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"Research on Airborne Noise of Battery Electric Vehicles Based on Transfer Path Analysis"
"With the popularity of battery electric vehicles, the engine of the vehicle disappears, so the problem of road noise in cars is becoming more and more prominent. Road noise into the car can be divided into structure-borne noise and airborne noise, this paper only focuses on the airborne noise above 500Hz, completely ignoring the structure-borne noise. A transfer path analysis model with “Intermediate Response Points” is proposed to accurately represent the transfer path of each airborne noise through the setting of “Intermediate Points”. In the Vehicle Semi-Anechoic Room With 4×4 NVH Chassis Dyno, it is possible to create a working condition with only four tires running, so only the tire noise is considered in this paper. The frequency response function is tested in the Semi-Anechoic Chamber and the operating data is tested in the Vehicle Semi-Anechoic Room With 4×4 NVH Chassis Dyno. The calculations are performed by the Conventional Transfer Path Analysis (CTPA) method and the Operational Transfer Path Analysis (OPA) method, respectively. The total responses were calculated for the three operating conditions of 60 kph, 90kph, and 120kph. Both the CTPA and OPA methods have errors within an acceptable range, but the CTPA method is more accurate. The CTPA method requires testing a large number of frequency response functions, which is time-consuming, while the OPA method is more efficient."
"A Practical Approach towards Reducing the HVAC Flow Noise"
"Automotive heating ventilating and air conditioning (HVAC) noise is becoming a big concern area as the demand for acoustic comfort increases day by day. Vehicles are manufactured in recent years with quieter powertrain, reduced body leakage, better suspension. The other quieter technologies like electrification, hybridization of vehicle further complicate the whole subject of vehicle cabin noise issue. The HVAC noise is the major noise source inside the cabin. Hence designing a HVAC with very low sound pressure level is quite challenging and poses many difficulties in meeting other basic performances due to certain trade-off while meeting the noise requirement. However in recent years engineers have done extensive research and come up with various feasible and non-feasible solutions in order to reduce the HVAC noise significantly. Most commonly used tools and techniques are numerical simulation and experimental investigation or combined numerical simulation followed by experimental investigation. The present paper describes the way an existing HVAC noise is reduced by extensive experimental investigations. First the HVAC was dismantled and the flow path inside the HVAC was examined in details along with special features. Areas with chances of flow separations, vortices and high turbulent kinetic energy (TKE) were identified. Smoke tracing was also used in order to actually understand that phenomenon. After having deep investigation into those areas, existing HVAC was modified and series of experiments were carried out on this modified HVAC in a semi-anechoic chamber and noise data was captured at different voltages. In all these changes it is always aimed at keeping the airflow same or better than existing HVAC. It is observed that a significant improvement upto 3-4 dB(A) is achieved in overall noise level both at bench level and vehicle level. So this study provides a deeper insight into how HVAC overall noise level is reduced and hence further it can be very well applied at initial stage of design to make the noise level within desired limit."
"Rattle and Squeak Investigation on the Interior Components of Automobile"
"Automotive rattle and squeak performance is an important factor affecting passenger comfort and perceived quality. In the current work, finite element simulation is developed to analyze the noise potential of adjacent interior components. The statistical “3σ” limit is adopted to assess the rattle risk at adjacent surfaces assuming a Gaussian distribution. The probability expressions about noise registration are derived for the symmetric and asymmetric tolerance zones of an initial nominal gap. Also the acoustical effects of material pairs are tested by stick-slip experiments. Results show modified polypropylene is compatible in frictional contact with itself but expresses noise when paired to adjacent components manufactured of modified acrylonitrile-butadiene-styrene terpolymer under multiple conditions."
"Further Study of the Vehicle Rattle Noise with Consideration of the Impact Rates and Loudness"
"With the prevalent trend of the pure electric vehicle, vehicle interior noise has been reduced significantly. However, other noises become prominent in the cabin. Especially, the BSR noise generated by friction between parts and the clearance between components become the elements of complaints directly affect the quality of vehicles. Currently, the BSR noises are subjectively evaluated by experts, and the noise samples are simply labeled as ‘qualified’ or ‘unqualified’. Therefore, it is necessary to develop an evaluation model to assess the BSR noise objectively. In this paper, we study the vehicle rattle noise intensively. Several types of rattle noise were recorded in a semi-anechoic room. The recorded signals were then processed in the LMS test lab. to extract the single impact segments. A pool of simulated signals with different impact rates (number of impacts per second) and various loudness was synthesized for analyzation. To verify the universality of the assessment, the in-vehicle background noises were also recorded. The in-vehicle background noises were added to the rattle noise samples to simulate the in-vehicle test environment. Sound metrics were calculated and compared for all the processed samples. Jury assessment with 5 experts were performed to evaluate the rattle noise samples. The correlation between the subjective evaluation and the impact rates as well as sound metrics were studied. Consequently, an objective assessing model for vehicle rattle noise was developed based on the above analysis. This study can be used to assess the rattle noise effectively, and it has bright prospect and great value in engineering."
"Development of Tearing Pattern Prediction Model of Laser Scored Region on Invisible Passenger Side Airbag Door"
"The tear seam of invisible passenger side airbag door is made on the back of an instrument panel by laser scoring method and it is not shown outside. One of the requirements for the invisible passenger side airbag door is that the airbag module should deploy with no fragmentation at hot, room and cold temperature conditions. In this paper, a section model was developed by detail inspection of tearing phenomena at the laser-scored region. To validate the model, the finite elements of continuous and dot type laser-scored tear seam were built and analyzed in room and cold temperature conditions. Finally, a three-dimensional equivalent shell model was developed and it was proved that the section model and the equivalent shell model could represent well the tearing phenomena of the airbag door. It is expected that the tearing pattern prediction models developed in this study can be used to design the types of laser scoring and the airbag door with the minimum of real deployment tests."
"Airflow Simulation Relative to Door-Closing Operability"
"Easiness in closing a vehicle door has been often evaluated on a physical vehicle body, and in most cases, has not been fully studied by computer-aided engineering (CAE) in an earlier developing stage. The authors have developed a numerical method for reproducing the behavior of a closing door with a high fidelity. Characteristics of this method are that moving grid is used to reproduce the unsteady air motion caused by closing the door, and that external reaction forces including cabin pressure are coupled with the equation of the door motion to achieve a high fidelity. This method has made it possible to quantitatively evaluate cabin pressure rise and determine minimum door closing velocity, and the method has turned out to be effective."
"The Use of in Vehicle STL Testing to Correlate Subsystem Level SEA Models"
"For the assessment of vehicle acoustics in the early design stages of a vehicle program, the use of full vehicle SEA models is becoming the standard analysis method in the US automotive industry. One benefit is that OEM's and Tier 1 suppliers are able to cascade lower level acoustic performance targets for NVH systems and components. Detailed SEA system level models can be used to assess the performance of systems such as dash panels, floors and doors, however, the results will be questionable until test data Is available. Correlation can be accomplished with buck testing, which is a common practice in the automotive industry for assessing the STL (sound transmission loss) of vehicle level components. The opportunity to conduct buck testing can be limited by the availability of representative bodies to be cut into bucks and the availability of a transmission loss suite with a suitably large opening. In addition, the temporary fixture used to mount the test structure does not typically provide representative boundary conditions. Boundary conditions are particularly important when the in-vehicle performance is dependent on point connections at hinges / locking mechanisms and flexible seals at the perimeter of the system such as found in doors or lift-gate. In this paper the use of in-vehicle testing on prototype vehicles to assess the STL for the vehicle systems and the SEA models are discussed. Results are presented for a dash panel, floor system and door systems. The measurements are compared with predictions from system level SEA (Statistical Energy Analysis) models of the test systems. It is concluded that subsystem level SEA models can be used to assess the design and correlate well with STL measurements from in-vehicle tests."
"Modular door system for side impact safety of motor vehicles"
"Side impact collision is one of the toughest safety challenges facing the Auto Industry today. Over thirteen thousand deaths, due to side impact, occurred during 1998 in the United States alone. The main difficulty in designing for side impact collisions is the limited crumple zone between the impacting vehicle and the impacted occupant. This paper presents a proprietary side impact protective door system within the space between the outer skin of a car door and the occupant, which will be as efficient as those already standard in frontal impact. The main objective for introducing the side impact structural system is to maximize energy absorption and minimize injury to the occupant. The developed structural side impact door system acts as a Primary Structure, to be assembled as a truly modular entity. This primary structure is also packaging modular in the sense that it acts as a carrier for the door latch, window regulator and hinges. A variation in safety and structural performance of the developed door system can be achieved by integrating the structural modular door with the vehicle body, using a patented integration system known as Door And Chassis-frame Integration Technology (DACIT). Unlike the traditional doors, that are just suspended weights, the modular door is truly structural and therefore adds strength to the vehicle body. When DACIT is used with the door system the vehicle door becomes part of the overall vehicle structure. The design and development of the side impact modular door system for different size vehicles with and without DACIT will be discussed. In addition, the five stars rating achieved during several side impact crash tests simulating Sport Utility Vehicles hitting mid-size vehicles, equipped with the developed modular door system, will be presented."
"Simulation of Warm Forming Assisted Hemming to Study the Effect of Process Parameters on Product Quality"
"Current trends in the auto industry requiring tighter dimensional specifications combined with the use of lightweight materials, such as aluminum, are a challenge for the traditional manufacturing processes. The hemming process, a sheet metal bending operation used in the manufacturing of car doors and hoods, poses problems meeting tighter dimensional tolerances. Hemming is the final operation that is used to fasten the outer panel with the inner panel by folding the outer panel over the inner panel. Roll in/out is one of the main quality concerns with hemming, and keeping it under tolerance is a high priority issue for the auto manufacturers. Current hemming process technology, given the mechanical properties of current materials, has reached its saturation limit to deliver consistent dimensional quality to satisfy customers and at the same time meet government standards. Combining warm forming techniques with the traditional hemming process represents a new approach with the potential to overcome the current hemming limitation and to provide a satisfactory solution to all the requirements. The main objective of this research is to understand the effect of localized heating on the final quality in the hemming process by quantifying the influence of key geometrical and process parameters. To achieve this goal, a hemming finite element model, taking into consideration the mechanical properties as function of temperature is developed, and statistical methods to quantify the effect of key variables are employed. As an outcome to this study, the effectiveness of using warm forming techniques to improve hemming quality is assessed for A5182O aluminum, one of the most common used materials for this application."
"Comparative Dimensional Quality of Doors: A Benchmarking Study"
"A comparative benchmarking study of the dimensional door quality 14 vehicles from Ford, General Motors, Daimler-Chrysler, Toyota, Nissan, BMW, Volvo, and Renault was conducted. Various aspects of the door design, manufacturing, assembly and hanging system were studied. This paper focuses on the dimensional quality of the doors and relates it to the final vehicle quality in terms of gaps and flush as well as customer satisfaction as established by J. D. Power Initial Quality Survey (IQS). For confidentiality reasons, all vehicles in the study are referred to by a coded designation."
"Comparative Datuming and Hanging Strategies of Doors: A Benchmark Study"
"This paper discusses the results of a door benchmark study performed on 14 vehicles. The major focus is on the selection of datums or reference points and its impact on the product quality of the door system. The results indicate that there can be a relationship between datum utilization and quality metrics at any stage in the production process. Specific examples show the impact of various strategies on product performance."
"Conductive Plastics Leading Fuel Door Technology"
"This paper will discuss, compare, and contrast current materials, designs, and manufacturing options for fuel filler doors. Also, it will explore the advantages of using conductive thermoplastic substrates over other materials that are commonly used in the fuel filler door market today. At the outset, the paper will discuss the differences between traditional steel fuel filler doors, which use an on-line painting process, and fuel filler doors that use a conductive thermoplastic substrate and require an in-line or off-line painting process. After reviewing the process, this paper will discuss material options and current technology. Here, we will highlight key drivers to thermoplastics acceptance, and look at the cost saving opportunities presented by the inline paint process option using a conductive thermoplastic resin, as well as benefits gained in quality control, component storage and coordination."
"The Effect of Turbulence on Peak and Average Pressures on a Car Door"
"The influence of turbulence on automotive aerodynamics requires further investigation. This paper provides evidence that turbulence directly affects average and peak forces on the front door of a sedan automobile. Wind tunnel and several on-road test conditions were investigated. The results include instantaneous peak and average force coefficients, together with experimental pressure contour plots for a sedan front door. The pressure distribution over the front door of an automobile is important for efficient structural and door seal design. Door pressure distributions vary with flow turbulence characteristics. The results presented in this paper show that turbulent properties of the flow are of importance when investigating flow over the front door of a sedan automobile."
"A Robust Solution for a Power-Train Mounting System for Automotive NVH Refinements"
"Production variations of a heavy duty truck for its vibrations were measured and then analyzed through an Ishikawa diagram. Noise and Control factors of the truck idle shake were indentified. The major cause was found to be piece to piece variations of its power-train (PT) rubber mounts. To overcome the same, a new nominal level of the mount stiffness was sought based on minimization of a cost function related to vibration transmissibility and fatigue damage of the mounts under dynamic loadings. Physical prototypes of such mounts were proved to minimize the variations of the driver's seat shake at idling among various trucks of the same design. These learning's are useful for design of various subsystems or components to refine the full vehicle-Noise Vibration Harshness (NVH) at the robust design level."
"Structural Diffuse Field Excitation Synthesis by Synthetic Array (SFS-SA), Application to Cars Panels Contributions"
"Diffuse field or turbulent boundary layer excitations of vehicles are of huge interest in automotive industry. For such excitations reverberation chambers or wind tunnels are necessary, this means high cost experiments. The idea of sound field synthesis to create the acoustic effect corresponding to diffuse field or turbulent boundary layer excitation, is of major interest to reduce drastically the cost of experiments. Originally, techniques based on loudspeakers antenna were used, however, a major difficulty appeared due to driving simultaneously a huge number of sources. To avoid this difficulty a new technique based on synthetic antenna is used here; instead of an array of loudspeakers, just one source is used for scanning the surface where the acoustic field excite the structure. A post processing step, based on plane wave decomposition, is then applied to collected experimental data in order to get the response of the structure or the sound transmission through the structure. Validation of the method is presented by comparing synthetic antenna results to standard measurements of panels sound transmission between two reverberation chambers. The present paper is focusing on panels contributions in a car, leading to an experimental process avoiding the cumbersome masking technique generally used in automotive industry."
"Engine Sound Reduction and Enhancement Using Engine Vibration"
"Over the past decade, there have been many efforts to generate engine sound inside the cabin either in reducing way or in enhancing way. To reduce the engine noise, the passive way, such as sound absorption or sound insulation, was widely used but it has a limitation on its reduction performance. In recent days, with the development of signal processing technology, ANC (Active Noise Control) is been used to reduce the engine noise inside the cabin. On the other hand, technologies such as ASD (Active Sound Design) and ESG (Engine Sound Generator) have been used to generate the engine sound inside the vehicle. In the last ISNVH, Hyundai Motor Company newly introduced ESEV (Engine Sound by Engine Vibration) technology. This paper describes the ESEV Plus Minus that uses engine vibration to not only enhance the certain engine order components but reduce the other components at the same time. Consequently, this technology would produce a much more diverse engine sound."
"The Design of Wind Noise Transducers to Separate Acoustic and Turbulent Pressures"
"A four element wind noise transducer has been designed with surface mounted electret microphones in an array pattern which allows for the separate determination of the acoustic and turbulent pressures in wind noise. Three closely spaced transducers, defining an x-y coordinate system, are positioned to determine the velocity and direction of the turbulent flow. A fourth transducer is positioned at a greater distance such that the correlation of the turbulent flow will be diminished while the correlation of the acoustic pressure remains due to its longer wavelength. By averaging the cross-spectral densities of the pressure signals over time, the two contributors to wind noise can be differentiated. In addition, a wireless interface has been designed to minimize the flow disturbance of the transducer array."
"Prediction of Automotive Air-Handling System Flow Noise Sound Quality Using Sub-System Measurements"
"This paper presents the methodology of predicting vehicle level automotive air-handling system air-rush noise sound quality (SQ) using the sub-system level measurement. Measurement setup in both vehicle level and sub-system levels are described. To assess the air-rush noise SQ, both 1/3 octave band sound pressure level (SPL) and overall Zwicker's loudness are used. The “Sound Quality Correlation Functions (SQCF)” between sub-system level and vehicle level are developed for the specified climate control modes and vehicle segment defined by J.D. Power & Associates, while the Zwicker's loudness is calculated using the un-weighted predicted 1/3 octave band SPL. The predicting models are demonstrated in very good agreement with the measured data. The methodology is applied to the development of sub-system SQ requirement for upfront delivery of the optimum design to meet global customer satisfaction"
"A Unique Noise & Vibration Software Tool for Automotive Troubleshooting"
"A unique Matlab-based coded engineering software tool (Time-Frequency Analyzer Core®) was developed that allows users to process acquired time data to help in identifying sources and paths of noise and vibration (in the experience of the authors). The Time-Frequency Analyzer Core (TFAC) software does not replace commercial off the shelf software/hardware NV specific tools such as modal analysis, ODS, acoustic mapping, order tracking, etc., rather it aims at providing basic, yet powerful data inspection and comparison techniques in a single software tool that facilitates drawing conclusions and identifying most effective next steps. The features and advantages of using this software tool will be explained, along with a description of its application to a few different cases (automotive and off highway/agricultural)."
"Operational Determination of Car Window Damping"
"Wind noise can be a significant event for automotive design engineers. The greenhouse glass plays an important role in the wind noise process. Robust estimates of the greenhouse glass damping are necessary for both understanding and modeling the role of the glass in the wind noise process. One unanswered question is whether the aerodynamic loads affect the window glass damping. To make this determination a method to assess the operational damping is required. The civil engineering community uses the random decrement technique to assess operational damping due to wind loads. The random decrement technique has been shown to be a normalized autocorrelation function. In this paper the damping is estimated directly from the autocorrelation function. In the first section the relationship between the damping and autocorrelation function is examined for white noise excitation. A single oscillator is examined as the first case. Extension to higher modal densities is discussed. Finally application to a car window is presented. The window results were limited by signal to noise problems."
"An Experimental Study of Mechanism of Body Panel Vibration in Booming Noise Reduction of Passenger Vehicles"
"In a typical passenger vehicle, there can be different types of noises generated which are broadly categorized as Interior Noise and Exterior Noise. The interior noise sources can be further classified into noises which can be Structure Borne or Air Borne. One of the major sources of both structure borne and airborne noise generation is the powertrain of the vehicle. The structure-borne noise and vibrations generated from the powertrain is usually transferred to the vehicle body through its attachment points to the body and the powertrain driveline. These induced body vibrations can sometimes cause the acoustic cavity of the passenger cabin to go into resonance which results in an annoying and disturbing noise for the passengers, called Booming Noise. Very often, one or more than one vehicle body panels show a dominant contribution in inducing this acoustic cavity resonance. In this research, the backdoor of the selected passenger cars were identified to be one of the primary contributors in causing the booming noise phenomena. The objective of this research was to study the mechanism of the contribution of backdoor towards booming noise in these hatchback style passenger vehicles. The study was carried out on three differently styled hatchbacks namely Model A, Model B, and Model C. The study of the mechanism behind this contribution was carried out in three phases. The first phase included the response measurements of the individual grid points created on the backdoor which were excited using a low frequency sound source. In the second phase, a computer model of the grid structure of the backdoor was created and the response measurements obtained were superimposed on the geometry model to identify the modal parameters of the backdoor. The identification of the modal parameters helped in understanding the modal behavior of the backdoor which is causing the acoustic resonance of the cabin cavity thus creating the booming noise phenomena. In the third phase, in cabin acoustic measurements were carried out during vehicle acceleration tests and the results were correlated with the modal parameter data. This helped in identification of the dominant modal frequencies to be targeted for further design improvements during concept & vehicle design stage."
"The Effects of Unsteady Flow Conditions on Vehicle in Cabin and External Noise Generation"
"A vehicle driving on the road experiences unsteady flow conditions which are not generally reproduced in the development environment. This paper investigates the potential importance of this difference to aeroacoustics and hence to occupant perception and proposes a methodology to enable better ranking of designs by taking account of wind noise modulation. Two approaches of reproducing the effects of unsteady wind on aeroacoustics were investigated: an active wind tunnel Turbulence Generation System (TGS) and a quasi-steady approach based on measurements at a series of fixed yaw angles. A number of tools were used to investigate the onset flow and its impacts, including roof-mounted probe, acoustic heads and surface microphones. External noise measurements help to reveal the response of separate exterior noise sources to yaw. The noise experienced by the driver or passenger ear facing the side-glass is dominated by increased sound pressure levels when the adjacent side-glass is the leeward side of the vehicle with some non-linear effects as leeward yaw produces first accelerated flow and then separation. In part because of non-linearity in response to yaw, a challenging parameter for a wind tunnel simulation of dynamic yaw is achieving a wide enough variation in yaw angle and this work suggests that considering an appropriate range of yaw angles is more important than capturing the dynamics. In terms of passenger perception, the most important effect of a time-varying onset flow was demonstrated to be the modulation of wind noise rather than the increase in time-averaged cabin noise. For the case considered, at 130 km/h, the impact of wind-noise modulation was found to be equivalent to an extra 1-2 dBA in terms of passenger perception, while the increment in time-averaged cabin noise would be only 0.2 dBA."
"Daimler Aeroacoustic Wind Tunnel: 5 Years of Operational Experience and Recent Improvements"
"Since 2013 the new Daimler Aeroacoustic Wind Tunnel (AAWT) is in operation at the Mercedes-Benz Technology Center in Sindelfingen, Germany. This construction was the second stage of a wind tunnel center project, which was launched in 2007 and started with the climatic wind tunnels including workshop and office areas. The AAWT features a test facility for full-scale cars and vans with a nozzle exit area of 28 m2, a five-belt system, and underfloor balance to measure forces with best possible road simulation. With a remarkable low background noise level of the wind tunnel, vehicle acoustics can be investigated under excellent conditions using high-performance measurement systems. An overview is given about the building and the design features of the wind tunnel layout. The aerodynamic and aeroacoustic properties are summarized. During the first years of operation, further improvements regarding the wind tunnel background noise and vehicle handling were made. Changes in the surface of the contraction and the reduction of rough surfaces in the test section reduced the self-noise of the wind tunnel. For the standard test section configuration (used for daily operation) with smooth center belt, an overall sound pressure level of 57.2 dB(A) could be achieved, for a further optimized configuration with taped gaps and covered shutters and belts even 55.2 dB(A) were measured. Since the manual ride height adjustment of a vehicle in the test section showed to be very time-consuming, a new automatic ride height measuring system was developed. It significantly reduces the setup time before the first measurement. For the rising demands to document surface changes after a test campaign, a separate room for 3D surface scanning was already provided in the workshop area. The technical layout could only be finished with delay. Now the room houses a frontal area measurement system, vehicle lifts, and a robot for 3D surface scanning. This paper describes these new features and reports about the experiences of the first years of operation."
"Surface treatment to reduce squeak noise in vinyl parts"
"It is a common practice of automotive industry to avoid dynamic contact between two surfaces with similar roughness for plastics and interior trim parts. That means reduce the friction and, consequently the squeak noise to the minimum level to meet zero noise level. Unfortunately, for design or economics reasons, that is not possible for some applications and a very disturbing noise may bother the costumer. A material incompatibility leads to an acute noise when two similar surfaces have relative movement due to multiple adherences between the surfaces, that is called stick-slip phenomenon. To characterize this noise, a Squeak and Rattle Evaluation testing should be performed in the worst case condition over the life of the vehicle. As a result, a scale of Risk Priority Number (RPN) provides a pass/fail judgement to implement any improvement required to address the issue. There are several ways to avoid this phenomenon during the product development: applying lubricants, tapes, coatings, material change or surface treatments. To solve this kind of undesirable user experience, an anti-squeak treatment was developed in water base using polymeric material, applied in a process similar to coating and cured thereafter by heat. The concept of this anti-squeak treatment is to reduce surface tension and the resistance of relative movement when fractioning similar material that leads to a reduction of noise, consequently. The aim of this paper is to show how this surface treatment can reduce the noise level related to material similarity, applying this into a vinyl surface, with no changes in mechanical properties and no need to run a new design verification plan. In the present study, it could be observed a reduction from 10 RPN to 2 RPN, related to an improvement from material match critical to material match in order. This corresponds to a customer satisfaction perception improvement from material audible annoying noise caused by stick- slip expected to not perceived noise."
"Designing In-Cab Sound of Vehicles as per the Customer Driving Pattern on Roads"
"Vehicle refinement from point of view reduction in its Noise, Vibrations and Harshness (NVH) affects customer’s buying decision and it also directly influences his/her driving experience on road at different speeds. Customer voice, however, indicates that a traditional process of developing design solutions is not aligned with the customers’ expectations. Traditionally the load cases for NVH development are focused only on quietness of passengers’ cabin at idling and in 3rd gear wide open throttle cruising on smooth roads. In reality, the Driver of a premium sedan car or a Sports Utility Vehicle (SUV) or a Compact Utility Vehicle (CUV) expects something different than merely the low sound pressure level inside the cabin. His/her driving pattern over a day plays a crucial role. A vehicle-owner wishes to balance various attributes of the in-cab sound and tactile vibrations at a time. A single value Customer-Voice-Index (CVI) is developed here based on study of critical drive load cases faced by common customers classified with C: Critical to customer perception; O: Occurrence of each drive load case throughout running of the vehicle and D: Duration of each load case. Cost to Benefit Ratio of various design solutions then could be evaluated effectively in a vehicle by monitoring its CVI. This is demonstrated here on a new SUV to give the desired sound character of the vehicle with low cost solutions and thus make the customers fall in love with it during cruising on highways at high speeds."
"Low Frequency In-Cab Booming Noise Reduction in the Passenger Car"
"In-cab booming noise is low frequency (20 Hz∼300 Hz) phenomenon excites the cabin structure, which occurs mainly due to excitations from the powertrain, exhaust system, road input, etc. Annoyance due to booming noise affects the In-cab sound quality, which results in passenger discomfort. A diesel passenger car observed booming noise issue when operated at stationary as well as dynamic run-up conditions. In order to increase passenger comfort, experimental root cause analysis conducted on the vehicle to investigate the dominant sources for the cavity boom. Exhaust hanger and one of the engine mount identified as major reason for the booming noise in the cabin. A detailed study was carried out on dynamic property optimization of rubber hanger and possibility to relocate the hanger to improve the vibration transmissibility. Operational measurements conducted on vehicle by attaching finalized exhaust mount to confirm the significant booming noise reduction in the cabin."
"Investigation of Cabin Noise while Accelerating on Low Mu Track through Simulation Approach Using Full Vehicle ADAMS/Car Model"
"Cabin noise is a significant product quality criteria which enables the customers for product differentiation. There are various sources of cabin noise such as wind, structures(panels), engine, suspension, tire and roads. During product development phase, extensive tests has been conducted to improve vehicle dynamics behavior on various climatic conditions. One such test is accelerating vehicle on low mu or icy surface. While performing acceleration manoeuvre (tractions) on a low mu tracks, Cabin noise with source identified from front underbody & low tractive torque build up is reported. This undesirable behavior may occur due to following reason (1) Excitation of coupled modes between suspension and powertrain which induces torque fluctuation. (2) Transmissibility of various subsystem can be the reason for above problem statement. (3) Poorly chosen tire compounds and design leads to fluctuation in torque. A detailed simulation based study using ADAMS/CAR has been performed to assess the contribution of various full vehicle sub-systems, primarily suspension & powertrain sub-system towards the said problem statement. The dynamic interaction between road, suspension, powertrain and BIW has been is the focus of study both in time and frequency domain. This simulation helped understand the factor effects and contribution levels and correlates well with the subjective feel observed on the physical vehicle on low-mu track. This model has been further used to provide design recommendation on the compliance parameters to overcome the issue at hand. Test has been conducted with recommended tire grip properties and suspension bushing parameters which lead to reduction in cabin noise"
"Design of Super Silent Enclosure for Diesel Genset Using Statistical Energy Analysis (SEA) Technique"
"Diesel engine generators are commonly used as a power source for various industrial and residential applications. While designing diesel generator (DG) enclosures requirements of noise control, ventilation and physical protection needs to be addressed. Indian legislation requirement demands DG enclosure insertion loss (IL) to be minimum 25 dB. However for certain critical applications like hospitals, residential apartments customer demands quiet DG sets than the statutory limits. IL targets for such application ranges between 35-40 dB. The objective of this paper is to develop methodology to design ‘Super Silent’ enclosure with IL of 35 dB by Statistical Energy Analysis (SEA) approach for small capacity DG set. Major challenge was to achieve IL of 35 dB with single enclosure and making use of SEA technique for small size enclosure wherein modal densities is very less. Major airborne noise sources like engine, radiator fan and exhaust were modelled by capturing noise source test data. Structure-borne sources like panel vibrations were also modelled via vibration measurements. Noise control treatments (NCT) were sculpted using BIOT parameters. The predicted sound levels for an existing DG enclosure model were validated with its test data to ensure correctness of SEA model. Further critical noise paths identification and ranking was done through simulation. Based on results of above step, modifications were suggested on NCT, louvers, baffles, ducts and muffler to arrive at optimized enclosure. Proto for optimized enclosure was tested. Test showed IL of 35.5 dB against predicted IL of 35 dB showing very good correlation."
"Computational Aeroacoustics Based on a Helmholtz-Hodge Decomposition"
"Using existing aeroacoustic wave equations, we propose a general hybrid aeroacoustic method, based on compressible flow data. By applying the Helmholtz-Hodge decomposition on arbitrary domains, we extract the incompressible projection (non-radiating base flow) of the compressible flow velocity by solving the vector valued curl-curl equation with the vorticity as forcing term. The resulting vortical flow part is used for computing the acoustic source term. This method maintains the favorable properties of the hybrid aeroacoustic method, while still considering acoustic feedback on the flow field."
"Numerical Design of Loudspeaker Systems in a Car Cabin"
"These days loudspeaker systems in vehicles are gaining more and more of importance. Usually quite a few speakers are installed and driven in combination in order to obtain a convincing sound environment for the occupants/customers. Sometimes even a 3D sound experience shall be reached, where up to 20 loudspeakers might become necessary. No doubt that such a number of speakers and their proper placement in the car cabin is a rather challenging task, leading to extensive measurements in different cabin environments. In the current contribution, it is suggested to simulate the scenario by means of specially combined computer models. These allow not only a rather economic possibility to investigate different changes/variants without expensive new setups but also an additional gain of knowledge. For the numerical representation of the loudspeaker system a multiphysics approach is needed, namely physical aspects of electromagnetics, structural dynamics, and acoustics have to be considered and combined. Doing so, the different fields might be accounted for by models obeying different levels of detail, where the spectrum might reach from simple 1D approaches to highly detailed 3D models. In view of this, different methodologies such as the finite element method, the boundary element method or energy based formulations need to be coupled. In the current contribution a methodology for the numerical design of loudspeaker systems is developed and discussed by means of representative examples."
"Correlation Analysis of Interior and Exterior Wind Noise Sources of a Production Car Using Beamforming Techniques"
"Beamforming techniques are widely used today in aeroacoustic wind tunnels to identify wind noise sources generated by interaction between incoming flow and the test object. In this study, a planar spiral microphone array with 120 channels was set out-of-flow at 1:1 aeroacoustic wind tunnel of Shanghai Automotive Wind Tunnel Center (SAWTC) to test exterior wind noise sources of a production car. Simultaneously, 2 reference microphones were set in vehicle interior to record potential sound source signal near the left side view mirror triangle and the signal of driver’s ear position synchronously. In addition, a spherical array with 48 channels was set inside the vehicle to identify interior noise sources synchronously as well. With different correlation methods and an advanced algorithm CLEAN-SC, the ranking of contributions of vehicle exterior wind noise sources to interested interior noise locations was accomplished. The results demonstrate that the advanced deconvolution algorithm CLEAN-SC has significant improvement against limitations of spatial resolution and dynamic range of conventional Beamforming technique. It has great potential for vehicle wind noise transmission path analysis and wind noise optimization work in the wind tunnel. In addition, Correlation analysis result of interior and exterior noise sources using virtual and real reference microphones was compared and discussed as well."
"An Analysis on Automotive Side Window Buffeting Using Scale Adaptive Simulation"
"Automotive window buffeting is a source of vehicle occupant’s discomfort and annoyance. Original equipment manufacturers (OEM) are using both experimental and numerical methods to address this issue. With major advances in computational power and numerical modelling, it is now possible to model complex aero acoustic problems using numerical tools like CFD. Although the direct turbulence model LES is preferred to simulate aero-acoustic problems, it is computationally expensive for many industrial applications. Hybrid turbulence models can be used to model aero acoustic problems for industrial applications. In this paper, the numerical modelling of side window buffeting in a generic passenger car is presented. The numerical modelling is performed with the hybrid turbulence model Scale Adaptive Simulation (SAS) using a commercial CFD code. While the acoustic generation is modelled by solving compressible Navier-Stokes equation, integral method Ffowcs-Williams & Hawkings (FWH) is used to model acoustic propagation in the computational domain. Certain investigation on the influence of rear view mirror (RVM) & divide pillar on buffeting noises are analyzed using a few flow and spectral techniques. Differences in the noise levels between front and rear window buffeting are also investigated. A 3D-cavity test model is considered to validate the modelling methodology. Investigations have shown the installation of a divide pillar on window have significantly minimized noise levels and appendages like the glass mounted RVM have a minimizing effect on the buffeting intensity. Also the noise levels of rear window buffeting are found to be higher than front window buffeting. Modelling window buffeting using a SAS model have shown to be a reliable and computationally less expensive option. The investigations using spectral technique like Fast Fourier Transform (FFT) band analysis gave a better insight in to buffeting problem."
"Acoustic Enclosure Optimization for a Higher Capacity Diesel Generator Set Using Statistical Energy Analysis (SEA) Based Approach"
"Diesel powered electric generators are used in a variety of applications, such as emergency back-up power, temporary primary power at industrial facilities, etc. As regulatory and customer requirements demand quieter designs, special attention is given to the design of acoustic enclosures to balance the need of noise control with other performance criteria like ventilation and physical protection. In the present work, Statistical Energy Analysis (SEA) approach augmented by experimental inputs is used to carry out Vibro-acoustic analysis of an enclosure for higher capacity Diesel generator set. The exterior sound radiated from an enclosed generator is predicted and further enclosure is optimized for an improved sound-suppression. The airborne sources such as engine, alternator, radiator fan and exhaust are modelled explicitly using experimental noise source characterization. Structure borne inputs are also captured in the test for improving modelling accuracy. The vibroacoustic performance of the enclosure and sound absorbers are modelled through Biot parameters and experimentally validated with a good agreement between test and simulated results within 2 dB for overall levels. Further, path contribution and sensitivity analysis has been done on base enclosure to find out major contributors to exterior radiated noise. Optimization is done using parameters like: noise path modifications (ducts, partitions), leakage minimization and acoustic louver designing based on preceding analysis results. Optimized enclosure has resulted in 3 dB reduction in overall noise level"
"Sound Quality Evaluation of a Brake and Clutch Pedal Assembly used for Automotive Applications"
"Sound Quality (SQ) of brake and clutch pedal assembly plays an important role in contributing to vehicle interior noise and perception of sound. Quiet operation of brake and clutch units also reflects the vehicle built and material quality. Noise emitted from these sub-assemblies has to meet certain acceptance criteria as per different OEM requirements. Not much work has been carried on this over the years to characterize and quantify the same. An attempt has been made in this paper to study the sound quality of brake and clutch pedal assemblies at component level and validate the same by identifying the parameters affecting SQ. Effect on noise at different environmental conditions was studied with typical operating cycles in a hemi-anechoic chamber. The effect of sensor switches integrated within the clutch and brake pedal on sound quality is analyzed. It is found that the operating characteristics of switches drives the noise and SQ. Wavelet analysis was carried out to correlate loudness sound quality metric with time-frequency amplitude modulations. Jury evaluation was performed to correlate subjective to objective data. Structural modifications were then suggested to improve the perception of sound. Significant improvement in the brake and clutch pedal assembly sound quality was achieved in product development with marginal impact on cost."
"A Study on the Vehicle Body Effect on Brake Noise"
"Creep groan noise occurs in a just moving vehicle by the simultaneous application of torque to the wheel and the gradual release of brake pressure in-vehicle. It is the low frequency noise giving the driver a very uncomfortable feeling. Recently, the field claims regarding the creep groan noise are increasing. So far, creep groan noise has been improved by means of chassis modification the transfer system. But vehicle body the response system does not. In this paper, the effect between vibration characteristics of vehicle body, creep groan noise was analyzed. Then presented analysis method for vehicle body effect regarding creep groan noise."
"C-17 Cargo Ramp and Door Automated Drilling & Fastening System - Project Overview"
"To further reduce airframe costs associated with fastener installation, an Automated Drilling & Fastening System (ADFS) has been implemented on the C-17 Program to enhance current Mold Line attachment processes. The ADFS will automate up to 90% of all Cargo Ramp and Door Mold Line fastener installations. Implementation of the C-17 ADFS captures a five goal technological approach identified at project onset: 1) Increase the use of automated drilling and fastening equipment, 2) System shall be Numerically Controlled, 3) High speed drilling techniques shall be used, 4) Minimize the use of current tooling, and 5) Design the system to use components common to other Boeing drilling & fastening machines."
"Mechanical and Structural Aspects of the C-17 Cargo Ramp and Cargo Door ADFS"
"The cargo ramp and cargo door are two major C-17 components that are built in St. Louis, MO and shipped by rail for final assembly in Long Beach, CA. A major portion of the total build time for the ramp and door assemblies consisted of the hand installation of approximately 16,000 moldline fasteners and 19,400 moldline fasteners, respectively, attaching the skin to the substructure. In addition, several thousand fasteners are also installed in the floor sections of the ramp and door. A major cost savings opportunity existed to reduce the cost of the ramp and door assemblies by automating the installation of these fasteners. Boeing-St. Louis contracted Brotje Automation of Wiefelstede, Germany to design and build an automated drilling and fastening system (ADFS). Automation is expected to reduce cost by reducing the time required to build the ramp and door assemblies. In addition, automation is expected to improve fastener hole quality and fastener installation quality. Another important reason for undertaking this project was to enable Boeing-St. Louis to strengthen its position as an industry leader and innovator in aerospace manufacturing. This paper describes the mechanical and structural challenges (associated with hoisting and supporting the assemblies) that were overcome to implement this initiative."
"A Direct Method for Designing Fuel Filler Door with Torsional Spring"
"A direct method is developed for designing a vehicle fuel filler door with torsional spring. The design parameters include the door's geometrical parameters and spring dimensions. The design requirements are based on the finger force curve during closing and opening, and the bending stress in the spring. An example is included to demonstrate the effectiveness of the new method."
"An Ultra-Light Thin Sliding Door Design - A Multi-Product Multi-Material Solution"
"Sliding door designs are applied to rear side doors on vans and other large vehicles with a trend towards dual sliding doors with power operation. It is beneficial for the vehicle user to reduce the weight of and space occupied by these doors. Alcoa, in conjunction with Ford, has developed a multi-product, multi-material-based solution, which significantly reduces the cost of an aluminum sliding door and provides both consumer delight and stamping-assembly plant benefits. The design was successfully demonstrated through a concept readiness/technology demonstration program. The key findings of the joint effort demonstrated: Reduced system cost through parts reduction/consolidation and associated reduction of stamping and joining/assembly operations, gauge reduction and optimized material utilization Reduced thickness of the door by over 60mm and weight reduction by over 11kg, Equivalent functional performance to the current steel door Manufacturability using robust processes at desired quality and reliability levels. Improved quality and reliability of assembling the door hardware, which significantly improved serviceability over traditional designs. The basic door design concept is also applicable to other types of doors."
"Integrated Test Platforms: Taking Advantage of Advances in Computer Hardware and Software"
"Ongoing hardware, software, and networking advances in low-cost, general-purpose computing platforms have opened the door for powerful, highly usable, integrated test platforms for demanding industrial applications. With a focus on the automotive industry, this paper reviews the pros and cons of integrated test platforms versus single-purpose and stand-alone testers. Potential improvements in in-process testing are discussed along with techniques for effectively using such testing to improve daily production quality, to maintain high production rates, to avoid unplanned downtime, and to facilitate process and product improvements and refinements through the use of monitoring, data collection, and analysis tools."
"Optimal Design of Panel Reinforcing Material Using Practical Measurement Technique"
"Expandable reinforcing material such as that used for the outer panel of a door has been used to compensate for the lack of stiffness in automotive body panels. This material can improve panel stiffness and reduce vibration that causes radiated noise. Material properties in practical use have generally been evaluated by sensory methods. These properties, however, have not been sufficiently quantified to optimally design reinforcing material. We have developed evaluation methods aimed at ensuring reinforcement and also at reducing vibration and deformation in a panel. By employing these evaluation methods along with simulation of a material's basic properties, we are able to achieve the optimal design of materials for outer body panels."
"Quantitative Assessment of Cosmetic and Structural Quality in Automotive Outer Body Panels Using ARAMIS Stereo Photogrammetry System"
"The methodology described enables high accuracy in the measurement of static and dynamic stiffness and dent resistance. Among the parameters being evaluated are: stiffness and dent resistance of the automotive outer body assembled panels – under both static and dynamic loading and the effect of the stiffening features in the panel shape, upon its deformation characteristics under dynamic excitation and dynamic wave propagation following slow projectile impact. This methodology will help part and process designers to correctly position and manufacture outer and inner body features like door handle embossment shape and location, feature lines, lamp and mirror embossments, hemming lines and side bar locations. Measurements are carried out using the stereo photogrammetry system ARAMIS – a fast and cost effective tool with a high accuracy of displacement measurement in both static and dynamic conditions. Measurements were performed in real time related to the phase of elastic wave generated by projectile impact. Parameters of the elastic wave were defined using laser displacement sensors and accelerometers with a linear accuracy of 0.5 μm."
"Visualization and Classification of Strategy for Entering Car"
"This paper proposes a method for visualizing and classifying the variation in the motions of a person when entering a passenger vehicle. Entering behaviors vary greatly between individuals, especially if the vehicle door is designed to have large clearance. The present study was conducted with the aim of supporting the design process of seats and front doors by visualizing possible variations of entering motions using a motion database, rather than calculating a single representative movement. The motion database is consist of different motions caused by various seats, and the motions are classified by mapping them into two-dimensional plane according to the similarities between them. A representative entering motion for a clustered motion strategy group is synthesized and visualized on the 2D distribution plane by interpolating existing motions in the database."
"Development and Application of High-Strength Steel for Auto Outer Panel in Baosteel"
"The characteristics of China's automotive steel sheets and high strength steels (including bake-hardening, high strength IF and isotropic steel) developed recently by Baosteel for automotive outer panels are briefly reviewed. Among these steels, bake-hardening (BH) steel is often used to make outer panel parts, such as hoods, decklids, and front and rear doors. In this paper, we present results from an investigation of the effect of baking process (temperature and time) on the bake hardening index value of BH220 steel, and through evaluation of tensile specimens cut from a production hood and simulated part. The results show that BH value is more than 30 MPa when the baking time is more than 2 minutes (at a temperature of 170°C) or the baking temperature is more than 90°C (for baking time of 20 minutes). Measurements on an actual hood and simulated part showed that baking has no effect to enhance the yield strength of the panel, but it can enhance the dent resistance. One needs to consider other factors when using the empirical equation (DR∝K×ta×YS) to evaluate dent resistance of automotive panels."
"Advanced High-Strength Steels and Hydroforming Reduce Mass and Improve Dent Resistance of Light Weight Doors In UltraLight Steel Auto Closures Project"
"In May 2000, the UltraLight Steel Auto Closure (ULSAC) Consortium unveiled a lightweight frameless steel door design that achieves 42 percent weight savings over the average benchmarked (1997 model year vehicles) frameless door and 22 percent savings over the lightest benchmark, a framed door. ULSAC was commissioned by this international consortium of 31 sheet steel producers to assist their automotive customers with viable lightweighting steel solutions. The ULSAC design and engineering team, Porsche Engineering Services, Inc. (PES), Troy, Michigan USA, accomplished this significant weight savings by using high and ultra high strength steels, combined with technologies such as tailored blanks and hydroforming. The door outer panel of this first round of demonstration hardware is made of stamped 0.7 mm Bake Hardenable (BH) 260 sheet steel. During the design and development of the ULSAC frameless door, the ULSAC Consortium evaluated further mass reduction, using sheet hydroforming for the door outer. Consequently, the ULSAC Validation Phase continued beyond May 2000 with sheet hydroforming process development for the door outer as a means to compile practical research documentation for this developmental process with mass reduction potential. Door structures were successfully manufactured with 0.6 mm Dual Phase (DP) 600 hydroformed steel outer panels achieving additional weight savings."
"Economic Analysis of Two Different Door Architectures"
"In the past, materials selection for automotive components has been managed on a part-by-part basis. As a result, the economics of these selections have often been reduced to comparing material price/property ratios, rather than technological options. More recently, the debate around modular designs and their advantages and disadvantages has shifted the emphasis towards a higher level viewpoint that deals with more complex systems. This approach provides the opportunity to search for new combinations of product architecture and materials that may exploit specific material advantages better than the classic part-by-part replacement. This paper presents the results of an economic analysis for two different door designs. The door designs differ both with regards to their product architectures and with regards to the materials they employ. The economic analysis considers the following process steps: parts fabrication, subassembly, paint, and final assembly (trim) for two production scenarios. The case study reveals several findings. First, the analysis concludes that both door designs offer a potential economic advantage depending on the final production volume. Specifically, the conventional design is considered more appropriate for high volume production, whilst the alternative design is more cost effective at production volumes typical of niche and derivative vehicles. Second, since the choice of design architecture has an influence on all sub systems, meaningful comparisons between the architectures may be made only through the adoption of comprehensive cost models. For example, the case study demonstrates that the choice of certain product architectures can help mitigate disadvantages caused by higher input material costs. Finally, the case study finds that the cost savings from ‘commonization’ of components vary depending on the base production volume."
"Open Bay Door Analysis Process for Hubble Space Telescope Servicing Mission 3B"
"During Servicing Mission 3B (SM3B) for the Hubble Space Telescope (HST) the Power Control Unit (PCU) will be replaced. The PCU was not originally designed to be replaced on orbit but was later identified as having the capability of being removed and replaced on orbit. The PCU has many connectors and bolts, some of which are difficult for the astronauts to reach. Due to the added difficulty, the replacement will take an entire six hour Extra Vehicular Activity (EVA) day. For four of these six EVA hours the door of the Support Systems Module (SSM) Equipment Section (ES) bay where the PCU is found will be open to allow the astronauts access to the PCU and its connectors. This bay, SSM ES Bay 4, also contains the four Power Distribution Units (PDUs), which house the busses, switching, fusing, and monitoring circuits that distribute power to the telescope. These PDUs are attached to the bay door and will be seeing a much colder than normal environment with the door open. The PCU controls power for the entire telescope and therefore when it is replaced all power to the telescope will be turned off. With power removed and the bay door open the PDUs will cool rapidly. In order to be sure that the PDUs remain above their turn-on and operating temperature limits during the change out, a detailed open bay door analysis was conducted. For this analysis a Thermal Synthesizer System (TSS) model was created of Bay 4 and it’s components. The model was used to calculate radiation couplings and heat rates with the bay door open. The FORTRAN code used to analyze the Servicing Mission timeline was modified and the new radiation couplings and heat rates added. This paper deals with the creation of the detailed TSS model as well as the modifications made to the timeline code in order to run the analysis. It will also present the temperature predictions for the PDUs during the PCU change out."
"Passive Sensing of Driver Intoxication"
"A sensor that passively monitors the driver for intoxication has been demonstrated. The driver's blood alcohol concentration (BAC) is obtained by sensing alcohol and CO2 in air drawn from the vehicle cabin. With a legally drunk driver, the steady state alcohol concentration can be as low as 0.3 ppm, even with the doors and windows closed. The sensor uses infrared transmission to quantify alcohol vapor and CO2. A vapor concentrator increases alcohol sensitivity - an adsorber collects alcohol vapor and releases it as a concentrated burst at 1 minute intervals. A valid measure of driver BAC is ordinarily available 1.5 minutes after the driver gets in. Sensed CO2 must be above a threshold for a valid measurement."
"The Truck that Jack Built: Digital Human Models and their Role in the Design of Work Cells and Product Design"
"Henry Ford is credited with the invention of the assembly line and for 100 years now we have manufactured high quality cars and trucks. The process to bring cars and trucks into production has seen many changes with the introduction of new technology, however the principle is still the same; designers draw concept designs and engineers transform these designs into functional parts. The first time the engineering community has a real feel for the design and process compatibility is at a physical prototype build. The money invested in the designs and prototype parts alone make the thought of a design change this late in the game, unbearable. The design of the manufacturing process along with product design has embraced virtual tools and digital human models to assess assembly feasibility. The major incentive to utilizing such tools is to reduce costly re-engineering of parts and to decrease prototype costs. Virtual technology allows ergonomists and engineers to perform “virtual builds”. This opens up doors for early ergonomic evaluation on the product design, process and tooling. Digital human models, motion capture technology, and biomechanical evaluations are all critical in performing accurate ergonomic analysis. This paper demonstrates how digital human technology is being utilized every day to drive sound engineering decisions in automotive manufacturing."
"Low Gloss ABS Advancements for Automotive Interior Components"
"Automotive Original Equipment Manufactures (OEM's) desire interior plastic components being used on consoles, doors, trim areas, and instrument panels to have very low gloss levels. In fact, some OEM's have specified a 2.0 or lower sixty degree Gardner gloss level for most first surface interior components molded in color (MIC) and without paint or a secondary finishing process such as a vinyl wrap. While a trend in the industry is to move toward PP based materials because PP parts are believed to provide lower gloss aesthetics and lower gloss gradients, key features and benefits of ABS products such as dimensional stability, impact, load bearing at elevated temperatures, and scratch resistance, are compromised. Recently, Dow Automotive has developed lower gloss capable ABS resins which also exhibit typical ABS physical and thermal properties. This paper will detail the gloss and gloss gradient advantages of these new low gloss ABS products over a standard talc filled PP material and two traditional ABS products as observed in a glove box outer injection molding trial."
"Child Safety via Anti-Trap Proximity Technology"
"Sir Galahad™ anti-trap windows prevent injury and death, creating a new standard of care for automotive power closures. NHTSA estimates 500 people, approximately 50% of which are children, are treated in hospital emergency rooms each year for injuries related to power windows [11]. Sir Galahad™ technology is easy to install and works on all applications, independent of window shape or geometry. The system is ideally suited for power windows, sunroofs, tailgates, sliding doors, trunks and any other power closures. This paper describes the design and operation of Sir Galahad™ anti-trap windows, including experience of sensitivity response to both animate and inanimate objects. Also discussed are vehicle installation, performance test results, and competitive performance comparisons."
"Tailor-Welded Aluminum Blanks for Liftgate Inner"
"Tailor welded steel blanks have long been applied in stamping of automotive parts such as door inner, b-pillar, rail, sill inner and liftgate inner, etc. However, there are few known tailor welded aluminum blanks in production. Traditional laser welding equipment simply does not have the capability to weld aluminum since aluminum has much higher reflectivity than steel. Welding quality is another issue since aluminum is highly susceptible to pin holes and undercut which leads to deterioration in formability. In addition, high amount of springback for aluminum panels can result in dimension control problem during assembly. A tailor-welded aluminum blank can help reducing dimension variability by reducing the need for assembly. In this paper, application of friction stir and plasma arc welded blanks on a liftgate inner will be discussed."
"Use of SEA for Vehicle Target Setting and Efficient Realization of Vehicle Acoustic Goals"
"Statistical Energy Analysis (SEA) is an established technique for predicting vehicle NVH. Since SEA is more sensitive to certain parameters such as material properties, damping, absorption, and treatment thickness and coverage than to fine details of geometry, using SEA is especially practical and can be particularly advantageous in the early design phase of a vehicle development project. Different concepts for various vehicle subassemblies such as dash, doors, roof, floor, etc., can be effectively evaluated for feasibility at a very early stage in the design process. Such concept studies can prevent design failures and can also be used to improve subassembly NVH target setting. An introduction to SEA and summary of the established use of SEA for vehicle NVH design and development are presented. A proposed methodology for application of SEA to vehicle design is presented, addressing model validation, contribution analysis, target setting, design sensitivity analysis, and optimization for different design concepts and proposed configurations of the vehicle and vehicle subassemblies. A concrete example of an SEA vehicle subassembly model and modeling considerations is presented, followed by a summary and set of conclusions."
"A New Approach for Best Fit Assembly Based on the Behaviour of Components"
"Best fit assembly is now a widely spread assembly technique that consists in finding an optimal position of measured components in order to get an assembly that fits its tolerance specifications. The rigid body assumption does not apply for compliant assemblies that can be slightly deformed and for which the geometrical variations are cleared by the flexibility of components to be assembled. We are proposing a best assembly process that takes into account through simulation the flexibility of components. Thanks to this more realistic simulation, the best fit application scope can be enlarged and confidently applied. It leads to reduced fitting times for over-constrained parts or interchangeable items, like doors, during assembly integration and in service replacements."
"Two-Reference Beam Double-Pulsed Holographic Interferometry with Direct Phase Measurement in Transient Processes Study"
"Holographic interferometry has been successfully employed to characterize both static and dynamic behavior of diverse types of structure under stress. Double-exposure pulsed holographic interferometry has been extensively used in performing the vibration analysis and qualitative investigations of deformation of the non-stationary objects. One of the most important advantages of this technique is that it can be used for quantitative measurements of the transient processes (e.g. shock wave propagation). However, in conventional double-pulsed interferometry it is sometimes difficult to get phase information from a single set of holograms. Applying two-reference beam recording set-up to double-exposure pulsed holographic interferometry makes it possible to obtain phase-shifted interferograms from a single interferogram of the tested object and retrieve the phase information for OPD (optical path difference) map creation. Two-reference beam double-pulsed Ruby laser holographic interferometer has been adapted to transient and continuous phenomena studies. It is non-destructive, real-time, and definitive approach in identification of vibrational modes, displacements, and motion geometries. Results of a vibration study performed by double-pulsed Ruby laser holographic interferometry for wave excited by shaker with continuous sinusoidal excitation and propagated over the car door panel surface are presented in this paper."
"Active vibration control of automotive like panels"
"Automotive panels can be great transmitter of undesired sound from external sources. The ability of controlling the noise and vibration performance of such panels is critical to the perceived quality of a vehicle. Passive vibration systems are currently used in vehicles, but they tend to be heavy in nature and capable of covering only a frequency range above 100-200 Hz. Active vibration control is a potential alternative to passive control. Its cost and adaptability of an active system has been the primary concern for implementation in the automotive sector. Recent developments in the control implementation and lower cost of electronics in general have made the gap between active and passive much smaller than before. An active vibration control has been developed and demonstrated into an automotive-like panel. Such panel was sized to represent a door of a military vehicle. Several excitation sources were considered and included engine excitation, road excitation and blast excitation due to the military design constraints. The active vibration control system is comprised of strain sensors, piezoelectric actuators, a control system and a power amplifier to drive the control actuators. Several control strategies were used depending on the source of excitation. Once of the primary features of all the control strategies used was their adaptability to the change in conditions. A 10 to 15 dB vibration reduction was obtained over the frequency range of interest. As the physically conditions changed (shift in frequency), the control algorithm adapted to the new conditions and vibration reduction could be obtained achieving the same level of performance as during the initial target. The cost of the solution was maintained to a minimum, and its potential production costs for automotive quantities was estimated to be in the order of few tens of dollars (US)."
"Analysis of Determining Parameters of Acoustical Comfort Inside Vehicles"
"The description of subjectively perceived acoustical comfort inside vehicle compartments is a complex challenge. On the one hand, it depends on physically measurable events like acoustical stimuli with a defined sound pressure level and frequency distribution. On the other hand, it is also strongly dependent on further factors like the customer's individual expectations, the previously made experiences and other contextual influences. Furthermore, many different driving conditions have to be considered for a customer-related assessment of driving comfort. In this paper, the mechanisms of acoustical comfort inside vehicle compartments are described on basis of various measurements, listening tests and qualitative assessments. The acoustical properties of driving noises at various driving conditions were taken into account as well as room-acoustical parameters of vehicle interiors and factors of speech communication between passengers. An interview-based qualitative assessment did confirm the importance of speech communication aspects for the comfort experience and well-being of both driver and passengers. These aspects are for example the speech intelligibility, the quality of conversational speech and further the increase in the vocal effort during a conversation in the presence of driving noises. In addition, the characteristics of driving noises at stationary and non-stationary driving conditions were under examination, both in a listening studio and on a test track. The results of the listening tests and customer surveys are connected to acoustical and psychoacoustical parameters to identify the customer-preferred properties of driving noises. This identification is further itemized to an empirically determined optimal ratio between the main noise components (powertrain-induced, chassis-induced and wind-induced noises). As a result of all these investigations, a prediction model of acoustical comfort will be developed in the future."
"Research on the Application of Aluminum Door Beam for Automobiles"
"Door beams are attached inside car doors as one way to protect passengers from shock when the car is side impacted. Though door beams made of high tensile strength steel predominate now, the use of aluminum is growing rapidly to reduce weight. The effects of cross-section and types alloy on the performance of aluminum extrusions as door beams were investigated. As the result, aluminum door beams were developed which have bending proper2ties comparing favorably with those of door beams made of high tensile strength steel with a tensile strength of 1470 N/mm2. Since the shape of the cross-section of aluminum extrusions is versatile, non-symmetric cross-sections composed of regions with different wall thicknesses and lengths can be produced. On the basis of this technology, a technology to design door beams with required bending properties for any car model was developed. This technology is already been utilized in various automobiles. In this paper, the characteristics of these newly developed aluminum door beams will be introduced along with the results of practical use of them [1]."
"A Magnetorheological Door Check"
"Several shortcomings of mechanical door checks are overcome using a magnetorheological damper. Because the damper is electrically actuated, it can check in any desired position. The logical decision to activate or release the door check can be made either by passive circuitry based on input signals from switches attached to door handles or under microprocessor control, in which case the decision can take into account a variety of unconventional input factors, including the magnitude of the force applied to the door, the rate of change of the applied force, and the angle of door opening. With the addition of an appropriate proximity sensor, the controllable damper can prevent the door from inadvertently hitting a nearby obstacle. Details of the damper mechanism are described, and several implemented control strategies, both passive and microprocessor based, are discussed."
"Enhanced Security Flight Deck Doors-Commercial Airplanes"
"In the wake of the 9/11/2001 hijacking events, the Federal Aviation Administration (FAA) has emphasized the need for enhanced flight deck doors on commercial airplanes. The paper describes enhanced flight deck door, which meets the new FAA requirements for intrusion resistance and ballistic protection. In addition, the new door meets the existing requirements for rapid decompression, flight crew security and rescue."
"Design of Experiments (DOE) and Other 6-Sigma Tools Used to Minimize Rear Door Opening Vibration on a Vehicle"
"Very often, engineering problems involve several variables that have different physical behavior making theoretical modeling complex and difficult. In the present paper, 6-Sigma tools were used to develop an experimental model that describes the system. The issue in focus was the vibration observed at the top of rear door during normal opening operation, causing the impression of a fragile structure. The resulting experimental model was able to explain door opening vibration with only 15% of error. In addition, it was possible to choose the best combination and setting for each variable in order to achieve a product benchmarking value."
"Passive Close-Off Feature for Sample Acquisition and Retention"
"The current coring bit and percussive drilling style works very well for strong rocks; however, when coring into weak, crumbling rock, the core tends to break apart and simply fall out of the bit. These rocks, powder, and other debris can have useful information that is lost when they fall out of the bit after the core has been made, as there is no retention feature in place. A retention mechanism for coring into weak rocks was developed."
"SPSCGR"
"SPSCGR generates a contact graph suitable for use by the ION (Interplanetary Overlay Network) DTN (Delay/Disruption Tolerant Network) implementation from data provided by the JPL SPS (Service Preparation System) Portal. Prior to SPSCGR, there was no way for a mission or other entity to route DTN traffic across the DSN without manually constructing a contact graph. SPSCGR automates this process of contact graph construction."
"Reactionless Drive Tube Sampling Device and Deployment Method"
"A sampling device and a deployment method were developed that allow collection of a predefined sample volume from up to a predefined depth, precise sampling site selection, and low impact on the deploying spacecraft. This device is accelerated toward the sampled body, penetrates the surface, closes a door mechanism to retain the sample, and ejects a sampling tube with the sample inside. At the same time the drive tube is accelerated, a sacrificial reaction mass can be accelerated in the opposite direction and released in space to minimize the momentum impact on the spacecraft. The energy required to accelerate both objects is sourced locally, and can be a spring, cold gas, electric, or pyrotechnic. After the sample tube is ejected or extracted from the drive tube, it can be presented for analysis or placed in a sample return capsule."
"Wallops Flight Facility 6U Advanced CubeSat Ejector (ACE)"
"Six-unit (6U) CubeSats are recognized as the next nanosatellite to be considered for standardization. The CubeSat standard established by California Polytechnic University (Cal Poly), which applies to 1U–3U sizes, has proven to be a valuable asset to the community. It has both provided design guidelines to CubeSat developers and a consistent, low-risk interface to launch service providers. This has ultimately led to more flight opportunities for CubeSats. A similar path is desired for the 6U CubeSat. Through this process of standardization, a consistent, low-risk interface for the 6U needs to be established."
"The Future of Aircraft Electrification"
"A resounding applause fills an auditorium in Fort Worth, Texas, as engineers, researchers, and business leaders stand in unison to celebrate the closing keynote of another aerospace conference. Participants grab their belongings and file out into the street where they clamor for rides to the airport. I hail a cab and glance at my watch, noting that in 45 minutes, I'm expected at a meeting in Austin-about 200 miles away. Just then, a taxi pulls up to the curb. I step inside, and as soon the door closes, I'm up in the air. Fifteen minutes later, I land in Austin beside my car; I hop in and head to the meeting location. I arrive soon after, with time to spare. Stories like this were used in the past to paint a futuristic picture of the transportation industry. Visionaries would share them to entice businesses to invest in new modes of travel that, at the time, seemed only possible in dreams."
"SAE Electronics + Connectivity 2012-11-28"
"Integration opens the door Semiconductor suppliers are integrating many functions into power devices while also cutting power consumption in an environment, automotive doors, where 8-bit microcontrollers still hold sway."
"Safety with Convenience: Applying Low Cost Obstacle Detection Technology to Powered Closure Systems with Express Motion"
"There is a growing market for Powered Closure Systems and a strong trend to incorporate express motion for convenience. This drives the need to incorporate obstacle detection using anti-pinch technology for safety reasons according to vehicle safety standards applicable in the governing region. Powered Closure systems include windows, sunroofs, rear hatches, trunk lids and sliding doors with other applications under consideration. This paper will investigate the application of the technology in a cost-effective manner to these systems. A brief comparison of technologies will be considered and the paper will review motor-based control to explore the range of conditions required for obstacle detection. The challenge to provide good protection for obstacle intrusion without causing inadvertent system reversals due to environmental conditions will be presented. A primary focus of the paper will discuss the development of a technology “toolbox” to allow adaptation for the various applications and system to system variation. There is some hesitancy in the market to introduce this available technology due to lack of understanding or concern over cost. This paper seeks to show that the uses of low cost technology can be applied to provide improved safety while increasing convenience to the vehicle operator."
"Innovative Thermoplastic Cavity Filler Design Solutions"
"The use of acoustic cavity fillers or “baffles” to prevent the propagation of air borne and structure borne noise, water and dust into the interior spaces of vehicle structures has been in practice for many years. Continuous development of new OEM requirements has pushed the state of the art concerning the design and functionality of these cavity sealing systems. Various technologies are available to OEMs to provide sealing that will prevent water and dust penetration, maximize performance of vehicle HVAC systems, and minimize the propagation of noise from the body structure into the interior compartment under operating conditions. Generally, three types of cavity sealing systems are available: pre-formed thermoplastic-based systems that incorporate a heat reactive thermoplastic sealer applied to a nylon or steel “carrier” for attachment to the body structure; heat reactive rubber-based sealer systems that incorporate a carrier, push pin or pressure sensitive adhesive layer for attachment; and bulk applied chemically reactive two component polyurethane or expandable “foam” systems. In this case study, a challenge undertaken by this supplier was to provide a thermoplastic baffle design of equal or lesser weight compared to a competitive, die-cut rubber-based technology currently in production at a particular OEM, while achieving equivalent acoustical performance. This paper will document the alternative design proposals and development activities that were pursued to meet this particular objective."
"Optimization through NVH Analysis to Improve the Vehicle Acoustics and Quality of Transmission Shifter"
"Gear shift quality and feel determines the performance of the transmission. It is dependent on the synchronizer, shift system, gear shifter etc in a transmission. In this study the impact of the transmission shifter on the gear shift feel is detailed. More focus is paid towards the feel in terms of NVH characteristics. The rear wheel drive transmission shifter can be bifurcated into direct and indirect shift type. Indirect shifter are of two types, the rod type shifter and the cable shifter. The rod type shifter is analyzed in detail. All the shifters are connected to the gear shift top lever which is the customer interface for gear shifting. The design of the top lever is critical in getting the optimal feel of shifting and the mounting of the shifter is critical to improve its NVH characteristics. Different design iteration of the top lever are studied to illustrate the impact of the weight and stiffness on the vibration. CORRELATION OF A SEMI REMOTE SHIFTER MOUNTING ON VEHICLE ACOUSTICS AND VIBRATION is also established. The shifter dynamics are simulated and its NVH characteristics were studied for 4 cylinder engine and 3 cylinder engine. The shifter strength is analyzed with CAE on hyper mesh. The mechanical links involved and the iterations done to improve the shift quality as well the vibration levels of the hand ball are described. The biasing and shifting force and the travel of the knob in each gear are optimized by verifying through GSQA. Various rear wheel drive transmission have been used as an example to illustrate the shifter dynamics and efficiency. In a three cylinder engine the optimization of the semi remote shifter for the vibration and noise is critical. The solution can be common with a 4-cylinder engine if the arrangement is similar. The extent of benefit would be less on the 4-cylinder than with the 3-cylinder engine as it is more balanced. This study deals primarily with the mounting scheme of the semi remote shifter and its impact on the vehicle NVH. As the 3-cylinder engine configuration has the maximum drive train vibration, it enables a better understanding of the impact of the semi remote shifter mounting scheme on the vehicle. The analysis would help in the selection of the optimum semi remote shifter configuration and material with design adaptation suited to the engine configuration providing better NVH result on the vehicle."
"Vibro-Impact Analysis of Manual Transmission Gear Rattle and Its Sound Quality Evaluation"
"Experimental schemes, frequency characteristics, subjective and objective sound quality evaluation and sound quality prediction model establishment of a certain mass-production SUV (Sport Utility Vehicle, SUV) manual transmission gear rattle phenomenon were analyzed in this paper. Firstly, vehicle experiments, including experiment conditions, vibration acceleration sensor and microphone arrangements and especial considerations in experiments, were described in detail. Secondly, through time-frequency analysis, broadband characteristics of manual transmission gear rattle noise were identified and vibro-impact of gear rattle occurs in the frequency range of 450~4000Hz on the vehicle idle condition and the creeping condition. Thirdly, based on bandwidth filtering processing of gear rattle noise, subjective assessment experiments by a paired comparison method were carried out. Evaluation results passed triangular loop verification and Spearman correlation coefficient examination, and then subjective annoyance results of each noise sample were calculated. Further, objective evaluation results, based on two physical acoustics parameters and six psychological acoustics parameters, were obtained respectively. Finally, comprehensive evaluation of subjective and objective results was analyzed by the MLR (Multiple Linear Regression, MLR) method. It’s concluded that AI (Articulation Index) was the appropriate parameter that’s closely related to subjective annoyance results, and correlation coefficient of AI and subjective annoyance results was up to 0.948. Sound quality prediction model of gear rattle was then established on the vehicle idle condition and the creeping condition. Overall in this paper, research achievements could be adopted to solve practical engineering problems (especially gear rattle problem), and furthermore it could reduce R&D (Research and Design, R&D) cycle, labor costs and material costs dramatically."
"Systems Engineering Approach for Voice Recognition in the Car"
"In this paper, a systems engineering approach is explored to evaluate the effect of design parameters that contribute to the performance of the embedded Automatic Speech Recognition (ASR) engine in a vehicle. This includes vehicle designs that influence the presence of environmental and HVAC noise, microphone placement strategy, seat position, and cabin material and geometry. Interactions can be analyzed between these factors and dominant influencers identified. Relationships can then be established between ASR engine performance and attribute performance metrics that quantify the link between the two. This helps aid proper target setting and hardware selection to meet the customer satisfaction goals for both teams."
"A Tailgate(Trunk) Control System Based on Acoustic Patterns"
"When customers use a tailgate (or trunk), some systems such as power tailgate and smart tailgate have been introduced and implemented for improving convenience. However, they still have some problems in some use cases. Some people have to search for the outside button to open the tailgate, or they should take out the key and push a button. In some cases, they should move their leg or wait a few seconds which makes some people feel that it is a long time. In addition, they have to push the small button which is located on the inner trim in order to close the tailgate. This paper proposes a new tailgate control technology and systems based on acoustic patterns in order to solve some inconvenience. An acoustic user interaction (AUI) is a technology which responds to human’s rubbing and tapping on a specific part analyzing the acoustic patterns. The AUI has been recently spotlighted in the automotive industry as well as home appliances, mobile devices, musical instruments, etc. The AUI is a technology that can extend to rich-touch beyond multi-touch. The AUI can be easily applied and adapted even to the systems which need a large touch recognition area or have complex shape and surface. This paper addresses how to recognize the users’ intention and how to control the tailgate using acoustic sensors and patterns. If someone who has the smart key wants to open the tailgate, he or she only needs to knock on the outer panel of the tailgate twice. When they want to close the tailgate, just touching anywhere of the inner trim of the tailgate will do. Various digital filters and algorithms are used for acoustic signal processing, and the effectiveness of the proposed methods is shown by a real tailgate system with a micro control unit. Finally, we suggest other applications of vehicles which use AUI technology."
"A CFD Analysis Method for Prediction of Vehicle Exterior Wind Noise"
"High frequency wind noise caused by turbulent flow around the front pillars of a vehicle is an important factor for customer perception of ride comfort. In order to reduce undesirable interior wind noise during vehicle development process, a calculation and visualization method for exterior wind noise with an acceptable computational cost and adequate accuracy is required. In this paper an index for prediction of the strength of exterior wind noise, referred to as Exterior Noise Power (ENP), is developed based on an assumption that the acoustic power of exterior wind noise can be approximated by the far field acoustic power radiated from vehicle surface. Using the well-known Curle’s equation, ENP can be represented as a surface integral of an acoustic intensity distribution, referred to as Exterior Noise Power Distribution (ENPD). ENPD is estimated from turbulent surface pressure fluctuation and mean convective velocity in the vicinity of the vehicle surface. Therefore calculations and visualizations of ENP and ENPD can be implemented in an unsteady Computation Fluid Dynamics (CFD) simulation without extra cost for acoustical computation. Applications of ENP and ENPD in vehicle development process can provide not only quantitative information about the acoustic power of exterior wind noise in parts of vehicle but also an indication of the location of dominant sources of exterior wind noise as well as the associated turbulent flows. The information of ENP and ENPD are helpful in order to set targets for exterior wind noise around each part of vehicle and to establish countermeasure designs for reduction of exterior wind noise."
"Reanalysis of Linear Dynamic Systems using Modified Combined Approximations with Frequency Shifts"
"Weight reduction is very important in automotive design because of stringent demand on fuel economy. Structural optimization of dynamic systems using finite element (FE) analysis plays an important role in reducing weight while simultaneously delivering a product that meets all functional requirements for durability, crash and NVH. With advancing computer technology, the demand for solving large FE models has grown. Optimization is however costly due to repeated full-order analyses. Reanalysis methods can be used in structural vibrations to reduce the analysis cost from repeated eigenvalue analyses for both deterministic and probabilistic problems. Several reanalysis techniques have been introduced over the years including Parametric Reduced Order Modeling (PROM), Combined Approximations (CA) and the Epsilon algorithm, among others. It has been shown that the Modified Combined Approximations (MCA) method - an improvement over CA - is the most efficient reanalysis technique for problems with a large number of degrees of freedom. This paper proposes an improvement of the MCA method using frequency shifts. Numerical examples are presented and results are compared with existing methods."
"Comparative Study of Adaptive Algorithms for Vehicle Powertrain Noise Control"
"Active noise control systems have been gaining popularity in the last couple of decades, due to the deficiencies in passive noise abatement techniques. In the future, a novel combination of passive and active noise control techniques may be applied more widely, to better control the interior sound quality of vehicles. In order to maximize the effectiveness of this combined approach, smarter algorithms will be needed for active noise control systems. These algorithms will have to be computationally efficient, with high stability and convergence rates. This will be necessary in order to accurately predict and control the interior noise response of a vehicle. In this study, a critical review of the filtered-x least mean square (FXLMS) algorithm and several other newly proposed algorithms for the active control of vehicle powertrain noise, is performed. The analysis examines the salient features of each algorithm, and compares their system performance. Numerical simulations utilizing synthesized data, are conducted to study the convergence rates of these algorithms. These convergence rates are critical for the noise control outcome. Furthermore, measured powertrain noise response is employed, to verify the system’s performance under more realistic conditions. The individual engine orders are targeted for attenuation or enhancement, to achieve the desired vehicle interior sound quality."
"Frontloading Approach for Sound Package Design for Noise Reduction and Weight Optimization Using Statistical Energy Analysis"
"First time right vehicle performance and time to market, remains all automotive OEMs top priority, to remain competitive. NVH performance of product communicates impression to customer, remains one of the most important and complex attribute to meet, considering performances to be met for 20 Hz -6000 Hz. Frontloading techniques (FEM/BEM/SEA/MBD) for NVH are critical and necessary to achieve first time right NVH performance. Objective of this paper is to present a frontloading approach for automotive sound package optimization (absorber, barrier and damper elements) for SUV vehicle. Current process of designing sound package is mainly based on experience, competitive benchmarking of predecessor products. This process (current process) heavily depend on testing and validation at physical prototype and happens at later stages of program, especially on tooled up body. This is because, structure borne noise development, sealing and leakage path treatment refinement assume priority over sound package development. This way of working has impacted on validation timelines, late changes in peripheral system, leading to cost increase and time delays. High frequency simulations (using statistical energy analysis) provides opportunity in terms of being able to evaluate design options and frontload sound package design in parallel with structure borne NVH development. In this exercise, SEA (statistical energy analysis) was used to predict full vehicle cabin noise (400 Hz-6000 Hz) by modelling all major paths (structure borne and air borne) present in vehicle. All major sources of excitation such as powertrain vibrations, suspension vibrations and engine bay noise, tyre patch noise, exhaust noise were used to predict cabin noise. Static and dynamic load cases were used to validate modelling confidence and model updating. Contribution analysis was used to identify dominant sources, transfer paths for optimization of sound package for performance and weight."
"Uncertainty Analysis of High-Frequency Noise in Battery Electric Vehicle Based on Interval Model"
"The high-frequency noise issue is one of the most significant noise, vibration, and harshness problems, particularly in battery electric vehicles (BEVs). The sound package treatment is one of the most important approaches toward solving this problem. Owing to the limitations imposed by manufacturing error, assembly error, and the operating conditions, there is often a big difference between the actual values and the design values of the sound package components. Therefore, the sound package parameters include greater uncertainties. In this article, an uncertainty analysis method for BEV interior noise was developed based on an interval model to investigate the effect of sound package uncertainty on the interior noise of a BEV. An interval perturbation method was formulated to compute the uncertainty of the BEV’s interior noise. The sound absorption coefficient and transmission loss of the sound package were obtained through tests, and a statistical energy analysis model of the BEV was established. The acoustic loads of the BEV were tested and the interior noise of the cabin was analyzed under certain working conditions. Uncertain parameters were introduced to describe the sound package system of the firewall. The sensitivities of the uncertain parameters were analyzed using the numerical sensitivity analysis method. The effect of interior noise was predicted through the interval perturbation method, and the robustness of the system was analyzed under the influence of uncertain parameters."
"Road Noise Evaluation by Sound Quality Simulation Module"
"An objective evaluation of sound quality is a technical bridge connecting sound pressure level (SPL) and human auditory sensation. In this paper, an algorithm is proposed for calculating objective evaluation parameters of sound quality (including loudness, sharpness and articulation index), considering acoustic characteristics of human external ear, middle ear and inner ear to reflect auditory sensation. A sound quality simulation (SQS) module is coded according to the algorithm. The module is used for evaluating sound quality of road noise from an SUV in three steps. Firstly, interior noise is predicted by integrating finite-element method (FEM), hybrid FE-SEA method, and statistical energy analysis (SEA) for low frequency (20~315 Hz), medium frequency (315~500 Hz), and high frequency (>500 Hz) in 1/3 octave band, respectively. The predicted interior noise SPLs are compared with the measured results, with deviations less than 3dB in average. Secondly, the sound quality parameters are calculated using the predicted SPLs in the SQS module. The predicted and measured loudness, sharpness, and articulation index are compared, with average deviations less than 5%. Finally, the predicted interior noise is filtered by the SQS module in 1/3 octave band, to determine the dominant contribution bands for the sound quality parameters. Several optimized designs are implemented to optimize the sound quality parameters, and validated by experiments."
"Windshield Glare from Bus Interiors: Potential Impact on City Transit Drivers at Night"
"Windshield glare at night is a safety concern for all drivers. Public transit bus drivers also face another concern about glare caused by interior lighting sources originally designed for passenger safety. The extent to which interior light reflections contribute to glare is unknown. Unique methods for measuring discomfort and disability glare during bus driving were developed. An initial simulation study measured windshield luminance inside of a New Flyer D40LF diesel bus parked in a controlled, artificial, totally darkened test environment. Findings indicated significant disability glare (from elevated luminance) in the drivers’ primary field of view due to interior reflections. Any reduction in contrast would result in less prominent glare if actual driving conditions differ. To assess this, levels of windshield glare were also measured with the bus parked on the roadside under the “background glow” of the urban environment. Findings reveal that under road conditions the extent of disability glare from interior reflections is much less, but not negligible, when contrast is reduced. The information gathered in these studies may be useful to manufacturers and transit authorities to improve conditions for drivers and the travelling public. Measurement methods developed in this study may prove useful for assessing elements of interior design. The difference between disability and discomfort glare is discussed. The results provide directions for implementation of glare control strategies."
"Lockheed Martin Low-Speed Wind Tunnel Acoustic Upgrade"
"The Lockheed Martin Low-Speed Wind Tunnel (LSWT) is a closed-return wind tunnel with two solid-wall test sections. This facility originally entered into service in 1967 for aerodynamic research of aircraft in low-speed and vertical/short take-off and landing (V/STOL) flight. Since this time, the client base has evolved to include a significant level of automotive aerodynamic testing, and the needs of the automotive clientele have progressed to include acoustic testing capability. The LSWT was therefore acoustically upgraded in 2016 to reduce background noise levels and to minimize acoustic reflections within the low-speed test section (LSTS). The acoustic upgrade involved detailed analysis, design, specification, and installation of acoustically treated wall surfaces and turning vanes in the circuit as well as low self-noise acoustic wall and ceiling treatment in the solid-wall LSTS. The preservation of the aerodynamic flow quality and the reduction in background noise levels in the LSTS were demonstrated by a series of measurements that were performed both prior to and after the acoustic upgrade."
"Advancement in Vehicle Development Using the Auto Transfer Path Analysis"
"This paper presents the most recent advancement in the vehicle development process using the one-step or auto Transfer Path Analysis (TPA) in conjunction with the superelement, component mode synthesis, and automated multi-level substructuring techniques. The goal is to identify the possible ways of energy transfer from the various sources of excitation through numerous interfaces to given target locations. The full vehicle model, consists of superelements, has been validated with the detailed system model for all loadcases. The forces/loads can be from rotating components, powertrain, transfer case, chain drives, pumps, prop-shaft, differential, tire-wheel unbalance, road input, etc., and the receiver can be at driver/passenger ears, steering column/wheel, seats, etc. The traditional TPA involves two solver runs, and can be fairly complex to setup in order to ensure that the results from the two runs are consistent with subcases properly labeled as input to the TPA utility. However, auto TPA allows necessary data needed for the TPA analysis to be requested in a single frequency response analysis run. The TPA breaks down the total response to partial contributions from interface points under operation loads. Partial contributions to total response are then computed by multiplying transfer function with the force transmitted through each interface location. By comparing the results of two-step TPA with auto TPA, the effectiveness and efficiency of the auto TPA have been demonstrated for three load cases: a) powertrain excitation for cruising acceleration to engine torque (A/T) and noise to engine torque (P/T), b) propshaft imbalance, and c) rough road excitation, which is based on the power spectral density (PSD) function."
"Development of Feedback-Based Active Road Noise Control Technology for Noise in Multiple Narrow-Frequency Bands and Integration with Booming Noise Active Noise Control System"
"When a vehicle is in motion, noise is generated in the cabin that is composed of noise in multiple narrow-frequency bands and caused by input from the road surface. This type of noise is termed low-frequency-band road noise, and its reduction is sought in order to increase occupant comfort. The research discussed in this paper used feedback control technology as the basis for the development of an active noise control technology able to simultaneously reduce noise in multiple narrow-frequency bands. Methods of connecting multiple single-frequency adaptive notch filters, a type of adaptive filter, were investigated. Based on the results, a method of connecting multiple filters that would mitigate mutual interference caused by different controller transmission characteristics was proposed. This method made it possible to implement controllers with amplitude and phase characteristics in multiple narrow-frequency bands corresponding to design values, and to achieve the target noise-reduction. Additionally, in feedback-based road noise control, the amplitude of the control output signal changes drastically depending on the frequency characteristics of the road surface. When this technology was integrated with the already-commercialized booming noise control system, a method to adjust the range of each controller output automatically was applied, achieving integration while balancing noise reduction performance under normal conditions with control stability when the vehicle passes over a large-input surface."
"Source-Path-Contribution Methodologies across a Wide Range of Product Types"
"Source-path-contribution (SPC) analysis, or transfer-path-analysis, is a test based method to characterize noise and vibration contributions of a complex system. The methodology allows for the user to gain insight into the structural forces and acoustic source strengths that are exciting a system, along with the effects of the structural and acoustic paths between each source and a receiver position. This information can be utilized to understand which sources and/or paths are dominating the noise and vibration performance of a system, allowing for focused target cascading and streamlined troubleshooting efforts. The SPC process is widely used for automotive applications, but is also applicable for a wide range of product types. For each unique application the basic SPC principles remain constant, however best practices can vary for both measurement and analysis depending on the type of system being evaluated. In this paper the application of the SPC process is described across a range of different applications including automotive, agricultural, small engine, and smaller component-level applications."
"Current Status and Future Developments of ANC Systems"
"Active Noise Control (ANC) has long been seen as emerging technology. During recent years, however, it became popular in new vehicle and infotainment platforms within a broad range of OEMs. This paper summarizes the current status and lessons learned of production systems (as well as those entering production soon) and gives an outlook on how ANC and related technologies will integrate in future vehicles and audio/infotainment architectures."
"Coupling CFD with Vibroacoustic FE Models for Vehicle Interior Low-Frequency Wind Noise Prediction"
"With the reduction of engine and road noise, wind has become an important source of interior noise when cruising at highway speed. The challenges of weight reduction, performance improvement and reduced development time call for stronger support of the development process by numerical methods. Computational Fluid Dynamics (CFD) and finite element (FE) vibroacoustic computations have reached a level of maturity that makes it possible and meaningful to combine these methods for wind noise prediction. This paper presents a method used for coupling time domain CFD computations with a finite element vibroacoustic model of a vehicle for the prediction of low-frequency wind noise below 500 Hz. The procedure is based on time segmentation of the excitation load and transformation into the frequency domain for the vibroacoustic computations. It requires simple signal processing and preserves the random character as well as the spatial correlation of the excitation signal. The aeroacoustic load is applied on the entire outer surface of the vehicle body. The computed results are validated against wind tunnel measurements on a production vehicle. The numerical and experimental investigations provide some insight into the mechanisms involved in underbody wind noise."
"Sideglass Turbulence and Wind Noise Sources Measured with a High Resolution Surface Pressure Array"
"The authors report on the design and application of a high resolution micro-electro-mechanical (MEMS) microphone array for automotive wind noise engineering. The array integrates both sensors and random access memory (RAM) chips on a flexible circuit board that eliminates high channel count wiring and allows the array to be deployed on automobile surfaces in a convenient “stick-on/peel-off” configuration. These arrays have potential application to the quantitative evaluation of interior wind noise from measurements on a clay model in the wind tunnel, when used in conjunction with a body vibro-acoustic model. The array also provides a high resolution turbulence measurement tool, suitable for validation of computation fluid dynamics (CFD) simulations for wind noise. The authors' report on the wavenumber-frequency structure of flow turbulence measured in different flow regions on a side glass and the corresponding contributions to interior wind noise."
"Prediction of Interior Noise in a Sedan Due to Exterior Flow"
"Aero-vibro-acoustic prediction of interior noise associated with exterior flow requires accurate predictions of both fluctuating surface pressures across the exterior of a vehicle and efficient models of the vibro-acoustic transmission of these surface pressures to the interior of a vehicle. The simulation strategy used in this paper combines both CFD and vibro-acoustic methods. An accurate excitation field (which accounts for both hydrodynamic and acoustic pressure fluctuations) is calculated with a hybrid CAA approach based on an incompressible unsteady flow field with an additional acoustic wave equation. To obtain the interior noise level at the driver's ears a vibro-acoustic model is used to calculate the response of the structure and interior cavities. The aero-vibro-acoustic simulation strategy is demonstrated for a Mercedes-Benz S-class and the predictions are compared to experimental wind tunnel measurements."
"Optimization of a Porous Ducted Air Induction System Using Taguchi's Parameter Design Method"
"Taguchi method is a technology to prevent quality problems at early stages of product development and product design. Parameter design method is an important part in Taguchi method which selects the best control factor level combination for the optimization of the robustness of product function against noise factors. The air induction system (AIS) provides clean air to the engine for combustion. The noise radiated from the inlet of the AIS can be of significant importance in reducing vehicle interior noise and tuning the interior sound quality. The porous duct has been introduced into the AIS to reduce the snorkel noise. It helps with both the system layout and isolation by reducing transmitted vibration. A CAE simulation procedure has been developed and validated to predict the snorkel noise of the porous ducted AIS. In this paper, Taguchi's parameter design method was utilized to optimize a porous duct design in an AIS to achieve the best snorkel noise performance. The virtual experiments based on an orthogonal array in the parameter design method were conducted by the developed simulation procedure and the optimized design was recommended. Furthermore, the parts based on the optimized design are manufactured and tested to verify if the intended performance and other high priority requirements for the AIS are met. It was concluded that a traditional CAE analysis enhanced with robustness technique is an efficient tool to optimize the AIS design in this case study."
"The Predictive Simulation of Exhaust Pipe Narrow-band Noise"
"A method of predictive simulation of flow-induced noise using computational fluid dynamics has been developed. The goal for the developed method was application in the vehicle development process, and the target of the research was therefore set as balancing the realization of a practical level of predictive accuracy and a practical computation time. In order to simulate flow-induced noise, it is necessary to compute detailed eddy flows and changes in the density of the air. In the research discussed in this paper, the occurrence or non-occurrence of flow-induced noise was predicted by conducting unsteady compressible flow calculation using large eddy simulation, a type of turbulence model. The target flow-induced noise for prediction was narrow-band noise, a type of noise in which sound increases in specific frequency ranges. Assuming the area of generation of flow-induced noise to be the exhaust pipe, including the complex shape of the muffler, predictive accuracy was verified under conditions that modeled measurements in steady-state flow test equipment. In order to reduce computation time while maintaining predictive accuracy, calculation methods were combined and computation times compared. This made it possible to reduce computation time by 61% against that in the initial stage of development of the method. In addition, a study utilizing multiple exhaust pipe shapes indicated that a correlation existed between the number of computation cells and computation time. The developed method has made it possible to predict the occurrence of narrow-band noise within a practical computation time."
"Automobile Wind Noise Speed Scaling Characteristics"
"Wind noise, an aeroacoustic phenomenon, is an important attribute that influences customer sensation of interior quietness in a moving vehicle. As a vehicle travels faster, occupants' sensation of wind noise becomes increasingly objectionable. The purpose of this work is to investigate the increase of wind noise level perceived by a driver in response to an increase in wind speed. Specifically, it explores how much the level of wind noise at the DOE (driver outboard ear) would vary in response to a change in wind speed based on the test data obtained in a wind tunnel from ten vehicles that belong to several different passenger vehicle segments. The first part of this work studies the change of the SPL (sound pressure level) in response to a change in wind speed U. It shows that the SPL(dBA) approximately scales to U5.7 at the DOE and to U6.3 in the far-field, which could be interpreted as the dominance of dipoles. The second part of this work looks into the scaling of loudness measured in Zwicker sones that represent the human auditory sensation of wind noise level. It shows that the human perception of the wind noise loudness scales to U1.7 approximately, which indicates that the wind noise loudness sensation is doubled when the vehicle speed incurs a 50% increase."
"Assessing the Aeroacoustic Response of a Vehicle to Transient Flow Conditions from the Perspective of a Vehicle Occupant"
"On-road, a vehicle experiences unsteady flow conditions due to turbulence in the natural wind, moving through the unsteady wakes of other road vehicles and travelling through the stationary wakes generated by roadside obstacles. Separated flow structures in the sideglass region of a vehicle are particularly sensitive to unsteadiness in the onset flow. These regions are also areas where strong aeroacoustic effects can exist, in a region close to the passengers of a vehicle. The resulting aeroacoustic response to unsteadiness can lead to fluctuations and modulation at frequencies that a passenger is particularly sensitive towards. Results presented by this paper combine on-road measurement campaigns using instrumented vehicles in a range of different wind environments and aeroacoustic wind tunnel tests. A new cabin noise simulation technique was developed to predict the time-varying wind noise in a vehicle using the cabin noise measured in the steady environment of the wind tunnel, and a record of the unsteady onset conditions on the road, considering each third-octave band individually. The simulated cabin noise predicted using this quasi-steady technique was compared against direct on-road cabin noise measurements recorded under the same flow conditions to assess the response of the vehicle to oncoming flow unsteadiness. The technique predicted the modulation of the wind noise under unsteady on-road conditions with good fidelity. This is because the cabin noise response to oncoming flow unsteadiness remained generally quasi-steady up to fluctuation frequencies of approximately 2 to 5 Hz, with fluctuations at higher scales having a progressively smaller impact, and because most of the onset flow fluctuation energy on the road occurs at frequencies below this threshold. The relative impact of the baseline level of cabin noise and the sensitivity of the cabin noise to changes in yaw angle were assessed in terms of occupant perception and this highlighted the importance of modulation. This can provide guidance when assessing the on-road wind noise performance of vehicle geometry modifications and of different vehicles."
"Planetary Airlock and Suitlock Requirements and Alternate Approaches"
"This study describes the operational requirements for planetary surface access and compares the performance of a hatch, airlock, suitlock, and suitport. The requirements for mitigating dust, performing EVA (ExtraVehicular Activity) by only part of the crew, and use on Mars as well as the Moon are strong reasons to prefer an airlock over a simple hatch, which would require depressurizing the habitat and sending all the crew on EVA. A requirement for minimum cost would favor the hatch above all. A suitlock provides better dust mitigation than an airlock, but at higher cost and complexity. A suitlock accommodating two crew meets requirements for buddy assistance and ability to help an incapacitated crewmember. Two suitlocks would provide redundant airlocks. A suitport, similar to a suitlock but having a suit-bulkhead pressure seal and no outer airlock door, provides dust mitigation and operational flexibility similar to the suitlock at lower cost, but increases risk and limits contingency response. A combined airlock/suitlock/suitport has the broadest capability and flexibility."
"The Study of Roller Hemming Process for Aluminum Alloy via Finite Element Analysis and Experimental Investigations"
"Recently the automotive industry faces many competitive challenges including weight and cost reduction to meet the needs for high fuel efficiency. Therefore, the use of light metals such as aluminum alloys has been increased to produce the body structure of light-weight vehicles. However, since the formability of aluminum alloy is not as good as that of steel, it needs a special attention to body manufacturer during their forming process. Roller hemming technology has been introduced as a new production technique which has several advantages in terms of cost and time saving for trial and error. Since hemming is the last forming process in stamping, it determines the external quality of automotive outer parts such as doors, hood and trunk-lid. In this study, the implicit finite element analysis of roller hemming process on the flat surface-straight edge panel was performed by using the commercial code ANSYS. This study shows the process of roller hemming simulation with Von Mises stress and effective strain results. In addition, experimental investigations have been done to compare the results between the simulation and experiment."
"A Modern Development Process to Bring Silence Into Interior Components"
"Comfort and well-being have always been connected with a flawless interior acoustic, free of any background noise or BSR, (buzz, squeak and rattle). BSR noises dominate the interior acoustic and represent one of the main sources for discomfort often causing considerable warranty costs. Traditionally BSR issues have been identified and rectified through extensive hardware testing, which by its nature intensifies toward the end of the car development process. In the following paper the integration of a virtual BSR validation technique in a modern development process by the use of appropriate CAE methods is presented. The goal is to shift, in compliance with the front loading concept, the development activities into the early phase. The approach is illustrated through the example of an instrument panel, from the early concept draft for single components to an assessment of the complete assembly. In a second and innovative example a combination of a virtual door slam analysis with a subsequent BSR analysis is examined. Every analysis result shown in the paper will be compared with corresponding test results."
"Obstacle Detection for Power Folding Seats"
"In the past years the automotive industry has equipped it's vehicles with more and more automated power driven functions. Starting with the “express up/down ” functions for power windows and “easy entry/exit” functions of memory seats, automated power movements have also been introduced into power sliding doors as well as power liftgates. In contrast to “press & hold” switch activated movement, where the operator takes responsibility for the movement, the control unit of the “automated” or “one-touch” movement has to provide some sort of obstacle detection or pinch protection. This paper deals with the adaptation of a pinch protection algorithm for linear movements like power windows or memory seat applications to the rotational movement of power folding seats. With the considerable weight of a seat that is involved the motor torque changes along the travel of the seat, sometimes even reaching negative values in those positions where obstacles would most likely need to be detected. On the other hand, obstacle detection must be less sensitive in areas where the seat needs to be moved against gravity and where complex seat mechanics introduce non-linear torque requirements. The paper addresses these issues and describes basic functionality, such as how to obtain a voltage compensated torque equivalent signal from a hall sensor speed signal. It also describes the challenges that arise from rotational movement."
"Using Spherical Beamforming to Evaluate Wind Noise Paths"
"Microphone array based techniques have a growing range of applications in the vehicle development process. This paper evaluates the use of Spherical Beamforming (SB) to investigate the transmission of wind-generated noise into the passenger cabin, as one of the alternative ways to perform in-vehicle troubleshooting and design optimization. On track measurements at dominant wind noise conditions are taken with the spherical microphone array positioned at the front passenger head location. Experimental diligence and careful processing necessary to enable concise conclusions are briefly described. The application of Spherical Harmonics Angularly Resolved Pressure (SHARP) and the Filter-And-Sum (FAS) algorithms is compared. Data analysis variables, run-to-run repeatability and system capability to identify design modifications are studied. It is demonstrated that the Spherical Beamforming is a powerful tool to visualize dominant noise paths in vehicle, providing valuable information for the wind noise control at the transmission paths rather than using the standard single microphone operational data at the observer location."
"Study of Coupling Behavior of Acoustic Cavity Modes to Improve Booming Noise in Passenger Vehicles"
"Interior sound quality is one of the significant factors contributing to the comfort level of the occupants of a passenger car. One of the major reasons for the deterioration of interior sound quality is the booming noise. Booming noise is a low frequency (20Hz∼300Hz) structure borne noise which occurs mainly due to the powertrain excitations or road excitations. Several methods have been developed over time to identify and troubleshoot the causes of booming noise [1]. In this paper an attempt has been made to understand the booming noise by analyzing structural (panels) and acoustic (cavity) modes. Both the structural modes and the acoustic modes of the vehicle cabin were measured experimentally on a B-segment hatchback vehicle using a novel approach and the coupled modes were identified. Panels contributing to booming noise were identified and countermeasures were taken to modify these panels to achieve decoupling of structural and cavity modes which results in the reduction of cabin noise levels. This is followed by countermeasure validation resulting into booming noise reduction."
"Multidisciplinary Design Optimization of BEV Body Structure"
"Blade Electric Vehicle (BEV) with a light body plays an important role in saving the energy and reducing the exhaust emission. However, reducing the body weight need to meet the heterogeneous attributes such as structural, safety and NVH (Noise, Vibration and Harshness) performance. With the rapid development of finite element (FE) analysis technology, simulation analysis is widely used for researching the complex engineering design problem. Multidisciplinary Design Optimization (MDO) of a BEV body is a challenging but meaningful task in the automotive lightweight. In present research, the MDO is introduced to optimize a BEV Body-in-White (BIW). The goal of optimization is to minimize the mass of the BIW while meeting the following requirements: structural performance (the bending and torsion stiffness is increased), NVH performance (the first overall torsion frequency is increased), and safety performance (the roof crush resistance is improved).The sample points were obtained by using Design of Experiment (DOE) with optimal Latin hypercube. The approximation models of mass, bending stiffness, torsion stiffness, modal and safety were established with the polynomial response surface method (RSM). The thicknesses of nine parts of the BIW were selected to be optimized by Muti-island Genetic Algorithm (MGA) method. After the MDO of the BIW, the paper drew the following conclusions: 1.The predictive values of the approximation and the results of FE simulation had a good agreement with an error less than 5.00% and the former met the engineering requirements; 2.The weight of the BIW was reduced by 2.00% and the optimized BIW met all prescribed requirements about structural, NVH and safety performance."
"Approach to Control the in Cab Noise without Affecting Passenger Comfort in AC Midi Buses"
"This paper discusses various fruitful iterations / experiments performed to reduce air flow induced noise without compromising on total air flow requirement for thermal comfort and ways to avoid heat ingress inside the bus. Also the paper discusses the devised process for noise reduction through front loading of computer aided engineering and computational fluid dynamics analysis. Air conditioning buses in light commercial vehicle (LCV) segment is growing market in India, especially for applications like staff pick-up and drop, school applications and private fleet owners. The air-conditioning system is typically mounted on bus roof top and located laterally and longitudinally at center. It is an easiest and most feasible way to package air conditioning system to cater the large passenger space (32 to 40 seats) with the conditioned air. This makes air conditioning duct design simple and commercially viable. Most of the LCV buses are with front engine configuration which adds more heat and noise to driver and passenger compartment, this demands for isolation of driver's area from passenger area by means of partition in between. In case of buses without partition engine noise is more dominant, but in case of buses with partition, blower noise of roof mounted AC system is more perceivable in passenger area. The larger glass area, limitation on glass tint percentage and mandate for not to use curtain added more challenges in front of thermal engineer to device effective cabin cooling system to cater huge heat load and achieve required human comfort."
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