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Technical Paper

Design Optimization of Differential Bevel Gear for NVH Improvement

2019-06-05
2019-01-1552
With fast pacing development of automobile industry and growing needs for better driving experience, NVH performance has become an important aspect of analysis in new driveline product development especially in hybrid and electric powered vehicles. Differential bevel gear has significant role in the final drive. Unlike parallel axis gears such as spur or helical gear, bevel gear mesh shows more complicated characteristics and its mesh parameters are mostly time-varying which calls for more extensive design and analysis. The purpose of this paper is to conduct design study on a differential bevel gear unit under light torque condition and evaluate its NVH characteristics. Unloaded tooth contact analysis (UTCA) of those designs are conducted and compared for several design cases with different micro geometry to investigate their pattern position and size variation effects on NVH response.
Technical Paper

Tonal Annoyance Metric Development for Automotive Electric Vehicles

2019-06-05
2019-01-1467
Historical metrics intended to drive the development of vehicle powertrains have focused on sounds that are characteristic of IC engines. The interior noise contribution of the propulsion system in electric vehicles has significantly more tonal noise (and much less impulsive and broadband noise) than their IC engine counterparts. This tonal noise is not adequately represented by current propulsion systems metrics. While metrics exist today that were developed to represent the presence of tones in sounds most have focused on the level aspect of the tones relative to the surrounding noise or masking level, some examples include tonality, tone-to-noise ratio, and prominence ratio. A secondary, but also important aspect of tones is the annoyance as a function of frequency. This paper will highlight the development of a tonal annoyance weighting curve that can be used to account for the frequency aspect of tonal annoyance relative to electric vehicles.
Technical Paper

Understanding the Stick Slip Behavior of Plastics and Target Setting: An OEM Perspective

2019-06-05
2019-01-1465
Automotive OEMs are aggressively using different materials for interiors due to value proposition and variety of options available for customers in market. Excessive usage of different grade plastics with zero gap philosophy can cause stick slip effect leading to squeak noise. Even though systems and subsystems are designed using best practices of structural design and manufacturing tolerances, extreme environmental conditions can induce contacts leading to squeak noise. Appropriate selection of interface material pairs can minimize the possibilities of squeak conditions. Stick-slip behavior of different plastics is discussed in the present study, along with critical parameters during material compatibility testing in a tribological test stand. Friction coefficient of different material pairs for a defined normal load and sliding velocity are analyzed for patterns to recognize squeaks versus time.
Technical Paper

Structural Vibration of an Elastically Supported Plate due to Excitation of a Turbulent Boundary Layer

2019-06-05
2019-01-1470
High-Reynolds number turbulent boundary layers are an important source for inducing structural vibration. Small geometric features of a structure can generate significant turbulence that result in structural vibration. In this work we develop a new method to couple a high-fidelity fluid solver with a dynamic hybrid analytical-numerical formulation for the structure. The fluid solver uses the Large-Eddy Simulation closure for the unresolved turbulence. Specifically, a local and dynamic one-equation eddy viscosity model is employed. The fluid pressure fluctuation on the structure is mapped to the dynamic structural model. The plate where the flow excitation is applied is considered as part of a larger structure. A hybrid approach based on the Component Mode Synthesis (CMS) is used for developing the new hybrid formulation. The dynamic behavior of the plate which is excited by the flow is modeled using finite elements.
Technical Paper

Calculation Process with Lattice Boltzmann and Finite Element Methods to Choose the Best Exterior Design for Wind Noise

2019-06-05
2019-01-1471
Wind noise in automobile is becoming more and more important as the customer expectations increase. On the other hand, great progress has been made on engine and road noises, especially for electric and hybrid vehicles. Thus, the wind noise is now by far the major acoustic source during road and motorway driving. As for other noises, automobile manufacturers must be able, for a new car project, to specify, calculate and measure each step of the acoustic cascading: Source Transfers, both solid and air borne In the case of the automotive wind noise, the excitation source is the dynamic pressure on the vehicle’s panels. This part of the cascading is the one influenced by the exterior design. Even if many others components (panels, seals, cabin trims) have a big influence, the exterior design is a major issue for the wind noise. The wind noise level in the cabin may change significantly with only a small modification of the exterior design.
Technical Paper

Wind Noise Transmission Loss for Separated Flow Conditions

2019-06-05
2019-01-1469
The transmission of turbulent flow pressures through panels to the interior noise depends on the spatial matching of the pressure and vibration fields. Since the exterior pressure field on a moving vehicle includes both turbulent pressure and acoustic pressure, both need to be factored into a noise transmission loss calculation. However, these two exterior pressure fields have very different spatial patterns. This is further complicated when the exterior flow is separated from the surface due to an obstruction. This study uses wind tunnel and road tests to measure and model the wind noise transmission loss through the side glass of a vehicle. The results are seen to be very different from the traditional sound transmission loss curves for an acoustic pressure source.
Technical Paper

Dual Clutch Transmission Vibrations during Gear Shift: A Simulation-Based Approach for Clunking Noise Assessment

2019-06-05
2019-01-1553
A novel methodology, for the assessment of Dual Clutch Transmission vibrations during gear shifts, is proposed in this paper. It is based on the capability to predict through numerical simulation a typical dynamic quantity used to objectively evaluate the vibrational behavior of a gearbox during experimental tests, i.e. the acceleration of a point on the external surface of the gearbox housing. To achieve this result, a two-step approach is proposed: an accurate simulation of the internal transmission dynamics and an offline uncoupled computation of the gearbox housing acceleration from the output of the simulation. The first step required the definition of a suitable nonlinear lumped parameter model of the car equipped with a DCT that was implemented in Amesim software.
Technical Paper

Machine Learning Algorithm for the Prediction of Idle Combustion Uniformity

2019-06-05
2019-01-1551
Combustion stability is a key contributor to engine shake at idle speed and can impact the overall perception of vehicle quality. The sub-firing harmonics of the combustion torque are used as a metric to assess idle shake and are, typically, measured at different levels of engine break mean effective pressure (BMEP). Due to the nature of the combustion phenomena at idle, it is clear that predicting the cycle-to-cycle and cylinder-to-cylinder combustion pressure variations, required to assess the combustion uniformity, cannot be achieved with the state of the art simulation technology. Inspired by the advancement in the field of machine learning and artificial intelligence and by the availability of a large amount of measured combustion test data, this paper explores the performance of various machine learning algorithms in predicting the idle combustion uniformity.
Technical Paper

Multiphysics Multi-Objective Optimization for Electric Motor NVH

2019-06-05
2019-01-1461
Prediction and reduction of noise/vibration at the early design stage is important for motor design. Rapid design iterations require a platform where electromagnetic, structural and acoustic solvers can communicate with each other without user scripting or interventions. Based on the platform, multiple designs in a given design space need to be analyzed by distributed high performance computers automatically. To demonstrate such a multiphysics multi-objective optimization workflow, four geometrical variables for an interior permanent magnet motor are selected for optimizing the electric and acoustic performance (Figure 1). Average torque and equivalent radiated power level (ERP) are calculated for multiple design points and response surfaces are then created for the sensitivity study and optimization.
Technical Paper

Improved Measurement Procedures for Engine Noise Reduction with Advanced Microphones

2019-06-05
2019-01-1463
The acoustic environment inside the car is a primary comfort parameter. With the change from internal combustion engines (ICE) to electrical (BEV) or electrically assisted (HEV) propulsion systems, a renewed focus on old and new noise sources in the engine bay and the transmission paths to the cabin is required. A way to study this is by using a reverse transmission technique, placing a sound source in the receiver position in the cabin and measure the resulting sound pressure levels in the engine bay. Assuming reciprocity, the attenuation of transmission from sound sources in the engine bay to the cabin can be estimated. These measurements are cumbersome as they involve the placement of 20 or more microphones in the engine bay. This has traditionally been performed using off-the-shelf free-field measurement microphones. To optimize this procedure a new pressure-field microphone has been tested by Volvo Cars.
Technical Paper

Noise and Vibration End-of-Line Production Testing and Analysis Challenges

2019-06-05
2019-01-1464
Theoretical modeling continues to play a larger role in noise and vibration engineering; however, until products are perfectly made, there will be a need to evaluate their end of the production line performance. Manufacturing production of a wide range of items has classically involved some amount of subjective and/or evolved objective quality testing along, or at the end of the production line. This testing can have goals of determining product safety, durability, functionality, and/or the vibration/sound quality. A vibration-based measurement approach is frequently used for many of those goals. Often, many modern products utilize some combination of electric motors, internal combustion engines, and power transmission rotational components. The end-of-line testing for many of these rotational components is after many years now heavily refined in the measurement and analysis methods, and the separation of good, bad and marginally bad samples may not always be challenging.
Technical Paper

Psychoacoustic Order Tonality Calculation

2019-06-05
2019-01-1466
Quantifying tonalities in technical sounds according to human perception is a task of growing importance. The psychoacoustic tonality method, published in the 15th edition of the ECMA-74 standard, is a new method that is capable of calculating the perceived tonality of a signal. Other methods, such as Prominence Ratio or Tone-to-Noise Ratio do not consider several essential psychoacoustic effects. The psychoacoustic tonality is based on a model of human hearing and thus is able to model human perception better than other methods. The algorithm described in ECMA-74 calculates tonality over time and frequency. In practice, tonalities often originate from rotating components, for example, parts of an electric motor. In these cases, quantification of the tonality of orders is often more interesting than the tonality over frequency. In this paper, an extension of the psychoacoustic tonality according to ECMA-74 is presented.
Technical Paper

Investigation on Cyclic Noise in Vehicle Creeping during Stop-Go Traffic Conditions

2019-06-05
2019-01-1557
Now-a-days, customers are turning more sensitive towards vehicle NVH performance. In order to enhance customer NVH comfort, a specific noise phenomenon was investigated during product development. While testing stop-go traffic conditions, cyclic noise was observed in the 1st gear with the vehicle creeping. The noise was similar to a gear rattling noise. It was perceived unpleasant due to low background noise and wide frequency range of cyclic noise. This paper explains the root cause of this cyclic noise through various drivetrain experiments and also elaborates the experimental analysis approach in order to arrive to the solution in gear and clutch design for cyclic noise elimination.
Technical Paper

New Half Shaft Bench Test Methodology for NVH Characterization

2019-06-05
2019-01-1558
The main purpose of this paper is to develop a reliable bench test to understand the vibratory behavior of the half shafts under applied torque comparable to an idle condition. In some cases, the half shaft path is a major factor influencing the idle vibration in the vehicle. At idle condition vehicle vibrations are caused by engine excitation and then they pass through different paths to the body structure. Half shaft manufacturers generally characterize shaft joints for their frictional behavior and typically there is no data for vibration characteristics of the half shaft under idle conditions. However, for predictive risk management, the vibratory behavior of the half shaft needs to be identified. This can be achieved from measured frequency response functions under preloaded test conditions.
Technical Paper

Structural Vibration and Acoustic Analysis of a 3-Phase AC Induction Motor

2019-06-05
2019-01-1458
This paper aims to study the NVH and acoustic performance of a 3-phase AC induction motor in order to develop an approach to reduce the magnetic component of noise from an electric motor in an electric vehicle (EV). The final goal of this project is to reduce the magnetic component of sound from the motor by making modifications to the end bracket of the motor housing. EVs are being considered the future of mobility mainly due to the fact that they are environment-friendly. As many companies are already investing in this technology, electric drives are set to become extremely popular in the years to come. The heart of an EV is its motor. Modern electric vehicles are quiet, furthermore with the lack of an IC engine to mask most sounds from other components, the sound from the electric motor and other auxiliary parts become more prominent.
Technical Paper

Determination of Vehicle Interior Noise due to Electric Motor

2019-06-05
2019-01-1457
This paper introduces an approach that uses a statistical energy analysis (SEA) method for prediction of noise in the vehicle cabin from an electric motor sound source placed in the engine compartment. The study integrates three different physics, namely, electromagnetics, harmonics, and acoustics. A 2004 Prius permanent magnet synchronous motor with an interior permanent magnet was used for performing the integrated CAE analysis, as the motor’s design details were readily available. The Maxwell forces on the stator teeth were first calculated by an electromagnetic software package. These forces were then mapped into a finite element model of the motor stator to predict the velocity profiles on the stator frame. Velocity profiles were considered as boundary conditions to calculate sound pressure levels and the equivalent radiated sound power level in the acoustic environment.
Technical Paper

Improvement of Hypoid Gears Dynamics Performance Based on Tooth Contact Optimization

2019-06-05
2019-01-1563
The meshing noise of hypoid gear has a significant influence on driving axle system. It should be strictly controlled in order to reduce the whole vehicle noise. Meshing internal excitation of hypoid gear is a main source of vibration noise, closely connected with geometrical shape and meshing status. There is no comprehensive analysis on the impact of various contact patterns on vibration noise in previous studies. Therefore, the method for controlling contact characteristics of hypoid gears is studied in this paper, which includes adjusting the position and length of contact pattern, direction of contact trace and the theoretical transmission error. Also, a non-linear dynamic model with multi-freedom for the hypoid gear pair of the driving axle is established to evaluate the dynamic response of the gear pair. Then an example was carried out to improve the dynamic characteristic of hypoid gears by tooth profile modification.
Technical Paper

Gear System Parameters and Its Influence on Gearbox Noise

2019-06-05
2019-01-1562
Tonal noise due to gears is one of the fundamental noise problems in a gearbox. Gear tooth deflections generate dynamic forces that lead to unwanted load fluctuations, thus noise. Different factors that are considered to control this noise, some to mention like proper gear macro design, microgeometry corrections, and housing compliance. However, identifying the appropriate variable as a measure of contribution to the overall response helps in getting more accurate remedial solutions. Some outputs to track are different harmonic components of TE, temperature effects, components of forces, rim compliance and friction. For evaluation, usually, the amplitudes of individual harmonics of transmission error are related to the respective orders of the noise levels assuming it as one of the primary excitation parameters of gear noise.
Technical Paper

Performance Testing and Analysis of Multi-Channel Active Control System for Vehicle Interior Noise Using Adaptive Notch Filter

2019-06-05
2019-01-1567
It is considered that slow convergence speed and large calculation amount of commonly used adaptive algorithm in the active control system for vehicle interior noise yield noise reduction performance and hardware requirements problems. In this paper, a 4-channel active control of vehicle interior noise based on adaptive notch filter is established, and road test is carried out to test and analyze the performance of the control system. Firstly, the general mathematic model of the multi-channel active control system based on adaptive notch filter is established. The computational complexity of the algorithm is analyzed and compared with that of the FXLMS algorithm. Secondly, a hardware-in-the-loop test bench based on multi-channel adaptive notch filter is set up, to measure the noise reduction performance of ANC system under various working conditions.
Technical Paper

Effects of the Feature Extraction from Road Surface Image for Road Induced Noise Prediction Using Artificial Intelligence

2019-06-05
2019-01-1565
Next generation vehicles driven by motor such as electric vehicles and fuel cell vehicles have no engine noise. Therefore the balance of interior noise is different from the vehicles driven by conventional combustion engine. In particular, road induced noise tends to be conspicuous in the low to middle vehicle speed range, therefore, technological development to reduce it is important task. The purpose of this research is to predict the road induced noise from the signals of sensors adopted for automatic driving for utilizing the prediction result as a reference signal to reduce road induced noise by active noise control (ANC). Using the monocular camera which is one of the simplest image sensors, the road induced noise is predicted from the road surface image ahead of the vehicle by machine learning.
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