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Role of Dynamic Stiffness in Effective Isolation

Deere & Company-Yuzhen Yang
John Deere India Pvt, Ltd.-Balavardhan Reddy Dasabai
  • Technical Paper
  • 2019-01-1495
To be published on 2019-06-05 by SAE International in United States
In any machinery, avoiding noise and vibration completely is a difficult task due to the structural dynamic behaviors of components. To safeguard the operator, it is important to best isolate the operator station from NVH environment. Cabin isolation is an important aspect to minimize structure-borne noise and tactile vibrations to be transferred into the cabin. Isolators are selected based on the isolation system inertial properties at mounting locations in the operating frequency range interested. The most important assumption to select isolators is that the active side and passive side of the isolators are nearly rigid so impedance mismatch is created for effective isolation. This paper describes the importance of dynamic stiffness of the structures on both the active and passive side for better NVH performance. NVH performance of passive side is evaluated analytically and computationally in terms of tactile vibrations and structure-borne noise for various ratios of the dynamic stiffness over isolator stiffness. The isolator selection criterion is also discussed based on rigid body modes, operating frequency range, transmissibility ratio, and kinematic energy distributions.

Developing a Custom Data Acquisition Software Package for a Self-contained Acoustic Testing Facility

Kolano and Saha Engineers Inc-Sagar Patil, Pranab Saha
Kolano and Saha Engineers Inc.-Richard Kolano
  • Technical Paper
  • 2019-01-1501
To be published on 2019-06-05 by SAE International in United States
This paper provides an overview of custom software developed for the sound generation, control and data acquisition of a self-contained acoustic testing facility system used for conducting random incidence sound absorption tests and sound transmission loss tests on small samples in accordance with SAE J2883 and J1400 standards, respectively. The paper discusses the thoughts behind developing user friendly algorithms and graphical user interfaces (GUI) for sound generation, control, data acquisition, and signal processing to obtain good data and precautions should there be any anomalies in the data.

Sound Analysis Method for Warble Noise in Electric Actuators

General Motors-Nathan T. Parker
  • Technical Paper
  • 2019-01-1521
To be published on 2019-06-05 by SAE International in United States
Multiple automotive applications exist for small electric motors that are activated by vehicle occupants for various functions such as window lifts and seat adjusters. For such a motor to be described as high quality, not only should the sound it produces be low in amplitude, but it also needs to be free from pulsations and variations that might occur during its (otherwise) steady-state operation. If a motor’s sound contains pulsations or variations between 2 and 8 cycles per second, the variation is described as warble. Warble noise needs to be measured and quantified in parts and vehicles, such that appropriate limits can be established whereby quality noise performance is conveyed in vehicles. Building on existing Sound Quality metrics such as Loudness and Pitch Variation, a method is established by which processed sound data is further processed via Fourier Analysis as a secondary operation. Thus warble can be reduced to a single value, and in this way, noise engineers have a basis to measure and report warble, and to facilitate product development with A/B comparisons. Depending…

Assessment of Automotive Environmental Noise on Mobile Phone Hands Free Call Quality

FEV North America, Inc.-Jeffrey Pruetz, Channing Watson, Todd Tousignant, Kiran Govindswamy
  • Technical Paper
  • 2019-01-1597
To be published on 2019-06-05 by SAE International in United States
Environmental noises such as wind, road, powertrain, and HVAC are important aspects to consider when implementing a hands-free terminal for mobile phone calling. Traditionally these environmental noises have been exclusively considered for driver comfort, however, with the introduction of the hands-free terminals (HFT) and increasing consumer demand relative to mobile phone call quality, a broader implication of high background noise levels should be considered. HFT algorithm development and implementation can and does provide a high level of background noise suppression to mitigate these concerns, however, this is often done at the expense of computational power and cumulative delay during a phone call. A more advantageous solution would be to address the problem from a source and path perspective, however, this in itself is a challenging task and one that vehicle manufactures have and will continue to pursue as part of conventional vehicle development activities. The assessments shown throughout this paper establishes a sensitivity of HFT call quality to background noise levels, based on industry-standard metrics, including those defined by International Telecommunication Union (ITU) standards. This…

Fault Feature Extraction of Elliptically Shaped Bearing Raceway

South China University of Technology-Yingying Guo, Xuezhi Zhao
  • Technical Paper
  • 2019-01-1564
To be published on 2019-06-05 by SAE International in United States
The elliptically shaped bearing (ESB) with a rigid, elliptical inner race and a flexible, thin-walled outer race is the most easily damaged core component of harmonic drive. The ESB rotates under cycle load of alternating stress due to its special elliptic structure. Hence, the impact noise produced by alternating between long axis and short axis is apt to conceal the fault features of ESB such as fatigue spalling and pitting. In order to diagnose the fault on raceway surface of ESB, a new method of CMWT-FH based on Continuous Morlet Wavelet Transform (CMWT) and FFT-based Hilbert (FH) spectrum analysis is proposed to extract the fault feature. First, the formulas of fault feature frequency is deduced based on the geometry and kinematic characteristic of ESB; then the CMWT method is employed to decompose the fault signal of ESB; finally, the FH spectrum analysis is performed to extract the fault feature frequency of ESB from the decomposition signal with the largest kurtosis value in the first several layers. Compared with the conventional FH method, the proposed CMWT-FH…

A Case Study on Golf Car Powertrain NVH Sources and Mitigation Methods

Club Car, LLC-Adam Clark
Roush Industries Inc-Steven Carter, Kenneth Buczek, Mayuresh Pathak
  • Technical Paper
  • 2019-01-1478
To be published on 2019-06-05 by SAE International in United States
Throughout North America the golf market has remained nominally flat in recent history and has grown worldwide. With this growth a trend has been seen where the number of young adults as well as adults over the age of 65 years involved with the game has increased. The demographics in golf showing the most growth also have high standards for the operation of the golf car and have transcended their expectations to align with some of the qualities expected of automobiles. These shifts in consumer expectations along with market competition drive OEMs to deliver refined golf cars making noise and vibration a key aspect in development. This paper showcases a recent study to improve the powertrain N&V performance of an I.C. engine golf car. Primarily, a test-based approach was followed. Chassis rolls and on road testing were performed for vehicle benchmarking and target setting. System and component tests were completed to identify root cause and provide input to mitigation methods applied. Structural modifications were applied to reduce structure-borne noise and perceived vibration. Component modifications and…

Target Setting Process for Hybrid Electric Drives Using TPA, Jury Studies, and Torque Management

FCA US LLC-Vinod Singh, Anil Charan
  • Technical Paper
  • 2019-01-1453
To be published on 2019-06-05 by SAE International in United States
The idea of improved efficiency without compromising the “fun to drive” aspect has renewed the auto industry’s interest toward electrification and hybridization. Electric drives benefit from having multiple gear ratios which can use advantageous operating set points thus increasing range. Hybrid vehicles benefit significantly from frequent decelerations and stopping as is experienced in city driving conditions. To recuperate as much energy as possible, deceleration is done at high torque. This presents an interesting but serious sound quality issue in the form of highly tonal whine harmonics of rapidly changing gears that do not track with vehicle speed thus being objectionable to the vehicle occupants. This paper presents an NVH target setting process for a hybrid electric transmission being integrated into two existing vehicles, one belonging to the premium segment and another aimed at enthusiasts with off-road applications. The demand for power has shifted from mechanical domain into electrical domain, and as such, the solution to electric drive NVH issues also lies partly, in the way these drive systems are calibrated. A time-domain Transfer Path Analysis…

Fast accurate non-destructive measurement of absorber impedance and absorption

3M-Jon Alexander
Bruel & Kjaer S&V Measurement A/S-Jason Kunio, Flemming Larsen
  • Technical Paper
  • 2019-01-1584
To be published on 2019-06-05 by SAE International in United States
Cabin acoustic comfort is a major contributor to the potential sales success of new aircraft, cars, trucks, and trains. Recent design challenges have included the increased use of composites, and the switch to electrically powered vehicles, each of which change the interior noise spectral content and level. The role of acoustic absorption in cabins is key to the optimisation of cabin acoustic comfort for modern vehicles, with acoustic impedance data needed in order to assess and optimise the impact of each component of a given lay-up. Measurements of absorbing interior trim are traditionally performed using either sample holder tests in a static impedance tube (impedance and absorption), or through tests in reverberation rooms (absorption only). Both of these procedures present challenges. In-tube absorption and impedance measurements are destructive, requiring highly accurate sample cutting and sealing. Reverberation room absorption measurements are subject to the effects of varying room diffusion, along with the impact of edge diffraction, sample geometry, and location. Finally, while non-destructive methods using hand-held probes also measure absorption, they are not able to measure…

Improved measurement procedures for engine noise reduction with advanced microphones

GRAS Sound & Vibration-Jan Hansen, Per Rasmussen
  • Technical Paper
  • 2019-01-1463
To be published on 2019-06-05 by SAE International in United States
Introducing a new transducer concept has resulted in considerable reduction in setup time and at the same time improved accuracy and repeatability for engine bay noise transfer studies. The acoustic environment inside cars are one of the primary comfort parameters. This is made up of a number of contributions from drivetrain, auxiliary equipment, wind noise and tire noise, and all are influenced by the transfer from the source to the receiver. With the change from purely internal combustion engines to electrical or electrical assisted propulsion systems, a new set of noise sources are introduced in the engine compartment and this requires renewed focus on the transmission paths to the receivers inside the car cabin. Typically, one of the tools to study these mechanisms is by using a reverse transmission technique, placing a well-defined sound source in the receiver position inside the car and measure the resulting sound pressure levels in the engine compartment. Assuming reciprocity, these measurements can be used to estimate the attenuation of transmission from sound sources in the engine compartment to the…

Understanding the Stick Slip behaviour of plastics and target setting: An OEM Perspective

Mahindra & Mahindra Ltd-Sundaralingam Somasundharam, Amit Kumar, Riyazuddin Mohammed, Prasath Raghavendran
  • Technical Paper
  • 2019-01-1465
To be published on 2019-06-05 by SAE International in United States
Automotive OEMs are aggressively using different materials in their interior. This trend has increased in recent years due to value proposition and variety of options available for customers in market. Visual harmony, touch haptics, craftmanship and comfort are the driving factors to create different designs and options for customization. New trends like self-driving car and electrification increases the importance of comfort. Excessive usage of different grade plastics with zero gap philosophy can cause to stick slip effect leading to audible discomfort called squeak. Even though systems and subsystems are designed in best approach of structural design and manufacturing tolerances they are vulnerable to extreme environmental conditions and incompatible mating materials can initiate contacts leading to Squeak noise. One way to minimize the possibilities of squeak is by appropriate selection of mating material pairs. In present study, an understanding of stick slip behavior of different plastics is discussed, along with parameters required to focus during material incompatibility testing using a tribology test stand. Friction coefficient of different material pairs are analyzed for observing behavior patterns of…