For random vibration of airborne platform, the accurate evaluation is a key indicator to ensure normal operation of airborne equipment in flight. However, only limited power spectral density（PSD） data can be obtaine...For random vibration of airborne platform, the accurate evaluation is a key indicator to ensure normal operation of airborne equipment in flight. However, only limited power spectral density（PSD） data can be obtained at the stage of flight test. Thus, those conventional evaluation methods cannot be employed when the distribution characteristics and priori information are unknown. In this paper, the fuzzy norm method（FNM） is proposed which combines the advantages of fuzzy theory and norm theory. The proposed method can deeply dig system information from limited data, which probability distribution is not taken into account. Firstly, the FNM is employed to evaluate variable interval and expanded uncertainty from limited PSD data, and the performance of FNM is demonstrated by confidence level, reliability and computing accuracy of expanded uncertainty. In addition, the optimal fuzzy parameters are discussed to meet the requirements of aviation standards and metrological practice. Finally, computer simulation is used to prove the adaptability of FNM. Compared with statistical methods, FNM has superiority for evaluating expanded uncertainty from limited data. The results show that the reliability of calculation and evaluation is superior to 95%.展开更多
内孤立波(internal solitary wave,ISW)的传播扰动声速场,进而引起声场周期起伏。本文利用数值仿真的研究手段,研究了内孤立波在不同类型的初始发射角度声线的多个声线上转折区域中传播时对声场产生的周期性影响,分析了对于声线掠射角...内孤立波(internal solitary wave,ISW)的传播扰动声速场,进而引起声场周期起伏。本文利用数值仿真的研究手段,研究了内孤立波在不同类型的初始发射角度声线的多个声线上转折区域中传播时对声场产生的周期性影响,分析了对于声线掠射角度、声能量到达时间这两个物理量的起伏频率,发现利用声学参数-时间曲线两点间的斜率与差值的偶次平方的乘积(product of the slope and the even square of the difference between two points of the acoustic parameter-time curve,PSD)处理方法更容易从这两种物理量中提取到显著的声场起伏特征。此外,讨论了高阶PSD参数对声场起伏特征提取效果的影响。结果表明,合适的高阶PSD参数可以提高PSD处理方法对声场起伏特征的提取能力。展开更多
基金supported by Aeronautical Science Foundation of China (No. 20100251006)Technological Foundation Project of China (No. J132012C001)
文摘For random vibration of airborne platform, the accurate evaluation is a key indicator to ensure normal operation of airborne equipment in flight. However, only limited power spectral density（PSD） data can be obtained at the stage of flight test. Thus, those conventional evaluation methods cannot be employed when the distribution characteristics and priori information are unknown. In this paper, the fuzzy norm method（FNM） is proposed which combines the advantages of fuzzy theory and norm theory. The proposed method can deeply dig system information from limited data, which probability distribution is not taken into account. Firstly, the FNM is employed to evaluate variable interval and expanded uncertainty from limited PSD data, and the performance of FNM is demonstrated by confidence level, reliability and computing accuracy of expanded uncertainty. In addition, the optimal fuzzy parameters are discussed to meet the requirements of aviation standards and metrological practice. Finally, computer simulation is used to prove the adaptability of FNM. Compared with statistical methods, FNM has superiority for evaluating expanded uncertainty from limited data. The results show that the reliability of calculation and evaluation is superior to 95%.
文摘内孤立波(internal solitary wave,ISW)的传播扰动声速场,进而引起声场周期起伏。本文利用数值仿真的研究手段,研究了内孤立波在不同类型的初始发射角度声线的多个声线上转折区域中传播时对声场产生的周期性影响,分析了对于声线掠射角度、声能量到达时间这两个物理量的起伏频率,发现利用声学参数-时间曲线两点间的斜率与差值的偶次平方的乘积(product of the slope and the even square of the difference between two points of the acoustic parameter-time curve,PSD)处理方法更容易从这两种物理量中提取到显著的声场起伏特征。此外,讨论了高阶PSD参数对声场起伏特征提取效果的影响。结果表明,合适的高阶PSD参数可以提高PSD处理方法对声场起伏特征的提取能力。
