Mine Countermeasures Research Articles

무인잠수정 기뢰 탐색 효과도 분석

Mine countermeasure missions(MCMs) may induce the loss of human and ship because of the covert of mine. In recent years, unmanned underwater vehicles(UUVs) have emerged as viable technical solution for conductimg underwater search, surveillance, and clearance operations in support of mine countermeasure missions because of her autonomy and long time endurance capability. This paper introduces a technical approach to mine countermeasure mission effectiveness analysis and presents some simulation-based analysis results for engineering of the UUV system definition which could be support analysis of alternatives for system definition and design.

무인잠수정 기반 기뢰대항전체계 개발을 위한 소요기술 분석

One of the most significant UUV(Unmanned Underwater Vehicle) applications is MCM(Mine Countermeasure), which makes good use of UUV characteristics to provide covert, rapid, controlled and efficient survey of a potential minefield without risking a human operator. In this paper, a survey of the today's MCM missions where UUVs will play a role, the vehicle systems that are either under development or planned in the future are presented. And examines principal technical challenges and outline new enabling technologies. Particularly, this paper analyses current approaches to tacking these technologies and technological limitation of UUVs as a MCM platform, and research efforts to develop the technology necessary to meet the domestic MCM mission needs.

The reset disambiguation policy for navigating stochastic obstacle fields

The problem we consider is a stochastic shortest path problem in the presence of a dynamic learning capability. Specif- ically, a spatial arrangement of possible obstacles needs to be traversed as swiftly as possible, and the status of the obstacles may be disambiguated (at a cost) en route. No efficiently computable optimal policy is known, and many similar problems have been proven intractable. In this article, we adapt a policy which is optimal for a related problem and prove that this policy is indeed also optimal for a restricted class of instances of our problem. Otherwise, this policy is generally suboptimal but, nonetheless, it is both effective and efficiently computable. Examples/simulations are provided in a mine countermeasures application. Of central use is the Tangent Arc Graph, a polynomially sized topological superimposition of exponentially many visibility graphs. © 2011 Wiley Periodicals, Inc. Naval Research Logistics 58: 389-399, 2011

Multibeam Sonar-Based Navigation of Small UUVs for MCM Purposes

AbstractAutonomous vehicles (AxV), surface (ASV) and underwater (AUV), are being considered for the following maritime security missions: Mine Countermeasures (MCM) and Harbor Protection (HP). Applicable threats include attack swimmers/divers, bottom and moored mines, mines or improvised explosive devices placed on pilings, quays, or hulls of ships at anchor or in port. This article focuses on solutions for mine reacquisition and neutralization (RN). One concept for an overall RN system is two collaborating vehicles, an AxV and a unmanned underwater vehicle (UUV). The main task of the RN AxV is to reacquire a bottom target with multibeam imaging sonar, maintain distance while pointing at the target, and perform circular inspection around a target while varying the circle diameter. The main task of the RN UUV is to converge towards the desired line once deployed from the AxV. UUV guiding is accomplished by automatically processing sonar imagery onboard of the AxV and passing sonar position, and UUV range and bearing information to the UUV which processes this information to drive itself to the desired location.

Development of Modular Mission Packages Providing Focused Warfighting Capability for the Littoral Combat Ship

The US Navy has been involved in the development of a new class of combatant ship called the Littoral Combat Ship (LCS). The LCS is designed to operate more effectively in the littoral environment by providing enhanced maneuverability through the seaframe's inherent ability to operate at high speeds and in shallow waters. Additionally, to counter the high threat environment of the littorals and to enhance the mission commander's options at reasonable cost, the LCS is designed to augment its core self-defense capability with modular mission packages (MPs) that provide focused warfighting capabilities. The LCS MPs are classified as systems-of-systems (SoSs) as they are made up of: mission systems, support equipment, software, mission crew detachments, and aviation systems; and then integrated into a larger SoS to deliver unique capability. To support the accelerated development schedule, PMS 420 is using an evolutionary acquisition process to provide continuous improvements in warfighting capability over time. The initial MP increments are specifically designed to augment the warfighting areas of Anti-Submarine Warfare (ASW), Mine Countermeasures (MCM), and Surface Warfare (SUW). Modularity, an open business model, and open system architectures are key enablers supporting the future insertion of new technologies into the MP baseline. The paper will provide a brief overview of the LCS seaframe designs as they impact MP development, but will focus on the development and maturation of the MPs as SoSs. A definition of what composes an MP will be presented along with the perceived benefits and challenges of developing focused warfighting capability separate from the seaframe design. The present status of the SUW, ASW, and MCM MPs will be reviewed as well as their respective incremental development plans. The joint developmental relationship between PMS 420 and PMS 501 will be discussed with respect to the definition and management of seaframe-MP interfaces. The techniques and methodologies used by PMS 420 in controlling SoS development and evaluating the technical and programmatic performance of the three MPs will be presented. The extensive use of the government laboratories to fulfill the lead system integration role will be presented and the methodology used by PMS 420 in transitioning technologies developed by PMS 420 and/or other program offices for incorporation into MPs will be reviewed.

High-Resolution Sonars: What Resolution Do We Need for Target Recognition?

Target recognition in sonar imagery has long been an active research area in the maritime domain, especially in the mine-counter measure context. Recently it has received even more attention as new sensors with increased resolution have been developed; new threats to critical maritime assets and a new paradigm for target recognition based on autonomous platforms have emerged. With the recent introduction of Synthetic Aperture Sonar systems and high-frequency sonars, sonar resolution has dramatically increased and noise levels decreased. Sonar images are distance images but at high resolution they tend to appear visually as optical images. Traditionally algorithms have been developed specifically for imaging sonars because of their limited resolution and high noise levels. With high-resolution sonars, algorithms developed in the image processing field for natural images become applicable. However, the lack of large datasets has hampered the development of such algorithms. Here we present a fast and realistic sonar simulator enabling development and evaluation of such algorithms. We develop a classifier and then analyse its performances using our simulated synthetic sonar images. Finally, we discuss sensor resolution requirements to achieve effective classification of various targets and demonstrate that with high resolution sonars target highlight analysis is the key for target recognition.

A Meta Study of Transfer of Training

A Meta study of four empirical studies of simulator training was performed. The empirical studies were performed at a battle tank simulator, a combat vehicle simulator, an active sonar anti-submarine warfare simulator, and at a simulated command and control staff exercise of an international naval mine countermeasures mission. The combined number of participants in the Meta study made use of inferential and causal statistics possible. The results showed higher ratings of motivation/fun and effect on reality than fidelity. This suggests that a simulator can provide both motivating and valuable training even if it does not have very high fidelity. The casual analysis with LISREL provided a model showing that the feeling of involvement in the simulation influences the training in the simulator, which in turn has a positive influence on the transfer of training to real world performance. Since the analysis is based on amalgamated data from different studies with partly different conditions, site specific models may be different.

Improving autonomy and control of autonomous surface vehicles in port protection and mine countermeasure scenarios

AbstractRecent experimentation with autonomous surface vehicles (ASVs) has focused on the use of such platforms to perform tasks of classification or identification of objects first discovered by another sensor. The ASV generally carries small sensors capable of high‐resolution imaging, but only at relatively short ranges. Reacquisition of a contact is inherent in the problem of classification and involves positioning of the surface vehicle with good precision such that the object of interest is in the field of view of the sensors aboard the ASV. This critical task of positioning the vehicle such that the classification sensors can be effectively brought to bear is the primary goal of our autonomy development. Experimental results from a variety of sensors are presented, but the most important in our present work has been a high‐resolution multibeam imaging sonar operating at 450 kHz. This sensor has been successfully used to image divers and bottom objects, with telemetry data sent back to shore via wireless LAN. Although classification was done by a human operator ashore, the vehicle has the capability to keep an object in view of the sensor, representing an important operational advantage of the autonomy. Future work could expand the role of the unmanned platform to deployment of effectors—warning devices or entanglement devices in the case of harbor protection missions or neutralization devices in the case of countermine operations. © 2010 Wiley Periodicals, Inc.

Mechanical Properties of Epoxy Resin – Fly Ash Composite

There has been significant increase in use of glass fibre reinforced composites as structural materials in naval mine countermeasure surface ships. Sea mines when detonated emit underwater shock waves, which could impart severe loading to naval ship structure; there are attempts to model the response of a ship structure to this loading. For the model to be accurate & useful material property data determined experimentally by taking different weight percentage of glass fibers (E-300, mat form) with epoxy resin & comparison with fly ash reinforced composite. Specimens in the form of cube of size 10X10X10 (mm’s) are used & results are presented. Fracture behaviour of composite can also be studied using SEM. SEM analysis is done to observe distribution of fly ash particles in matrix, resin fly ash interface, glass fibre matrix interface, glass fibre distribution etc,.

Space-time-frequency analysis of the scattered acoustic wave field from elastic shells recorded by bistatic sonar systems.

An ongoing challenge for underwater sonar systems is to discriminate a man made target (shell) from surrounding clutter returns and to provide robust classification features for the estimation of the physical target characteristics (e.g., shell thickness and material properties). To this end, time-frequency analysis, and, in particular, Wigner–Ville analysis, has been shown to provide a robust processing tool for interpreting the evolutional time dependent aspect of the scattered acoustic wave field from elastic shells. The design of a robust space-time-frequency bistatic sonar system to enhance the target detection of shells with the use of a sensor array will be presented. Practical implications for bistatic mine countermeasure sonar systems, using a network of autonomous underwater vehicles, will be discussed.

An efficient underwater coverage method for multi-AUV with sea current disturbances

This paper presents an online coverage method for the exploration of unknown oceanic terrains using multiple autonomous underwater vehicles (AUVs). Working from the concept of planar algorithm developed by Hert, this study attempts to develop an improved method. Instead of theoretical research, it focuses on the practical aspects of exploration by considering the equations of motion for AUVs that are actually used in oceanic exploration as well as on the characteristics of complex oceanic topography and other realistic variables, such as sea current. These elements are used to calculate cross track error (CTE) and path width for AUV movement. The validity of the improved algorithm for terrain coverage is first verified mathematically and then by a simulation of the real underwater environment that analyzes the path length and time taken for the coverage as well as the missed areas, which is the key element of efficiency. In order to apply the improved method to the multi-AUV operation, each AUV was assigned a covering or a scanning role by means of a dynamic role-changing mechanism. The results showed that the multi-AUV operation has an advantage over a single-AUV operation in many ways. The method proposed in this study will be useful not only for commercial applications but also for mine counter-measures (MCMs) and rapid environmental assessments (REAs) as part of naval military operations as well. We also believe that it will be ideal for use in variable oceanic environment, particularly in shallow water terrains. For the purposes of this study, we assume that the communication between AUVs is problem-free.

Coherent space‐time‐frequency processing to enhance the bistatic detection and classification of elastic shells in shallow water.

For underwater sonar, time‐frequency analysis has been shown to be a powerful tool for detection and classification of man‐made targets. For instance, with traditional monostatic systems, a key energetic feature of spherical shell is the coincidence pattern, or midfrequency enhancement, that results from antisymmetric Lamb‐waves propagating around the circumference of the shell. The development by the Navy of mine countermeasure sonar systems, using a network of autonomous systems, provides a mean for multiple bistatic measurements, and thus potentially bistatic enhancement for target detection. However, time‐frequency representations of bistatic simulations of scattered signals from spherical shell show that this coincidence pattern typically shifts in both time and frequency with respect to the monostatic case. Hence, this time‐frequency shift is challenging for bistatic target detection algorithms based on standard array processing techniques. Design of robust multistatic sonar system based on the generalized space‐time‐frequency coherence of the bistatic measurements will be discussed. The influence of the source‐receiver configuration and interface reflections on the proposed approach have been investigated numerically and experimentally using data collected in shallow water with an elastic spherical shell [Work supported by ONR Code321, N000140810087.]

Weak shock propagation in the ocean and marine sediments.

The nonlinear progressive wave equation (NPE) [B. E. McDonald and W. A. Kuperman, JASA 81, 1406 (1987)] was initially developed to model weak shock waves in a refracting medium (specifically, ocean acoustic convergence zones). It has been refined to include high-angle and two-way propagation. Inclusion of two-way propagation improves agreement with empirical power laws for peak pressure from an explosive as a function of range and explosive charge. The NPE is currently being used to examine weak shock propagation into marine sediments for studies related to mine countermeasures. An intriguing behavior results from the stress-strain relation for Hertzian granular media, in which stress is proportional to the 3/2 power of strain rate. Numerical and analytic solutions with the Hertzian nonlinearity reveal its most nonlinear behavior (shock formation) near zero stress, whereas in a fluid, shock formation results from high stress. Numerical experiments are presented to determine whether shocks resulting from Hertzian nonlinearity can be observed with nominal values of frequency-linear attenuation common to granular media. [Work supported by the Office of Naval Research.]

Use of the AN/AQS-20A tactical mine-hunting system for on-scene bathymetry data

The effectiveness of mine countermeasures is dependent, in part, on how well warfighters know the ocean environment. Often, knowledge is outdated, in error or absent, requiring rapid environmental assessment on-scene. One way to obtain this assessment is to make dual use of the tactical data from military sensors to extract environmental information. Here, we discuss calibration and data uncertainty associated with using the multibeam volume search sonar onboard a AN/AQS-20A towed mine hunting system to extract multibeam bathymetry data based on data sets obtained from five demonstration flights conducted off the coast of Panama City, Florida. We compare the extracted bathymetry to overlapping data sets from dedicated multibeam echo-sounder systems and find a bias correction for the system. We also identify inaccurate knowledge of the sound velocity profile as a source of measurement error, discuss mitigation of it where possible, and assess how this error affects the uncertainty of the bias correction.

Superellipse Fitting for the Recovery and Classification of Mine-Like Shapes in Sidescan Sonar Images

Mine-like object classification from sidescan sonar images is of great interest for mine counter measure (MCM) operations. Because the shadow cast by an object is often the most distinct feature of a sidescan image, a standard procedure is to perform classification based on features extracted from the shadow. The classification can then be performed by extracting features from the shadow and comparing this to training data to determine the object. In this paper, a superellipse fitting approach to classifying mine-like objects in sidescan sonar images is presented. Superellipses provide a compact and efficient way of representing different mine-like shapes. Through variation of a simple parameter of the superellipse function different shapes such as ellipses, rhomboids, and rectangles can be easily generated. This paper proposes a classification of the shape based directly on a parameter of the superellipse known as the squareness parameter. The first step in this procedure extracts the contour of the shadow given by an unsupervised Markovian segmentation algorithm. Afterwards, a superellipse is fitted by minimizing the Euclidean distance between points on the shadow contour and the superellipse. As the term being minimized is nonlinear, a closed-form solution is not available. Hence, the parameters of the superellipse are estimated by the Nelder-Mead simplex technique. The method was then applied to sidescan data to assess its ability to recover and classify objects. This resulted in a recovery rate of 70% (34 of the 48 mine-like objects) and a classification rate of better than 80% (39 of the 48 mine-like objects).

Time-frequency variations of the bistatic scattering response of proud and buried elastic shells in shallow water: Implication for mine counter-measure sonar systems.

For underwater sonar, time-frequency analysis has been shown to be a relevant tool for the detection and classification of man-made targets (shell). For instance, for traditional monostatic systems, a key energetic feature of spherical shell is the coincidence pattern, or midfrequency enhancement, that is created by the coherent addition of antisymmetric Lamb-waves propagating clockwise and counterclockwise around the shell. The development by the Navy of mine countermeasure sonar systems, using a network of autonomous systems in unmanned vehicles, provides a mean for bistatic measurements, and thus potentially bistatic enhancement for target detection. We have investigated the time-frequency variations of the bistatic scattering response of elastic shells. The influence of the medium parameters as well as the source-receiver configuration will be investigated in free space and then extended to the case of a shallow water waveguide. In particular, we studied the bistatic variations of the coincidence pattern for classification purposes. Finally, the design of a robust space-time-frequency bistatic sonar system will be discussed to enhance the target detection of shells with the use of multiple sensors.

Advanced ATR techniques based on High-Resolution SAS Sensors

Automatic Target Recognition (ATR) is a key element of expeditionary Mine Countermeasures (MCM) and port protection operations. Most existing approaches to ATR are currently based on high resolution sonar sensors, which provide enough information to obtain satisfactory detection and classification performance for the large World War 2 mine types (e.g., 2 m long cylinder). False alarm rates, however, are still unacceptably high for modern mines, which constrains the way operations are undertaken and often requires either confirmation or re-evaluation by a human operator. The introduction of new AUV-mounted Synthetic Aperture Sonars (SAS) increases the resolution, quality and range of acquired sonar images, which broadens the set of machine vision and computer image analysis techniques that can be used for underwater ATR operations. In this paper we study the impact that the increased quality and resolution have on performance gains and false alarm reduction. A number of classification algorithms are selected to represent the pool of existing approaches to target detection and classification, and their performances are estimated using both simulated and real image data in order to quantify the benefits associated to the new SAS technology. Evolution and near-future plans are discussed, introducing emerging bio-sonar sensors, anomaly detectors and autonomous AUV systems.

Multiple-sensor fusion approach to seabed classification

Seabed classification is key issue for civilian and military underwater applications, from offshore exploitation to mine counter measure. Most of the existing automated classification techniques relies on the analysis of the data provided by a single sensor, supposed to unambiguously separate the different classes of seabed. In this paper we present a different approach which considers that, even if a sensor cannot tell the differences between two classes, classification will improve by considering that the seabed belongs to one of these two classes, and, further, that the analysis of the data from another sensor can resolve the ambiguity. For each sensor, the classification is achieved in a conventional way by feature extraction and supervised classification. The fusion of the results implements the theory of evidence through Dempster-Shafer method. After a description of the method, the paper discusses the experimental results from the fusion of information delivered by three sensors: an imaging sidescan sonar, a vertical echo sounder and an interferometric bathymetric sonar. The major part of the experimental data has been acquired by towed or hull mounted sensors. As these sensors are a subset of the payloads operated simultaneously by the new DGA-SHOM DAURADE AUV, preliminary seabed classification results in covert REA missions will also be presented and discussed.

Naval Mine Countermeasure Missions

Undersea operations using autonomous underwater vehicles (AUVs) provide a different and in some ways a more challenging problem than tasks for unmanned aerial vehicles and unmanned ground vehicles. In particular, in undersea operations, communication windows are restricted, and bandwidth is limited. Consequently, coordination among agents is correspondingly more difficult. In traditional approaches, a central planner initially assigns subtasks to a set of AUVs to achieve the team goal. However, those initial task assignments may become inefficient during real-time execution because of the real-world issues such as failures. Therefore, initial task allocations are usually subject to change if efficiency is a high concern. Reallocations are needed and should be performed in a distributed manner. To provide such flexibility, we propose a distributed auction-based cooperation framework, distributed and efficient multirobot-cooperation framework (DEMiR-CF), which is an online dynamic task allocation (reallocation) system that aims to achieve a team goal while using resources effectively. DEMiR-CF, with integrated task scheduling and execution capabilities, can also respond to and recover from real-time contingencies such as communication failures, delays, range limitations, and robot failures.

Disambiguation Protocols Based on Risk Simulation

Suppose there is a need to swiftly navigate through a spatial arrangement of possibly forbidden regions, with each region marked with the probability that it is, indeed, forbidden. In close proximity to any of these regions, you have the dynamic capability of disambiguating the region and learning for certain whether or not the region is forbidden - only in the latter case may you proceed through that region. The central issue is how to most effectively exploit this disambiguation capability to minimize the expected length of the traversal. Regions are never entered while they are possibly forbidden, and thus, no risk is ever actually incurred. Nonetheless, for the sole purpose of deciding where to disambiguate, it may be advantageous to simulate risk, temporarily pretending that possibly forbidden regions are riskily traversable, and each potential traversal is weighted with its level of undesirability, which is a function of its traversal length and traversal risk. In this paper, the simulated risk disambiguation protocol is introduced, which has you follow along a shortest traversal - in this undesirability sense - until an ambiguous region is about to be entered; at that location, a disambiguation is performed on this ambiguous region. (The process is then repeated from the current location, until the destination is reached.) We introduce the tangent arc graph as a means of simplifying the implementation of simulated risk disambiguation protocols, and we show how to efficiently implement the simulated risk disambiguation protocols that are based on linear undesirability functions. The effectiveness of these disambiguation protocols is illustrated with examples, including an example that involves mine countermeasures path planning.