Search Results

This work presents an application of airborne source path contribution analysis with emphasis on prediction of wideband sounds inside a cabin from measurements made around a stand-alone engine. The heart of the method is a time domain source path receiver technique wherein the engine surface is modeled as a number of source points. Nearfield microphone measurements and transfer functions are used to quantify the source strengths at these points. This acoustic engine model is then used in combination with source-to-receiver transfer functions to calculate sound levels at other positions, such as at the driver's ear position. When combining all the data, the in-cabin engine sound can be synthesized even before the engine is physically installed into the vehicle. The method has been validated using a powertrain structure artificially excited by several shakers playing band-limited noise so as to produce a complicated vibration pattern on the surface.

Active noise control (ANC) technique with the filtered-x least mean square (FXLMS) algorithm has proven its efficiency and drawn increasingly interests in vehicle noise control applications. However, many vehicle interior and/or exterior noises are exhibiting non-Gaussian type with impulsive characteristic, such as diesel knocking noise, injector ticking, impulsive crank-train noise, gear rattle, and road bumps, etc. Therefore, the conventional FXLMS algorithm that is based on the assumption of deterministic and/or Gaussian signal may not be appropriate for tackling this type of impulsive noise. In this paper, an ANC system configured with modified FXLMS (MFXLMS) algorithm by adding thresholds on reference and error signal paths is proposed for impulsive noise control. To demonstrate the effectiveness of the proposed algorithm, an experimental study is conducted in the laboratory.

The complexity of drivetrain system design lies in the need for diligent consideration of individual component specifications, their effect on various performance aspects of the overall system, as well as any performance trade-offs that may further add to the complexity of system design. This paper describes a design methodology developed by capturing best practices for conducting design architecture analysis in full account of key design components critical to ensuring efficient and effective development of drivetrain systems. This methodology is derived from the architecture analysis based on core competencies and architecture strategy, the veteran's way of practical selection of design items and determining the sequence of the study process.

Recently, high energy density battery attracts public attention with the application to power source of electric vehicle and electric energy storage system in solar and wind generation. Magnesium electrode has large theoretical capacity as much as 3839 mAh cm-1. Besides, magnesium compounds are abundant in the earth's crust and most of them are nontoxic. Therefore, rechargeable magnesium battery, whose negative electrode reaction is magnesium deposition / dissolution, is one of the most expected candidates. However, rechargeable magnesium deposition and dissolution is not achieved in most electrolytes. Magnesium has extensively high reactivity, leading the formation of surface films in the electrolytes. These films cannot conduct magnesium ion and inhibit magnesium deposition and dissolution reactions. So far, reversible magnesium deposition and dissolution can be achieved only in RMgX (R = alkyl or aryl, X = halogen), Mg(BR4)2 or Mg(AlCl2RR')2 / ether solutions [1,2,3].

The electrochemical intercalation of lithium-ion into natural graphite cannot take place in propylene carbonate (PC)-based electrolytes. Continuous decomposition of PC, accompanied by the exfoliation of graphite, is observed instead of the intercalation of lithium-ion. One of the plausible hypotheses to explain this behavior is that PC-solvated lithium-ion intercalates into graphite during the first charge, resulting in the exfoliation of graphite. Therefore, we consider that the solvation structure of lithium-ion in PC-based electrolytes should strongly influence the charge-discharge behavior of natural graphite. We studied the charge-discharge properties of natural graphite in binary electrolytes consisting of PC and dimethyl carbonate (DMC) with various mixing ratios. The average solvation numbers of PC molecules per lithium-ion (NPC,ave) in PC:DMC binary electrolytes were evaluated with Raman spectroscopy.

An enhanced, frequency domain filtered-x least mean square (LMS) algorithm is proposed as the basis for an active control system for treating powertrain noise. There are primarily three advantages of this approach: (i) saving of computing time especially for long controller’s filter length; (ii) more accurate estimation of the gradient due to the sample averaging of the whole data block; and (iii) capacity for rapid convergence when the adaptation parameter is correctly adjusted for each frequency bin. Unlike traditional active noise control techniques for suppressing response, the proposed frequency domain FXLMS algorithm is targeted at tuning vehicle interior response in order to achieve a desirable sound quality. The proposed control algorithm is studied numerically by applying the analysis to treat vehicle interior noise represented by either measured or predicted cavity acoustic transfer functions.

The authors conducted sled tests using the MAMA-2B pregnant dummy to analyze the mechanisms of injuries to pregnant drivers during frontal collisions. The seating position of the dummy was determined from the means of anthropometric values obtained from pregnant Japanese women. Deceleration waveforms with a delta-V of 13, 26 and 40 km/h were applied to the sled and tests were run with and without a seatbelt. Without a seatbelt, at a delta-V of 13 km/h, abdominal pressure peaked at the point where the dummy contacted the steering wheel. However, tests without a seatbelt and with a higher delta-V, the dummy slipped down the seat, consequently its torso slid below the airbag without a significant peak of abdominal pressure. This finding indicated that fetal outcome should be predicted based on more than just internal pressure of pregnant drivers, taking the overall status of the mother’s health into account.

A laboratory experiment is designed to examine the clunk phenomenon. A static torque is applied to a driveline system via the mass of an overhanging torsion bar and electromagnet. Then an applied load may be varied via attached mass and released to simulate the step down (tip-out) response of the system. Shaft torques and torsional and translational accelerations are recorded at pre-defined locations. The static torque closes up the driveline clearances in the pinion/ring (crown wheel) mesh. With release of the applied load the driveline undergoes transient vibration. Further, the ratio of preload to static load is adjusted to lead to either no-impact or impact events. Test A provides a ‘linear’ result where the contact stiffness does not pass into clearance. This test is used for confirming transient response and studying friction and damping. Test B is for mass release with sufficient applied torque to pass into clearance, allowing the study of the clunk.

Generally within engineering design, the current emphasis is on biasing the development process towards increased virtual prototyping and reduced “real” prototyping. Therefore there is a requirement for more CAE based automated optimisation, Design of Experiments and Design for Six Sigma. The main requirements for these processes are that the model being analysed is parametric and that the solution time is short. Prediction of gear whine behaviour in automatic transmissions is a particularly complex problem where the conventional FEA approach precludes the rapid assessment of “what if?” scenarios due to the slow model building and solution times. This paper will present an alternative approach, which is a fully parametric functionality-based model, including the effects of and interactions between all components in the transmission. In particular the time-varying load sharing and misalignment in the planetary gears will be analysed in detail.

A series of laboratory driveline clunk experiment was conducted by using an overhung torsion bar and electromagnet to create a sudden change in torque loading in the driveline system. The change of the torque loading was designed to force the driveline to go through the gear lashes inside the rear axle and result in clunk phenomenon. The study was investigated by using a simulation code developed in Matlab and ADAMS CAE. The analytical study enabled parametric investigation of component contribution to various time responses exhibited in the experiment. The results also revealed intricate interaction between the friction properties and the driveline torsional dynamics which were observed in the experiment.

In order to effectively evaluate automatic transmission gear noise and vibration performance using a hemi-anechoic test facility, it is essential to understand the coupling mechanism between the transmission internals and the dynamometers and associated shafting. Once this coupling mechanism is well understood, each major frequency response of the resulting torsional vibration operating data can be properly categorized according to the source: transmission-internal, facility, or driveshaft. This knowledge helps noise and vibration engineers properly manage vibration peaks in transmission operating data by ensuring that the issue of concern is not inadvertently influenced by the facility system. Analytical simulations and tests were performed on a transmission operated in a hemi-anechoic facility to evaluate gear vibration using various driveshafts, followed by a program of vehicle testing.

An application involving noise source reconstruction on a full automotive powerplant including the engine, manifolds and the transmission is considered herein, to demonstrate the versatility of modern generalized acoustical holography. The complex source geometry necessitates measurements on non-conforming surfaces. The acoustic pressures were experimentally acquired at three different engine excitations. Accelerometers were mounted at select locations on the powerplant in order to study the accuracy of the reconstructed vibrations from acoustical holography. Through a series of synthetically generated holograms with added random noise, it is conclusively demonstrated that the error margins in the reconstructed vibrations on the powerplant are consistent with errors in reconstructed vibrations from numerically synthesized holograms of a similar Signal to Noise Ratio (SNR).

The Ford Spin Torsional NVH TEST Facility developed and completed in 1999 as a state-of-the-art powertrain NVH development facility(1). Since then, various designed capabilities have been verified with test vehicles for multiple applications to facilitate powertrain NVH development. This paper describes fundamental capabilities of the test facility, including input module to simulate engine torque signatures of arbitrary engines (“virtual engine” capability) and absorbing dynamometer systems, functioning as a precision 4WD/AWD chassis dynamometer. The correlation between road test/chassis dynamometer test and Spin-Torsional test is then illustrated, verifying high correlation of vehicle/sub-system responses between conventional vehicle testing and Spin-Torsional test results.

Generation mechanism of transmission gear whine varies significantly by gear position, frequency and path/amplifier of the total system. Although controlling the source, namely transmission error/dynamic meshing force of the gears is desirable; it is not always feasible as well as most effective. This paper describes the root cause analyses of high frequency gear whine (overdrive position) of commercial vehicle, which combined in-depth experimental and CAE analyses. The generation mechanism of the gear whine is clarified efficiently utilizing Ford Spin-Torsional AWD NVH Test Facility, state-of-the-art Powertrain NVH development test cell, combining vehicle and sub-system NVH measurement. The analyses results showed the O/D gear whine is driveshaft airborne, due to alignment of driveshaft higher bending resonance to air-borne mode (“breathing mode”).

Effectively managing transmission noise, vibration and harshness (NVH) has become increasingly important for maximizing customer satisfaction and fostering the perception of quality in contemporary cars and trucks. As overall vehicle and engine masking levels have dramatically decreased in recent times, low level tonal noises generated by transmission internals have gained significance and therefore have a greater effect on the NVH performance of vehicles. Recognizing the importance of this trend, Ford Motor Company recently designed and built a state-of-the-art research and development facility to be used for reducing noise and vibration generated by automatic and manual vehicle transmissions. The significant design features and validation results of this facility are described in this paper.

An All Wheel Drive Spin-Torsional Dynamometer facility has been constructed at the Advanced Engineering Center of Ford Motor Company, adding unique capability for powertrain NVH testing. This state-of-the-art facility is designed to concurrently deliver controlled rotational and torsional engine inputs to the drivetrain. While the facility supports the use of a live engine for input, it is also equipped with an engine simulator to allow detailed examination of the NVH characteristics of new powertrain configurations before prototype powerplants are available, without the need for a live engine. This will reduce development timing for new powertrains significantly. The virtual engine consists of a driving dynamometer coupled with a high frequency servo-hydraulic torsional actuator.

Engine noise is still one of the dominating sources to vehicle interior noise. Among the engine components, engine covers are often the significant contributors to overall engine noise, requiring in-depth acoustic investigation to achieve substantial reduction. Ford Motor Company has acquired a 150 channel Nearfield Acoustic Holography (NAH) system for powertrain NVH development. This system provides new acoustic information with various metrics and visualization of non-stationary sound field in time domain to facilitate better understanding of noise generation/propagation mechanism. This paper focus on investigating the design of engine covers which radiate chain whine, fully utilizing the capability of this system including spatial transformation. Based on reconstruction of noise sources, effective design change to achieve significant reduction of chain whine is derived and then verified in very short time compared to previous methods.

Gear whine can be reduced through a combination of gear parameter selection and manufacturing process design directed at reducing the effective transmission error. The process of gear selection and profile modification design is greatly facilitated through the use of simulation tools to evaluate the details of the tooth contact analysis through the roll angle, including the effect of gear tooth, gear blank and shaft deflections under load. The simulation of transmission error for a range of gear designs under consideration was shown to provide a 3-5 dB range in transmission error. Use of these tools enables the designer to achieve these lower noise limits. An equally important concern is the dynamic mesh stiffness and transmissibility of force from the mesh to the bearings. Design parameters which affect these issues will determine the sensitivity of a transmission to a given level of transmission error.

Piston slap impact noise has been investigated using a piston secondary motion simulation. This simple model accurately estimates piston slap impact, by considering the hydrodynamic effects of the piston skirt oil film and the friction forces at various contact points. The results were compared with the actual piston motion measured by a link mechanism. Consequently, the calculation accuracy was confirmed to be sufficient to make precise estimates of piston slap noise.

As the quietness of vehicles has been continually improved in recent years, there have been stronger requirements to reduce transmission gear noise and thereby improve transmission quality. So far efforts to achieve quieter gears have generally focused on ways of reducing the excitation forces of individual gears. In addition to these traditional methods, there is a greater need today to adopt a new approach to gear noise reduction in which improvements are made to the gear train itself as the transmitter of vibration in the transmission. This paper describes the systematic approach taken to reduce the overall gear noise of the new RE4F04A four-speed automatic transaxle.The cross-sectional view is shown in Fig. 1. The vibration characteristics of this automatic transaxle were first identified by finite element analysis, and an investigation was made of a gear train structure that would be effective in reducing gear noise.