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船舶环境激励下的结构模态参数识别研究
Study on Identification of Structure Modal Parameters Based on the Excitation of Ship Operational Condition
【作者】 刘硕；
【导师】 洪明；
【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2011， 硕士
【摘要】 模态参数的识别对于船舶结构设计,特别是结构减振设计,具有非常重要的指导意义。传统的结构模态识别方法大多需要知道激励信号,而对于船舶这样的大型结构而言,其激励信号是很难测定的,而人工施加激励不仅容易对结构造成损害,并且耗资较高。近年来发展起来的运行模态识别方法通过一定的技术手段,可以无需知道具体的激励信息,仍然能比较良好的识别结构的模态参数。这在工程上具有很高的使用价值。船舶运行环境中,其激励相对复杂,但可以看做是白噪声信号与单频激励的叠加。本文在分析了船舶环境下各激励特点的基础上,选择了NExT技术和ERA法来识别结构的模态参数。该方法在精度和计算速度上都比较理想。为了证明NExT技术和ERA法在船舶运行环境下来识别结构的模态参数的可行性,本文首先对于其基本原理进行了详细的推导,并且分类讨论了船舶运行环境下各激励的特点。然后通过编制相应的计算机程序,对于典型结构的模态结构参数进行识别,得到了比较可靠的结果。最后,通过自行设计结构模型并进行水池试验进一步验证了NExT技术和ERA法来识别结构的模态参数的可行性,并通过分析实验中出现的问题为该方法向工程实际的转化奠定了基础。
【Abstract】 The identification of structure parameters has great instructive in ship and marine design, especially in vibration attenuation design. Traditional identification method need to know the excitation signal, but it is extremely difficult to get from a huge structure like ship or marine structure. If we load the excitation on the structure in manual way, it is not only easy to harm the structure, but also very expensive.Operational modal identification method can identify the modal parameters well without the excitation signal by technical way. It has a high value in engineering practice. The excitation is very complicated in ship operational condition, but it can be considered as white noise combined with single frequency excitation. On the base of analysis the feature of the excitations which is on the ship operational condition, the author chose NExT and ERA technique to identify the structure parameters. And this method is precise and fast.To prove the feasibility of NExT and ERA technique in identifying the structure parameters on the ship operational condition, the author derived the theory in details, and discussed the feature of excitation on the ship operational condition.Then the author identified the parameters of a typical structure by using the programs. And the result is pretty good.At last, the experiment in the water with the ship modal which is designed by the author proved the feasibility of NExT and ERA technique in the field of identification of structure parameters.