【作者】 薛敬宏；

【导师】 乔晓林；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2007， 博士

【摘要】 声相关计程仪利用“波形不变性原理”进行测速,是一种适合装备在潜艇及自主水下运载器的导航设备,相比于声多普勒计程仪而言,由于采用垂直向下发射宽波束,不但可以得到更强的回波信号,而且在相同换能器尺寸的前提下,可以采用更低的工作频率以减少海水吸收和传播损失,从而使相关计程仪要比多普勒计程仪作用距离远得多。声相关计程仪的研究对维护我国的海洋权益,科学开发海岛、利用海洋资源具有重要意义。论文根据声相关计程仪的工作原理进行仿真系统的总体方案设计,将系统仿真分为海底回波仿真、波形设计、海底探测、换能器基阵设计、构造代价函数及寻优算法等若干模块,模块化的设计理念有利于系统的维护及今后向硬件平台的移植。论文根据单脉冲发射体制对相位编码的要求,采用截短的Gold序列平衡码作为子码,构成所需位数的长码,所产生编码的自相关函数具有双相关峰特性,这与双脉冲发射的测速体制相对应,解决了双脉冲发射体制测速中脉冲宽度和脉冲发射间隔时间之间的矛盾。论文将Kirchhoff海底散射模型和混响网络模型相结合,实现了海底回波信号的仿真。利用时-空相关函数,推导出一维到三维船速,采用平面阵进行接收时,两基元接收回波相关性最大的条件,该结论对声相关计程仪回波信号的仿真及平面阵测速研究具有一定的理论指导意义。换能器基阵结构设计在声相关测速技术中具有重要地位,由于测速原理是根据接收换能器基元之间形成的不同位置矢量而不是不同的基元位置来提高测速的空间分辨力,因此换能器基阵结构设计实际上是在保证阵列孔径利用率一定的前提下,能够采用尽量少的换能器基元实现声相关测速的需求。论文根据声相关计程仪的测速特点,研究了一维、二维基阵的设计方法,在借鉴传统的约束最小冗余线阵概念的基础上,重新定义了冗余因子、建立理想位置矢量图模型、提出位置矢量覆盖率等概念,进而实现了适合应用于声相关测速需求的二维基阵的快速设计。针对海底混响回波信号具有“拖尾”的特性,论文研究了冲激响应具有二阶导数特性的匹配滤波器,补偿了传播损失对信号幅度衰减的影响,提高了检测概率,同时采用脉冲压缩技术,提高了距离分辨力,冲激响应具有二阶导数特性的匹配滤波器设计与脉冲压缩技术相结合,解决了测量深度、幅度衰减和距离分辨力之间的矛盾。论文在利用理论和数据协方差矩阵构成似然函数作为寻优代价函数的基础上,提出了一种有界的单纯形算法与模式算法相结合的混合算法,理论上证明了该算法的收敛性,并将自适应模拟退火算法引入到声相关计程仪测速中,从而提高了声相关计程仪的测速精度。更多还原

【Abstract】 The principle of“waveform invariance”is used for the velocity measurement among acoustic correlation log (ACL), which is suitable to be equipped on submarines and autonomous underwater vehicles (AUV). The ACL has striking advantages compared with the acoustic Doppler log (ADL). It can work with a single beam pointing directly down at the sea bed and the return signal is much larger than from the ADL because of the normal incidence. Furthermore the beam can be fairly broad and, for the same size of transmit transducer, this enables the use of lower acoustic frequencies for which the attenuation is less. The ACL has the potential therefore for operating on the sea bed echoes at much greater depths than is possible with the ADL. The design and utilization of ACL become more and more important both for the defense of the national ocean sofereignty and for the scientific research and exploitation of islands and ocean rescource.In this dissertation, the overall scheme of the ACL simulation system is planned based on the principle of“waveform invariance”. The whole system is divided into several modules, including seabed reverberation simulation module, waveform design module, bottom tracking module, transducer arrays design module, velocity measurement and optimization algorithm module. The final goal of the module design and research in ACL simulation system is developing a suit of software used in the whole design processing and the migration to hardware platform.According to the single transmitted pulse system in this dissertation, the truncating Gold sequences which contains the same number of 0’s and 1’s are used as code subsections to form the encoded pulse. The pulse coding technique used involves pseudo-random codes which are now generated by a new optimal code finding program. The nature of the coded pulse is such that the autocorrelation function of the pulse possesses a temporal autocorrelation peak at a predetermined time lag so as to achieve the same function as a repetitive pulse system. Thus, the trade-off between impulse width and pulse interval time has been obtained. A realization of the seafloor reverberation simulation based on the Kirchhoff approximation scattering model and the network model was presented. On the basis of the field investigation and research results of others, the case of a plane array is analyzed from one dimensional to three dimensional velocity and sufficient conditions to keep the normalized space-time correlation function of reverberation close to 1 are obtained. The conclusion provides guidance for the application to the seafloor reverberation simulation and the velocity measurement.The design method of transducer arrays assembly plays a key role in the velocity measurement for the ACL. The purpose is to make better use of the array aperture and fully utilization of sensors because spatial discrimination depends on differences in hydrophone locations rather than hydrophone locations. A design method of one dimension and two dimension arrays for the ACL is studied in this dissertation. Based on the method of restricted minimum-redundancy linear array (RMRLA), the redundancy factor is redefined, an ideal positional vector map is built, the conception of positional vector coverage rate is proposed and a fast two-dimensional arrays design method is obtained.By taking the second derivative of the filtered signal with respect to time in literature [75], the sonar system will compensate for signal losses due to spreading. As a result, the detection probability will increase although the seafloor reverberation signal is extremely slow-decaying. With the combination of the matched filtering method mentioned above and the pulse compress method, the dissertation solves the conflicting problems among ocean depth, range resolution and amplitude attenuation. Based on the likelihood function proposed as the cost function which is constructed by a model covariance matrix and a sample one, one of the main contributions of this dissertation is a hybrid algorithm being put forward and the convergence being proved. The algorithm is combined of the simplex method and the pattern search method for bound constrained function minimization which comes from the two subclasses of the direct search methods (DSM). Based on the study on the classical simulated annealing (CSA), which is a method of finding a global minimin, another main contribution is the adaptive simulated annealing (ASA) algorithm being proposed to improve the precision of measure velocity.更多还原