The 31st Student Poster Competition was held at OCEANS ’12 MTS/IEEE October 14–19, 2012. The venue was the Virginia Beach Convention Center and provided an ideal arrangement for the Student Poster presentation in the Exhibition Hall. The right aisle was designated “University Row” and had exhibition booths from various universities on one side and the Student Posters along the other side of the aisle. Hence the students received many visitors. The Student Poster competition was organized by Mr. Robert Heitsenrether, NOAA/NOS/CO-OPS and assisted by Dr. Christophe Sintes, Institut TELECOM Bretagne, France. The program was funded by a grant from the Office of Naval Research. Eighty four student poster abstracts were received and reviewed. Twenty four posters were accepted. Six were unable to attend and at the last minute one additional student dropped out. Seventeen posters were displayed, reviewed, and judged.
The Student Program began with an organizational meeting on Monday. October 14, 2012. The students were given instructions on when to be at their posters along with expense report forms and general instructions on meeting with the visitors. Each student was then introduced and gave a short summary of their work and poster. Following the opening plenary session on Tuesday morning the students went to their posters and continued there at break times and noon times. Each judge received a package of judging forms and instructions as to when to have them completed. All proceeded well and on Wednesday afternoon the judges turned in their forms and Mr. Heitsenrether and Mr. Norman D. Miller selected the winning posters.
The Student Awards Presentation was held in the Exhibition Area during the lunch break on Thursday 17 October. Mr. Heitsenrether called the students forward and each received a certificate of participation from the Conference Chairman, Mr. Ray Toll. Mr. Heitsenrether then called Mr. Norman Miller, OES Student Activities Coordinator, to come forward to present the awards. Each award winner received an engraved plaque along with a prize check. Photos were taken at each presentation. At the conclusion of the awards Mr. Miller welcomed them all to “The OCEANS Student Poster Alumni Association” and they were all given a big hand. Group photos were then taken and the awards ceremony was concluded. The students receiving awards were:
||Giancarlo Troni—Johns Hopkins University
||Augustin Saucan, Institut Telecom-Bretange and Bruno Ferrrita, Faculty of Engineering, University of Porto
||Amy Gao, Massachusetts Institute of Technology, Jonathan Odom, Duke University, and Jon Loftis, Virginia Institute of Marine Science
The students, their schools, poster titles and abstracts are listed below:
Amy Gao, Massachusetts Institute of Technology, Bio-Inspired Pressure Sensing for Active Yaw Control of Underwater Vehicles
Abstract—A towed underwater vehicle equipped with a bioinspired artificial lateral line (ALL) was constructed and tested with the goal of active detection and correction of the vehicle’s angle of attack. Preliminary experiments demonstrate that a low number of sensors are sufficient to enable the discrimination between different orientations, and that a basic proportional controller is capable of keeping the vehicle aligned with the direction of flow. We propose that a model based controller could be developed to improve system response. Toward this, we derive a vehicle model based on a first-order 3D Rankine Source Panel Method, which is shown to be competent in estimating the pressure field in the region of interest during motion at constant angles of attack, and during execution of dynamic maneuvers. To solve the inverse problem of estimating the vehicle orientation given specific pressure measurements, an Unscented Kalman Filter is developed around the model. It is shown to provide a close estimation of the vehicle state using experimentally collected pressure measurements. This demonstrates that an artificial lateral line is a promising technology for dynamically mediating the angle of a body relative to the oncoming flow.
Enric Galceran, University of Girona, Coverage Path Planning for Marine Habitat Mapping
Abstract—A framework for generating coverage paths for marine habitat mapping is proposed in this paper. The framework combines two existing coverage path planning algorithms with new ideas to provide automated, efficient survey paths that take into account the particularities of the application. On one hand, a recent algorithm especially targeted for marine environments is used to generate a survey path of a previously unmapped area. The method has the advantage of minimizing repeated coverage when using a surface vehicle or while surveying at constant depth with an underwater vehicle. On the other hand, only the regions where the marine habitat is present (which often come in the form of widespread “blobs”) need to be surveyed in future monitoring missions in the area. However, due to the changing nature of the marine habitats, determining the exact extent of those regions prior to mission is not possible. Rather than surveying the whole area anew, we propose to use a sensor-based planner that, given their approximate locations from a previous survey, covers the regions of interest (ROIs) on-line using acoustic or optical camera information. Additional procedures to generate a path that visits all the ROIs are provided. The approach is tested in simulation using a real world bathymetric dataset and synthetic ROIs. Results show the feasibility of the proposed approach.
Yukihiro Kida, Kyoto University, Applications of Full-Wave Intervention techniques to the estimation of the sound velocity structure in the ocean
Abstract—The travel-time inversion method has been developed using a ray-tracing scheme in the Munk’s Ocean Acoustic Tomography (OAT) method. The method has some similarity with seismic exploration both in the theory and data processing methods except for the direct utilization of waveform in seismic exploration. The waveform analysis is a powerful tool to investigate the velocities in the areas of interest, and the importance to use waveform is widely recognized in seismic explorations. However there are few precedent studies dealing with waveform inversion in the application of OAT. This study investigates the effectiveness and applicability of the full waveform inversion method to estimate underwater sound velocity structures. We use an adjoint-state method for the calculation of the gradient in an iterative inversion based on a pre-conditioned conjugate gradient method. We first demonstrate results from a full waveform inversion method applied to a synthetic dataset that reflects the sound velocity structure. The results are then compared with those from a conventional ray-based travel time inversion method to evaluate the effectiveness of the method. The results show that the full waveform inversion method could provide more precise image with higher resolution than the ray-based method. The full waveform inversion method is also applied to a VCS experiment field data in Lake Biwa. In spite of very limited path condition using only direct arrival wave, the full waveform inversion method could describe the horizontal velocity structure possibly due to seasonal thermocline in the lake. We conclude that the FWI method could be the key success factor for the higher resolution at estimation of underwater sound velocity structure.
Katrina Legursky, University of Kansas, A Modified Model, Simulation, and Tests of a Full-Scale Sailing Yacht
Abstract—Sailing yachts have great potential to act as future long-term oceanic observing platforms, yet to date there have not been complete autonomous sailing systems robust enough to handle long term operation in the harsh and continually changing ocean environment. The basis of control system design is a mathematical model capable of describing and capturing the physics based dynamics of the sailboat. The mathematical model represents the system to be controlled, however, a sailing yacht is a very difficult system to model from a controls perspective because of its heavy reliance on the uncontrolled spatial and temporal distribution of the wind. Presented in this paper is a modified aerodynamic force model which includes the sail angle as a control input to the sailing yacht system. The new model has been incorporated into a 4 degree of freedom (DOF) rigid body dynamic yacht model, and implemented in MATLAB/Simulink. The simulations shows model exhibits similar behavior to that observed in full scale sailing yacht sea trial data. Data taken aboard a Precision 23 day-sailer is analyzed, and it is found that the model is a likely candidate for including sail input to a physics based dynamic model for identification and control system design.
Paul Perez, Clarkson University, Techniques to enhance the performance of hybrid lidar-radar ranging systems
Abstract—Hybrid lidar-radar uses a combination of techniques to enhance underwater detection, ranging, and imaging. In turbid water, the lidar return signal includes a significant amount of backscatter in addition to the object-reflected light. System performance is highlylimited by the backscatter which results from volumetric scattering of the transmitted light signal off the particulates existing in the water channel. A new backscatter reduction technique based on spatial frequency filtering will be discussed. The spatial filter algorithm leverages radar techniques developed to enhance through the wall imaging (TTWI) performance. Algorithm validation via experimental data is provided.
Jonathon Odom, Duke University, Time-varying Array Shape Estimation by Mapping Acoustic Field Directionality
Abstract—This paper introduces a towed-array shape estimation technique that exploits the directional structure of the time-varying acoustic field. Unlike conventional array shape estimation methods that use discrete sources of opportunity, the proposed approach does not assume knowledge of the number of sources in the field or their estimated directions. Instead, the entire time-varying field directionality map is used. Additionally, maneuverability of the array is exploited to improve endfire resolution and left/right discrimination for a nominally linear array. The algorithm forms an approximate joint maximum likelihood estimate of time-varying field directionality and array shape using an iterative Expectation-Maximization (EM) approach. Simulations are given to evaluate the array shape estimation error during a maneuver. In a simulated multi-source scenario, the proposed method is shown to be more robust than methods that rely on direction-of-arrival estimation when the full field around the array is considered.
Heather Beem, Massachusetts Institute of Technology, Characterization of a harbor seal whisker-inspired flow sensor
Abstract—A sensor with the undulatory geometry of a harbor seal whisker has been designed, fabricated, and characterized for use as a mechanical sensor of flow velocity. Bend sensors at the whisker base provide deflection information in four directions. A waterproof design with a pressure housing has been made, allowing the sensor to operate at depth, in a stand-alone configuration. Characterization was performed by correlating tip deflection to voltage output in each of the four sensors.
Augustin Saucan, Institut Telecom-Bretagne, Enhanced sonar bathymetry tracking in multi-path environment
Abstract—In this paper we address DOA estimation for the side scan sonar in the presence of multiple interfering echoes. We illustrate the potential usage of high resolution methods and tracking algorithms. The proposed tracking algorithm is based on a apriori information on the sea-floor DOA angle. Because of the non-linearity of the model and non-Gaussian behavior of the observed 4600 data, the implementation of the proposed algorithm is based on the particle filter. The proposed tracking algorithm is shown to be able to resolve the multi-path interference problem. The heavy-tailed/non-Gaussian character of the data is noted and the Laplace distribution is shown to better characterize the tails of the observed data. The multivariate Laplace distribution is derived for the observed data and the particle filter coupled with the multivariate Laplace distribution is shown to provide better estimates than with the Gaussian assumption.
Aaron Fittery, Massachusetts Institute of Technology, OmniEgg: A Smooth, Spheroidal Appendage Free Underwater Robot capable of 5 DOF Motion
Abstract—This paper describes the performance of a new type of highly maneuverable underwater robot developed at MIT. The robot, titled “Omni-Egg,” is smooth, spheroidal, and completely appendage free. Propulsion is provided using a novel pump-jet system that can be completely built into the streamlined shell. No fins or stabilizers are used on the vehicle, and directional stability is instead achieved using feedback control. Experimental results show how the turning performance of this smooth design is superior to a similar one that uses fins to achieve stability. Due to this unique design the robot is capable of unique motions such as forward and reverse motions, high speed turning, and sideways translations. This type of robot is designed for tasks requiring a large degree of maneuverability within tight spaces. Some examples of such tasks include the inspection of water-filled infrastructure and the exploration of cluttered environments. Such applications have a high risk of collisions or snagging on obstacles, so a smooth outer shape is desirable. The vehicle is designed to be capable of 5 DOF, and surge, sway, heave, and yaw are all demonstrated in this paper. Pitch, the 5th DOF, remains under development.
Jesse Pentzer, The Pennsylvania State University, Autonomous Underwater Navigation Using Inter-Vehicle Ranging
Abstract—One-way-travel-time (OWTT) acoustic ranging has received considerable attention as improvements to acoustic modems and electronic clocks have made it a feasible navigation tool. This paper reports the results of simulations investigating the effect of utilizing inter-vehicle ranging for autonomous underwater vehicle (AUV) navigation. In these simulations, a fleet of AUVs operates in shallow water with a pair of fixed transponders. A rigid timing cycle for acoustic communications was implemented with a message queuing approach to simulate the handicaps of underwater acoustic communication. Furthermore, a simple path following algorithm was used to navigate the AUVs through a waypoint course, and a kinematic motion model was used to simulate AUV movement. The position of each vehicle in the fleet was estimated independently by combining the propagation steps of an extended Kalman filter with the update equations of an extended information filter. Results of the simulations showed the addition of inter-vehicle ranging improved accuracy by 1-2 cm when navigating using four fixed transponders and by 9-24 cm when navigating using two fixed transponders.
Giancarlo Troni, Johns Hopkins University, Experimental Evaluation of a MEMS Inertial Measurements Unit for Doppler Navigation of Underwater Vehicles
Abstract—This paper reports the results of an in-water laboratory experimental evaluation of the attitude estimation accuracy of a low-cost micro-electro-mechanical systems (MEMS) attitude and heading reference system (AHRS), and the effect of the accuracy of this sensor on Doppler-based underwater navigation. We report a comparative analysis of Doppler navigation obtained employing MEMS AHRS in comparison to Doppler navigation obtained with a high-accuracy inertial navigation system (INS) including a true-North-seeking gyrocompass and high precision accelerometers. The data indicate that Doppler navigation performance with MEMS AHRS is sensitive to instrument calibration including Doppler/AHRS alignment calibration, calibration of AHRS magnetometers for hard-iron & soft-iron errors, and calibration of AHRS angular rate sensors. When carefully calibrated, MEMS AHRS Doppler navigation error is shown to be within an order-of-magnitude of that obtained with high-end INS for the conditions and vehicle trajectories studied. The goal of this evaluation is to quantify Doppler navigation performance using MEMS AHRS. These results may be useful in the development of lower-cost Doppler navigation systems for small and low-cost underwater vehicles.
Yoann Ladroit, Institut Telecom-Bretagne, Maximum Likelihood Estimator based on Quality Factor for Bathymetric Multibeam Echosounder
Abstract—For modern multibeam echosounders, the use of a robust and reliable quality estimator associated with each sounding is an absolute necessity. Indeed, due to the large volume of data acquired, a lot of time is lost, both during the survey and the post-processing. This is a costly problem for hydrographers. The definition of a quality estimator based on the characteristics of the beamformed signal gives an answer to this problem. It has been successfully implemented by several sonar manufacturers and its relevance in measuring the quality of each sounding has been demonstrated. Based on the Quality Factor and on the existing way of processing a sounding, we defined a new sounding estimator using a maximum likelihood approach. This new approach was developed under several hypothesis which are plausible under certain conditions. This new estimator was successfully tested and implemented on real data with good results.
Yukang Liu, University of Kentucky, Phase Modes Circular Array Superdirective Beamforming
Abstract—Circular arrays are widely used in underwater acoustics array signal processing due to their two dimensional symmetrical characteristics. In this paper a new method to analytically calculate the superdirective mode coefficients of the phase modes circular array beamforming is proposed. The maximum Directivity Index (DI) achievable for phase modes circular array beamforming is also derived. Computer simulation is held for a circular array composed of 12 separate hydrophones mounted on either open sphere or rigid sphere. The calculated DI achieved by the proposed superdirective beamforming corresponds to the theoretical maximum DI for up to the 5th order. The proposed method to calculate the superdirective mode coefficients is also applicable for calculating mode coefficients for arrays of any shape and any kind of expansion, indicating its wide range of applications in superdirectivity beamforming.
Samir Ouelha, DCNS, On time-frequency representations for underwater acoustic signal
Abstract—In order to develop a new human perception inspired process useful for underwater acoustic signal processing, the purpose of this paper is to present a new human physiology based time-frequency representation. This method is based on the use of the Mel filters, classicaly used for the voice recognition. Several experimentations on real underwater signals are presented and discussed.
Bruno Ferreira, INSEC TEC—University of Porto, Towards cooperative localization of an acoustic pinger
Abstract—This paper tackles the problem of localization of an acoustic pinger by a team of cooperative marine robots. A pinger, whose location is unknown, intermittently emits an acoustic ping which is sensed by hydrophones mounted on marine robots. In addition to position, the instant of emission is unknown. A team of robots carrying a total of four hydrophones is therefore (theoretically) required to estimate the position without ambiguity. The precision of the estimate and the uncertainty critically depend on the position of the hydrophones. In order to obtain the best possible estimation, we explore the possibility of using a cooperative method that leads the robots to points where the overall observability is improved.
Carissa Wilkerson, Virginia Institute of Marine Science, Analysis of Extreme Water Levels in the Lower Chesapeake Bay
Abstract—The lower Chesapeake Bay (LCB) experiences coastal flooding due to both tropical and extratropical systems. Water levels produced from these events is often called storm surge; however, storm tide (a combination of the predicted tide, storm surge, and local anomaly), is a more appropriate term. Storm tide levels vary spatially in the LCB. Here we assess this spatial variability relative to local datums, such as highest astronomical tide (HAT) and mean lower low water (MLLW). We determined whether there was any difference in hours above HAT between each of our stations for each storm. We revealed a trend that central bay stations, such as Windmill Point and Lewisetta, spend more time above HAT than the stations in the south bay and Washington. The maximum water level above MLLW and HAT was determined for each station and storm and then analyzed for spatial trends. We found that, in general, central bay stations have smaller maximum heights above HAT than the south bay stations. Washington does not follow the pattern of other large tidal-range stations, such as the south bay stations.
Jon Loftis, Virginia Institute of Marine Science, Simulation of Coastal Inundation Instigated by Storm Surge, River Discharge, and Precipitation in the Chesapeake Bay Using Sub-grid Modeling with LIDAR Digital Elevation Models
Abstract—A storm surge is an aperiodically anomalous rise of sea level accompanied by a tropical or extratropical storm system, wherein water level is the distinction between the observed sea level and the forecasted water level (Blain et al., 1994). Several distinct processes can potentially alter the water level in tidal regions; the pressure effect, the wind effect, the Coriolis effect, the wave effect, and the rainfall effect (Harris, 1963). Coastal inundation initiated via storm surge along the U.S. East Coast is a substantial threat to residential properties, community infrastructure, and human life. Furthermore, prolonged inundation from heavy precipitation and upland drainage during and after the storm has passed can significantly increase coastal flood damage. There are additional implications for inundated coastal habitats, as a major flood event can dramatically alter the regular function of an ecosystem. In order to mitigate human life loss and damage of coastal properties, several numerical models have been developed to provide an early warning system for storm surge and inundation events in various coastal study areas. Modeling of the Chesapeake Bay has been successfully performed previously with the serial version of SELFE (Cho, 2009). To expand upon this success, this study will make use of the MCI parallel version 3.1 of SELFE to capitalize on the additional computing power provided to process a large domain cast on a spherical coordinate system. These features being of paramount importance for a large-scale super regional model, the entire model domain covers the U.S. Atlantic coastline from 30 to 42°N (Figure 1). This expansive large domain grid increases the likelihood of properly modeling the effects of an approaching tropical storm system.