基于EMD和时频分析的低振动机体结构优化研究

Structural optimization of a low-vibration block based on EMD and time-frequency analysis

为降低柴油机机体振动,开展了基于经验模态分解(EMD)和时频分析的低振动机体优化设计研究。首先建立了机体有限元模型,通过机体模态试验验证了有限元模型正确性;然后,采用多体动力学和有限元相结合的方法计算了机体振动响应,并将计算结果与试验结果进行了对比验证,两者比较吻合;进而采用EMD对机体裙部振动速度信号进行分解,对分解得到的结果中能量较大的分量进行小波时频变换,通过时频分析得到结构优化的主要依据;最后对优化前后振动响应分别采用小波和Hilbert变换进行定性和定量的对比验证。结果表明,优化后整机振动烈度降低了26.81%,整机的振动水平得到了明显的降低,从而验证了该方法的有效性。

In order to reduce diesel engine block vibration,a low-vibration block optimization design was proposed based on empirical mode decomposition （EMD）and time-frequency analysis.Firstly,Multibody Dynamics and finite element method were used to simulate the engine block vibration and the simulation results were verified very well compared with the test results.Then,EMD was used to decompose the vibration velocity signal of crankcase skirt of an engine.And one component of the decomposed results having the largest vibration energy was transformed with wavelet time-frequency analysis.The time-frequency analysis results provided a main basis for structural optimization.At last,the vibration responses of the original block and those of the optimized structure were compared qualitatively with the wavelet analysis and quantitatively with Hilbert transformation,respectively.Results showed that the vibrating intensity of the optimized block decreases 26.81% and the engine vibration is dramaticlly reduced;therefore,the effectiveness of the proposed method is verified.