scholarly journals Two-Mode Operation Engine Mount Design for Automotive Applications

2012 ◽  
Vol 19 (6) ◽  
pp. 1267-1280 ◽  
Author(s):  
Reza Tikani ◽  
Nader Vahdati ◽  
Saeed Ziaei-Rad
Keyword(s):  
Control Strategy ◽  
High Frequency ◽  
Frequency Noise ◽  
Automotive Applications ◽  
Low Frequencies ◽  
Engine Mounts ◽  
Mode Operation ◽  
Damping Characteristics ◽  
Engine Mount ◽  
Driving Condition

Hydraulic engine mounts are applied to the automotive applications to isolate the chassis from the high frequency noise and vibration generated by the engine as well as to limit the engine shake motions resulting at low frequencies. In this paper, a new hydraulic engine mount with a controllable inertia track profile is proposed and its dynamic behavior is investigated. The profile of the inertia track is varied by applying a controlled force to a cylindrical rubber disk, placed in the inertia track. This design provides a hydraulic engine mount design with an adjustable notch frequency location and also damping characteristics in shake motions. By using a simple control strategy, the efficiency of the proposed hydraulic engine mount in two-mode operation meaning isolating mode in the highway driving condition and damping mode in the shock motions, is investigated.

scholarly journals The dual-slope conversion improvement

2014 ◽  
Vol 11 (3) ◽  
pp. 351-363
Author(s):  
Radojle Radetic ◽  
Marijana Pavlov-Kagadejev ◽  
Nikola Milivojevic
Keyword(s):  
High Frequency ◽  
Frequency Noise ◽  
Good Resolution ◽  
Practical Realization ◽  
Digital Conversion ◽  
Low Frequencies ◽  
Analog To Digital ◽  
High Frequency Noise ◽  
Low Input ◽  
Analog To Digital Conversion

The dual-slope ADC (DSADC) is a type of analog-to-digital conversion with low input bandwidths. It is pretty slow, but its ability to reject high-frequency noise and fixed low frequencies such as 50 Hz or 60 Hz makes it useful in noisy industrial environments and applications. It provides very good resolution. For the practical measurements in the Institutes laboratory an instrument is designed and realized. The base DSADC method is used, but improved by multiple conversions to make the measuring more precise and the time shorter. The special attention is paid to the problems occurred in practical realization and the way to overcome them. The paper describes the proposed and applied solutions, functional principles and achieved performances of the realized instrument.

scholarly journals On the universal trends in the noise reduction due to wavy leading edges in aerofoil–vortex interaction

2019 ◽  
Vol 871 ◽  
pp. 186-211 ◽  
Author(s):  
Jacob M. Turner ◽  
Jae Wook Kim
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Broadband Noise ◽  
Current Work ◽  
Source Distribution ◽  
Source Analysis ◽  
Frequency Noise ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Leading Edges

Existing studies suggest that wavy leading edges (WLEs) offer substantial reduction of broadband noise generated by an aerofoil undergoing upstream vortical disturbances. In this context, there are two universal trends in the frequency spectra of the noise reduction which have been observed and reported to date: (i) no significant reduction at low frequencies followed by (ii) a rapid growth of the noise reduction that persists in the medium-to-high frequency range. These trends are known to be insensitive to the aerofoil type and flow condition used. This paper aims to provide comprehensive understandings as to how these universal trends are formed and what the major drivers are. The current work is based on very-high-resolution numerical simulations of a semi-infinite flat-plate aerofoil impinged by a prescribed divergence-free vortex in an inviscid base flow at zero incidence angle, continued from recent work by the authors (Turner & Kim, J. Fluid Mech., vol. 811, 2017, pp. 582–611). One of the most significant findings in the current work is that the noise source distribution on the aerofoil surface becomes entirely two-dimensional (highly non-uniform in the spanwise direction as well as streamwise) at high frequencies when the WLE is involved. Also, the sources downstream of the LE make crucial contributions to creating the universal trends across all frequencies. These findings contradict the conventional LE-focused one-dimensional source analysis that has widely been accepted for all frequencies. The current study suggests that the universal trends in the noise-reduction spectra can be properly understood by taking the downstream source contributions into account, in terms of both magnitude and phase variations. After including the downstream sources, it is shown in this paper that the first universal trend is due to the conservation of total (surface integrated) source energy at low frequencies. The surface-integrated source magnitude that decreases faster with the WLE correlates very well with the noise-reduction spectrum at medium frequencies. In the meantime, the high-frequency noise reduction is driven almost entirely by destructive phase interference that increases rapidly and consistently with frequency, explaining the second universal trend.

scholarly journals VSG Control Strategy Incorporating Voltage Inertia and Virtual Impedance for Microgrids

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4263
Author(s):  
Zipeng Ke ◽  
Yuxing Dai ◽  
Zishun Peng ◽  
Guoqiang Zeng ◽  
Jun Wang ◽  
...  
Keyword(s):  
Control Strategy ◽  
High Frequency ◽  
Synchronous Generator ◽  
Frequency Noise ◽  
Control Effect ◽  
High Frequency Noise ◽  
Distributed Generator ◽  
Voltage Change ◽  
Power Fluctuations ◽  
Virtual Impedance

Virtual synchronous generator (VSG) control lacks voltage inertia and powerful decoupling capabilities. The voltage of the distributed generator (DG) unit controlled by the VSG will be easily affected by power fluctuations and high-frequency noise, and the DG coupling usually makes the VSG control effect unsatisfactory. In order to effectively reduce power fluctuations, the influence of high-frequency noise on voltage, the influence of coupling on the power regulation, and effectively improve the economy of the economic system, the improved VSG control that combines voltage inertia and virtual impedance is proposed in this paper. The second-order inertia in the proposed VSG control strategy can minimize the voltage change rate and filter high-frequency noise from the excitation and virtual impedance. The virtual impedance in the proposed VSG control strategy can simulate the actual impedance to change the line characteristics, so the coupling of the DG unit can be reduced. Experimental results based on the microgrid platform prove the feasibility of improving the VSG control.

scholarly journals Optimal fluid passageway design methodology for hydraulic engine mounts considering both low and high frequency performances

2019 ◽  
Vol 25 (21-22) ◽  
pp. 2749-2757
Author(s):  
Yuan Li ◽  
Jason Zheng Jiang ◽  
Simon A Neild
Keyword(s):  
High Frequency ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Relative Displacement ◽  
Wide Frequency Range ◽  
Performance Criteria ◽  
Frequency Model ◽  
Engine Mounts ◽  
Engine Mount ◽  
And Performance

This paper investigates the potential for improving the performance of hydraulic engine mounts through fluid passageway designs. In previous studies, a few simple inertia track designs have been investigated with moderate improvements obtained. However, there are countless alternative design possibilities existing; while analyzing each one of them in turn is impracticable. To this end, this paper introduces a systematic methodology to optimize fluid passageway designs in a hydraulic engine mount. First, beneficial fluid passageway configurations are systematically identified using a linearized low-frequency model that captures the relative displacement transmissibility. A nonlinear model is then used to fine-tune the fluid passageway designs for the low-frequency transmissibility improvement, and also for the assessment of high-frequency dynamic stiffness performance. The obtained beneficial designs present performance advantages over a wide frequency range. The design approach introduced in this study is directly applicable to other engine mount models and performance criteria.

Case study: Simulation and control of high frequency noise for commercial vehicle cab considering leak

2019 ◽  
Vol 67 (4) ◽  
pp. 315-329
Author(s):  
Rongjiang Tang ◽  
Zhe Tong ◽  
Weiguang Zheng ◽  
Shenfang Li ◽  
Li Huang
Keyword(s):  
High Frequency ◽  
Commercial Vehicle ◽  
Frequency Noise ◽  
High Frequency Noise ◽  
Simulation And Control ◽  
And Control

Aerodynamic noise from an asymmetric airfoil with perforated extension plates at the trailing edge

2020 ◽  
pp. 1475472X2097838
Author(s):  
CK Sumesh ◽  
TJS Jothi
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Pore Diameter ◽  
Low Frequency ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Trailing Edge ◽  
High Frequency Noise ◽  
Displacement Thickness

This paper investigates the noise emissions from NACA 6412 asymmetric airfoil with different perforated extension plates at the trailing edge. The length of the extension plate is 10 mm, and the pore diameters ( D) considered for the study are in the range of 0.689 to 1.665 mm. The experiments are carried out in the flow velocity ( U∞) range of 20 to 45 m/s, and geometric angles of attack ( αg) values of −10° to +10°. Perforated extensions have an overwhelming response in reducing the low frequency noise (<1.5 kHz), and a reduction of up to 6 dB is observed with an increase in the pore diameter. Contrastingly, the higher frequency noise (>4 kHz) is observed to increase with an increase in the pore diameter. The dominant reduction in the low frequency noise for perforated model airfoils is within the Strouhal number (based on the displacement thickness) of 0.11. The overall sound pressure levels of perforated model airfoils are observed to reduce by a maximum of 2 dB compared to the base airfoil. Finally, by varying the geometric angle of attack from −10° to +10°, the lower frequency noise is seen to increase, while the high frequency noise is observed to decrease.

scholarly journals Earless toads sense low frequencies but miss the high notes

2017 ◽  
Vol 284 (1864) ◽  
pp. 20171670 ◽  
Author(s):  
Molly C. Womack ◽  
Jakob Christensen-Dalsgaard ◽  
Luis A. Coloma ◽  
Juan C. Chaparro ◽  
Kim L. Hoke
Keyword(s):  
High Frequency ◽  
Species Differences ◽  
Low Frequency ◽  
Auditory Brainstem ◽  
Low Frequencies ◽  
Hearing Sensitivity ◽  
Sensory Pathways ◽  
Airborne Sound ◽  
Vibrational Sensitivity ◽  
Species Specific

Sensory losses or reductions are frequently attributed to relaxed selection. However, anuran species have lost tympanic middle ears many times, despite anurans' use of acoustic communication and the benefit of middle ears for hearing airborne sound. Here we determine whether pre-existing alternative sensory pathways enable anurans lacking tympanic middle ears (termed earless anurans) to hear airborne sound as well as eared species or to better sense vibrations in the environment. We used auditory brainstem recordings to compare hearing and vibrational sensitivity among 10 species (six eared, four earless) within the Neotropical true toad family (Bufonidae). We found that species lacking middle ears are less sensitive to high-frequency sounds, however, low-frequency hearing and vibrational sensitivity are equivalent between eared and earless species. Furthermore, extratympanic hearing sensitivity varies among earless species, highlighting potential species differences in extratympanic hearing mechanisms. We argue that ancestral bufonids may have sufficient extratympanic hearing and vibrational sensitivity such that earless lineages tolerated the loss of high frequency hearing sensitivity by adopting species-specific behavioural strategies to detect conspecifics, predators and prey.

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