基于海洋平臺(tái)單點(diǎn)系泊原型測量的模態(tài)分析
發(fā)布時(shí)間：2018-09-19 06:56
【摘要】：海洋平臺(tái)是海上油氣開發(fā)的主要設(shè)施,其健康狀況與石油開采和工作人員的安全生產(chǎn)作業(yè)密切相關(guān)。海洋平臺(tái)是大型振動(dòng)結(jié)構(gòu),通過水池模型試驗(yàn)來研究其結(jié)構(gòu)會(huì)受到縮尺效應(yīng)的影響,仿真的外部激勵(lì)也不能完全模擬海洋環(huán)境荷載,這些為結(jié)構(gòu)的設(shè)計(jì)和分析帶來很大困難。因此,海洋平臺(tái)原型測量對相關(guān)的研究具有重要意義。本文對浮式生產(chǎn)儲(chǔ)油卸油裝置(FPSO)單點(diǎn)系泊系統(tǒng)的原型測量進(jìn)行了研究,獲得了系泊系統(tǒng)的原型測量數(shù)據(jù)。為了保證FPSO的安全生產(chǎn)作業(yè),需要通過單點(diǎn)系泊系統(tǒng)限制FPSO的運(yùn)動(dòng)范圍,但是長期使用會(huì)給系泊造成一定勞損。因此,需要通過監(jiān)測數(shù)據(jù)分析系泊的健康狀況,其目標(biāo)之一是對系泊進(jìn)行損傷識(shí)別,而準(zhǔn)確地識(shí)別出模態(tài)參數(shù)是結(jié)構(gòu)損傷識(shí)別的關(guān)鍵。FPSO長期處在復(fù)雜的環(huán)境激勵(lì)下,系泊運(yùn)動(dòng)具有明顯的非平穩(wěn)特征。響應(yīng)中的非平穩(wěn)成分使隨機(jī)減量偏離指數(shù)衰減信號,且系泊響應(yīng)的模態(tài)分布密集,用已有方法識(shí)別出的模態(tài)相互耦合。針對以上問題,提出一種基于平穩(wěn)化濾波器—獨(dú)立分量分析(filter-ICA)的模態(tài)識(shí)別方法。在ICA的預(yù)處理中引入滑動(dòng)平均平穩(wěn)化濾波器,消除了非平穩(wěn)成分對模態(tài)參數(shù)識(shí)別的影響。在多自由度仿真系統(tǒng)的模態(tài)識(shí)別中,識(shí)別結(jié)果與理論值吻合。用該方法分析了FPSO單點(diǎn)系泊系統(tǒng)的原型測量數(shù)據(jù),與已有方法的識(shí)別結(jié)果相比,模態(tài)分布明顯,與模態(tài)振型對應(yīng)的系泊運(yùn)動(dòng)軌跡表現(xiàn)出單一運(yùn)動(dòng)形式。在對結(jié)構(gòu)的長期監(jiān)測中,阻尼從能量損耗的角度反映了結(jié)構(gòu)的特征,其變化可以在一定程度上反映結(jié)構(gòu)的損傷情況。但是基于監(jiān)測數(shù)據(jù)對結(jié)構(gòu)的識(shí)別中,特別是對具有非平穩(wěn)響應(yīng)的動(dòng)力系統(tǒng)來說,阻尼比的識(shí)別精度不高。因此,本文提出一種基于時(shí)頻ICA的結(jié)構(gòu)阻尼比識(shí)別方法,減小阻尼比對模態(tài)識(shí)別準(zhǔn)確度的影響,在仿真實(shí)驗(yàn)中驗(yàn)證了該方法的有效性。通過原型測量數(shù)據(jù)的分析,識(shí)別了FPSO單點(diǎn)系泊系統(tǒng)的阻尼比。將相同頻率段的阻尼比識(shí)別結(jié)果進(jìn)行比較,驗(yàn)證了該方法的穩(wěn)定性更好。以上研究從時(shí)不變系統(tǒng)角度對系泊進(jìn)行了模態(tài)分析,但船體發(fā)生縱蕩運(yùn)動(dòng)時(shí),系泊系統(tǒng)的軟剛臂伸展長度會(huì)變化,此時(shí)可將系泊看作時(shí)變系統(tǒng)。當(dāng)結(jié)構(gòu)發(fā)生損傷時(shí),其模態(tài)參數(shù)會(huì)發(fā)生變化,而瞬時(shí)頻率能夠更直觀地反映出這種變化。本文提出一種基于系泊響應(yīng)的瞬時(shí)頻率識(shí)別方法,通過仿真實(shí)驗(yàn)及六自由度模型試驗(yàn)驗(yàn)證了該方法的有效性。將該方法應(yīng)用于原型測量數(shù)據(jù)的分析,識(shí)別結(jié)果的準(zhǔn)確度好于希爾伯特—黃變換(HHT)方法。
[Abstract]:The offshore platform is the main facility for offshore oil and gas development, and its health is closely related to the oil exploitation and the safety work of the staff. The offshore platform is a large vibrating structure, which will be affected by scale effect through tank model test, and the external excitation of simulation can not completely simulate the marine environmental load, which brings great difficulties to the design and analysis of the structure. Therefore, prototype measurement of offshore platform is of great significance to related research. In this paper, the prototype measurement of (FPSO) single point mooring system of floating production oil storage and unloading device is studied, and the prototype measurement data of mooring system are obtained. In order to ensure the safe operation of FPSO, it is necessary to limit the movement range of FPSO through single point mooring system, but the long-term use will cause certain strain to mooring. Therefore, it is necessary to analyze the health status of mooring by monitoring data. One of its objectives is to identify the mooring damage, and the accurate identification of modal parameters is the key of structural damage identification. FPSO is under complex environment excitation for a long time. Mooring motion has obvious non-stationary characteristics. The nonstationary component of the response makes the random decrement deviate from the exponential attenuation signal and the mooring response is densely distributed. The modes identified by the existing methods are coupled with each other. Aiming at the above problems, a modal recognition method based on stationary filter and independent component analysis (filter-ICA) is proposed. A moving average stationary filter is introduced into the preprocessing of ICA to eliminate the influence of non-stationary components on modal parameter identification. In the modal identification of multi-degree-of-freedom simulation system, the recognition results are in agreement with the theoretical values. The prototype measurement data of FPSO single point mooring system are analyzed by using this method. Compared with the existing identification results, the modal distribution is obvious, and the mooring track corresponding to the modal mode shows a single motion form. In the long-term monitoring of the structure, damping reflects the characteristics of the structure from the point of view of energy loss, and its variation can reflect the damage of the structure to a certain extent. However, in the identification of structures based on monitoring data, especially for dynamic systems with non-stationary response, the identification accuracy of damping ratio is not high. Therefore, a structural damping ratio identification method based on time-frequency ICA is proposed in this paper to reduce the influence of damping ratio on the accuracy of modal identification. The effectiveness of this method is verified by simulation experiments. The damping ratio of FPSO single point mooring system is identified by analyzing the prototype measurement data. The results of damping ratio identification in the same frequency range are compared to verify the stability of the proposed method. The modal analysis of mooring is carried out from the point of view of time-invariant system, but the length of flexible rigid arm of mooring system will change when the ship is swinging, and the mooring can be regarded as time-varying system at this time. When the structure is damaged, the modal parameters will change, and the instantaneous frequency can reflect the change more intuitively. In this paper, a mooring response based instantaneous frequency identification method is proposed. The effectiveness of the method is verified by simulation and six degrees of freedom model tests. The method is applied to the analysis of prototype measurement data and the accuracy of the recognition results is better than that of Hilbert-Huang transform (HHT) method.
【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】：2016
【分類號】：P752
[Abstract]:The offshore platform is the main facility for offshore oil and gas development, and its health is closely related to the oil exploitation and the safety work of the staff. The offshore platform is a large vibrating structure, which will be affected by scale effect through tank model test, and the external excitation of simulation can not completely simulate the marine environmental load, which brings great difficulties to the design and analysis of the structure. Therefore, prototype measurement of offshore platform is of great significance to related research. In this paper, the prototype measurement of (FPSO) single point mooring system of floating production oil storage and unloading device is studied, and the prototype measurement data of mooring system are obtained. In order to ensure the safe operation of FPSO, it is necessary to limit the movement range of FPSO through single point mooring system, but the long-term use will cause certain strain to mooring. Therefore, it is necessary to analyze the health status of mooring by monitoring data. One of its objectives is to identify the mooring damage, and the accurate identification of modal parameters is the key of structural damage identification. FPSO is under complex environment excitation for a long time. Mooring motion has obvious non-stationary characteristics. The nonstationary component of the response makes the random decrement deviate from the exponential attenuation signal and the mooring response is densely distributed. The modes identified by the existing methods are coupled with each other. Aiming at the above problems, a modal recognition method based on stationary filter and independent component analysis (filter-ICA) is proposed. A moving average stationary filter is introduced into the preprocessing of ICA to eliminate the influence of non-stationary components on modal parameter identification. In the modal identification of multi-degree-of-freedom simulation system, the recognition results are in agreement with the theoretical values. The prototype measurement data of FPSO single point mooring system are analyzed by using this method. Compared with the existing identification results, the modal distribution is obvious, and the mooring track corresponding to the modal mode shows a single motion form. In the long-term monitoring of the structure, damping reflects the characteristics of the structure from the point of view of energy loss, and its variation can reflect the damage of the structure to a certain extent. However, in the identification of structures based on monitoring data, especially for dynamic systems with non-stationary response, the identification accuracy of damping ratio is not high. Therefore, a structural damping ratio identification method based on time-frequency ICA is proposed in this paper to reduce the influence of damping ratio on the accuracy of modal identification. The effectiveness of this method is verified by simulation experiments. The damping ratio of FPSO single point mooring system is identified by analyzing the prototype measurement data. The results of damping ratio identification in the same frequency range are compared to verify the stability of the proposed method. The modal analysis of mooring is carried out from the point of view of time-invariant system, but the length of flexible rigid arm of mooring system will change when the ship is swinging, and the mooring can be regarded as time-varying system at this time. When the structure is damaged, the modal parameters will change, and the instantaneous frequency can reflect the change more intuitively. In this paper, a mooring response based instantaneous frequency identification method is proposed. The effectiveness of the method is verified by simulation and six degrees of freedom model tests. The method is applied to the analysis of prototype measurement data and the accuracy of the recognition results is better than that of Hilbert-Huang transform (HHT) method.
【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】：2016
【分類號】：P752
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5 何v浝，
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