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Sectional view of the SMIS-USV, 1 sensor-platform, 2 fuel cell, 3 LiPo-batteries, 4 watertight casted components, 5 gas container
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... heavy sea states the reliable communication area shrinks to the intersection of all resulting sound beams due to the pitch and roll motion of the USV. Transferred to the cone approximation, the angle of beam spread is reduced by the pitch and roll angles and the swept area becomes an elliptic shape. In that way, the vehicle used as deep-sea communication node has to be designed in a special way, as described in Section 4. Furthermore, the automation system and the GNC system have to be developed to secure a reliable localization of the underwater vehicles even in case of harsh environmental conditions. Therefore, the basic dynamic characteristics of the USV will be considered in Section 5. The main requirements influencing the USV design are minimal motions in waves, self-righting behavior after capsizing and minimal resistance. Furthermore, internal space for the equipment has to be provided. In order to limit production costs and efforts, a simplified line arrangement is considered. The requirement of a minimal response to waves and the fast recovery of stability after capsizing seem to be inconsistent. Therefore, a submerged body with three surface piercing struts is considered for the USV, Fig. 6. Moreover, this SWA-Concept (Small Waterplane Area) influenced design reduces the excitation forces due to waves. As reaction to heeling due to lateral wind load, the struts immerge, which generate additional buoyancy and counteract the heeling moment. Moreover, the three surface piecing struts build the base for the antenna platform for terrestrial radio communication and satellite data transfer and provide a ventilation trunk for the fuel cell. The operational components and the payload are located underneath the waterline. The hull wraps the components and forms a hydrodynamic beneficial shape. Most of the components are placed in flooded sections. This has the advantage that heat is released into the environment, and possible gas leakages cannot lead to an explosive mixture. The gas containers supply the hybrid energy concept. The electric motor is supplied by waterproof batteries with an energy capacity for some hours of operation. The SOFC reloads the batteries permanently and extends the operational range up to one week. Dry compartments can be found at the top end of the submerged body and in the center. The fuel cell for instance has to be placed into a dry environment. At the bottom of the USV a modular payload keel is arranged. It enables the user to customize the vehicle to different operational tasks. In the SMIS-arrangement, the acoustic USBL- modem is covered by a streamlined hood, but also scientific sensors like an ADCP (Acoustic- Doppler-current-profiler), a multi-beam sonar or a sub-bottom-profiler are possible payloads. The spatial separation of the heavy elements as batteries and payload at the bottom and air filled compartments at the top leads to a low center of gravity. The center of buoyancy is higher; thereby a positive initial stability is accomplished. The open hull design with flooded compartments makes the vehicle light weight and manageable on deck of an expedition ship, but at the same time inertial enough in operation state to counteract wave and wind loads. The weight in air is about 500 kg but the hull displaces 1250 liters. This feature makes the USV the perfect choice as communication node between satellites and underwater vehicles such as AUVs and stationary bottom based vehicles. For the underwater communication, it is essential to reduce the body motion and keep position above specific coordinates. Every movement (rolling or pitching) would scatter the emission of the acoustic cone over a distance of up to 6000 m. An ambitious task is to determine the hydrodynamic properties. Due to unsteady flow pattern and thereby generated pressure distribution on the vehicles surface, spontaneously increasing moments, mostly in pitch, can appear. This phenomenon, based on the so called Munk-Moment, Munk (1979), and the effect of waves generated from a vehicle on or near the surface, has to be estimated for the autonomous operation over the full speed range. This pitch-/heave instability is also known from SWATH-ships or submarines in surface operation. Therefore, many different variants of the USV (variation of bow geometry, positions of center of gravity, position of struts and so on) were analyzed by unsteady CFD with focus on the dynamic motion behavior over the complete speed range. The final version has an optimized stern to reduce the resistance and due to the arrangement of the struts the pitch-/heave instability could be prevented over the complete speed range with an option to extend the speed range by 50%, Ritz et al. (2014) . The results are shown in Fig. 7. There are still heave and pitch motions with raising velocity, but no immediate instability. Besides analytical and computer aided calculations, a lot of hands-on experience was considered in order to find a suitable design. From several on site expeditions to the Baltic Sea and the Atlantic Ocean on German research vessels, some improvements to existing research equipment can be found in the USV design. The complete stern geometry is made of robust fiber-reinforced plastic and is easily removable in order to increase the accessibility of the complex electronic components. New materials such as lightweight aluminum-foam sandwich panels are used to enhance stiffness and resistance against wave loads. Moreover, hatch covers are installed on deck, thereby quick access to data loggers, gas containers and the fuel cell is guaranteed. A very important aspect of working with research vehicles on site is th e launch and recovery procedure. The seaman’s task to recover the vehicle can be simplified by adding big lugs or handles to the superstructure. The USV has a tightened cable rope between bow tip and first strut. On the aft deck big handles are provided. Nevertheless, cost efficiency is a design criterion as well. The CFD resistance optimized vehicle length reduces the operational cost or increases the operational radius respectively. The midship section geometry is greatly influenced by the dimensions of the fuel cell. This box-shaped section continues along the parallel central body then bends with single-curved alloy-sheets towards the bow tip. The stern is molded, to support a harmonic propeller inflow. To improve the propulsion efficiency, a steering duct was designed. Hence, the ship length could be reduced as the rudder stock is located in the propeller plane and not behind it. Different model descriptions are used during the design process and the operation of marine vessels. In the design process preferably quasi-static models are used in form of motion response amplitude operator (RAO) to identify extreme values in the motion of the vehicle at certain wave frequencies and wave heights. For guidance, navigation and control of marine vehicles, dynamical models of the vessel are needed to be used during the operation. The complexity of the used model depends on its application. For conventional operations of USV for hydrographic surveys in calm water, it is possible to reduce the equations of motion to a lower order dimension. For instance, the given GNC task for measuring USV allows limiting the motion to the nearly undisturbed water surface and neglecting the motions in heave, roll and pitch. Dynamic modeling and parameterization for GNC of measuring USV was described in Kurowski et al. (2015). Obviously, the attitude of the vehicle, especially in roll and pitch, has to be considered with respect to accomplish applications as communication node in a deep-sea monitoring system. On the one hand, the attitude information is fed into the communication system to improve the acoustic localization. On the other hand, the control system uses these data to predict the vehicle motion and adapts the mission control task itself. Motion RAOs are used to determine the behavior of a ship operating in a given state of sea. They are calculated by using potential theory to compute frequency-dependent added mass , potential damping coefficients , restoring matrix as well as amplitudes and phases of the first -order wave load between the vehicle and the waves for a given wave direction and frequency. This correlation can be written in linear case as equation of ...
Context 2
... for the equipment has to be provided. In order to limit production costs and efforts, a simplified line arrangement is considered. The requirement of a minimal response to waves and the fast recovery of stability after capsizing seem to be inconsistent. Therefore, a submerged body with three surface piercing struts is considered for the USV, Fig. 6. Moreover, this SWA-Concept (Small Waterplane Area) influenced design reduces the excitation forces due to waves. As reaction to heeling due to lateral wind load, the struts immerge, which generate additional buoyancy and counteract the heeling moment. Moreover, the three surface piecing struts build the base for the antenna platform ...
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Citations
... [22] Test communication ability based on underwater sound. [23] conducted ocean communications and tested long-distance communications. ...
Surface Vehicles are the product of the development of marine technology. As a new type of technical means, it has been widely used in the field of marine commissioning and defense. However, the testing technology of Unmanned Surface Vehicles is not comprehensive now, and in order to ensure the smooth progress of scientific research projects, testing is necessary, so testing technology is also a smooth part of scientific research projects. This article classifies the existing test research, summarizes the test and evaluation methods, summarizes the tests that have been carried out and speculates the tests that will be carried out in the future for the testing of Unmanned Surface Vehicles.
... In the last decade, much effort has been put into horizontal UWA communication in shallow-water environments. 1-13 By comparison, the vertical UWA communication has attracted much less attention despite its wide deep-sea applications, e.g., the communications between manned submersibles and their mother ships, [14][15][16][17][18][19] the data transmission from autonomous underwater vehicles (AUVs) to the surface, [20][21][22] the data return of seafloor sensors, 23 and vertical uplink transmissions in underwater sensor networks, etc. In this paper, we focus on the deep-sea vertical UWA communication employing the single-carrier transmission technique. ...
... Attributed to the a priori p 1;k , the noise is suppressed in the a posteriori estimation z 1;k , given in Eq. (23). The denoiser then outputs the Gaussian extrinsic PDF with the mean p 2;k and inverse-variance # 2;k given by ...
Vertical underwater acoustic (UWA) communications play a crucial role in deep-sea applications. A vertical UWA channel generally features a moderate multipath but with time-varying Doppler shifts as well as loud impulsive noise. To achieve a robust vertical single-carrier UWA communication, this paper proposes an enhanced iterative receiver. First, a spline interpolation-based timing estimation approach is proposed to compensate for the time-varying Doppler effects efficiently. Then, the residual timing errors and the multipath interference are tackled by a fractionally spaced self-iterative soft equalizer (SISE) based on the vector approximate message passing (VAMP) algorithm. The VAMP-SISE consists of four parts: an inner soft slicer and an inner soft equalizer for symbol detection as well as a denoiser and a minimum mean-squared error estimator for impulsive noise suppression. Different parts iteratively exchange extrinsic information to improve the equalization performance. Last, a channel-fitting irregular convolutional code and a unity-rate code are employed at the transmitter to lower the signal-to-noise ratio threshold for reliable communications. Deep-sea experiments verify the performance superiority of the proposed receiver over existing schemes.
... With the increasing trend of deep ocean activities, underwater acoustic vertical communication has been successfully tested and used in many scenarios. Representative results include communications with the human occupied vehicles (HOV) (Roberts et al., 2012;Zhu et al., 2013), data collection from the seafloor sensors to the unmanned surface vehicle (USV) (Kurowski et al., 2015), real-time seafloor image transmission from the Autonomous Underwater Vehicle (AUV) (Ahn et al., 2017), and communication between the gliders and the satellite surface moorings (Trask and Farrar, 2018). The acoustic communication sys-tem of the HOV Deepsea Challenger, which documented human communication across full ocean depth for the first time, was described by Roberts et al. (2012). ...
... To suppress the noise, a transducer array of 4 elements was lowered to 200-300 m depth, and then four communication methods, including the coherent modulation, the noncoherent modulation, the spread spectrum and the single sideband voice modulation, were simultaneously verified at the distance of up to 7.7 km in the sea trials (Zhu et al., 2013). Kurowski et al. (2015) tested the slant communication and positioning between the USV and the underwater part. A reliable link up to a depth of 6000 m in heavy sea states was assured, and the packages success ratio was smaller than 90% over the distance of 4500 m. ...
... Therefore, the ship noise often leads to a low SNR. Many effective engineering methods have been applied, such as decreasing the data rate, using the low-noise surface platforms (Roberts et al., 2012;Kurowski et al., 2015), or lowering the transducer array to a certain depth (Zhu et al., 2013). Advanced communication techniques without loss of operational convenience or data rate, such as capacity approaching code and modulation schemes (Stojanovic and Beaujean, 2016;Tao, 2016), are more attractive. ...
The Shipborne acoustic communication system of the submersible Shenhai Yongshi works in vertical, horizontal and slant channels according to the relative positions. For ease of use, an array combined by a vertical-cone directional transducer and a horizontal-toroid one is installed on the mothership. Improved techniques are proposed to combat adverse channel conditions, such as frequency selectivity, non-stationary ship noise, and Doppler effects of the platform’s nonlinear movement. For coherent modulation, a turbo-coded single-carrier scheme is used. In the receiver, the sparse decision-directed Normalized Least-Mean-Square soft equalizer automatically adjusts the tap pattern and weights according to the multipath structure, the two receivers’ asymmetry, the signal’s frequency selectivity and the noise’s spectrum fluctuation. The use of turbo code in turbo equalization significantly suppresses the error floor and decreases the equalizer’s iteration times, which is verified by both the extrinsic information transfer charts and bit-error-rate performance. For noncoherent modulation, a concatenated error correction scheme of nonbinary convolutional code and Hadamard code is adopted to utilize full frequency diversity. Robust and low-complexity synchronization techniques in the time and Doppler domains are proposed. Sea trials with the submersible to a maximum depth of over 4500 m show that the shipborne communication system performs robustly during the adverse conditions. From the ten-thousand communication records in the 28 dives in 2017, the failure rate of the coherent frames and that of the noncoherent packets are both below 10%, where both synchronization errors and decoding errors are taken into account.
... During the experiments maximum slant ranges resulting in an angle of beam spread and finally the radius of the base of the communication cone have been calculated by trigonometrical relations. Hence, the acoustical outshined volume or rather the swept area is obtained by the circular surface as shown in Kurowski et al. (2015b). ...
This paper describes the basic characteristics of a six degrees of freedom dynamic model of an innovative ocean-going unmanned surface vehicle. The model is used in an explicit and implicit way to ensure the operation of the autonomously acting vehicle, which serves as communication node between surface and underwater parts of a complex deep-sea monitoring system. In practice, it is a cumbersome task to identify the unknown parameters of such nonlinear models, due to strong couplings of the motion variables, measurement noise and unknown disturbances. In order to parameterize the models, special maneuvers have been carried out to decouple the motions and identify the corresponding parameters. Properties of the acoustic communication has been taken into account when designing the unmanned surface vehicle. Finally, it has been built as a shallow submerged vehicle with water surface-piercing towers to assure a reliable acoustic communication and positioning link up to a depth of 6.000 meters even in heavy sea states. As the vehicle motion has a decisive impact on its operation, the basic characteristics of the motion of the vehicle in waves have been investigated from the quasi-static case using potential theory to simpler dynamic models for the specific degree of freedom. Further, these models are used to design feed forward and feedback controller to ensure the autonomous vehicle operation. The paper concludes with a performance evaluation of the proposed controllers based on data recorded at field trials.
... Weil an der ehemaligen Arbeitsgruppe des Projektleiters an der Universität Rostock mit Messin [32], AGaPaS [28], MarSpeed [29] und SMIS [26] bereits mehrere autonom agierende Fahrzeuge über, auf, unter dem Wasser als auch geschleppt im Projekt MJ2000 [25] entwickelt wurden, stellt diese Kooperation eine strategische Bindung dar, um diese Geräte mit notwendigen und praktikablen Planungsmodulen zu versehen und so einen wichtigen Schritt in Richtung Marktreife zu gehen. Aufgrund der dazu notwendigen Präzession ist eine uneingeschränkte Kenntnis und Verfügbarkeit der Prozessparameter sowohl für Planung als auch für Reglerentwurf notwendig. ...
Gegenwärtig in der Schifffahrt eingesetzte Bahnführungssysteme sind nicht in der Lage, Schiffe mit Querschubeinrichtungen effektiv unter verschiedenen Umwelteinflüssen in Revieren zu steuern. Eine Ausnahme stellen sogenannte DP-Systeme (Dynamic Positioning) dar, weil diese für überwiegend meeresbergbauliche Zwecke das zu steuernde Fahrzeug/Plattform ohne Einsatz von Anker- und Mooring- Anlagen auf seiner vorgegebenen Position halten. Mit einer solchen Zielstellung sind die Anlagen daher nicht zum Navigieren/Manövrieren in begrenzten Revieren für Handelsschiffe geeignet. Ihnen fehlt die Integration in eine zur Navigation geeigneten Geo-Datenbasis. Das weiterführende Ziel dieses Projektes besteht daher in der Integration von DP-ähnlichen Regelsystemen am Beispiel des an der Universität Rostock unter Mitwirkung des Projektleiters entwickelten ADANAV-Reglers in die integrierende User-Schnittstelle ECDIS (Electronic Chart Display and Information System), für die seitens der IMO eine Ausrüstungspflicht für neue Schiffe besteht, um die Vorzüge der komplexen Regelung mit denen der modernen Navigation/Schiffsführung zu verknüpfen.
