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08.06 Electric, Hybrid & Alternative Drivetrains

Auralization of electric vehicle’s interior noise SEA simulation
Time: 6:00 am

Author: Eunsoo Jo

Abstract ID: 2250

Statistical Energy Analysis (SEA) has become an essential step to minimize the vehicle interior noise level. The outcome of SEA is typically 1/3 octave spectrum, and consequently it is difficult to understand the subjective effect of interior noise. This study investigated two approaches to achieve the binaural synthesis of SEA results. One is directly from the SEA 1/3 octave result and the measured coherence function. The other makes use of Source Path Contribution (SPC) to estimate the time signals on the exterior panels and subsequently applies the SEA results as a set of Finite Impulse Response (FIR) functions. Both approaches seem to result in realistic binaural signals as well as the correctly scaled sound pressure levels at the receivers. The one using SPC results can generate the input data for an NVH driving simulator by decomposing the harmonics and the masking noises. This means that the SEA result can be experienced by driving the simulated vehicle freely.

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Automated Material Parameter Calibration for an Electric Motor Stator
Time: 7:20 pm

Author: Gil Jun Lee

Abstract ID: 2409

For accurate prediction of E-motor noise and vibration performance at the design stage, it is important to model the E-Motor stator structural behavior with high fidelity. Orthotropic material properties have been widely used in practice to simulate laminated steel in the stator. In these models, material constants are calibrated to match natural frequencies of critical modes such as oval/triangle/square modes. Typically, identifying accurate material properties is a manual, time-consuming process, involving lots of trial and error. This study presents an automated workflow to calibrate the material properties for the stator with Ansys Mechanical and optiSLang. The developed workflow can track natural frequencies and corresponding mode shapes of critical modes, and adjust material constants automatically to find best material parameters for the given frequencies. It can rotate the mode shapes and find the orientation that gives best match to the measurements based on modal assurance criteria (MAC).  This workflow has shown a good correlation between simulation and test in terms of natural frequencies and corresponding mode shapes for the stator of a switched reluctance motor (SRM). Such an automated workflow enables the fast, efficient material calibration process, therefore accurate electric powertrain NVH simulations.

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Effect of junction type on the vibroacoustic response of a system of plates
Time: 6:00:00 AM

Author: Marcell Treszkai

Abstract ID: 2565

Modelling of junctions is one of the most challenging tasks in vibroacoustics, especially for Statistical Energy Analysis (SEA), where the results heavily depend on the damping (DLF) and coupling loss factors (CLF). Also, it is an interesting question to determine that to what extent does the DLF or CLF contribute to the overall vibroacoustic characteristics of a structure? The aim of this paper is to investigate via measurements and SEA simulations the effect of the ratio of DLF and CLF on the response of a system for various junctions, such as riveting, bolting, line and point welding, between two steel plates. Loss matrices are determined experimentally by the Power Injection Method in the 200-1600 Hz frequency range. The simulation was performed in the ESI VA One software by using its analytical CLF formulations and compared to experimental data. For the reference case, a bended plate structure was considered, representing an ideal junction between two subsystems. This was equipped with damping foils to ensure the same weight and then compared to the results from other joints. Results showed that increasing the CLF could be more effective than focusing on increasing the DLF.

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Development of a virtual biomechanical manikin used in vibrations studies in occupied spaces
Time: 7:40 am

Author: Eusebio Conceição

Abstract ID: 2641

In this paper is developed and applied a virtual biomechanical manikin used in occupied spaces. This multi-nodal numerical model is applied in the vibrations of the different sections of the human body, under transient conditions. The integration of second order equations systems, based in Newton equation, after being converted in a first order equation system, is solved through the Runge-Kutta-Fehlberg method with error control. This multi-nodal numerical model will be used, in this work, in the study of the vibrations that a standing person is subjected when stimuli are applied to the feet. The influence of various types of stimuli is analyzed, with periodic irregularities, in the dynamic response of the vibrations in different sections of the human body. The signals of the stimuli, the displacement of some sections of the body and the power spectrum of the same signals will be presented. In the study the influence of the floor vibration in the human body sections is analyzed and presented.

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Measurement and Analysis of Torque Ripple in Inverter Driven Electric Machines
Time: 6:20 pm

Author: Mitchell Marks

Abstract ID: 1373

Torque ripple in electric machines can create both noise and vibration. While torque ripple is often well understood theoretically, it is much more difficult to accurately predict and measure. Often torque ripple is measured as a function of magnets and slot interaction at extremely low speed, but this can only be extrapolated to understand its implications for noise and vibration and is not useful for understanding torque response during dynamic scenarios like a change in load. The slow speed method of measurement also neglects possible switching effects on the torque profile. This paper will explore challenges in measuring the different sources of torque ripple and give an alternative method to measure torque ripple at higher speeds and also dynamically. This will include best practices and examples.

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Eccentricity Effects on NVH Performance of Interior Permanent Magnets Machines for Hybrid and Electric Vehicles
Time: 6:40 pm

Author: Peng Zhang

Abstract ID: 2124

For the hybrid electric vehicles (HEVs) and electric vehicles (EVs) applications, the electric machine drive unit system provides the main noise source, especially in the presence of faults. Eccentricity is one of the most common faults, which is mainly caused by the motors’ package design and assembling process. There are four main types of eccentricity for motors: static offset, dynamic offset, static tilt and dynamic tilt, which are presented and analyzed. Both two-dimensional (2D) and 3-dimentional (3D) finite element analysis (FEA) are utilized in the electromagnetic field analysis for an Interior Permanent Magnet (IPM) motor. The corresponding methodologies for the mesh and force mapping to the mechanical FEA for the NVH analysis are presented. The NVH test shows that both 2D and 3D FEA can provide reasonable accuracy for the motor eccentricity fault analysis. The 2D FEA is the most common method used in the design optimization and early performance prediction for electrical. For the 3D FEA, due to the high requirement for the computer hardware and computation capability, it is usually used in the final validation for electrical machines’ performance. The sensitivity of motor performance versus the airgap heights and eccentricities are studied.

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Application of Blocked Force Methodology in NVH development of Electrical Machines
Time: 7:00 pm

Author: Keyu Chen

Abstract ID: 2399

To determine excitation forces of electrical machines from measurements, Transfer Path Analysis is commonly used. Transfer Path Analysis yields input forces indirectly utilizing measured responses and transfer functions. When conducting transfer function measurement, it is recommended that the source of excitation is mechanically isolated from the receiver structure. However, in practice this is difficult to achieve without affecting the transfer path itself. The concept of the Blocked Force method introduces blocked forces which are independent of the receiver structure, thus allowing measurement of transfer functions without isolating the source. In this research, a stator / rotor assembly is considered as the source.  This assembly is bolted to a test-housing, considered as the receiver. Blocked forces are determined at the mounting locations between stator and test-canister. The correctness of the calculated blocked forces is verified by comparing the predicted and measured responses at selected target points which were not used for determining the blocked forces.

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Measurement and Assessment on Environmental Noise Impact of Electric Vehicles in Accelerating Condition
Time: 8:00 pm

Author: Katsuya Yamauchi

Abstract ID: 2631

Noise emission from the vehicles propelled by electric system (such as pure electric and hybrid electric vehicles, EVs) is usually lower than the conventional internal combustion engine vehicles. Some previous studies have been shown the difference in A-weighted sound power level of EVs from the conventional ones.  The difference is not dramatically large, i.e. less than 4 dB when the cars running at constant speed of 20 km/h. In this paper, we present the additional measurement results of sound power level of EVs in accelerating condition. Because when the cars in accelerating condition, the difference of propulsion systems becomes more significant on noise emission. The results are shown as regression model of sound power level depending on the vehicle speed. Moreover, the environmental noise impact of growing population of EVs is assessed through a prediction of at a case of intersection.

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An influence of characteristics of amplitude fluctuation on detectability of alert sound of electric powered vehicles
Time: 8:20 pm

Author: Nozomiko Yasui

Abstract ID: 2779

The motor sound on electric powered vehicle is quiet at low speeds. Thus, pedestrians have difficulty detecting the vehicles approaching them under urban noise. Although the vehicles were designed to play an alert sound to solve this problem, it has not been solved yet. Our previous studies found that characteristics of amplitude fluctuation, fluctuation frequency, non-periodic fluctuation and amplitude envelope, are effective to make them detect approaching vehicles. However, those studies were investigated under only a specific actual environment, weren’t examined validity of detectability in those studies. Here, this paper investigates under another actual environment, examine the validity. Investigations were carried out by using synthesized complex sounds which were designed to have periodic and non-periodic amplitude fluctuations. Those complex sounds have characteristics of amplitude fluctuations in gasoline powered vehicle. Amplitude envelopes such as modulation wave in amplitude-modulated sound were set for deviations for time and amplitude, and amplitude-modulated complex sounds were synthesized using sine wave, sawtooth wave, and rectangle wave. Then, their effects on detectability by pedestrians were assessed in another actual environment. The results found that amplitude fluctuation enhances the ability with which people detect approaching electric powered vehicles in case of some complex sound.

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Design and performance exploration of a cymbal piezoelectric energy harvester under the excitation of power transformer vibration
Time: 8:40 pm

Author: Xishan Jiang

Abstract ID: 3148

With the rapid application of internet of things technology and wireless sensor in transformer station, the demand for stable and reliable power source becoming increasingly stronger. Power transformer operates with high energy density vibration, which provides a suitable energy source for health monitoring sensors. A cymbal piezoelectric transducer is designed to harvest the energy of vibration?which is made of cymbal end cap and piezoelectric ceramic to convert mechanical energy to electricity. Also, the power circuit is designed to realize the transmission and storage of electric energy. Then, the performance of the cymbal piezoelectric energy harvester is explored by FEM and experiment. The influence of mechanical vibration characteristics on the charging power of piezoelectric transducer is studied, including amplitude, frequency and preload. The experimental results show that the cymbal piezoelectric energy harvester can provides stable and reliable power, which allows the possibility of large-scale application of wireless sensor in transformer station. The present work provides a new design concept for developing the novel cymbal harvesters used in large-sized vibratory equipment, such as power transformer, to harvest vibration energy.

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