利用重力异常匹配技术实现潜艇导航

潜艇的惯性导航误差是随时间积累的,利用重力异常数据进行辅助导航可以对惯性导航的漂移误差进行校正.首先利用2′×2′重力异常数据库作为基础信息,结合Kalman滤波算法对某区域进行了模拟计算,模拟过程采用了增益系数和信息更新序列的新方法进行Kalman 滤波的处理,结果表明在重力异常变化幅度较大的地区,重力异常可以进行潜艇的辅助导航.     

Environmental and social aspects of underwater logging

Underwater logging is a relatively new concept in forestry that has significant economic benefits but also consequences for the environment and local communities. Underwater logging has traditionally been undertaken by divers. However, safety concerns mean that conventional harvesting methods using divers need to be replaced by more sophisticated mechanized harvesting techniques. This paper outlines the environmental and social aspects of underwater logging, highlighting issues that must be considered before any underwater harvesting operations are executed. While the economic reasons for harvesting underwater logs seem compelling, as do the associated social benefits, such as employment generation, there are significant environmental impacts of removing trees from reservoirs, as submerged trees serve as important ecological habitat for aquatic life. Due to the absence of any regulatory regimes encompassing underwater logging, we propose best-practice guidelines for underwater logging operations and suggest the need for a comprehensive sustainability framework based on internationally recognized criteria and indicators to ensure underwater logging operations are environmentally safe, socially beneficial and economically viable.     

A new global alignment approach for underwater optical mapping

Lately, underwater vehicles have become important tools for exploration, monitoring and creation of maps of the seabed. Within mapping applications, the maps obtained from optical data are becoming essential in different study areas such as biological, geological and archaeological surveys, or in detection of benthic temporal changes. However, the underwater medium is very challenging for optical sensors and does not allow the area of interest to be imaged in a single image. Therefore, image mosaicing methods are necessary. Although recent advances in detection of correspondences between images have resulted in highly effective image registration methods, global alignment methods are still needed to obtain a globally coherent mosaic. In this paper, we propose a new global alignment method which works on the mosaic frame and does not require non-linear optimisation. Additionally, a simple image rectifying method is presented to reduce the down-scaling effect which might occur when minimising errors defined in the mosaic frame. Moreover, this rectifying method can also be seen as an alternative and straightforward way of incorporating different sensor information if available. The proposed framework has been tested with underwater image sequences. The resulting method is faster than its counterparts while providing the same level of registration quality.     

Robust coordinated motion control of an underwater vehicle-manipulator system with minimizing restoring moments

For autonomous manipulation in water, an underwater vehicle-manipulator system (UVMS) should be able to generate trajectori9es for the vehicle and manipulators and track the planned trajectories accurately. In this paper, for trajectory generation, we suggest a performance index for redundancy resolution. This index is designed to minimize the restoring moments of the UVMS during manipulation, and it is optimized without impeding the performance of a given task. As a result, the restoring moments of the UVMS are decreased, and control efforts are also reduced. For tracking control of the UVMS, a nonlinear H_∞ optimal control with disturbance observer is proposed. This control is robust against parameter uncertainties, external disturbances, and actuator nonlinearities. Numerical simulations are presented to demonstrate the performance of the proposed coordinated motion control of the UVMS. The results show that control inputs for tracking are reduced, and the UVMS can successfully track generated trajectories.     

A simplified approach to design fuzzy logic controller for an underwater vehicle

Fuzzy logic controller (FLC) performance is greatly dependent on its inference rules. In most cases, the more rules being applied to an FLC, the accuracy of the control action is enhanced. Nevertheless, a large set of rules requires more computation time. As a result, an FLC implementation requires fast and high performance processors. This paper describes a simplified control scheme to design a fuzzy logic controller (FLC) for an underwater vehicle namely, deep submergence rescue vehicle (DSRV). The proposed method, known as the single input fuzzy logic controller (SIFLC), reduces the conventional two-input FLC (CFLC) to a single input FLC. The SIFLC offers significant reduction in rule inferences and simplifies the tuning process of control parameters. The performance of the proposed controller is validated via simulation by using the marine systems simulator (MSS) on the Matlab/Simulink^® platform. During simulation, the DSRV is subjected to ocean wave disturbances. The results indicate that the SIFLC, Mamdani and Sugeno type CFLC give identical response to the same input sets. However, an SIFLC requires very minimum tuning effort and its execution time is in the orders of two magnitudes less than CFLC.     

自适应海洋观测

“自适应海洋观测”指固定或移动的海洋观测平台能够根据海洋环境和信号的变化,自主调节测量和运行参数,获取最关键的海洋信息.自主水下航行器运用自适应检测和采样技术,在研究上升流锋面等实验中显示出前所未有的观测准确度和效率.一个海洋观测系统的综合效能,取决于固定平台和移动平台的功能互补以及自适应观测能力的增强.     

云南地下水中Rn和Hg震兆特征对比分析

以大量的实际观测资料及多次震例 ,深入研究了地下水中Rn和Hg的震兆特征。结果表明 :Hg对地壳岩石应力应变的反应程度比Rn更灵敏 ,更有利于地震预报。通过研究得出以下几点认识 :(1)大震前 ,Hg有 1年左右的中期趋势异常且都出现在距震中较近的有利部位 ,Rn有 1— 2年的趋势异常出现在距震中 5 0 0km范围内 ;(2 )大震前 ,大多数观测台站能观测到Hg突出的短临异常 ,而Rn出现短临异常的台站数只有Hg的1/ 2 ,且异常幅度小 ;(3)中强地震前 ,在距震中较近的观测台站 ,能观测到Hg异常 ,相同条件下的Rn异常则不明显。地下水中Rn和Hg的这些异常特征对未来地震三要素的预报有一定帮助。     

Development and deployment of a stable tow body

With the introduction of improved underwater transducers, there is a need for a stable tow body for oceanographic measurements. This paper summarizes the development of a 260 kg, 1.83×1.06×0.81 m tow body. It covers the performance requirements, the tow body design and manufacture as well as its tow trials off of Biloxi, Mississippi aboard the R.V. Tommy Munro.     

An inverse method for underwater bottom topography by using SAR imagery

I~IOXThe image technology of the synthetic aperture radar (SAR) is one of most important advances in spaceberne microwave remote sensing (Larson et al., 1976). It has extensive application in the ocean remote sensing, such as inversion of the sea subdue winds and currentS, reconstruction of underwater hatom topography and so on. Owing tO the high conductivity of sea water, an electromagnetic wave actually cannot penetrate into the sea water, with extremely smallPenetration depth (abbot 1 c…