【作者】 赵景波；

【导师】 赵国良； 吴建华；

【作者基本信息】 哈尔滨工程大学 ， 控制理论与控制工程， 2006， 博士

【摘要】 海水是一种很强的腐蚀性介质，舰船处于海洋环境中，钢质船壳不可避免地要发生腐蚀。为了使船体不受腐蚀，舰船普遍采用外加电流阴极保护的保护方法。由于施加阴极保护系统，在舰船的周围产生由阴极保护系统的电流产生的腐蚀静电场和极低频电磁场，为舰船的安全性带来了威胁，因此对舰船腐蚀电磁场进行研究，具有重要的军事意义。本文的工作是利用我们设计的基于虚拟仪器的舰船腐蚀电磁场的测量系统，主要对舰船的轴频特性信号的提取和舰船腐蚀静电场和极低频电磁场防护方法等问题进行研究。首先针对随着传播距离的增大极低频电场衰减很快，很容易被环境噪声所掩盖，研究了基于谐波小波的自适应谱线增强器来提高微弱轴频电场远程检测能力的方法，利用该方法对舰船电磁场缩比模型产生的轴频电场的实测数据进行处理。然后针对谐波小波在时域衰减速度慢的缺点，对其在频域进行光滑处理，得到了性质更好的改进的谐波小波，并利用改进的广义谐波小波算法实现了轴频特征提取。同时为了自适应地“无限细分”整个频带以提取信号中的有用频率成分，本文研究了最优小波包基的自适应谐波小波算法。此外船体防腐蚀保护的有效性与阴极保护系统设计有关，因此本文研究了双区域阴极保护系统，对双区域阴极保护系统进行了优化设计，实现既满足船体防腐蚀，同时又降低腐蚀静电场，同时为了降低轴频电场，在分析有源轴接地系统原理的基础上，提出利用信号处理的方法进行电压补偿的思想。另外基于相似性原理，分析了舰船电磁场缩比模型，同时设计1∶100舰船电磁场缩比模型，利用缩比模型研究了不同转速下的舰船轴频电场的特征。最后利用三维电场传感器，同时基于虚拟仪器的思想构建了舰船腐蚀电场的测量系统，实现了舰船腐蚀静电场和极低频轴频电场的快速、准确的测量。更多还原

【Abstract】 Vessels in the seawater, a strong corrosive medium, will inevitably suffer a corrosion problem. In view of this, a current cathodic protection system is then commonly adopted to handle this problem onboard. However, the application of the cathodic protection system unfavorably creates a corrosive electrostatic field, and an ELF (extremely low frequency) electromagnetic field around the vessel due to the current of protection systems. The ship corrosion electromagnetic field brings the threat to the ship security. Therefore, it is important in military significance to study characteristics of corrosion electromagnetic field of ships.The main work of the dissertati physical physical on consists of study on characteristics extraction of shaft-rate modulated electric field and method preventing from corrosion electrostatic field and ELF based on the measurement system with virtual instrument developed in the lab.Because the strength of electric field with ELF is getting weaken very quickly as the propagation distance increases, it is easily disturbed by the ambient noise. A new method by using a spectral line enhancer on harmonic wavelet is put forward to improve the long-range detectability of shaft-rate modulated electric field with weak strength. The new method is applied to processing the measured data of the shaft-rate modulated electric field collected in the tests of the physical scale model of ships.Regards of shortcoming of harmonic wavelet with slow decay speed in time domain, a method of smooth processing the harmonic wavelet in the frequency domain is proposed to get improvement generalized harmonic wavelet with better properties. The characteristics extraction of shaft-rate modulated electric field is realized by using the improvement generalized harmonic wavelet. In order to "indefinitely subdivide" the whole frequency band self-adaptively to pick up some valid frequency components, a self-adaptive harmonic wavelet algorithm with optimum wavelet packet basis is studied in this dissertation.In addition, the effectiveness of hull corrosion protection is related to the design of cathodic protection system .Therefore, the double-zone cathodic protection system is proposed in the dissertation. The optimization of the double-zone cathodic protection system is carried out in order to realize the hull corrosion protection as well as reduce the strength of corrosion electrostatic field. Furthermore, base on active earth grounding system using singnal processing voltage compensation is proposed to reduce the strength of the shaft frequency electric field.In the light of similarity theory, a physical scale model of vessel electromagnetic field is studied. A 1:100 physical scale model is designed and various characteristics of the shaft-rate modulated electric field under different r.p.m. are extracted based on the model.At last, according to concept of virtual instrument an electric field measurement system by using three dimensional electric field sensors is developed in the Lab such that the accuracy and speed of measurement for corrosion electrostatic field and the ELF shaft-rate modulated electric field of ships is reasonable.更多还原