小型挖掘机驾驶室低频噪声的结构件振动影响研究

发布时间：2018-04-08 17:24

本文选题：挖掘机　切入点：驾驶室结构件振动　出处：《山东大学》2017年硕士论文

【摘要】：挖掘机驾驶室振动噪声对驾驶员的驾乘舒适性和身心健康具有直接影响,并且随着国产挖掘机产品参与国际竞争程度的不断提高,挖掘机的NVH(Noise,Vibration and Harshness)性能要求也越来越高,因此对挖掘机驾驶室振动噪声控制展开研究具有重要的工程意义。驾驶室结构件同时受多个激励源的作用,对驾驶室内低频噪声具有决定性影响,明确其主要的振动源及传递规律从而采取合理的控制措施,是降低挖掘机驾驶室振动与低频噪声水平的重要手段。本文针对国产某小型挖掘机驾驶室噪声低频成分突出的问题,从衰减激励源传递至驾驶室结构件的振动能量的角度出发,采用EEMD与ICA结合的方法对影响驾驶室内低频噪声的主要结构件进行振源识别,结合驾驶室振动传递路径分析确定振动能量的传播规律,用于指导挖掘机驾驶室振动噪声性能改进。首先,为解决多源混叠造成的主要激励源难以辩识的问题,本文提出采用EEMD与ICA结合的振源识别方法对单通道信号进行解耦,提取出最为关键的源信号。该方法首先采用EEMD分解一维信号,利用综合相关系数和能量贡献率的筛选准则选择有效IMF分量,然后构建虚拟多通道信号作为ICA的输入,完成单一通道信号的源识别,最后根据估计的混合矩阵确定各源的贡献程度。仿真分析结果表明,协同EEMD与ICA的振源识别方法可以正确分离出一维非平稳混合信号的各源信号,且能量贡献度计算结果与实际情况相符,从而验证了该方法用于分析挖掘机振动信号的可行性。然后,利用小波包分解算法提取挖掘机驾驶室振声信号的低频成分,结合驾驶室振动噪声形成机理的分析,进行驾驶室振声信号频谱特性和频域相关性研究,对影响驾驶室内低频噪声的主要结构件进行振源识别并计算各振源的能量贡献度。分析结果表明,该挖掘机驾驶室噪声以低频声为主,仪表盘、右侧护板和右壁板是影响驾驶室低频噪声的主要结构件;发动机一阶和二阶燃烧激励在各结构件振动的能量构成中占据主要成分,是影响驾驶室低频振声水平的主要激励源。最后,进行驾驶室振动传递路径分析,确定振动能量的传播规律以及对驾驶室振动的影响。以频域振动传递率为指标评价发动机和驾驶室减振系统的性能;基于有限元模态分析研究上车架的振动特性,寻找易引起结构共振的模态频率和结构刚度不足的部位,改进上车架结构;结合工程经验,提出了控制挖掘机驾驶室振动噪声的改进方案。
[Abstract]:Vibration noise of excavator cab has direct influence on driver's driving comfort and physical and mental health. With the increasing of domestic excavator products' participation in international competition, the performance requirements of excavator's NVHN NoiseVibratory and are becoming more and more high.Therefore, the research on vibration and noise control of excavator cab is of great engineering significance.The cab structure is affected by multiple excitation sources at the same time, which has a decisive effect on the low frequency noise in the cab. The main vibration sources and transmission rules are clearly defined, and reasonable control measures are taken.It is an important means to reduce the vibration and low frequency noise level of excavator cab.In this paper, aiming at the prominent low frequency component of cab noise of a small excavator made in China, from the angle of vibration energy transmitted from attenuation excitation source to cab structure,The method of combining EEMD and ICA is used to identify the vibration source of the main structural parts which affect the low frequency noise in the cab, and the vibration energy transmission law is determined by the analysis of the vibration transfer path of the cab.It is used to improve the vibration and noise performance of excavator cab.Firstly, in order to solve the problem that it is difficult to identify the main excitation sources caused by multi-source aliasing, this paper proposes a method of vibration source identification combined with EEMD and ICA to decouple the single channel signal and extract the most critical source signal.In this method, EEMD is used to decompose one-dimensional signal, and the effective IMF component is selected by the screening criterion of comprehensive correlation coefficient and energy contribution rate. Then the virtual multi-channel signal is constructed as the input of ICA, and the source recognition of single channel signal is completed.Finally, the contribution of each source is determined according to the estimated mixing matrix.The simulation results show that the vibration source identification method based on cooperative EEMD and ICA can correctly separate the source signals of one-dimensional non-stationary mixed signals, and the calculated results of energy contribution are in accordance with the actual situation.The feasibility of using this method to analyze the vibration signal of excavator is verified.Then, the wavelet packet decomposition algorithm is used to extract the low frequency components of the vibration sound signal of the excavator cab, and the frequency spectrum characteristics and frequency domain correlation of the vibration sound signal are studied based on the analysis of the formation mechanism of the cab vibration noise.The main structural components which affect the low frequency noise in the cab are identified and the energy contribution of each vibration source is calculated.The analysis results show that the cab noise of the excavator is mainly low frequency sound, the instrument panel, the right side panel and the right wall panel are the main structural parts which affect the low frequency noise of the cab.The first and second order combustion excitation of the engine occupies the main component in the energy composition of the vibration of each structure and is the main excitation source that affects the low frequency vibration level of the cab.Finally, the transmission path of cab vibration is analyzed to determine the propagation law of vibration energy and its influence on cab vibration.The frequency domain vibration transfer rate is taken as the index to evaluate the performance of the engine and cab vibration absorption system, and based on the finite element modal analysis, the vibration characteristics of the upper frame are studied to find the parts which are apt to cause structural resonance modal frequency and structural stiffness deficiency.An improved scheme for controlling vibration and noise of excavator cab is put forward by improving the structure of upper frame and combining with engineering experience.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU621

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