Search Results

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 a measurement points' placement technique for the sound source identification using inverse acoustic analysis. In order to reduce noise in NVH problem for various kinds of machines including small size engine, it is necessary to identify the sound source. The inverse acoustic analysis is a technique that is effective for the sound source identification.[1,2] The inverse acoustic analysis identifies a surface vibration of an object by measuring the radiated sound and solving the inverse problem. Nakano et al. researched about the location of sound pressure measurement points for accurate improvement.[3] They clarified that the sound pressure measurement points on the concentric circle gave more accurate surface vibration than the measurement points on the square lattice.

This paper describes a prediction of vibration and the transfer path analysis (TPA) using an engine multi body dynamics (MBD) model and measured frequency response functions (FRFs). TPA is used in order to analyze each contribution of vibration transfer paths. In the TPA, input forces from vibration source to passive part should be identified accurately. In the traditional TPA, an identification of input forces is done using only experimental results. Therefore, a parametric study to an improvement of a structure or an isolation system is impossible. In this study, the MBD model of engine is constructed, and input forces from engine to mainframe of agriculture machine are predicted. The accuracy of prediction is confirmed, compared with the results from the traditional TPA method. The contribution of each transfer path is analyzed, and the vibration levels of operator position are predicted using the measured FRFs and the simulated input forces.

Researches for automated construction machinery have been conducted for labor-saving, improved work efficiency and worker's safety, where a tracking control function was proposed as one of the key control system strategies for highly automated productive hydraulic excavators. An optimized digging trajectory that assures as much soils scooped as possible and less energy consumption is critical for an automated hydraulic excavator to improve work efficiency. Simulation models that we used to seek an optimized digging trajectory in this study consist of soil models and front linkage models of a hydraulic excavator. We developed two types of soil models. One is called wedge models used to calculate reaction forces from soils acting on a bucket during digging operation, based on the earth pressure theory. The other is called Distinct Element Method (DEM) model used to analyze soil behaviors and estimate amounts of soils scooped and reaction forces quantitatively.

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.

Operator comfort is an important design criteria for hydraulic excavators during working and idling conditions. An engine, a cooling fan motor and a pump are installed on a hydraulic excavator. It is hard to identify the vibration contribution to a response because three sources are synchronizingly working. This paper describes the use of partial coherence measurement techniques for source identification. And it is examined to reduce the vibration of the source component identified by the partial coherence results. Finally, it is verified that the response acceleration is effectively decreased by reducing the vibration of the identified component.