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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.

This paper describes the comparison method of input powers and contribution rates from vibration sources to a small power generator's enclosure represented by a thin-walled plane structure determined by Statistical Energy Analysis (SEA) and Transfer Path Analysis (TPA). In the pursuit of efficient ways to analyze the design dynamics of small machines such as a small power generator, it is important to identify information and dynamics of input power sources during machine operation. SEA and TPA are two of the most efficient methods in identifying the dynamics of a structure during machine operation. SEA is used for systems with many resonant modes, and predicted results are based on space averages. On the other hand, TPA is based on estimation of a frequency response function between an excitation point and a response point. In this study, we proposed a method to compare SEA evaluated by power injection method and TPA evaluated by matrix inversion method.

The research into vibration characteristics of a loaded and rolling tire is essential for the prediction of spindle forces. There are tire vibration characteristics one of which is the first natural frequency of a loaded and rolling tire is lower than that of an unrolling tire. The vibration characteristics, for a loaded and rolling tire, are affected by the effect of rotation, restrictions of the vibration due to road contact, and the behavior of rubber dependent on amplitude strain. The consideration of the degradation of natural frequency is therefore necessary in the tire model for prediction of spindle forces. This paper describes an identification method for the tire equivalent stiffness of a tire model focused on vertical spindle forces. The first mode is dominant in vertical spindle forces. First, the natural frequencies in rolling and unrolling tires are identified by operational impact test.

This paper presents progressive techniques based on the previous SAE papers [1], [2] for vibration transmission analysis (VTA) on finite element (FE) model using Transfer Path Analysis (TPA). The techniques are: 1) a contribution calculation technique for structure with manifold and continuous transfer paths: 2) a visualization technique of the influence degree for efficient derivation of measures for response reduction. In VTA, influence degree of each DOF is calculated based on TPA. In order to understand characteristics of vibration transmission (VT) easily and visually by engineers, magnitude of influence degree is expressed by replacement to magnitude of displacement in the diagram of FE vibration shape. This visualization technique is applied to an automotive body structure. The proposed techniques are applied to automotive body structure consisting of members and panels. The members are such as pillars, cross members and side members, which are the main VT paths.

This paper describes a proposal of techniques on Transfer Path Analysis (TPA) to analyze transmission of vibration among the components in a complex structure. This proposal is evolved from the previous one [1] in the dimension which dominates the quality of the analysis in automotive body structure by TPA. The proper coordinate transformation was introduced to resolve the troublesome process on the application of the body structure in the previous proposal. The complications are caused by the treatment with a lot of transfer functions and transmitted forces at the conjunctions that are complexly assembled with many adjacent nodes. Dimension of the analytical region is expanded from two to three in this study. That is, from the cross section of interface of components to the structure itself where the vibration transmits between two components.

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.

This paper describes the application of inverse boundary element method (Inverse BEM) to vibration identification on surface of Co-generation System enclosure. This method is a kind of matrix inversion using singular value decomposition. Therefore it is significant to select proper tolerance in order to identify vibration accurately. In this study, the tolerance selection method is proposed. First step, the surface velocity of numerical model with unit input was obtained by Finite Element Method. The sound pressure around the model was obtained by BEM. Second step, random noise was mixed with obtained sound pressure. Third step, by using Inverse BEM, the surface velocity was identified from the sound pressure with noise. Next, the error between the identified velocity and the velocity obtained by FEM were evaluated and the tolerance is selected to minimize the error.

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.

This paper describes a steady vibration of an engine supported by rubber and hydraulic mounts at a relatively low frequency range, assuming an engine is a rigid body. We identify dynamic characteristics of a hydraulic mount with respect to frequency and amplitude. The equation of motion is solved numerically by the Newton-Raphson method, treating the mount characteristics as functions of frequency and amplitude. The excitation test to simulate an engine shake and an idling vibration was performed using a mass block instead of an actual engine. During the engine shake, we observed that the amplitude dependency of hydraulic mounts strongly influences the vibration, while idling, we investigated rolling vibration especially for the case where the torque axis does not pass through the engine's center of gravity. The theoretical predictions agree closely with the experimental results in both engine shake and idling vibration tests.

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.

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.

In this paper, the modeling technique of the dynamic characteristics of the monocoque-type tractor frame, and the reduction technique of the noise and vibration of the tractor by the design modification of the frame are proposed. First, the vibration characteristics on each part of the tractor, and the noise characteristic in the cabin are measured. Secondly, the full-structure of the frame is separated into the sub-structures of cases and joint parts, and each one is modeled. Then, the model accuracy is improved by using the model tuning method with the sensitivity analysis. Finally, the design change of the frame is carried out with the object of increasing stiffness while reducing weight. As the result of this modification, the cabin noise level can be effectively suppressed about 4 [dB].