Transfer Path Analysis Research Articles

A Modeling Method of the Body of Conceptual Design Phase and the Application of Which In Pure Electric Car

A method of modeling method of the body using the simple structure surface is proposed. The structure surface model of half-integral pure electric car body is built. By transfer path analysis, it is known that structure surfaces are balanced in the bearing force, force transfer is consecutive, and the structure surface model is integrated. In addition, four force matrix equations respectively in the bending condition and in the torsional condition are derived, which are the basis of computing the simplified structure surface model.

The transfer path analysis method on the use of artificial excitation: Numerical and experimental studies

Transfer path analysis (TPA) method is a powerful tool used to study the noise, vibration and harshness (NVH) behavior of mechanical systems. With the development of detecting and testing technology, more powerful and accurate tools for vibration and noise troubleshooting are required. The classical TPA works as the system is disassembled, and thus it is very time-consuming and the boundary conditions are not correct anymore. These topics makes classical TPA still an active research area.In this paper, a TPA method on the use of artificial excitation is presented. In the method artificial excitation is applied on the active part for providing sufficient incoherent forces to improve the estimation. The known force is applied on the passive part for establishing a relationship between the responses and loads. The advantages of this method are that it estimates the uncoupled transfer function of the passive part on the basis of in-situ measurements, without disassembling the system. The proposed method is validated by numerical and experimental case studies. Some remarks and practical aspects are discussed.

Vibration and Noise Source Positioning Method of Printing Equipment Based on Transfer Path Analysis

Excessive vibration affects the register accuracy and the noise is harmful to the operators. This paper aims at the sources and their excitation. For positioning the sources quickly, the transfer path analysis model was established, and the vibration-acoustic transfer function of printing equipment was derived by using operational transfer path analysis (OTPA). Through the comprehensively testing of vibration and noise synchronization for four-color offset printing press, a decoupling of the transfer function through singular value decomposition (SVD) of the input matrix was achieved, and furthermore vibration-acoustic contribution rate of each path to identify the main vibration & noise source was obtained. The result shows that main vibration & noise source of the printing machine is the gripper opening and closing mechanism subsystem. The conclusions can be used for vibration and noise reduction design of the printing machine.

Rapid Identification Method for Abnormal Noise of Suspension System Based on Transfer Path Analysis

In the development of a domestic passenger car, it is found that there is a severe abnormal noise of suspension system. In response to the problem, firstly, the frequency range of abnormal noise of the suspension system is identified through vehicle road test and subjective evaluation, secondly, the main path of abnormal noise source is acquired by transfer path analysis(TPA), finally, abnormal noise source of the key component of the main path is identified through the time difference method and the characteristic energy of wavelet analysis method. Through this method, the main abnormal noise source of suspension system can be identified quickly in a relatively short time. The result of the study can provide theoretical and practical guidance for other similar suspension abnormal noise problems.

Contribution evaluation of the structure to the vibration based on transfer path analysis

Contribution evaluation of the structure to the vibration based on transfer path analysis

Design, Analysis, Fabrication and Testing of a Formula Car Chassis

Formula car racing is always a rich sport and millions of research is been done on the development of highly optimised cars. The work shown in this paper consists of the design and fabrication of formula car chassis and testing of its weak points and expected life. CAD software is adopted to chassis design and further finite element analysis like static analysis, modal analysis, transient analysis and fatigue analysis were performed in ANSYS software before fabrication. Vibration transfer path analysis demonstrates the resulting performance of chassis as an alternative to the modal analysis approach for solving noise and vibration problems.

Aerodynamic Noise Separation of an EMU Trailer Bogie Area Using Train Operation Tests

The operation transfer path analysis (OTPA) technique was used to measure the vibration and noise transfer coefficient functions of wheel‐rail noise and radiated noise from an electric multiple unit (EMU) train (high‐speed train in China) trailer bogie structure to the central area of the trailer bogie for a train running at speeds of 0–5 km/h. By applying these transfer coefficient functions to the noise analysis of high‐speed train operation, the contributions of wheel‐rail noise and frame‐radiated noise to the noise of the bogie area at high speeds are obtained, and the aerodynamic noise is separated from the total noise, providing a reference for vibration damping and noise reduction in high‐speed trains. Analysis of test data shows that, in the central area of the trailer bogie of high‐speed trains, the low‐frequency noise mainly comes from the structural radiated noise of the bogie, and the mid‐ to high‐frequency noise is primarily due to aerodynamic noise. In addition, when an EMU train operates at speeds below 250 km/h, the noise in the central area of the trailer bogie is primarily caused by the structural radiated noise. When the operating speed is higher than 250 km/h, the noise in the central area of the trailer bogie is mainly due to aerodynamic noise, and the aerodynamic noise contribution increases with increase in speed.

Investigation and refinement of gearbox whine noise

Structure borne noises can be transmitted to interior cabin via physical connections by gearbox as well as other active components. Experimental Transfer Path Analysis (TPA) methods are utilized to investigate main paths of vibrations which are eventually perceived as noise components inside the cabin. In this study, contribution ranking of transmission paths from active system components through the physical connections into the interior cabin are investigated by Operational Path Analysis with Exogenous Inputs (OPAX) method. In addition, the sensitivity and rigidity characterization of the body through dominant paths according to OPAX were measured to reveal the reason for the whine noise to the inner cabin because of the operational forces generated in the dominant structure-borne paths. And also, operational modal analysis was carried out to examine the modes of the dominant path components. The modifications are applied on dominant transfer paths according to dominant paths characterization by operational deflection shape analyses. Thus, the root causes are investigated on vehicle level NVH tests while observing the variations in the interior cabin noise level.

Improved vehicle interior structure-borne noise induced by the powertrain using parallel dry friction damper

Because of the higher requirements for vehicle comfort and people’s increasing ecological consciousness, research on the interior noise in a vehicle has received wide attention, among which structure-borne noise is hard to diagnose. To solve the problem, the transfer path analysis method of powertrain structure-borne noise has been systematically analyzed. By introduction of the powertrain source-path-receiver model, this method enables the researchers to estimate and study the noise, vibration, and harshness transfer functions and their operational forces. The aim is to further improve noise, vibration, and harshness with minimal negative impact on other vehicle attributes, such as ride comfort, handling, drivability, durability, etc. In this article, a parallel dry friction damper was added to the vehicle nearside powertrain mount, which is the most significant one to the receiver of passenger vehicle for improving its interior structure-borne noise induced by the engine. The test vehicle was a midsize executive vehicle. Since the structure-borne noise is composed of multiple paths, then the transfer path analysis test of the vehicle was carried out, and the transfer function and operational data at speed range started from 20 to 100 km/h were obtained. On the basis of the transfer path analysis results and the above principle, the friction damper on the body side of the nearside mount is improved by combination of the experimental transfer path analysis and the final measurements. The results indicate that a significant reduction for the A-weighted sound pressure level of the interior noise has been gained when the frictional damper was added to conventional mount.

Contribution analysis of interior noise and floor vibration in high-speed trains by operational transfer path analysis

A study on the contribution analysis of interior noise and floor vibration in high-speed trains was conducted using operational transfer path analysis. Initially, noise and vibration measurement at...

전동차 실내소음 전달 경로 분석

전동차 실내소음 전달 경로 분석

Virtual decoupling method: a novel method to obtain the FRFs of subsystems

An important procedure in transfer path analysis (TPA) is to measure the frequency response functions (FRFs) of the decoupled passive subsystem. The classical TPA method obtains the passive subsystem’s FRFs by direct measuring when the system is disassembled. The main shortcoming of the classical method to measure the FRFs is that it is time-consuming due to the necessity to dismount the active part. In this paper, a novel method is proposed to estimate the passive subsystem’ FRF matrix without disassembling the coupled mechanical structure. The key idea of this method is that the effect of a coupled subsystem will be canceled out if the links which connect this subsystem with the other one have no deformation, since the coupled systems influence each other only through the links which can be regarded as combinations of connecting springs and dampers. Following this idea, the expression of the passive subsystem’s FRF matrix can be deduced from the entire system’s FRF matrix directly. The proposed method in this paper is called the virtual decoupling method, since the decoupling is not ‘real’ but ‘virtual’. Obviously, the actual decoupling procedure is avoided so that the shortcoming mentioned above is overcome. The method is validated by a numerical model and a finite element model.

Blocked pressure based Transfer Path Analysis (TPA) method to diagnose airborne sound transfer through building partitions

Airborne sound transmission through building elements or the sound insulation of the building element is usually rated by its Sound Reduction Index (SRI) or the Sound Transmission Class (STC). SRI/STC quantifies the overall sound transfer but gives no information about how the transfer takes place and what are the contributions of different sound transfer paths involved. Such problems are fairly common to the vehicle acoustics industry and are generally tackled by TPA techniques. The paper formulates an in-situ Airborne TPA technique to quantify the contributions of different sound transfer paths to the transmitted pressure. The airborne source is characterized by its blocked pressure and its direct measurement is discussed. Results are presented for dual leaf partitions excited by an airborne source. The method has shown to be significantly faster than the Blocked force based TPA method which relies on inverse measurement methods. The accuracy of the method is closely related to the wavelength of incident airborne waves.

Analytical transmissibility based transfer path analysis for multi-energy-domain systems using four-pole parameter theory

The increasing demand to minimize undesired vibration and noise levels in several high-tech industries has generated a renewed interest in vibration transfer path analysis. Analyzing vibration transfer paths within a system is of crucial importance in designing an effective vibration isolation strategy. Most of the existing vibration transfer path analysis techniques are empirical which are suitable for diagnosis and troubleshooting purpose. The lack of an analytical transfer path analysis to be used in the design stage is the main motivation behind this research. In this paper an analytical transfer path analysis based on the four-pole theory is proposed for multi-energy-domain systems. Bond graph modeling technique which is an effective approach to model multi-energy-domain systems is used to develop the system model. In this paper an electro-mechanical system is used as a benchmark example to elucidate the effectiveness of the proposed technique. An algorithm to obtain the equivalent four-pole representation of a dynamical systems based on the corresponding bond graph model is also presented in this paper.

Influences of system uncertainties on the numerical transfer path analysis of engine systems

Practical mechanical systems operate with some degree of uncertainty. In numerical models uncertainties can result from poorly known or variable parameters, from geometrical approximation, from discretization or numerical errors, from uncertain inputs or from rapidly changing forcing that can be best described in a stochastic framework. Recently, random matrix theory was introduced to take parameter uncertainties into account in numerical modeling problems. In particular in this paper, Wishart random matrix theory is applied on a multi-body dynamic system to generate random variations of the properties of system components. Multi-body dynamics is a powerful numerical tool largely implemented during the design of new engines. In this paper the influence of model parameter variability on the results obtained from the multi-body simulation of engine dynamics is investigated. The aim is to define a methodology to properly assess and rank system sources when dealing with uncertainties. Particular attention is paid to the influence of these uncertainties on the analysis and the assessment of the different engine vibration sources. Examples of the effects of different levels of uncertainties are illustrated by means of examples using a representative numerical powertrain model. A numerical transfer path analysis, based on system dynamic substructuring, is used to derive and assess the internal engine vibration sources. The results obtained from this analysis are used to derive correlations between parameter uncertainties and statistical distribution of results. The derived statistical information can be used to advance the knowledge of the multi-body analysis and the assessment of system sources when uncertainties in model parameters are considered.

Modified transfer path analysis considering transmissibility functions for accurate estimation of vibration source

In this study, we developed a modified transfer path analysis (MTPA) method to more accurately estimate the operational force of the main vibration source in a complicated system subjected to multiple vibration sources, base excitation and several disturbances. In the proposed method, transmissibility functions are adopted to compensate the disturbances due to base excitation or to reject transferred forces from other vibration sources. The MTPA method was verified numerically using a simple beam model and was practically applied to estimate vibration forces of a compressor in an outdoor air conditioner unit. Present results show that the MTPA method is feasible for predicting the pure operation forces of the compressor in an outdoor air conditioner unit regardless of the vibration sources due to a rotating fan and base excitations. The proposed MTPA method has very important advantages that it can be used to more accurately estimates the operational force of the main vibration source, properly rejecting other vibration sources and disturbances.

Analytical transmissibility based transfer path analysis for multi-energy-domain systems using bond graphs

The increasing demand for vibration reduction in several high-tech industries has motivated many researchers to investigate novel vibration isolation techniques. Understanding the vibration transfer paths within a system is an essential part of designing an effective vibration isolation strategy. In this paper, an analytical transfer path analysis algorithm is proposed suitable for multi-energy-domain systems. The bond graph modeling technique, which is an effective approach to model multi-energy-domain systems, is used to extend the concept of transmissibility to such systems. In this paper, an electro-hydro-mechanical system is used as a benchmark example to elucidate the effectiveness of the proposed technique. An energy based path ranking algorithm based on the bond graph model of the system is also conducted.

A system response prediction approach based on global transmissibilities and its relation with transfer path analysis methods

In this paper, a response prediction approach based on global transmissibilities is proposed to improve transfer path analysis (TPA) methods. The method allows predicting the system response when a subsystem becomes connected to the ground using easily measured variables of the original system. It avoids the necessity to perform demounting tests and to measure, or indirectly determine operational forces. The mathematical relationships between the proposed method and TPA methods are derived. Four TPA relations are discussed: the classical TPA relation, the OPA relation, the Advanced TPA relation and the Component-based TPA relation. The advantage of this method is that it estimates the properties of a mechanical system or subsystems using in-situ measurements. These properties are the transmissibility between two sets of responses, the coupled and uncoupled transfer functions between responses and forces. The TPA relationships are validated by numerical and experimental case studies.

Exactness of alternative force estimation methods and applications to power flow and transfer path analysis.

The alternative indirect methods to estimate interfacial force and moment are first given as theoretically exact methods which are derived from the equation of motion. How to directly acquire the F/Q (dynamic stiffness)-type frequency response functions and the blocked boundaries to apply are described in detail. As applications of interfacial force and moment, dissipated power exactly estimated by the total power or energy flows into a system and exactness of the transfer path analysis for structure-borne sound are described. Using a finite element model of a plate-beam structure, computational verifications are given for the equalities.

Prediction of the excitation force of an air compressor at the mounting position by vibration transfer path analysis

Prediction of the excitation force of an air compressor at the mounting position by vibration transfer path analysis