This study analyzes and summarizes seven main characteristics of the marine data sampled by multiple underwater gliders. These characteristics such as the big data volume and data sparseness make it extremely difficul...This study analyzes and summarizes seven main characteristics of the marine data sampled by multiple underwater gliders. These characteristics such as the big data volume and data sparseness make it extremely difficult to do some meaningful applications like early warning of marine environment. In order to make full use of the sea trial data, this paper gives the definition of two types of marine data cube which can integrate the big marine data sampled by multiple underwater gliders along saw-tooth paths, and proposes a data fitting algorithm based on time extraction and space compression(DFTS) to construct the temperature and conductivity data cubes. This research also presents an early warning algorithm based on data cube(EWDC) to realize the early warning of a new sampled data file.Experiments results show that the proposed methods are reasonable and effective. Our work is the first study to do some realistic applications on the data sampled by multiple underwater vehicles, and it provides a research framework for processing and analyzing the big marine data oriented to the applications of underwater gliders.展开更多
For consideration of both the eccentric rotatable rigid body and the translational rigid body, the dynamic model of the underwater glider is derived. Dynamical behaviors are also studied based on the model and can be ...For consideration of both the eccentric rotatable rigid body and the translational rigid body, the dynamic model of the underwater glider is derived. Dynamical behaviors are also studied based on the model and can be used as the guidance to underwater gliders design. Gibbs function of the underwater glider system is derived first, and then the nonlinear dynamic model is obtained by use of Appell equations. The relationships between dynamic behaviors and design parameters are studied by solving the dynamic model. The spiral motion, swerving motion in three dimensions and the saw-tooth motion of the underwater glider in vertical plane are studied. Lake trials are carried out to validate the dynamic model.展开更多
The formation of hybrid underwater gliders has advantages in sustained ocean observation with high resolution and more adaptation for complicated ocean tasks. However, the current work mostly focused on the traditiona...The formation of hybrid underwater gliders has advantages in sustained ocean observation with high resolution and more adaptation for complicated ocean tasks. However, the current work mostly focused on the traditional gliders and AUVs.The research on control strategy and energy consumption minimization for the hybrid gliders is necessary both in methodology and experiment. A multi-layer coordinate control strategy is developed for the fleet of hybrid underwater gliders to control the gliders’ motion and formation geometry with optimized energy consumption. The inner layer integrated in the onboard controller and the outer layer integrated in the ground control center or the deck controller are designed. A coordinate control model is proposed based on multibody theory through adoption of artificial potential fields. Considering the existence of ocean flow, a hybrid motion energy consumption model is constructed and an optimization method is designed to obtain the heading angle, net buoyancy, gliding angle and the rotate speed of screw propeller to minimize the motion energy with consideration of the ocean flow. The feasibility of the coordinate control system and motion optimization method has been verified both by simulation and sea trials. Simulation results show the regularity of energy consumption with the control variables. The fleet of three Petrel-Ⅱ gliders developed by Tianjin University is deployed in the South China Sea. The trajectory error of each glider is less than 2.5 km, the formation shape error between each glider is less than 2 km, and the difference between actual energy consumption and the simulated energy consumption is less than 24% actual energy. The results of simulation and the sea trial prove the feasibility of the proposed coordinate control strategy and energy optimization method. In conclusion, a coordinate control system and a motion optimization method is studied, which can be used for reference in theoretical research and practical fleet operation for both the traditional gliders and hybrid gliders.展开更多
In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate mode...In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate model is developed to replace the high-dimensional objective in shape optimization.Specifically,several First-stage Surrogate Models(FSMs)are built for the sectional airfoils,and the second-stage surrogate model is constructed with respect to the outputs of FSMs.Besides,a Multi-start Space Reduction surrogate-based global optimization method is applied to search for the optimum.In order to validate the efficiency of the proposed method,DSSO is first compared with an ordinary One-stage Surrogate-based Optimization strategy by using the same optimization method.Then,the other three popular surrogate-based optimization methods and three heuristic algorithms are utilized to make comparisons.Results indicate that the lift-to-drag ratio of the BWBUG is improved by 9.35%with DSSO,which outperforms the comparison methods.Besides,DSSO reduces more than 50%of the time that other methods used when obtaining the same level of results.Furthermore,some considerations of the proposed strategy are further discussed and some characteristics of DSSO are identified.展开更多
Control parameter optimization is an efficient way to improve the endurance of underwater gliders(UGs),which influences their gliding efficiency and energy consumption.This paper analyzes the optimal matching between ...Control parameter optimization is an efficient way to improve the endurance of underwater gliders(UGs),which influences their gliding efficiency and energy consumption.This paper analyzes the optimal matching between the net buoyancy and the pitching angle and proposes a segmented control strategy of Petrel-L.The optimization of this strategy is established based on the gliding range model of UG,which is solved based on the approximate model,and the variations of the optimal control parameters with the hotel load are obtained.The optimization results indicate that the segmented control strategy can significantly increase the gliding range when the optimal matching between the net buoyancy and the pitching angle is reached,and the increase rate is influenced by the hotel load.The gliding range of the underwater glider can be increased by 10.47%at a hotel load of 0.5 W.The optimal matching analysis adopted in this study can be applied to other UGs to realize endurance improvement.展开更多
The evolution of thermohaline structure at the upper ocean during three tropical cyclones(TCs)in the Northwest Pacific was studied in this study based on successive observation by two new-style underwater gliders duri...The evolution of thermohaline structure at the upper ocean during three tropical cyclones(TCs)in the Northwest Pacific was studied in this study based on successive observation by two new-style underwater gliders during fall 2018.These remote-controllable gliders with CTD sensor enabled us to explore high frequency responses of temperature,salinity,mixed and barrier layers in the upper ocean to severe TCs in this area.Results showed that three significant cooling-to-warming and stratification destructing-to-reconstructing processes at the mixed layer occurred during the lives of three TCs.The maximal cooling of SST all reached≥0.5℃although TCs with different intensities had different minimal distances to the observed area.Under potential impacts of solar radiation,tide and inertial motions,the mixed layer depth possessed significant high-frequency fluctuations during TC periods.In addition,barrier layers appeared and vanished quickly during TCs,accompanied with varied temperature inversion processes.展开更多
In this paper,we propose a hybrid forecasting model to improve the forecasting accuracy for depth-averaged current velocities(DACVs) of underwater gliders.The hybrid model is based on a discrete wavelet transform(DWT)...In this paper,we propose a hybrid forecasting model to improve the forecasting accuracy for depth-averaged current velocities(DACVs) of underwater gliders.The hybrid model is based on a discrete wavelet transform(DWT),a deep belief network(DBN),and a least squares support vector machine(LSSVM).The original DACV series are first decomposed into several high-and one low-frequency subseries by DWT.Then,DBN is used for high-frequency component forecasting,and the LSSVM model is adopted for low-frequency subseries.The effectiveness of the proposed model is verified by two groups of DACV data from sea trials in the South China Sea.Based on four general error criteria,the forecast performance of the proposed model is demonstrated.The comparison models include some well-recognized single models and some related hybrid models.The performance of the proposed model outperformed those of the other methods indicated above.展开更多
An intensive field observation experiment using 12 Chinese gliders equipped with conductivity-temperature-depth (CTD) sensors and 62 expendable CTD probes (XCTDs) was performed to investigate the 3-D structure and tim...An intensive field observation experiment using 12 Chinese gliders equipped with conductivity-temperature-depth (CTD) sensors and 62 expendable CTD probes (XCTDs) was performed to investigate the 3-D structure and time evolution of an anticyclonic eddy in the northern South China Sea (NSCS). The observed results showed that the anticyclonic eddy had a horizontal radius of about 80 km at surface and a vertical depth of impact of more than 1000 m. The largest temperature and salinity anomalies compared with the averaged values of the temperature and salinity profiles were 3.5°C and 0.4 psu at 120 m depth, respectively. Combined analysis of altimeter sea level and water mass properties indicated that the anticyclonic eddy was shed from the Kuroshio loop current. The vertical axis of the anticyclonic eddy tilted from surface to the observed maximum depth (1000 m) along its translation direction against the 2000 m isobath. The center of the anticyclonic eddy remained in the region east of Dongsha Island for more than half a month. During this time, the long axis direction of the eddy changed from across the slope to along the slope. Then, the eddy moved southward along the 2000 m isobaths. Both the geostrophic current and temperature distribution revealed that the eddy intensity weakened during the observation period gradually. These observations indicated strong interaction between the anticyclonic eddy and the slope topography of Dongsha Island.展开更多
The underwater glider changes its weight and the weight distribution through the battery use, to move up and down and forward in the sea. It enjoys many advantages such as a long endurance, and a long operational rang...The underwater glider changes its weight and the weight distribution through the battery use, to move up and down and forward in the sea. It enjoys many advantages such as a long endurance, and a long operational range with its unique device. The performance of the underwater glider can not evaluated only by the drag, the energy consumption is also one of the key factors. In this paper, the power conversion ratio is proposed according to the transfer efficiency from the gravitational potential energy to the available work, and the performances of three typical underwater gliders are evaluated from multi-angles, such as the drag, the power conversion ratio and the barycenter＇s offset. So the glide performance and the energy consumption in various motion states can be analyzed. The results of this paper can provide a theoretical basis for further study of underwater gliders.展开更多
Steering control for an autonomous underwater glider （AUG） is very challenging due to its changing dynamic char- acteristics such as payload and shape. A good choice to solve this problem is online system identifica...Steering control for an autonomous underwater glider （AUG） is very challenging due to its changing dynamic char- acteristics such as payload and shape. A good choice to solve this problem is online system identification via in-field trials to capture current dynamic characteristics for control law reconfiguration. Hence, an online polynomial estimator is designed to update the yaw dynamic model of the AUG, and an adaptive model predictive control （MPC） controller is used to calculate the optimal control command based on updated estimated parameters. The MPC controller uses a quadratic program （QP） to compute the optimal control command based on a user-defined cost function. The cost function has two terms, focusing on output reference tracking and move suppression of input, respectively. Move-suppression performance can, at some level, represent energy-saving performance of the MPC controller. Users can balance these two competitive control performances by tuning weights. We have compared the control performance using the second-order polynomial model to that using the filth-order polynomial model, and found that the tbrmer cannot capture the main characteristics of yaw dynamics and may result in vibration during the flight. Both processor-in-loop （PIL） simulations and in-lake tests are presented to validate our steering control performance.展开更多
Hybrid-driven technology,which can improve the sailing performance of underwater gliders(UGs),has been successfully used in ocean observation.However,a hybrid-driven UG(HUG)with an added tail propeller is still unable...Hybrid-driven technology,which can improve the sailing performance of underwater gliders(UGs),has been successfully used in ocean observation.However,a hybrid-driven UG(HUG)with an added tail propeller is still unable to achieve backward and turning motion with a body length radius,and the hydrodynamic pitch moment acting on the HUG that is mainly caused by the fixed-wing makes it difficult to achieve high-precision attitude control during fixed-depth navigation.To solve this problem,a two-degree-of-freedom bioinspired controllable wing mechanism(CWM)is proposed to improve the maneuverability and cruising ability of HUGs.The CWM can realize five motion modes:modifying the dihedral angle or anhedral angle,changing the frontal area of the wing,switching the wing from horizontal to be a vertical rudder,flapping the wing as propulsion,and rotating the wing as a vector propeller.First,the design process of the CWM is provided,and hydrodynamic forces in each motion mode of three CWMs with different trailing edge sweepback angles(TESA)and attitude angles are analyzed through computational fluid dynamics simulation.The relationship between hydrodynamics and the attitude angles or TESA of the CWM is analyzed.Then,experiments are conducted to measure the hydrodynamics of the CWM when it is in a flapping wing mode and rotating the wing as a vector propeller,respectively.The hydrodynamic forces obtained from the simulation are consistent with data measured by a force sensor,proving the credibility of the simulated hydrodynamics.Subsequently,by applying the results of the hydrodynamic force in this study,the flapping trajectory of the wingtip is planned using the cubic spline interpolation method.Furthermore,two underwater demo vehicles with a pair of CWMs are developed,and experiments are conducted in a water tank,further validating and demonstrating the feasibility of the proposed CWM.展开更多
An increasing number of underwater gliders have been applied to lake monitoring. Lakes have a limited vertical space. Therefore, good space-saving capacity is required for underwater gliders to enlarge the spacing bet...An increasing number of underwater gliders have been applied to lake monitoring. Lakes have a limited vertical space. Therefore, good space-saving capacity is required for underwater gliders to enlarge the spacing between monitoring waypoints. This paper presents a space-saving steering method under a small pitch angle （SPA） for appearance-fixed underwater gliders. Steering under an SPA increases the steering angle in per unit vertical space. An amended hydrodynamic model for both small and large attack angles is presented to help analyze the steering process. Analysis is conducted to find the optimal parameters of net buoyancy and roll angle for steering under an SPA. A lake trial with a prototype tiny underwater glider （TUG） is conducted to inspect the applicability of the presented model. The trial results show that steering under an SPA saves vertical space, unlike that under a large pitch angle. Simulation results of steering are consistent with the trial results. In addition, multiple-waypoint trial shows that monitoring with steering under an SPA covers a larger horizontal displacement than that without steering.展开更多
Global marine ecosystems are signiicantly endangered by microplastic pollution,leading to comprehensive investigations into its distribution and impacts on the health of ecosystem.This research employs the Alseamar Au...Global marine ecosystems are signiicantly endangered by microplastic pollution,leading to comprehensive investigations into its distribution and impacts on the health of ecosystem.This research employs the Alseamar Autonomous Underwater Vehicle(AUV)known as Glider to investigate microplastic concentrations within the Al Hoceima Marine Protected Area(MPA).Our objective is to identify spatial patterns that reveal pollution hotspots and furnish data for targeted conservation efforts and pollution prevention.We aim to identify regions with elevated microplastic concentrations by meticulously analyzing microplastic level graphs,with a speciic focus on temporal variations.The results reveal notable patterns,such as increased densities aroundishing harbors and near urban centers,potentially linked to anthropogenic activities.Additionally,we observe variations in pollution levels throughout different glider operation cycles,underscoring the importance of understanding the spatio‑temporal dynamics of microplastic distribution.Al Hoceima Marine protected areas exhibiting lower microplastic concentrations illustrate the eficacy of such zones in alleviating pollution impacts,thereby underscoring the signiicance of conservation efforts in safeguarding marine biodiversity and ecosystem resilience.Ultimately,our research enhances our comprehension of the pressures exerted by humans on marine environments and underscores the necessity of proactive conservation measures to shield marine ecosystems from the threats posed by microplastic pollution.展开更多
Underwater Gliders(UGs)have emerged as vital instruments in marine research,offering distinct advantages including low operational costs,extended range capabilities,and superior durability.Traditional UGs,however,face...Underwater Gliders(UGs)have emerged as vital instruments in marine research,offering distinct advantages including low operational costs,extended range capabilities,and superior durability.Traditional UGs,however,face limitations due to their substantial size,weight,cost,and deployment complexity.Moreover,the conventional oil pump method for buoyancy adjustment exhibits slow response times,resulting in increased unsteady gliding depth ratios.These constraints limit their application in shallow water environments such as ports,coastal waters,and inland water bodies.This paper presents the TL-200,a small-sized underwater glider that incorporates an integrated buoyancy-driven and attitude adjustment mechanism.Through the implementation of an innovative buoyancy drive unit,the TL-200 achieves enhanced buoyancy regulation response while maintaining a simplified structure compared to conventional gliders.A dynamic model for the TL-200 was developed and validated through comparative analysis of numerical results and experimental data.Utilizing this dynamic model,motion simulations were conducted to examine the influence of metacentric height on motion parameters.Additionally,the study evaluated the gliding efficiency and energy consumption of the TL-200 under varying buoyancy adjustments.The findings demonstrate the effectiveness of this small-sized underwater glider's integrated buoyancy-driven and attitude adjustment mechanism.展开更多
In this research,we examine how the Al Hoceima Marine Protected Area(MPA),located in the southwest Mediterranean Sea,can be effectively monitored using the SeaExplorer glider—an advanced autonomous underwater vehicle...In this research,we examine how the Al Hoceima Marine Protected Area(MPA),located in the southwest Mediterranean Sea,can be effectively monitored using the SeaExplorer glider—an advanced autonomous underwater vehicle(AUV)designed for long‑duration oceanographic missions.The study focuses on the glider’s ability to simultaneously observe a variety of environmental parameters,including temperature,conductivity,oxygen,and chlorophyll,during its deployment across multiple transects.The primary objective of the mission is to improve understanding of the vertical thermal structure and seasonal dynamics of the water column in this ecologically signiicant region.To achieve this,we apply Gaussian Process(GP)regression techniques to the glider‑derived temperature data.This statistical method enables the smoothing and interpolation of irregularly spaced in situ measurements,thereby improving the visibility and interpretation of stratiication patterns throughout the water column.Although the glider followed a predetermined course,the data‑driven analysis suggests that adaptive sampling strategies—such as adjustments based on real‑time outliers—could be valuable in future missions.Our results,which show distinct thermal layering and seasonal variability,are crucial for informing ecosystem function assessments and climate resilience planning.This study also discusses how integrating machine learning into glider‑based monitoring could enhance MPA observation systems and promote adaptive,evidence‑based management.展开更多
Unlike traditional propeller-driven underwater vehicles,blended-wing-body underwater gliders(BWBUGs)achieve zigzag gliding through periodic adjustments of their net buoyancy,enhancing their cruising capabilities while...Unlike traditional propeller-driven underwater vehicles,blended-wing-body underwater gliders(BWBUGs)achieve zigzag gliding through periodic adjustments of their net buoyancy,enhancing their cruising capabilities while mini-mizing energy consumption.However,enhancing gliding performance is challenging due to the complex system design and limited design experience.To address this challenge,this paper introduces a model-based,multidisciplinary system design optimization method for BWBUGs at the conceptual design stage.First,a model-based,multidisciplinary co-simulation design framework is established to evaluate both system-level and disciplinary indices of BWBUG performance.A data-driven,many-objective multidisciplinary optimization is subsequently employed to explore the design space,yielding 32 Pareto optimal solutions.Finally,a model-based physical system simulation,which represents the design with the largest hyper-volume contribution among the 32 final designs,is established.Its gliding perfor-mance,validated by component behavior,lays the groundwork for constructing the entire system’s digital prototype.In conclusion,this model-based,multidisciplinary design optimization method effectively generates design schemes for innovative underwater vehicles,facilitating the development of digital prototypes.展开更多
This study presents a comparative analysis of optimisation strategies for designing hull shapes of Autonomous Underwater Vehicles(AUVs),paying special attention to drag,lift-to-drag ratio,and delivered power.A fully i...This study presents a comparative analysis of optimisation strategies for designing hull shapes of Autonomous Underwater Vehicles(AUVs),paying special attention to drag,lift-to-drag ratio,and delivered power.A fully integrated optimisation framework is developed accordingly,combining a single-objective Genetic Algorithm(GA)for design parameter generation,Computer-Aided Geometric Design(CAGD)for the creation of hull geometries and associated fluid domains,and a Reynolds-Averaged Navier-Stokes(RANS)solver for evaluating hydrodynamic performance metrics.This unified approach eliminates manual intervention,enabling automated determination of optimal hull configurations.Three distinct optimisation problems are addressed using the proposed methodology.First,the drag minimisation of a reference afterbody geometry(A1)at zero angle of attack is performed under constraints of fixed length and internal volume for various flow velocities spanning the range from 0.5 to 15 m/s.Second,the lift-to-drag ratio of A1 is maximised at a 6°angle of attack,maintaining constant total length and internal volume.Third,delivered power is minimised for A1 at a 0°angle of attack.The comparative analysis of results from all three optimisation cases reveals hull shapes with practical design significance.Notably,the shape optimised for minimum delivered power outperforms the other two across a range of velocities.Specifically,it achieves reductions in required power by 7.6%,7.8%,10.2%,and 13.04%at velocities of 0.5,1.0,1.5,and 2.152 m/s,respectively.展开更多
Application of multiple hybrid underwater gliders （HUGs） is a promising method for large scale, long-term ocean survey. Attitude coordination has become a requisite for task execution of multi-HUG formation. In this...Application of multiple hybrid underwater gliders （HUGs） is a promising method for large scale, long-term ocean survey. Attitude coordination has become a requisite for task execution of multi-HUG formation. In this paper, a multibody model is presented for attitude coordination among agents in the HUG formation. The HUG formation is regarded as a multi-rigid body system. The interaction between agents in the formation is described by artificial potential field （APF） approach. Attitude control torque is composed of a conservative torque generated by orientation potential field and a dissipative term related with angular velocity. Dynamic modeling of the multibody system is presented to analyze the dynamic process of the HUG formation. Numerical calculation is carried out to simulate attitude synchronization with two kinds of formation topologies. Results show that attitude synchronization can be fulfilled based on the multibody method described in this paper. It is also indicated that different topologies affect attitude control quality with respect to energy consumption and adjusting time. Low level topology should be adopted during formation control scheme design to achieve a better control effect.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U1709202 and No.61502069)the Foundation of State Key Laboratory of Robotics(Grant No.2015-o03)the Fundamental Research Funds for the Central Universities(Grant Nos.DUT18JC39 and DUT17JC45)
文摘This study analyzes and summarizes seven main characteristics of the marine data sampled by multiple underwater gliders. These characteristics such as the big data volume and data sparseness make it extremely difficult to do some meaningful applications like early warning of marine environment. In order to make full use of the sea trial data, this paper gives the definition of two types of marine data cube which can integrate the big marine data sampled by multiple underwater gliders along saw-tooth paths, and proposes a data fitting algorithm based on time extraction and space compression(DFTS) to construct the temperature and conductivity data cubes. This research also presents an early warning algorithm based on data cube(EWDC) to realize the early warning of a new sampled data file.Experiments results show that the proposed methods are reasonable and effective. Our work is the first study to do some realistic applications on the data sampled by multiple underwater vehicles, and it provides a research framework for processing and analyzing the big marine data oriented to the applications of underwater gliders.
基金supported by the National Natural Science Foundation of China (Grant No.50835006)the Natural Science Foundation of Tianjin (Grant No.09JCZDJC23400)
文摘For consideration of both the eccentric rotatable rigid body and the translational rigid body, the dynamic model of the underwater glider is derived. Dynamical behaviors are also studied based on the model and can be used as the guidance to underwater gliders design. Gibbs function of the underwater glider system is derived first, and then the nonlinear dynamic model is obtained by use of Appell equations. The relationships between dynamic behaviors and design parameters are studied by solving the dynamic model. The spiral motion, swerving motion in three dimensions and the saw-tooth motion of the underwater glider in vertical plane are studied. Lake trials are carried out to validate the dynamic model.
基金Supported by National Key R&D Plan of China(Grant No.2016YFC0301100)National Natural Science Foundation of China(Grant Nos.51475319,51575736,41527901)Aoshan Talents Program of Qingdao National Laboratory for Marine Science and Technology,China
文摘The formation of hybrid underwater gliders has advantages in sustained ocean observation with high resolution and more adaptation for complicated ocean tasks. However, the current work mostly focused on the traditional gliders and AUVs.The research on control strategy and energy consumption minimization for the hybrid gliders is necessary both in methodology and experiment. A multi-layer coordinate control strategy is developed for the fleet of hybrid underwater gliders to control the gliders’ motion and formation geometry with optimized energy consumption. The inner layer integrated in the onboard controller and the outer layer integrated in the ground control center or the deck controller are designed. A coordinate control model is proposed based on multibody theory through adoption of artificial potential fields. Considering the existence of ocean flow, a hybrid motion energy consumption model is constructed and an optimization method is designed to obtain the heading angle, net buoyancy, gliding angle and the rotate speed of screw propeller to minimize the motion energy with consideration of the ocean flow. The feasibility of the coordinate control system and motion optimization method has been verified both by simulation and sea trials. Simulation results show the regularity of energy consumption with the control variables. The fleet of three Petrel-Ⅱ gliders developed by Tianjin University is deployed in the South China Sea. The trajectory error of each glider is less than 2.5 km, the formation shape error between each glider is less than 2 km, and the difference between actual energy consumption and the simulated energy consumption is less than 24% actual energy. The results of simulation and the sea trial prove the feasibility of the proposed coordinate control strategy and energy optimization method. In conclusion, a coordinate control system and a motion optimization method is studied, which can be used for reference in theoretical research and practical fleet operation for both the traditional gliders and hybrid gliders.
基金This research was financially supported by the National Natural Science Foundation of China(Grant Nos.51875466 and 51805436)the China Postdoctoral Science Foundation(Grant No.2019T120941)the China Scholarships Council(Grant No.201806290133).
文摘In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate model is developed to replace the high-dimensional objective in shape optimization.Specifically,several First-stage Surrogate Models(FSMs)are built for the sectional airfoils,and the second-stage surrogate model is constructed with respect to the outputs of FSMs.Besides,a Multi-start Space Reduction surrogate-based global optimization method is applied to search for the optimum.In order to validate the efficiency of the proposed method,DSSO is first compared with an ordinary One-stage Surrogate-based Optimization strategy by using the same optimization method.Then,the other three popular surrogate-based optimization methods and three heuristic algorithms are utilized to make comparisons.Results indicate that the lift-to-drag ratio of the BWBUG is improved by 9.35%with DSSO,which outperforms the comparison methods.Besides,DSSO reduces more than 50%of the time that other methods used when obtaining the same level of results.Furthermore,some considerations of the proposed strategy are further discussed and some characteristics of DSSO are identified.
基金jointly supported by the National Key R&D Program of Chinathe National Natural Science Foundation of China (Grant Nos. 11902219 and 51721003)the Natural Science Foundation of Tianjin City (Grant No. 18JCJQJC46400)。
文摘Control parameter optimization is an efficient way to improve the endurance of underwater gliders(UGs),which influences their gliding efficiency and energy consumption.This paper analyzes the optimal matching between the net buoyancy and the pitching angle and proposes a segmented control strategy of Petrel-L.The optimization of this strategy is established based on the gliding range model of UG,which is solved based on the approximate model,and the variations of the optimal control parameters with the hotel load are obtained.The optimization results indicate that the segmented control strategy can significantly increase the gliding range when the optimal matching between the net buoyancy and the pitching angle is reached,and the increase rate is influenced by the hotel load.The gliding range of the underwater glider can be increased by 10.47%at a hotel load of 0.5 W.The optimal matching analysis adopted in this study can be applied to other UGs to realize endurance improvement.
基金The National Key R&D Program of China under contract No.2018YFC0309800the National Natural Science Foundation of China under contract Nos 41666001,41576006,41676015 and U1709202+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA13030302the Chinese Academy of Sciences Frontier Basic Research Project under contract No.QYJC201910
文摘The evolution of thermohaline structure at the upper ocean during three tropical cyclones(TCs)in the Northwest Pacific was studied in this study based on successive observation by two new-style underwater gliders during fall 2018.These remote-controllable gliders with CTD sensor enabled us to explore high frequency responses of temperature,salinity,mixed and barrier layers in the upper ocean to severe TCs in this area.Results showed that three significant cooling-to-warming and stratification destructing-to-reconstructing processes at the mixed layer occurred during the lives of three TCs.The maximal cooling of SST all reached≥0.5℃although TCs with different intensities had different minimal distances to the observed area.Under potential impacts of solar radiation,tide and inertial motions,the mixed layer depth possessed significant high-frequency fluctuations during TC periods.In addition,barrier layers appeared and vanished quickly during TCs,accompanied with varied temperature inversion processes.
基金The National Natural Science Foundation of China under contract Nos U1709202 and 51809127the Natural Science Foundation of Shanxi ProvinceChina under contract No.201901D211248。
文摘In this paper,we propose a hybrid forecasting model to improve the forecasting accuracy for depth-averaged current velocities(DACVs) of underwater gliders.The hybrid model is based on a discrete wavelet transform(DWT),a deep belief network(DBN),and a least squares support vector machine(LSSVM).The original DACV series are first decomposed into several high-and one low-frequency subseries by DWT.Then,DBN is used for high-frequency component forecasting,and the LSSVM model is adopted for low-frequency subseries.The effectiveness of the proposed model is verified by two groups of DACV data from sea trials in the South China Sea.Based on four general error criteria,the forecast performance of the proposed model is demonstrated.The comparison models include some well-recognized single models and some related hybrid models.The performance of the proposed model outperformed those of the other methods indicated above.
基金supported by the Strategic Priority Research Programs of the Chinese Academy of Sciences (Grant Nos. XDA11010302, XDA11040101)the National Natural Science Foundation of China (Grant Nos. 41521005, 41776036, 41476012, 61233013, 41576012 and 41776026)+1 种基金the Science and Technology Program of Guangdong, China (Grant No. 2016A020224003)the National Key Scientific Instrument and Equipment Development Project (Grant No. 2013YQ16079303)
文摘An intensive field observation experiment using 12 Chinese gliders equipped with conductivity-temperature-depth (CTD) sensors and 62 expendable CTD probes (XCTDs) was performed to investigate the 3-D structure and time evolution of an anticyclonic eddy in the northern South China Sea (NSCS). The observed results showed that the anticyclonic eddy had a horizontal radius of about 80 km at surface and a vertical depth of impact of more than 1000 m. The largest temperature and salinity anomalies compared with the averaged values of the temperature and salinity profiles were 3.5°C and 0.4 psu at 120 m depth, respectively. Combined analysis of altimeter sea level and water mass properties indicated that the anticyclonic eddy was shed from the Kuroshio loop current. The vertical axis of the anticyclonic eddy tilted from surface to the observed maximum depth (1000 m) along its translation direction against the 2000 m isobath. The center of the anticyclonic eddy remained in the region east of Dongsha Island for more than half a month. During this time, the long axis direction of the eddy changed from across the slope to along the slope. Then, the eddy moved southward along the 2000 m isobaths. Both the geostrophic current and temperature distribution revealed that the eddy intensity weakened during the observation period gradually. These observations indicated strong interaction between the anticyclonic eddy and the slope topography of Dongsha Island.
基金Project supported by the National Natural Science Foundation of China(Grant No.51279184)
文摘The underwater glider changes its weight and the weight distribution through the battery use, to move up and down and forward in the sea. It enjoys many advantages such as a long endurance, and a long operational range with its unique device. The performance of the underwater glider can not evaluated only by the drag, the energy consumption is also one of the key factors. In this paper, the power conversion ratio is proposed according to the transfer efficiency from the gravitational potential energy to the available work, and the performances of three typical underwater gliders are evaluated from multi-angles, such as the drag, the power conversion ratio and the barycenter＇s offset. So the glide performance and the energy consumption in various motion states can be analyzed. The results of this paper can provide a theoretical basis for further study of underwater gliders.
基金supported by Beihang University and Institution of China Academy of Aerospace Aerodynamics
文摘Steering control for an autonomous underwater glider （AUG） is very challenging due to its changing dynamic char- acteristics such as payload and shape. A good choice to solve this problem is online system identification via in-field trials to capture current dynamic characteristics for control law reconfiguration. Hence, an online polynomial estimator is designed to update the yaw dynamic model of the AUG, and an adaptive model predictive control （MPC） controller is used to calculate the optimal control command based on updated estimated parameters. The MPC controller uses a quadratic program （QP） to compute the optimal control command based on a user-defined cost function. The cost function has two terms, focusing on output reference tracking and move suppression of input, respectively. Move-suppression performance can, at some level, represent energy-saving performance of the MPC controller. Users can balance these two competitive control performances by tuning weights. We have compared the control performance using the second-order polynomial model to that using the filth-order polynomial model, and found that the tbrmer cannot capture the main characteristics of yaw dynamics and may result in vibration during the flight. Both processor-in-loop （PIL） simulations and in-lake tests are presented to validate our steering control performance.
基金the National Key R&D Program of China(Grant No.2016YFC0301101)the National Natural Science Foundation of China(Grant No.51721003)+1 种基金the Natural Science Foundation of Tianjin City(Grant No.18JCJQJC46400)the Aoshan Talent Cultivation Program of QNLM(Grant Nos.2017ASTCP-OS05 and 2017ASTCP-OE01)。
文摘Hybrid-driven technology,which can improve the sailing performance of underwater gliders(UGs),has been successfully used in ocean observation.However,a hybrid-driven UG(HUG)with an added tail propeller is still unable to achieve backward and turning motion with a body length radius,and the hydrodynamic pitch moment acting on the HUG that is mainly caused by the fixed-wing makes it difficult to achieve high-precision attitude control during fixed-depth navigation.To solve this problem,a two-degree-of-freedom bioinspired controllable wing mechanism(CWM)is proposed to improve the maneuverability and cruising ability of HUGs.The CWM can realize five motion modes:modifying the dihedral angle or anhedral angle,changing the frontal area of the wing,switching the wing from horizontal to be a vertical rudder,flapping the wing as propulsion,and rotating the wing as a vector propeller.First,the design process of the CWM is provided,and hydrodynamic forces in each motion mode of three CWMs with different trailing edge sweepback angles(TESA)and attitude angles are analyzed through computational fluid dynamics simulation.The relationship between hydrodynamics and the attitude angles or TESA of the CWM is analyzed.Then,experiments are conducted to measure the hydrodynamics of the CWM when it is in a flapping wing mode and rotating the wing as a vector propeller,respectively.The hydrodynamic forces obtained from the simulation are consistent with data measured by a force sensor,proving the credibility of the simulated hydrodynamics.Subsequently,by applying the results of the hydrodynamic force in this study,the flapping trajectory of the wingtip is planned using the cubic spline interpolation method.Furthermore,two underwater demo vehicles with a pair of CWMs are developed,and experiments are conducted in a water tank,further validating and demonstrating the feasibility of the proposed CWM.
基金Project supported by the Science Fund for Creative Research Groups of the National Natural Science Foundation of China （No. 51521064） and the National High-Tecb R＆D Program （863） of China （No. 2014AA09A513 ）
文摘An increasing number of underwater gliders have been applied to lake monitoring. Lakes have a limited vertical space. Therefore, good space-saving capacity is required for underwater gliders to enlarge the spacing between monitoring waypoints. This paper presents a space-saving steering method under a small pitch angle （SPA） for appearance-fixed underwater gliders. Steering under an SPA increases the steering angle in per unit vertical space. An amended hydrodynamic model for both small and large attack angles is presented to help analyze the steering process. Analysis is conducted to find the optimal parameters of net buoyancy and roll angle for steering under an SPA. A lake trial with a prototype tiny underwater glider （TUG） is conducted to inspect the applicability of the presented model. The trial results show that steering under an SPA saves vertical space, unlike that under a large pitch angle. Simulation results of steering are consistent with the trial results. In addition, multiple-waypoint trial shows that monitoring with steering under an SPA covers a larger horizontal displacement than that without steering.
文摘Global marine ecosystems are signiicantly endangered by microplastic pollution,leading to comprehensive investigations into its distribution and impacts on the health of ecosystem.This research employs the Alseamar Autonomous Underwater Vehicle(AUV)known as Glider to investigate microplastic concentrations within the Al Hoceima Marine Protected Area(MPA).Our objective is to identify spatial patterns that reveal pollution hotspots and furnish data for targeted conservation efforts and pollution prevention.We aim to identify regions with elevated microplastic concentrations by meticulously analyzing microplastic level graphs,with a speciic focus on temporal variations.The results reveal notable patterns,such as increased densities aroundishing harbors and near urban centers,potentially linked to anthropogenic activities.Additionally,we observe variations in pollution levels throughout different glider operation cycles,underscoring the importance of understanding the spatio‑temporal dynamics of microplastic distribution.Al Hoceima Marine protected areas exhibiting lower microplastic concentrations illustrate the eficacy of such zones in alleviating pollution impacts,thereby underscoring the signiicance of conservation efforts in safeguarding marine biodiversity and ecosystem resilience.Ultimately,our research enhances our comprehension of the pressures exerted by humans on marine environments and underscores the necessity of proactive conservation measures to shield marine ecosystems from the threats posed by microplastic pollution.
基金financially supported by the National Key Research and Development Program of China(Grant No.2023YFC3008001)the National Natural Science Foundation of China(Grant No.52371357)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515240035)。
文摘Underwater Gliders(UGs)have emerged as vital instruments in marine research,offering distinct advantages including low operational costs,extended range capabilities,and superior durability.Traditional UGs,however,face limitations due to their substantial size,weight,cost,and deployment complexity.Moreover,the conventional oil pump method for buoyancy adjustment exhibits slow response times,resulting in increased unsteady gliding depth ratios.These constraints limit their application in shallow water environments such as ports,coastal waters,and inland water bodies.This paper presents the TL-200,a small-sized underwater glider that incorporates an integrated buoyancy-driven and attitude adjustment mechanism.Through the implementation of an innovative buoyancy drive unit,the TL-200 achieves enhanced buoyancy regulation response while maintaining a simplified structure compared to conventional gliders.A dynamic model for the TL-200 was developed and validated through comparative analysis of numerical results and experimental data.Utilizing this dynamic model,motion simulations were conducted to examine the influence of metacentric height on motion parameters.Additionally,the study evaluated the gliding efficiency and energy consumption of the TL-200 under varying buoyancy adjustments.The findings demonstrate the effectiveness of this small-sized underwater glider's integrated buoyancy-driven and attitude adjustment mechanism.
文摘In this research,we examine how the Al Hoceima Marine Protected Area(MPA),located in the southwest Mediterranean Sea,can be effectively monitored using the SeaExplorer glider—an advanced autonomous underwater vehicle(AUV)designed for long‑duration oceanographic missions.The study focuses on the glider’s ability to simultaneously observe a variety of environmental parameters,including temperature,conductivity,oxygen,and chlorophyll,during its deployment across multiple transects.The primary objective of the mission is to improve understanding of the vertical thermal structure and seasonal dynamics of the water column in this ecologically signiicant region.To achieve this,we apply Gaussian Process(GP)regression techniques to the glider‑derived temperature data.This statistical method enables the smoothing and interpolation of irregularly spaced in situ measurements,thereby improving the visibility and interpretation of stratiication patterns throughout the water column.Although the glider followed a predetermined course,the data‑driven analysis suggests that adaptive sampling strategies—such as adjustments based on real‑time outliers—could be valuable in future missions.Our results,which show distinct thermal layering and seasonal variability,are crucial for informing ecosystem function assessments and climate resilience planning.This study also discusses how integrating machine learning into glider‑based monitoring could enhance MPA observation systems and promote adaptive,evidence‑based management.
基金supported by the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20242194)the National Natural Science Foundation of China(Grant Nos.52175251 and 52205268)+1 种基金the Industry Key Technology Research Fund Project of Northwestern Polytechnical University(Grant No.HYGJXM202318)the National Basic Scientific Research Program(Grant No.JCKY2021206B005).
文摘Unlike traditional propeller-driven underwater vehicles,blended-wing-body underwater gliders(BWBUGs)achieve zigzag gliding through periodic adjustments of their net buoyancy,enhancing their cruising capabilities while mini-mizing energy consumption.However,enhancing gliding performance is challenging due to the complex system design and limited design experience.To address this challenge,this paper introduces a model-based,multidisciplinary system design optimization method for BWBUGs at the conceptual design stage.First,a model-based,multidisciplinary co-simulation design framework is established to evaluate both system-level and disciplinary indices of BWBUG performance.A data-driven,many-objective multidisciplinary optimization is subsequently employed to explore the design space,yielding 32 Pareto optimal solutions.Finally,a model-based physical system simulation,which represents the design with the largest hyper-volume contribution among the 32 final designs,is established.Its gliding perfor-mance,validated by component behavior,lays the groundwork for constructing the entire system’s digital prototype.In conclusion,this model-based,multidisciplinary design optimization method effectively generates design schemes for innovative underwater vehicles,facilitating the development of digital prototypes.
文摘This study presents a comparative analysis of optimisation strategies for designing hull shapes of Autonomous Underwater Vehicles(AUVs),paying special attention to drag,lift-to-drag ratio,and delivered power.A fully integrated optimisation framework is developed accordingly,combining a single-objective Genetic Algorithm(GA)for design parameter generation,Computer-Aided Geometric Design(CAGD)for the creation of hull geometries and associated fluid domains,and a Reynolds-Averaged Navier-Stokes(RANS)solver for evaluating hydrodynamic performance metrics.This unified approach eliminates manual intervention,enabling automated determination of optimal hull configurations.Three distinct optimisation problems are addressed using the proposed methodology.First,the drag minimisation of a reference afterbody geometry(A1)at zero angle of attack is performed under constraints of fixed length and internal volume for various flow velocities spanning the range from 0.5 to 15 m/s.Second,the lift-to-drag ratio of A1 is maximised at a 6°angle of attack,maintaining constant total length and internal volume.Third,delivered power is minimised for A1 at a 0°angle of attack.The comparative analysis of results from all three optimisation cases reveals hull shapes with practical design significance.Notably,the shape optimised for minimum delivered power outperforms the other two across a range of velocities.Specifically,it achieves reductions in required power by 7.6%,7.8%,10.2%,and 13.04%at velocities of 0.5,1.0,1.5,and 2.152 m/s,respectively.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51205277,51475319 and51575736)the National Key R&D Program of China(Grant No.2016YFC0301100)Tianjin University Elite Scholar Program
文摘Application of multiple hybrid underwater gliders （HUGs） is a promising method for large scale, long-term ocean survey. Attitude coordination has become a requisite for task execution of multi-HUG formation. In this paper, a multibody model is presented for attitude coordination among agents in the HUG formation. The HUG formation is regarded as a multi-rigid body system. The interaction between agents in the formation is described by artificial potential field （APF） approach. Attitude control torque is composed of a conservative torque generated by orientation potential field and a dissipative term related with angular velocity. Dynamic modeling of the multibody system is presented to analyze the dynamic process of the HUG formation. Numerical calculation is carried out to simulate attitude synchronization with two kinds of formation topologies. Results show that attitude synchronization can be fulfilled based on the multibody method described in this paper. It is also indicated that different topologies affect attitude control quality with respect to energy consumption and adjusting time. Low level topology should be adopted during formation control scheme design to achieve a better control effect.
