Showing papers in "International Journal of Vehicle Noise and Vibration in 2005"
TL;DR: In this paper, the authors reviewed numerical methods and analysis procedures used in the study of automotive disc brake squeal and found that the complex eigenvalue analysis is still the approach favored by the automotive industry and the transient analysis is gaining increasing popularity.
Abstract: This paper reviews numerical methods and analysis procedures used in the study of automotive disc brake squeal. It covers two major approaches used in the automotive industry, the complex eigenvalue analysis and the transient analysis. The advantages and limitations of each approach are examined. This review can help analysts to choose right methods and make decisions on new areas of method development. It points out some outstanding issues in modelling and analysis of disc brake squeal and proposes new research topics. It is found that the complex eigenvalue analysis is still the approach favoured by the automotive industry and the transient analysis is gaining increasing popularity.
398 citations
TL;DR: In this article, the acoustic performance of a dissipative expansion chamber with two concentric, annular layers of fibrous material with different resistances is investigated, and a two-dimensional analytical approach is used to determine the transmission loss of this dissipative silencer.
Abstract: The acoustic performance of a dissipative expansion chamber lined with two concentric, annular layers of fibrous material with different resistances is investigated. A two-dimensional analytical approach is used to determine the transmission loss of this dissipative silencer. From the boundary conditions at the rigid wall, and the interfaces between the fibre layers and the central airway, the characteristic function and thus eigenvalues and eigenfunctions for sound propagation in the dissipative chamber are obtained, leading to transmission loss through application of pressure and velocity matching. The effects of geometry and fibre properties on the acoustic attenuation are also discussed.
18 citations
TL;DR: Pang et al. as discussed by the authors presented the nonlinear characteristics of typical automotive seat cushion structure, and two nonlinear models were established to reveal this nonlinear phenomenon in the automotive seats, one of the models was combined with the ISO linear human body model to form a nonlinear seat-human body model.
Abstract: This paper presents the nonlinear characteristics of typical automotive seat cushion structure. As discussed in an earlier paper by the authors (Pang et al., 2004), the experimental transfer functions between the seat butt and the seat track vary with changes in the excitation levels. Both the magnitudes and frequencies of the transfer functions shift to smaller values as the excitation increases. Two nonlinear models are established to reveal this nonlinear phenomenon in the automotive seats. One of the models is combined with the ISO linear human body model to form a nonlinear seat-human body model. The simulated transfer functions between the head and the seat track, between the body and the seat track, and between the seat butt and the seat track are correlated with experimental results. The models proposed here are intended to help engineers optimise the ride quality of the vehicle.
9 citations
TL;DR: In this paper, a hybrid robust active noise controller (ANC) is proposed for reducing broadband noise in acoustic ducts, which consists of an adaptive controller with filtered-x least mean square (FXLMS) algorithm and a feedback structure with robust synthesis theory for obtaining robust performance and stabilisation.
Abstract: This paper describes the principle and application of a hybrid robust active noise controller (ANC) for reducing broadband noise in acoustic ducts. The proposed ANC system consists of an adaptive controller with filtered-x least mean square (FXLMS) algorithm and a feedback structure with robust synthesis theory for obtaining robust performance and stabilisation. In an active control structure, plant uncertainty is one of the major factors that may affect the performance as well as stability of a system and must be taken into account in controller design. In this study, the controller is designed by frequency domain method and implemented on a digital signal processor (DSP) platform for real time control. Experiments are carried out to evaluate the attenuation performance of the proposed control system for synthetic random noise in an acoustic duct. The experimental results indicate that the proposed hybrid controller is effective in suppressing the undesired broadband noise. Furthermore, characteristic analysis and experimental comparison of adaptive feedforward structure, pure feedback control structure and proposed hybrid structure for reducing the noise in a duct are also presented in this paper.
7 citations
TL;DR: In this article, a procedure to control this variation has been suggested in order to maintain noise and vibration performances within the limits of design, in which the assembly process variation is considered.
Abstract: The next generations of direct injection diesel engines have greatly improved their performances compared with petrol engines. However, one of the pending subjects is the noise and vibration levels, due to working cycle itself. The design effort to reduce the emissions of noise and vibration transmitted to the vehicle's driver could be lessened because of the assembly process variation. In this paper, a procedure to control this variation has been suggested in order to maintain noise and vibration performances within the limits of design.
6 citations
TL;DR: In this article, the powertrain bending of v6 engines mounted in east-west configuration was investigated and the objective was to maximise the powerplant/powertrain bending frequency outside some of the engine orders and minimise the potential for resonance.
Abstract: Once installed, the powertrain experiences a natural resonance that is usually referred to as the powerplant (and/or powertrain) bending. Such resonance manifests itself into noise, vibration, and harshness (NVH) concerns at the customer level. It also causes higher levels of amplitudes of the dynamic deformation and stresses leading to durability concerns. This paper addresses powertrain bending of v6 engines mounted in east-west configuration. The objective of this work is to maximise the powerplant/powertrain bending frequency. This will get such frequency outside some of the engine orders and minimise the potential for resonance. Vibration strategies have been developed and practical recommendations are made.
6 citations
TL;DR: In this article, the topology of the superelement is mapped with an arbitrary array of simplistic elements to determine the distribution of mass and stiffness necessary to achieve the performance goals specified without allowing smearing to adjacent component interconnection regions.
Abstract: Optimisation of models using desired targets is typically performed at the system level and result from the individual component dynamic characteristics. Optimisation can be performed when the component and system topology is defined. Previous work utilised Analytical Model Improvement techniques along with Localisation of Model Change procedures to determine the component target characteristics. However, the use of superelements or reduced component representations presents complications since no topology exists for these representations. The efforts in this work are directed towards the implementation of the technique using superelements as the component description. The topology of the superelement is mapped with an arbitrary array of simplistic elements to determine the distribution of mass and stiffness necessary to achieve the performance goals specified without allowing smearing to adjacent component interconnection regions.
6 citations
TL;DR: In this article, a hybrid robust controller is proposed for reducing vibration on single input/single output (SISO) and multiple input/multiple output (MIMO) engine mount systems, which is designed to achieve robust stability and fast convergence by using a combination of the filtered-x least mean squares (FXLMS) and H∞ robust control methods.
Abstract: In this paper, a hybrid robust controller is proposed for reducing vibration on single input/single output (SISO) and multiple input/multiple output (MIMO) engine mount systems. The controller is designed to achieve robust stability and fast convergence by using a combination of the filtered-x least mean squares (FXLMS) and H∞ robust control methods. Plant response is identified by a frequency-domain technique and implemented on a floating-point digital signal processor. Experiments are carried out to evaluate and compare the performance of feedforward control, feedback control and the proposed hybrid control for reducing vibration of two test engine mounts. The results show that the proposed hybrid technique is effective in reducing the vibration and, for the cases compared, results in the best performance for SISO and MIMO engine mount systems.
4 citations
TL;DR: In this paper, a comprehensive summary of the vibration diagnosis techniques used to detect the wear of the main journal bearings in a diesel engine is presented, including the load of the bearing, the minimum thickness of the oil film, the oil films pressure and the locus of the crankshaft center.
Abstract: A comprehensive summary of the vibration diagnosis techniques used to detect the wear of the main journal bearings in a diesel engine is presented. The load of the main journal bearing, the minimum thickness of the oil film, the oil film pressure and the locus of the crankshaft centre have been calculated based on the measured thermal parameters. Simulated wear experiments for the main journal bearing have been carried out in laboratory conditions. The strain and vibration on the main journal pedestals in the vertical direction were measured under various working conditions. The strain signals on the main journal bearing pedestal are related to the oil film forces, damped by the lubricant oil. The excitation sources and the vibration characteristics of the main journal bearing pedestal system were analysed by measuring the vibration signals. The relationships between the feature parameters of the vibration signals and the wear conditions of the main journal bearing have been obtained. It is promising, therefore, to develop and apply the vibration diagnosis technique further to detect the wear conditions of the main journal bearings online.
4 citations
TL;DR: In this paper, a parametric model was developed to correlate disc thickness variation measurements of different friction couples with variables affecting DTV, and the final model of disc cold wear takes an easy form compatible with the proposed mechanism of wear.
Abstract: The cold wear of brake disc is a phenomenon related to judder and other kinds of vibrations. The mechanism and the parameters concerning the cold wear of the disc are the basis for the comprehension of the sources of brake induced vibrations. As a continuation of prior research, a tribometric study was conducted with different disc materials: grey cast iron and inox steel. The wear rates of the above materials were measured at different pressure levels and with the same initial temperature. A parametric model was developed to correlate disc thickness variation (DTV) measurements of the different friction couples with variables affecting DTV. The final model of disc cold wear takes an easy form compatible with the proposed mechanism of wear. The balance among oxide layer-transfer, layer growth and heterogeneous wear is determinant for DTV formation and consequently, brake induced vibrations.
4 citations
TL;DR: In this article, a new technique is implemented to simplify vehicles' mount optimisation, which employs substructuring synthesis and standard NVH testing to obtain frequency response function (FRF) model of a vehicle.
Abstract: Engine and body mount systems play a crucial role in vehicles' comfort. Engine mounts protect the engine from excessive movement and forces due to low frequency road and high frequency engine excitations. On the other hand, body mounts protect the cabin from vibration forces exerted by the body. Normally, a complete set of mounts is conceived at early stages of design, subsequently the set is tuned in the refinement stage to improve the vehicle's noise, vibration, and harshness (NVH) response. Currently, noise path analysis (NPA) is used for mount tuning. This method is helpful, but it is based mostly on trial and error, and it does not lead to an optimum mounting set. In this work, a new technique is implemented to simplify vehicles' mount optimisation. This technique employs substructuring synthesis and standard NVH testing to obtain frequency response function (FRF) model of a vehicle. The model is linked to several optimisation routines to predict the optimum set of mounts for a desired objective function. For verification and evaluation, the method is applied to tuning the mounting set of a pick-up truck. Experimental measurements showed good correlation with optimised response.
TL;DR: In this article, the authors developed an optimisation algorithm that increases a specific structure's natural frequency such that it separates itself from the main band of the road excitation by using a series of iterations of modal analyses in a commercially available Finite Element Analysis (FEA) software package.
Abstract: The durability of a fan shroud is determined by its vibration response to the road, which in turn is determined by its natural frequencies relative to the frequencies from road excitation. The objective of the current study is to develop an optimisation algorithm that increases a specific structure's natural frequency such that it separates itself from the main band of the road excitation. The optimisation algorithm uses a series of iterations of modal analyses in a commercially available Finite-Element Analysis (FEA) software package. After each modal analysis, the key characteristics that contribute to the structural deformation are identified and evaluated. The thickness of each element is then adjusted in accordance with the contribution. As demonstrated in a case study of a fan shroud used in a sports vehicle, the optimisation algorithm works well in enhancing the fan shroud's natural frequency.