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The demand for quieter vehicle interiors increases year after year. The dynamic force transmission of rolling tires from the road surface to the spindles is a critical factor in vehicle interior noise. We investigated the dynamic force transmission of a rolling tire as it relates to reducing vehicle interior noise. A test with a tire rolling over a cleat was conducted in order to measure the road forces and the spindle forces. The transfer function of the rolling tire was identified from the experimental results by applying multi dimensional spectral analysis. In addition, Computer Aided Engineering (CAE) technology has advanced recently. This enables prediction of spindle forces early in the design stage. One of the most important issues in predicting spindle forces accurately is to clarify the distribution of road forces. This paper also describes the distribution of the dynamic road forces of the rolling tire.

This paper describes how use of multi-objective optimization of pulsating noise and backpressure improved an exhaust silencer for diesel drive equipment. Low frequency pulsating noise and backpressure were simultaneously predicted using one-dimensional fluid dynamics and acoustic analysis by BEM. In addition, an experiment was done to investigate the relation between high frequency noise including flow-induced noise and the dimensions of perforations in silencer pipes. Finally, a prototype of the exhaust silencer was built and examined in order to confirm the effects of these design methods mentioned. As predicted, exhaust noise was reduced without increasing backpressure.

Current simulation of Noise, Vibration and Harshness (NVH) using Computer Aided Engineering (CAE) often uses a large DOF and detailed finite element model along with improvement of CAE technology and computational performance. By using a detailed model, predictions of precise vibration characteristics become possible. However, the number of eigenmodes in the target frequency range increases and engineers require a lot of time to examine eigenmodes and establish countermeasures. In this paper, a practical method of efficient and effective analysis by classifying target eigenmodes into a small number of groups is proposed. The classification is executed based on the relation between the dynamic characteristics of the entire automotive body structure and substructures.

Improvement of vehicle interior noise is desired in recent years in the modern world of the demand of low weight, good fuel economy and offering technical advantages strongly. The dynamic force transmission of rolling tires from the road surface to the spindles is a critical factor in vehicle interior noise. We focus on structure-borne noise transferred through the spindle. It is necessary for effort of the effective tire/road noise reduction to predict spindle force excited by tire/road contact. The major issues in predicting spindle forces are to clarify the distribution of road forces and how to input on the simulation model. Therefore, it is important that road forces are measured accurately on the rolling tire. First, the dynamic road forces on the rolling tire are measured by using the tri-axial force sensor directly. In efforts to reduce interior noise due to structure-borne noise, it is necessary to predict spindle forces excited by the tire/road contact.

This paper describes the application of statistical energy analysis (SEA) to predicting sound power radiated from co-generation system enclosure. To predict vibration and noise accurately by using SEA, it is important to estimate parameter called loss factors. In this study, loss factors were estimated by power injection method. Next, the noise radiated from enclosure surface was predicted by the obtained vibration and radiation efficiency of enclosure panels. As a result, the calculated sound power was relatively corresponding to measured sound power. Finally, the sound power from modified enclosure was predicted. Coupling loss factors related to a modified subsystem were estimated by ratio of the number of structure modes. By using these steps, the noise from the system was reduced.

It’ll be expected that tandem riders increase in the future. So, there is a need to improve the motorcycle stability of tandem riding from the perspectives of safety and comfort. In this research, we focus on tandem riding at low speed because the motorcycle especially becomes unstable. In order to improve the stability of a motorcycle after disturbance is input by the passenger’s posture change, we design a front wheel steer control system that assists the rider’s driving operation. And we simulate it. It is necessary to consider cooperation with the rider’s driving operation. In this study, as a means to consider the cooperative control of the man-machine system, the fuzzy logic was applied to this system.

Generally, it is well known that road noise generated by vibration from automobile tires and suspensions can be reduced by changing the stiffness of the rubber mounts installed in the suspension systems. Such stiffness, however, is rarely changed to avoid riding discomfort and so on. In this paper, a stiffness optimization method for suspension system rubber mounts that reduces road noise, and improves riding comfort as well, is presented. In the process, Road Noise Contribution Analysis (RNCA) is applied to the target vehicle to specify the major factors of road noise. Furthermore, the suspension system of the vehicle is investigated by Sensitivity Analysis using Measured FRF data (SAMF) to identify the optimal stiffness combination of rubber mounts. As a result, an effective stiffness combination of two mounts is specified to reduce road noise and to improve riding comfort.

Recently, the development stage of agricultural vehicles such as the tractor has focused on new demands to improve the cabin environment. Especially the ride comfort has become increasingly important. For this purpose, rubber bushes have been installed the tractor to reduce road vibration to the driver in the cabin. However, this device does not sufficiently suppress vibration. This paper presents a method of vibration reduction that installs a semi-active suspension in the lateral and vertical directions at the cabin mount position of the tractor. In numerical simulation, the tractor model installed with a semi-active suspension is superior in performance to the conventional tractor model.

In a typical mechanical product such as an automobile or construction machinery, it is important to identify deformation modes, for which experiments and analyses can result in significant improvements. It is also important to consider how to improve the structure with high rigidity by using a technique such as the strain energy method in conventional design and development. However, the abovementioned method often generates conflicting results with regard to weight saving and cost reduction of development requirements. Transfer path analysis (TPA) using the finite element method (FEM) is an effective way to reduce noise and vibration in the automobile with respect to these issues. TPA can reveal the transfer path from the input to the response of the output point and the contribution of the path, and to efficiently consider improved responses.

The tire is one of the most important parts, which influence the noise, vibration, and harshness of the passenger cars. It is well known that effect of rotation influences tire vibration characteristics, and earlier studies presented formulas of tire vibration behavior. However, there are no studies of tire vibration including lateral vibration on effect of rotation. In this paper, we present new formulas of tire vibration on effect of rotation using a three-dimensional flexible ring model. The model consists of the cylindrical ring represents the tread and the springs represent the sidewall stiffness. The equation of motion of lateral, longitudinal, and radial vibration on the tread are derived based on the assumption of inextensional deformation. Many of the associated numerical parameters are identified from experimental tests.

To reduce tire/road noise, it is important to examine the noise generation mechanism. Noise generated by a rolling tire is mainly emitted from the tread block. However, it has recently been reported that smooth tires also generate noise recently. This paper remarks on a smooth tire vibration by rolling on the road. The vibration of a rolling smooth tire is mainly vibration excited from the road surface. It is difficult to measure the input from the road surface, so we measured the tire's vibration at the leading and trailing edges. Scan Laser Doppler Vibrometers were employed to measure the vibration of the tire tread.

In this study, the air suspension is newly applied to the engine mounting layout for getting the significant vibration isolation effect. In this case, the genetic algorithm so called GA is also applied for the optimization of many parameters, calculations of stiffness matrix and inverse stiffness matrix to prevent the coupled vibration of lateral and rolling modes and to obtain the displacement of each mounting point. As a result, inexperienced engineers can easily obtain the optimum engine mounting layout in a minute. By the confirmation test of FEM, the engine lateral vibration level at 25Hz dropped below 1/10 and its effect was significant.

The purpose of this paper is to establish a method of predicting the noise and vibration of tractor cabins in the engine-idling state by using Statistical Energy Analysis (SEA). At first, an analytical model of a tractor cabin is constructed, and power flow equations are formulated for the tractor cabin. To solve these equations, SEA parameters are estimated experimentally and analytically. These parameters are the modal density, loss factor, coupling loss factor, and input power. With these parameters, the noise and vibration responses of the tractor cabin are calculated. Good agreements are found between the analytical and experimental data.

This paper describes the identification of a sound source model for diesel engines installed on agricultural machines by using Inverse-Numerical Acoustic (INA) analysis, and noise predictions using the sound source model identified by INA. INA is a method of identifying surface vibrations from surrounding sound pressures. This method can be applied to sound sources with complicated shapes like those in engines. Although many studies on INA have been conducted, these past studies have focused on improvements to the identified accuracy and prediction of noise in free sound field or hemi-free sound field. The authors accurately predicted the sound pressure levels of engine enclosures using a sound source model identified by INA and a boundary element method (BEM). However, we had not yet verified the effectiveness of this sound source model against enclosures that had sound absorbing materials and openings.

This paper describes damping loss factor prediction in statistical energy analysis (SEA) for co-generation system (CGS) enclosures. To accurately predict vibration and noise by SEA, it is important to estimate parameters called the damping and coupling loss factors. In this study, the damping loss factors were estimated by the decay ratio method and a technique for calculating the modal damping ratio that uses a multi-degree of freedom curve fit. The calculated loss factor was applied to the vibration prediction of the co-generation system, and the influence of the internal loss factor calculation method on prediction accuracy was verified.

In this study, the authors analyze the concentration distribution of an evaporative spray mixture with LIEF (Laser induced exciplex fluorescence) method, which is a type of optical measurement. LIEF method is one of the optical measurements for obtaining the spray concentration distribution for separating vapor/liquid phases based on the fluorescence characteristics. In this paper, a quantitative concentration distribution analysis method for wall impingement spray in heterogeneous temperature field has been proposed. Then, a series of experiments were performed in varying injection pressure and ambient density. As a result, a two-dimensional concentration distribution was obtained for the free spray and wall impingement spray.