P.-P. Beaujean

Simulating communication during multiple AUV operations

Communication between multiple autonomous underwater vehicles is challenging and best addressed by considering it as a networking problem. Treating the vehicles as the nodes of an ad hoc network consolidates much of the complexity of the communication system in the networks routing protocol. We discuss the many issues associated with the development of routing protocols and consider some existing protocols. The number and duration of in situ trials necessary during the development, testing, evaluation and refinement of these protocols makes a simulation tool invaluable. The requirements of such a simulator are compared with the capabilities of several existing simulators. We propose the design for a new simulator and discuss its implementation.

High-level fuzzy logic guidance system for an unmanned surface vehicle (USV) tasked to perform autonomous launch and recovery (ALR) of an autonomous underwater vehicle (AUV)

There have been much technological advances and research in Unmanned Surface Vehicles (USV) as a support and delivery platform for Autonomous/Unmanned Underwater Vehicles (AUV/UUV) or Remotely Operated Vehicles (ROV). Advantages include extending underwater search and survey operations time and reach, improving underwater positioning and mission awareness, in addition to minimizing the costs and risks associated with similar manned vessel operations. The objective of this paper is to present the design and development a high-level fuzzy logic guidance controller for a WAM-V 14 unmanned surface vehicle (USV) in order to autonomously launch and recover a REMUS 100 autonomous underwater vehicle (AUV). The approach to meeting this objective is to develop ability for the USV to intercept and rendezvous with an AUV that is in transit in order to maximize the probability of a final mobile docking maneuver. Specifically, a fuzzy logic Rendezvous-Docking controller has been developed that generates Waypoint-Heading goals for the USV to minimize the cross-track errors between the USV and AUV. A subsequent fuzzy logic Waypoint-Heading controller has been developed to provide the desired heading and speed commands to the low-level controller given the Waypoint-Heading goals. High-level mission control has been extensively simulated using Matlab and partially characterized in real-time during testing. Detailed simulation, experimental results and findings will be reported in this paper.

Chirp FSK modem for high reliability communication in shallow water

A high reliability shallow water acoustic modem has been developed for communication between AUVs and for general oceanographic use. The modem uses 56 narrowband chirp FM pulses, each centered at a unique frequency located in the range of 20 kHz to 30 kHz. Communication rates vary from 300 bps to 2400 bps, depending on the transmission mode. Packets of information are synchronized using two dedicated chirp pulses, followed by transmission format information. In the auto-baud mode, the modem uses information gathered from previous transmissions for adaptation of baud rate to the acoustic environment. At the lowest rate (300 bps), frequency hopping in combination with a one-of-eight mode of transmission is used to provide maximum SNR and immunity to multipath interference. Performance analysis is presented.

Coherent path measurement for characterization of the underwater acoustic channel

A novel method of underwater acoustic communication is being developed that does not rely on single or multichannel adaptive equalization methods which degrade in the presence of severe time varying multipath. The new method, called the coherent path beamforming (CPB) method uses eigen vectors for characterizing the underwater acoustic communication channel. In the output of the CPB, each of the many channels represents a vertical beam that is focused in the direction of correlated acoustic energy arriving at the array of vertically spaced sonar elements. Within each of the CPB principal beams, nulls are formed in the direction of the remaining acoustic paths thereby canceling interference. A vertical array of 64 elements operating at 245 kHz has been used in shallow water experiments to evaluate performance under various conditions. The experiments were performed in shallow water high multipath conditions off Boca Raton. Results are presented for fixed platform communication.

High-resolution imaging sonar and video technologies for detection and classification of underwater munitions

This study explores two aspects of the munitions detection and classification process: (1) Multiple-Aspect Fixed-Range Template Matching (MAFR-TM) for detection and classification of the potential target; and (2) high-resolution mapping of an environment using a high-frequency sonar system to determine footprints of areas with munitions present, as well as target localization in a wide-area survey and to perform detailed surveys for individual detected items during a re-acquisition process. Testing on the MAFR-TEM approach was carried out using a test tank and a realistic field environment (a marina). The results indicate that the detection algorithm performs fairly well with the tank data and realistic field data.

SFOMC: A SUCCESSFUL NAVY AND ACADEMIC PARTNERSHIP PROVIDING SUSTAINED OCEAN OBSERVATION CAPABILITIES IN THE FLORIDA STRAITS

To succeed at developing a nationwide Integrated Ocean Observing System (IOOS), stakeholders in academia, government, and industry must forge and maintain strategic partnerships. The South Florida Ocean Measurement Center (SFOMC) is such a partnership model and mutually beneficial collaboration that is conducting year-in and year- out major at-sea operations, sustaining the operation of a complex array of sub sea sensors, and providing the maintenance and the shore-based infrastructure to support both. The transformation of a longstanding, narrowly focused, and somewhat antiquated (but highly capable) Navy test and evaluation facility is described. Formerly plagued with a decreasing customer base and increasing operational costs, the Centers transformation into this now fully integrated coalition has mitigated these forerunners of extinction while answering both Navy and academic needs. The successful partnership has resulted in modern facilities, a broad customer base, and steadily decreasing costs of operation. Examples are provided that demonstrate the ability of the Navys South Florida Testing Facility (SFTF) to realize user cost savings and to aid in the convergence of interest and capabilities among a variety of user groups toward the solution of problems of national concern, including naval research, homeland security, and environmental stewardship.

A Dynamometer for an Ocean Turbine Prototype: Reliability through Automated Monitoring

An ocean turbine extracts the kinetic energy from ocean currents to generate electricity. Machine Condition Monitoring(MCM) / Prognostic Health Monitoring (PHM) systems allow for self-checking and automated fault detection, and are integral in the construction of a highly reliable ocean turbine. This paper presents an onshore test platform for an ocean turbine as well as a case study showing how machine learning can be used to detect changes in the operational state of this plant based on its vibration signals. In the case study, seven widely used machine learners a retrained on experimental data gathered from the test platform, a dynamometer, to detect changes in the machinesstate. The classification models generated by these classifiers are being considered as possible components of the state detection module of an MCM/PHM system for ocean turbines, and would be used for fault prediction. Experimental results presented here show the effectiveness of decision tree and random forest learners on distinguishing between faulty and normal states based on vibration data preprocessed by a wavelet transform.

A belief theoretic approach for characterization of underwater munitions

Characterization, management and remediation of military munitions, especially in underwater environments, is a challenging task given all the technical and physical barriers. Optical cameras are better suited for identifying the physical shape of objects. But in underwater, low visibility almost prohibits the use of these cameras. Acoustic imaging is a good alternative to this, but the characteristics of imaging along with numerous artifacts of physical systems which are not easy to model, makes the object recognition task non-trivial. We explore here the possibility of exploiting the geometry of the object shadows for identification of objects itself. The inherited imperfections of the data and the numerous artifacts of sonar systems are counteracted via the use of a fusion algorithm which incorporates evidence from multiple perspectives. A Dempster-Shafer belief theoretic evidence updating scheme which is capable of modeling a wider variety of data imperfections is used for the fusion task. We illustrate the method via the use of real data obtained at a test site located in the Florida Atlantic University premises.

Development of a 3-D forward look electronically scanned sonar system

A 3-D forward look sonar system has been developed and built using the concepts described in the papers presented at the 5th International Symposium on Unmanned Untethered Submersibles [J.M. Cuschieri] and at Ocean 91 [Cuschieri and Ping]. The two main features of this sonar system are the generation of truly 3-D images and the use of continuous random projector signal. Having built the transducer hardware and a developed a method by which the random signal is generated and delayed for the electronic scanning, the first images were collected in a fresh water test tank. The initial images were rather poor due to poor energy distribution within the bandwidth of the projected signal. Modifications in the way the signal is generated have been implemented. Images were again collected in the fresh water test tank and the enhancements to the images documented.

Exploiting multiple sensor modalities for classification of underwater munitions: A Dempster–Shafer theoretic approach

Detection and classification of underwater UXOs (UneXploded Ordnance) is a task that is receiving considerable attention from the DoD and related agencies that are involved in management of military munitions. Achieving a reasonable accuracy in detection and classification of these objects is extremely difficult mainly due to the harsh cluttered underwater environment. It is now an accepted fact that no single sensing technology can be both accurate and cost-effective. Low visibility in underwater exposes a significant limitation to optical cameras which are usually better suited for identifying the physical shape of objects. While acoustic imaging is a good alternative, the characteristics of imaging and physical system artifacts make the object recognition task non-trivial. Multi-sensory fusion provides an avenue to exploit the strengths of individual sensors and modalities while mitigating their weaknesses. We address the problem of fusion of multiple sensory information for the task of underwater UXO ...