Powertrain NVH CAE Predictions with Gasket Consideration

<div class="htmlview paragraph">Low frequency torsional vibrations can be a significant source of objectionable vehicle vibrations and in-vehicle boom, especially with changes in engine operation required for improved fuel economy. These changes include lower torque converter lock-up speeds and cylinder deactivation.</div> <div class="htmlview paragraph">This paper has two objectives: <ol class="list nostyle"> <li class="list-item"><span class="li-label">1)</span><div class="htmlview paragraph">Examine the effect of increased torsional vibrations on vehicle NVH performance and ways to improve this performance early in the program using test and simulation techniques. The important design parameters affecting vehicle NVH performance will be identified, and the trade-offs required to produce an optimized design will be examined. Also, the relationship between torsional vibrations and mount excursions, will be examined.</div></li> <li class="list-item"><span class="li-label">2)</span><div class="htmlview paragraph">Investigate the ability of simulation techniques to predict and improve torsional vibration NVH performance. Evaluate the accuracy of the analytical models by comparison to test results.</div></li> </ol> </div> <div class="htmlview paragraph">A simple model is presented which gives fairly accurate results and can be included in a full vehicle finite element model to calculate vehicle level NVH responses. A procedure to calculate the loads to be applied to the model is also presented.</div>

<div class="section abstract"><div class="htmlview paragraph">While designing the exhaust system of passenger car on one hand there is stringent emission regulations, packaging constraints, high NVH performance requirement. On the other hand with lightweight vehicle design there is tremendous pressure on weight reduction of exhaust system while keep the same NVH performance levels. Exhaust system consist of muffler, bellows, pipes and hangers. For muffler design both acoustic (transmission loss, pass-by noise, tail pipe noise etc.) and non-acoustic (backpressure) parameters needs to be considered.</div><div class="htmlview paragraph">In the current paper, methodology for muffler design optimization using 1D acoustic simulation software is presented. The baseline exhaust design consist of two mufflers; main muffler and post muffler. Simulation methodology is developed to optimize main muffler design in order to eliminate post muffler requirement while achieving the same performance of baseline exhaust design. For this purpose a DOE study is conducted by varying primary muffler internal pipe dimensions, baffle location, perforation etc. to achieve transmission loss (TL) and backpressure (BP) of the baseline design.</div><div class="htmlview paragraph">Based on simulation study a physical prototype is made for optimized exhaust design consisting of only main muffler (with modified design compared to baseline main muffler). Transmission loss and backpressure is measured physically and confirmed that the optimized exhaust design is able to deliver the same NVH performance as that of the baseline exhaust design. Furthermore, a vehicle level physical test is conducted to compare the pass-by noise for optimized exhaust design and compared with baseline exhaust design. It is observed that the optimized exhaust design with one muffler is able to maintain the same pass-by noise level as that of the baseline exhaust design with two mufflers.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Over recent years, NVH refinement of engine is becoming increasingly important in buying decision and can significantly give competitive edge to the vehicle in market place. This paper deals with the development phase of a prototype engine in which a specific testing activity was carried out to improve the overall NVH behavior of the powertrain. In order to explain the optimization process in detail, a case study was described in this paper.</div><div class="htmlview paragraph">First, NVH targets of the engine were set via benchmark tests on existing competitive products. Then series of baseline tests, such as 1M sound pressure level test and noise source identification, were performed on the engine. Test results indicated that an obvious breathing vibration mode exist near the intake manifold, which radiates high level noise.</div><div class="htmlview paragraph">In order to achieve the NVH targets, a correlation validation was performed to find out the main reason that caused the vibration of intake manifold. And then its structure was optimized through CAE analysis to change its modal frequencies.</div><div class="htmlview paragraph">After the optimization work, the NVH performance of the engine was significantly improved.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The increasing trend toward electric and hybrid-electric vehicles (HEVs) has created unique challenges for NVH development and refinement. Traditionally, characterization of in-vehicle powertrain noise and vibration has been assessed through standard operating conditions such as fixed gear engine speed sweeps at varied loads. Given the multiple modes of operation which typically exist for HEVs, characterization and source-path analysis of these vehicles can be more complicated than conventional vehicles.</div><div class="htmlview paragraph">In-vehicle NVH assessment of an HEV powertrain requires testing under multiple operating conditions for identification and characterization of the various issues which may be experienced by the driver. Generally, it is necessary to assess issues related to IC engine operation and electric motor operation (running simultaneously with and independent of the IC engine), under both motoring and regeneration conditions. Additionally, mode transitions, including IC engine start/stop must be assessed.</div><div class="htmlview paragraph">An analysis is presented here, which explores the differences in NVH performance of multiple HEVs currently available in the US-market. Measurements were conducted on these vehicles to assess noise and vibration at the powertrain-level and vehicle interior. Two of the vehicles included in this investigation were then chosen for a more in-depth comparative analysis. The analysis of these two vehicles included assessment of source level excitations and vehicle NVH sensitivities, in the context of boundary conditions driven by their hybrid system architectures.</div><div class="htmlview paragraph">Based on the powertrain and vehicle NVH performance assessments, methods were explored for developing powertrain level NVH targets. For the initial phase of this target cascading process, the analysis was limited to full load (IC engine operational) and part load (EV-only) modes. Based on in-vehicle performance, and vehicle sensitivity information, test procedures and targets were defined for powertrain radiated noise and mount vibration content.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Long glass fiber reinforced (LGFR) composites have been widely used in automotive industry to reduce vehicle weight and maintain relatively high mechanical performances. Due to the injection molding process, the distribution of fiber orientations varies at different locations and through the panel thickness, resulting in anisotropic and non-uniform mechanical properties. The current practice of computer modeling of these materials is generally using isotropic properties adjusted by a certain scale factor. The effect of fiber orientation is not carefully considered due to the complexity of fiber orientation distribution in the LGFR parts.</div><div class="htmlview paragraph">The purpose of this paper is to identify key factors affecting vehicle attribute performances where LGFR composites are used; and provide an efficient way for accurate CAE modeling of LGFR composites. In this study, tensile coupons cut from a simple geometric injection molded plaque are tested. The tested material properties are compared to those from CAE predictions to understand how well the CAE predictions capture the material behavior with fiber orientation accounted for. The fiber orientation is obtained from injection molding simulations and mapped to the CAE model using Abaqus coupled with Digimat to perform micromechanical calculations on material properties. The stiffness of a more complex part at different locations is then compared between physical testing and CAE prediction. Finally the NVH performance of the whole panel is simulated using Abaqus to evaluate the fiber orientation effect.</div></div>

<div class="section abstract"><div class="htmlview paragraph">In this article, NVH performance of fully electric vehicles and some key technologies for NVH improvement are presented. A focus is made on a global NVH simulation methodology able to take into account the electromagnetic excitation sources and all the powertrain structure. Examples of simulation results are shown which allow us not only to predict the NVH performance, but also to understand better the fundamental NVH behavior of an electric motor. In an electric motor, the most important NVH phenomenon is the whistling noise, which is caused by the electromagnetic forces and amplified by the powertrain structure. With the current NVH simulation technology, e-motor whistling noise levels can be accurately simulated up to 4500 Hz.</div><div class="htmlview paragraph">The improvement of e-motor whistling noise can be achieved both by reduction of the electromagnetic forces at the source and by optimization of powertrain structure. As far as the powertrain structure is concerned, there are two modes which have predominant effects on the e-motor whistling noise: the torsional mode (<1000 Hz) and the breathing mode (5000-6000 Hz) of the stator-housing assembly. In the low motor speed range, the dominant phenomenon is the coupling between the 24<sup>th</sup> order tangential electromagnetic forces and the torsional mode of the stator assembly. In the high speed range, the dominant phenomenon is the coupling of radial excitations of 48<sup>th</sup> order with the radial breathing mode of the stator assembly. The choice of powertrain structure design must be made according to NVH targets and according to the constraints for powertrain layout and weight-lightening.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The goal of reducing fuel consumption and CO<sub>2</sub>-Emission is leading to turbo-charged combustion engines that deliver high torque at low speeds (down speeding). To meet NVH requirements damper technologies such as DMF (Dual Mass Flywheel) are established, leading to reduced space for the clutch system. Specific measures need to be considered if switching over from SMF (Single Mass Flywheel) to DMF [<span class="xref">8</span>]. Doing so has an impact on thermal behavior of the clutch system, for example due to reduced and different distribution of thermal masses and heat transfer to the surroundings. Taking these trends into account, clutch systems within vehicle powertrains are facing challenges to meet requirements e.g. clutch life, cost targets and space limitation. The clutch development process must also ensure delivery of a clutch system that meets requirements taking boundary conditions such as load cycles and driver behavior into account.</div><div class="htmlview paragraph">Relevant load cycles are derived based on feedback and analysis of driver behavior under varying road and traffic conditions. For example, one relevant load cycle is the overriding of the clutch in 1<sup>st</sup> or 2<sup>nd</sup> gear in dense traffic condition that causes high thermal clutch load due to heat energy generated at the clutch frictional surfaces. This heat energy is relevant for lifetime or can even destroy the clutch/clutch system if not considered properly within the clutch development process.</div><div class="htmlview paragraph">These load cycles are the input for a simulation based clutch optimization. The virtual optimization process is taking aspects such as thermal and lifetime performance for the given boundary conditions of the system, the available installation space, materials (i.e. friction facing), part geometry and of course the costs into account. This process is based on analytical calculations, thermal and thermal-mechanical simulation and CAD modelling. Recent development in thermal-mechanical simulation methods allow a more application-specific consideration of the thermal behavior of the system, also in the early design phase.</div><div class="htmlview paragraph">To validate simulation results, physical tests were carried out; 1<sup>st</sup> gear repeat vehicle launches on a gradient and 2<sup>nd</sup> gear launches on a flat road which includes temperature measurements to determine the rise in temperature until a certain number of cycles is reached. In this paper, the approach for clutch optimization is shown based on the analysis of two different clutch sets of the same size including experimental results based on vehicle measurements.</div></div>

<div class="htmlview paragraph">This paper reports the latest development of methodologies for testing and CAE modeling of the automobile mounts. The objective of this study is to provide dynamic mount properties for product evaluation and CAE modeling guideline for crashworthiness simulations. The methodology is divided into component, subsystem and full system levels. The study at the component level is to extract the dynamic parameters of mounts, such as stiffness and damping coefficient, based on the component tests. Furthermore, such parameters are employed to investigate the interaction between mount and connecting structures at the subsystem level. A robust connection mechanism from mount to surrounding structures is also developed during this process. Finally, the results from full vehicle system tests are compared with the CAE simulations to verify the methodology at the component and subsystem levels.</div> <div class="htmlview paragraph">A robust component test methodology is the first key element of this study. This paper mainly focuses on the development of a universal test fixture with required instrumentations to achieve acquisition of accurate data from which the mount dynamic properties are identified, and processed. Extracted results are then reduced to appropriate input formats for CAE modeling.</div>

<div class="section abstract"><div class="htmlview paragraph">Global automotive market is noticing an increase in competition from every corner of automobile world since decades and automotive OEMs are on the front line with this competition. Thus, the need of time for OEMs is to develop and maintain the brand image within the market until the launch of new models. Disparate factors within a car distinctly interlinks the customer perception towards a brand image. However, NVH as a factor equally affects the customer decision while choosing a particular brand as it is easily perceivable by any layman customer. NVH fraternity focuses on vibration induced within tactile locations, (i.e. seat, steering wheel, gear knob and floor) in a car. Among all these, Steering wheel and Seat plays a prominent role as it interdigitate directly towards customer comfort. In this detailed study we have focused on Seat as aggregate providing comfort to customer. This paper deals with the evaluation of a newly designed Seat headrest on seat modal analysis and Ventilation provided in Seat and its noise impression at idle condition.</div><div class="htmlview paragraph">However, the stipulation for comfort between customers and automobile OEMs instigating countless innovation within a vehicle components and sub-components. The ventilated seat is a paradigm of such an innovation within automobile world. This paper also deals with the study of inside vehicle cabin NVH performance with and without ventilated seat in operating condition. The whole study revolves around the radiated noise through ventilated seat under distinct probable operating conditions by customer throughout a driving cycle. These conditions encompasses idle, idle + AC with different permutations and combinations of HVAC blower speeds along with ventilated seat blower speeds. The effect on radiated noise of ventilated seat with and without human occupancy has also been studied and covered within this research. Moreover, the radiated noise with simultaneous operation of ventilated seats has also been incorporated within this paper. The whole study has been cascaded to component level to evaluate the effect of various subcomponents on ventilated seat NVH performance. These subcomponents consists of ducts, blowers, its positioning and its operating rpm. The whole research directs at target setting and accomplishing the same during project kick off. This in turn reduces development time and cost throughout the project duration of full vehicle NVH refinement.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The engine research and development has a significant contribution to meet the stringent emission norms and the changing global market demands. Leveraging the available virtual engineering methods to improve performance, velocity, quality and diminish the lead time is the key for any global brand to stay in the competition. It is the key element to reduce the research and development costs substantially by virtually developing the idea as it is conceived.</div><div class="htmlview paragraph">Engine development test cells consist of expensive test and measurement systems which demand skilled labor and advanced equipment. Effective utilization of the test cells is essential to meet the scheduled project deadlines and cost targets. Engine Design process and tools when used effectively can increase the efficiency and lower the test cell operation costs substantially. This paper discusses the examples for this application in the area of engine installation, sensitive instrumentation/assembly.</div></div>

<div class="htmlview paragraph">A look back at some of the failures of space shots shows that often the problems, whose solutions appear simple and obvious, have caused the majority of difficulties. Since experience has shown that these difficulties can generally be related to the packaging aspects, considerable emphasis is placed in this writing on packaging design and manufacturing techniques. While circuit applications have, to the most part, incorporated more standard approaches, it is quite often the package design which gives one a competitive advantage. It is for this reason that the package design considerations could not be covered in as much detail as one would have liked. The major point made here is that proper packaging design has actually a greater effect on reliability than the more theoretical aspect of a reliability program, and that power consumption, weight, size, and reliability must be considered jointly as design parameters.</div> <div class="htmlview paragraph">The welding process and welding controls are discussed in detail as part of the packaging scheme. Here, the importance of allowing enough time for preparation of weld schedules is perhaps the major area of emphasis. With respect to the formulation of encapsulated functional units, the importance of thermo-considerations, repair and maintainability are covered.</div> <div class="htmlview paragraph">In addition, a testing program for design evaluation of space equipment is discussed. It is indicated that present programs do not provide for demonstration of reliability to a meaningful statistical confidence and that other means have to be found to evaluate the design and manufacturing effectiveness to operational conditions. The disciplines discussed here describe such a testing program as seen by a subcontractor responsible for equipments and not systems. In this connection, it is pointed out that, in effect, testing disciplines are restrained by the testing program of the system contractor.</div> <div class="htmlview paragraph">Finally, the effect of scheduling on the implementation of a reliability program is covered, emphasizing the detrimental effects on reliability if other tasks are improperly scheduled or if the schedule is not kept.</div>

<div class="section abstract"><div class="htmlview paragraph">Since 2000, avionics is facing several changes, mostly driven by technological improvements in the electronics industry and innovation requirements from aircraft manufacturers. First, it has progressively lost its technological leadership over innovation processes. Second, the explosion of the electronics consumer industry has contributed to shorten even more its technology life cycles, and promoted the use of COTS. Third, the increasing complexity of avionics systems, which integrate more and more functions, have encouraged new players to enter the market.</div><div class="htmlview paragraph">The aim of this article is to analyze how technological changes can affect the competitiveness of avionics firms. We refer to criticality levels as a determinant of the market competitiveness. Certification processes and costs could stop new comers to bring innovations from the consumer electronics industry and protects traditional players.</div><div class="htmlview paragraph">The study will compare three avionics systems regarding their patent dynamics since 1980: flight controls, Integrated Modular avionics and Head-Up Displays. We assume that differences in the market competitiveness may appear due to their differences in their related criticality level. Systems belonging to Design Assurance Level A or B required wide-range of capabilities and long-term experience. The opportunity for new comers to introduce a certified-version of their product could be constrained by certification requirements.</div></div>

<div class="htmlview paragraph">One goal of modern power train control systems in heavy trucks is to damp driveline oscillations using appropriate controllers. Modern control algorithms like state-space controllers are based on a state-space model, which should accurately characterize the real process behavior. Otherwise, optimal control can not be guaranteed. These state-space models include a huge number of parameters, which have to be identified by an identification process. However, existing driveline models contain two serious problems: an increasing offset over time between measured and simulated data and an inadequate detection of the longitudinal dynamics of the truck. Therefore, this article deals with two goals: to optimize the offline identification process for the special use in driveline systems and to establish an online adaptation of the model parameters to guarantee an optimal model fit.</div> <div class="htmlview paragraph">The considered models of the driveline consists of two or more inertia masses, which are connected by spring-damper-elements. The identification of the resulting model parameters is realized by an adaptive algorithm, which minimizes a weighted cost function. Due to the existing problems, the weighting of the cost functions is extended by dividing the measured data in oscillation phases and scaling the weighting coefficients. A way to identify eigenfrequencies of measured data as well as a new identification routine solving the offset problem is established in this article. Moreover, a new way of benchmarking the identified state-space models is developed.</div> <div class="htmlview paragraph">Dealing with the problem of changing parameters over time, a useful online-identification process using advanced recursive least squares algorithms is implemented.</div> <div class="htmlview paragraph">The results of both methods - the offline and the online identification - are verified with measured data of a heavy truck and show a very good performance.</div>

<div class="section abstract"><div class="htmlview paragraph">Intake system is an important noise source for commercial vehicles, which has a significant impact on their NVH performance. To predict the intake noise more accurately, a new one-dimensional prediction model is proposed in this paper. An air compressor model is introduced into the traditional model, and the acoustic properties of the intake system are simulated by GT-power. The simulation data of the inlet noise is obtained to make a comparison with the inlet noise data acquired from a test. The result shows that the proposed model can make a more precise prediction of the inlet noise. Compared with the traditional model, the proposed model can identify the noise coming from the air compressor, and achieve a more accurate prediction of the total sound pressure level of the inlet noise.</div></div>

<div class="section abstract"><div class="htmlview paragraph">When the ambient temperature is too low, the performance of the lithium-ion battery will deteriorate, and the car will have the problems of difficult charging, fast power consumption, and even difficult to start, so the battery needs to be heated before use to provide a comfortable working environment for the lithium-ion. The high-frequency pulse heating system can quickly and evenly raise the temperature of the battery, but there is noise during operation, which affects the NVH performance of the vehicle itself, and its noise comfort needs to be further optimized. Firstly, the high-frequency pulse heating system is discussed in detail, and the parameters affecting the NVH performance are explored. Secondly, NVH tests and subjective and objective evaluations were carried out based on different system parameters, relevant data were collected to establish a model, the influence degree of each parameter was demonstrated, and the best parameter combination was determined. Finally, the feasibility of the variable frequency pulse heating strategy is explored, and it is shown that the effect of the variable frequency strategy is ideal and has a wide application prospect.</div></div>