck into a gasoline hybrid. Like the analysis of the Prius, we again find that the price of gasoline or social value of abating carbon dioxide would have to be higher than the base case values in order to payback the cost of converting the vehicle to an HEV. Finally, we find that at current gasoline prices and carbon dioxide valuation, a conventional vehicle would need to have a fuel economy of 13 mpg or less in order for a $4,000 cost of converting it to an HEV to get 30% better fuel economy would pay off. We conclude that HEV will not have significant sales unless fuel prices rise several-fold or unless regulators mandate them.</div>

<div class="htmlview paragraph">Tomorrow's winning powertrain solutions reside in those technology combinations providing optimized propulsion systems with zero emissions and no cost or performance penalty compared with today's vehicles.</div> <div class="htmlview paragraph">The recent Kyoto Protocol for CO<sub>2</sub> reduction and the California Air Resources Board (CARB) thrust for zero emission vehicles along with the European Regulatory community, motivate car manufacturers to adopt new light body structures with low aerodynamic drag coefficients, low-rolling resistance and the highest efficiency powertrains. The environmental equation expresses car manufacturers aptitude and desire to create zero emission vehicles at acceptable levels of performance unlike limited range electrical powered vehicle products.</div> <div class="htmlview paragraph">The cheapest solution to the environmental equation remains the conventional internal combustion engine ($30 to $50 per kW). However, new system optimization is necessary and will take many forms from alternative fuels enriched with hydrogen to diesel direct injected engines for light duty trucks and sport utility vehicles. Diesel fuel will probably be the favorite mid-term option with direct injection engines coupled with an electric motor. This combination gives higher efficiency, but a new optimized aftertreatment system will be necessary to satisfy emission mandates.</div> <div class="htmlview paragraph">Hybrid vehicles, the Toyota Prius being an excellent example, will increase in popularity with their high efficiency and driving smoothness.</div>

<div class="section abstract"><div class="htmlview paragraph">Due to stringent emission norms, all OEMs are shifting focus from Internal combustion engine (ICE) to Electric vehicle (EV). NVH refinement of EVs is challenging due to less background noise in EVs in comparison with ICE vehicles.</div><div class="htmlview paragraph">Motor whine noise is perceived inside cabin till the speed of 20 kmph. Vehicle is powered by electric powertrain (EPT). Electric powertrain is connected to the subframe with the help of three powertrain mounts. Subframe is connected to the body with the help of four mounts. With the help of Transfer Path Analysis (TPA), it is identified that the noise is structure borne and the dominant path is identified. By optimizing the stiffness of the EPT mounts, the structure borne noise levels are reduced. But reducing the stiffness of EPT mount deteriorated the road noise levels. The reason behind deterioration of road noise is investigated. The performance of double isolation of EPT is compared with single isolation of EPT with respect to both road and motor noise. Modal criteria which needs to be considered for EPT and subframe mount development in design stage with respect to road noise and structure borne motor noise is also discussed.</div></div>