【摘要】：小波變換作為一種數(shù)學(xué)工具,憑借其良好的多分辨分析能力,在諸多研究領(lǐng)域被廣泛地應(yīng)用。物理模型試驗是海洋工程領(lǐng)域重要的研究手段之一,但在物理模型試驗中采集到的數(shù)據(jù)往往會受到噪聲污染,因而在進(jìn)一步處理這類數(shù)據(jù)時,需要對數(shù)據(jù)信號進(jìn)行降噪處理以確保試驗結(jié)果的準(zhǔn)確性�；谏鲜銮闆r,本文通過基于離散小波變換的降噪方法對從軟鋼臂單點(diǎn)系泊浮式生產(chǎn)儲油卸油裝置(FPSO)物理模型試驗中采集到的數(shù)據(jù)進(jìn)行降噪處理,從而提高試驗數(shù)據(jù)的準(zhǔn)確性。本文首先詳細(xì)介紹了離散小波變換的基本概念和理論基礎(chǔ),然后對小波降噪方法的理論進(jìn)行了細(xì)致的介紹,重點(diǎn)介紹了常用的幾種小波函數(shù)和降噪過程中參數(shù)的選取規(guī)則以及數(shù)據(jù)降噪性能的評價指標(biāo)。隨后對單點(diǎn)軟剛臂系泊FPSO水池物理模型試驗進(jìn)行了簡單的介紹,通過對FPSO自由衰減信號中加入已知白噪聲形成帶噪信號,并應(yīng)用小波降噪方法對其進(jìn)行分析處理來評估不同小波函數(shù)、閾值選取以及重調(diào)方式的降噪效果,從而找出適合于船舶運(yùn)動量信號的最優(yōu)降噪?yún)?shù)選取組合。結(jié)果表明,db8和sym10小波函數(shù),Stein無偏風(fēng)險閾值選擇方法,sln重調(diào)方式的組合降噪效果最佳。將此種降噪組合應(yīng)用于單點(diǎn)軟鋼臂系泊FPSO試驗采集的運(yùn)動量數(shù)據(jù)進(jìn)行降噪處理,結(jié)果表明降噪效果良好。最后應(yīng)用小波降噪方法對系泊力數(shù)據(jù)進(jìn)行了降噪處理。系泊塔關(guān)鍵節(jié)點(diǎn)處的受力是系泊系統(tǒng)設(shè)計的主要依據(jù)。采用小波降噪方法對幾組工況下采集到的系泊力數(shù)據(jù)進(jìn)行降噪處理,并與傳統(tǒng)的低通濾波方法進(jìn)行了對比。結(jié)果表明小波閾值降噪方法可以很好地解決低通濾波方法濾去高頻瞬態(tài)系泊力的問題,其降噪結(jié)果較為合理,能夠反映真實的試驗現(xiàn)象。另外通過頻譜分析,發(fā)現(xiàn)小波降噪方法能夠準(zhǔn)確地分辨出真實信號和噪聲之間的差別,保留了信號中重要的高頻信息。最后,通過選取不同參數(shù),比較其對降噪效果的影響,得到對于實測系泊力信號的最優(yōu)降噪組合。
[Abstract]:Wavelet transform, as a mathematical tool, is widely used in many research fields with its good ability of multi-resolution analysis. Physical model test is one of the important research methods in the field of marine engineering, but the data collected in the physical model test are often contaminated by noise, so in the further processing of this kind of data, The noise reduction of the data signal is needed to ensure the accuracy of the test results. Based on the above situation, the noise reduction method based on discrete wavelet transform is used to reduce the noise of the data collected from the physical model test of the flexible steel arm single point mooring floating oil storage and unloading unit (FPSO), so as to improve the accuracy of the test data. In this paper, the basic concept and theoretical basis of discrete wavelet transform are introduced in detail, and then the theory of wavelet denoising method is introduced in detail. Several commonly used wavelet functions, the selection rules of parameters in the process of noise reduction and the evaluation indexes of data denoising performance are emphatically introduced in this paper. Then the physical model test of a single point flexible rigid arm mooring FPSO pool is briefly introduced. The noise signal is formed by adding known white noise to the FPSO free attenuation signal. The wavelet denoising method is applied to evaluate the noise reduction effect of different wavelet functions, threshold selection and resetting mode, so as to find the optimal combination of noise reduction parameters suitable for ship motion signal. The results show that the combination of Db8 and sym10 wavelet function Stein unbiased risk threshold selection method has the best effect on noise reduction. The noise reduction combination is applied to the noise reduction of mooring FPSO with single point soft steel arm mooring. The results show that the noise reduction effect is good. Finally, wavelet denoising method is used to deal with mooring force data. The stress at the key nodes of the mooring tower is the main basis for the design of the mooring system. The mooring force data collected under several working conditions are de-noised by wavelet denoising method and compared with the traditional low-pass filtering method. The results show that wavelet threshold denoising method can solve the problem of filtering high frequency transient mooring force by low pass filtering method. The result of noise reduction is reasonable and can reflect the real experimental phenomenon. In addition, through spectrum analysis, it is found that wavelet denoising method can accurately distinguish the difference between real signal and noise, and retain the important high-frequency information in the signal. Finally, by selecting different parameters and comparing their effects on the noise reduction effect, the optimal noise reduction combination for the measured mooring force signal is obtained.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P75

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本文編號：2130198