scholarly journals Physics-Based Modelling and Simulation of Multibeam Echosounder Perception for Autonomous Underwater Manipulation

2021 ◽  
Vol 8 ◽  
Author(s):  
Woen-Sug Choi ◽  
Derek R. Olson ◽  
Duane Davis ◽  
Mabel Zhang ◽  
Andy Racson ◽  
...  
Keyword(s):  
High Efficiency ◽  
Imaging System ◽  
Interaction Model ◽  
Simulation Method ◽  
Multibeam Echosounder ◽  
Sonar Image ◽  
Sonar Images ◽  
Ocean Environment ◽  
Underwater Manipulation ◽  
Correct Point

One of the key distinguishing aspects of underwater manipulation tasks is the perception challenges of the ocean environment, including turbidity, backscatter, and lighting effects. Consequently, underwater perception often relies on sonar-based measurements to estimate the vehicle’s state and surroundings, either standalone or in concert with other sensing modalities, to support the perception necessary to plan and control manipulation tasks. Simulation of the multibeam echosounder, while not a substitute for in-water testing, is a critical capability for developing manipulation strategies in the complex and variable ocean environment. Although several approaches exist in the literature to simulate synthetic sonar images, the methods in the robotics community typically use image processing and video rendering software to comply with real-time execution requirements. In addition to a lack of physics-based interaction model between sound and the scene of interest, several basic properties are absent in these rendered sonar images–notably the coherent imaging system and coherent speckle that cause distortion of the object geometry in the sonar image. To address this deficiency, we present a physics-based multibeam echosounder simulation method to capture these fundamental aspects of sonar perception. A point-based scattering model is implemented to calculate the acoustic interaction between the target and the environment. This is a simplified representation of target scattering but can produce realistic coherent image speckle and the correct point spread function. The results demonstrate that this multibeam echosounder simulator generates qualitatively realistic images with high efficiency to provide the sonar image and the physical time series signal data. This synthetic sonar data is a key enabler for developing, testing, and evaluating autonomous underwater manipulation strategies that use sonar as a component of perception.

Underwater Sonar Image Segmentation Based on Snake Model

2013 ◽  
Vol 448-453 ◽  
pp. 3675-3678
Author(s):  
Jun Peng Wu ◽  
Hai Tao Guo
Keyword(s):  
Image Segmentation ◽  
Greedy Algorithm ◽  
Echo Signal ◽  
Constraint Forces ◽  
Shape Accuracy ◽  
Snake Model ◽  
Sonar Image ◽  
Sonar Images ◽  
Underwater Target ◽  
Detection And Recognition

The underwater sonar image segmentation has been a topic of research for decades. Underwater sonar image is based on the interaction by the echo signal of sound toward the underwater objects or targets. Because of the serious noises polution and the dim target edge, the contrast and resolution of sonar images are obtaind in a decreased quanlity. This paper proposes an improved snake model that focuses on solving underwater target detection and recognition. According to the traditional snake model, it is defined as an energy minimizing spline which is influenced by external constraint forces, and it can guide the image forces to pull toward features, such as lines or edges. Compared with the traditional snake model, this snake model greedy algorithm can converge to the contours more quickly and more stably, especially in complex underwater environments. Examination of the results shows that using snake model greedy algorithm has a more clear shape accuracy.

A field-programmable gate array system for sonar image recognition based on convolutional neural network

2020 ◽  
pp. 095965182093934
Author(s):  
Chong Wang ◽  
Yu Jiang ◽  
Kai Wang ◽  
Fenglin Wei
Keyword(s):  
Neural Network ◽  
Energy Consumption ◽  
Convolutional Neural Network ◽  
Image Recognition ◽  
Field Programmable Gate Array ◽  
Oil And Gas ◽  
Sonar Image ◽  
Field Programmable ◽  
Sonar Images ◽  
Gate Array

Subsea pipeline is the safest, most reliable, and most economical way to transport oil and gas from an offshore platform to an onshore terminal. However, the pipelines may rupture under the harsh working environment, causing oil and gas leakage. This calls for a proper device and method to detect the state of subsea pipelines in a timely and precise manner. The autonomous underwater vehicle carrying side-scan sonar offers a desirable way for target detection in the complex environment under the sea. As a result, this article combines the field-programmable gate array, featuring high throughput, low energy consumption and a high degree of parallelism, and the convolutional neural network into a sonar image recognition system. First, a training set was constructed by screening and splitting the sonar images collected by sensors, and labeled one by one. Next, the convolutional neural network model was trained by the set on the workstation platform. The trained model was integrated into the field-programmable gate array system and applied to recognize actual datasets. The recognition results were compared with those of the workstation platform. The comparison shows that the computational precision of the designed field-programmable gate array system based on convolutional neural network is equivalent to that of the workstation platform; however, the recognition time of the designed system can be saved by more than 77%, and its energy consumption can also be saved by more than 96.67%. Therefore, our system basically satisfies our demand for energy-efficient, real-time, and accurate recognition of sonar images.

scholarly journals Numerical Simulation and Experimental Research on Material Parameters Solution and Shape Control of Sandwich Panels with Aluminum Honeycomb

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 556-565
Author(s):  
Dongsheng Li ◽  
Mingming Wang ◽  
Xianbin Zhou
Keyword(s):  
Shape Control ◽  
Sandwich Panel ◽  
High Efficiency ◽  
Sandwich Panels ◽  
Simulation Method ◽  
Equivalent Material ◽  
Fe Model ◽  
Material Parameters ◽  
Surface Deviation ◽  
Aluminum Honeycomb

Abstract This paper aims to solve two problems of the sandwich panel with aluminum honeycomb: material parameters solution and shape control. The accurate material parameters of the sandwich panels are the basis of shape control. Therefore, a mixed numerical-experimental method is proposed to inversely solve equivalent material parameters of the sandwich panel using genetic algorithm (GA) in the first place. Then a high efficiency FE model based on equivalent material parameters is established to study shape control of the sandwich panels. For shape control, the key issue aims to search optimum position and adjustment volume of control points where actuators are installed. Toward the end, the FE simulation method is deployed to optimize actuator position and adjustment volume one by one. Finally, an active control platform based on multi-point adjustment is developed to verify the practicability of the approach proposed in this paper. Through the experiment of shape control, the root mean square (RMS) of surface deviation of sandwich panel is decreased from 62.7μm to 15.5μm. The results show that the shape control can significantly improve the surface accuracy of the sandwich panels, and the validity of equivalent material parameters is also proved from the side.

scholarly journals Wide Swath and High Resolution Airborne HyperSpectral Imaging System and Flight Validation

Sensors ◽  
2019 ◽  
Vol 19 (7) ◽  
pp. 1667 ◽  
Author(s):  
Dong Zhang ◽  
Liyin Yuan ◽  
Shengwei Wang ◽  
Hongxuan Yu ◽  
Changxing Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Spectral Resolution ◽  
High Efficiency ◽  
High Spatial Resolution ◽  
Imaging System ◽  
High Sensitivity ◽  
Field Of View ◽  
High Spectral Resolution ◽  
Wide Swath

Wide Swath and High Resolution Airborne Pushbroom Hyperspectral Imager (WiSHiRaPHI) is the new-generation airborne hyperspectral imager instrument of China, aimed at acquiring accurate spectral curve of target on the ground with both high spatial resolution and high spectral resolution. The spectral sampling interval of WiSHiRaPHI is 2.4 nm and the spectral resolution is 3.5 nm (FWHM), integrating 256 channels coving from 400 nm to 1000 nm. The instrument has a 40-degree field of view (FOV), 0.125 mrad instantaneous field of view (IFOV) and can work in high spectral resolution mode, high spatial resolution mode and high sensitivity mode for different applications, which can adapt to the Velocity to Height Ratio (VHR) lower than 0.04. The integration has been finished, and several airborne flight validation experiments have been conducted. The results showed the system’s excellent performance and high efficiency.

Steady-State Heat-Flow Coupling Field of a High-Power Magnetorheological Fluid Clutch Utilizing Liquid Cooling

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Daoming Wang ◽  
Bin Zi ◽  
Sen Qian ◽  
Jun Qian
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
High Power ◽  
High Efficiency ◽  
Simulation Method ◽  
Temperature Fields ◽  
Liquid Cooling ◽  
Operation Conditions ◽  
Speed Regulation ◽  
Flow Coupling

Compared with traditional speed regulation (SR) approaches like variable frequency and hydraulic coupling, magnetorheological clutch (MRC) provides a more superior solution for high-efficiency energy saving SR. However, recent developments have demonstrated that severe heating is an outstanding challenge for MRC, especially in high-power applications. Among commonly used cooling methods, liquid cooling offers a viable alternative for the problem. Aiming at pre-evaluating the cooling efficiency of a liquid-cooled MRC in high-power situations, this study introduces a heat-flow coupling simulation method. In this paper, theoretical basis for the simulation is presented first, which is followed by an illustration of the heat-flow coupling simulation. This paper details the simulation model establishment, finite element meshing (FEM), boundary conditions, and simulation parameters. After the simulations, the results concerning the steady flow field of the internal coolant, along with the steady-state temperature fields of MRC, magnetorheological (MR) fluids and the coolant are presented and discussed. Finally, several heating tests of an MRC prototype under various operation conditions are performed and the results verify the correctness and rationality of the simulation.

Shallow Hidden Cave Seismic Wavefield Numerical Simulation Based on Gaussian Beam Method

2013 ◽  
Vol 353-356 ◽  
pp. 1871-1874
Author(s):  
Guo Hua Liu ◽  
Mei Xiao
Keyword(s):  
Numerical Simulation ◽  
Gaussian Beam ◽  
High Efficiency ◽  
Simulation Method ◽  
Field Work ◽  
Forward Modeling ◽  
Seismic Prospecting ◽  
Beam Method ◽  
Gaussian Beam Method ◽  
Seismic Wavefield

Hidden cave is one of the most common geological hazards and the seismic prospecting method is an efficient tool to detect it. Numerical simulation method is the main method of geophysical forward modeling and plays a very important role in seismic prospecting. Gaussian beam forward modeling method combines the wave equation and the ray theory closely, and it has the advantages of high efficiency and high precision. We used Gaussian beam method to simulate the seismic wavefield of shallow hidden cave, and the results showed that the seismic numerical simulation can effectively help us design and optimize the geometry in actual field work. With the help of seismic numerical simulation, the efficiency and precision of shallow seismic prospecting will be improved significantly.

Vibration study of a composite pipeline supported on elastic foundation using a transfer matrix method

2021 ◽  
pp. 107754632098537
Author(s):  
Dongyang Chen ◽  
Junwei Yang ◽  
Weican Guo ◽  
Yanjia Liu ◽  
Chaojie Gu
Keyword(s):  
Elastic Foundation ◽  
Transfer Matrix ◽  
Transfer Matrix Method ◽  
Matrix Method ◽  
High Efficiency ◽  
Fluid Velocity ◽  
Simulation Method ◽  
Pipeline System ◽  
Simulation Results ◽  
The Stability

Efficient and accurate simulation of the vibration characteristics of a composite pipeline system is the key to the study of the stability and vibration control of the pipeline system. A simulation method called transfer matrix method for multibody systems is used to predict the vibration of a composite pipeline resting on an elastic soil. The transfer matrix of the Euler–Bernoulli beams considering the internal fluid velocity and high-efficiency dynamics model of the pipeline system under the action of the elastic foundation are derived. The simulation results have good agreement with that of the literature and commercial software ANSYS Workbench which verified the accuracy of the numerical model. The simulation results show that with the increase of the velocity, the natural frequencies of each mode of the pipeline decrease continuously. When the first frequency is zero, the pipeline buckling occurs and the velocity reaches the critical velocity; the elastic coefficient and shear coefficient in the foundation coefficient are positively related to the stability of the pipeline system. The damping coefficient is negatively related to pipeline stability.

Simulation of Structural Evolution Using Time-Dependent Density-Functional Based Tight-Binding Method

2020 ◽  
Vol 20 (11) ◽  
pp. 7206-7209
Author(s):  
Seung Mi Lee ◽  
Thomas A. Niehaus
Keyword(s):  
Density Functional ◽  
High Efficiency ◽  
Tight Binding ◽  
Computational Cost ◽  
Structural Evolution ◽  
Simulation Method ◽  
Time Dependent ◽  
Excitation Energies ◽  
Carbon Chains ◽  
Experimental Values

A faster and more efficient quantum mechanical simulation method for application to complicated issues of real systems beyond model cases has long been sought after. The density-functional based tight-binding (DFTB) method has successfully explained the atomistic and electronic properties of semiconductors, surfaces, and nanostructures. In addition, the time-dependent formalism implemented in DFTB showed high efficiency in terms of computational cost. In this study, we demonstrated the structural and electronic evolution of small molecules induced by a laser pulse using the time-dependent DFTB (TD-DFTB) method. We identified the critical fluence of the input laser for structural dissociations in carbon chains and fullerenes, which related to the structural stability. The excitation energies of several molecules calculated by TD-DFTB agreed with the experimental values.

Robust Variable Structure Control for Compound Active-Clamp Three-Phase PFC Converter with Soft Switch

2012 ◽  
Vol 433-440 ◽  
pp. 610-616
Author(s):  
Xin Guo ◽  
Hai Peng Ren
Keyword(s):  
High Efficiency ◽  
Control Method ◽  
Variable Structure Control ◽  
Variable Structure ◽  
Simulation Method ◽  
Soft Switch ◽  
Structure Control ◽  
Three Phase ◽  
Parameter Perturbations ◽  
Good Potential

Compound active clamping three-phase Boost PFC converter with soft-switch has a good potential application because of its high power factor, high efficiency and simple structure. The mathematical model of this converter is analyzed. A variable structure control method with the robustness item is proposed for the control of this converter, in order to overcome the shortcoming of the existing method, when the converter parameters changes. The time-varying boundary layer is used to smooth the control discontinuity. Simulation is performed using PSIM and MATLAB hybrid simulation method. The results indicate that the proposed method possesses not only better transient and steady state performance under the nominal parameters, but also better robustness under the parameter perturbations, compared with the traditional PI control and the former variable structure control without the robustness item.

Sign in / Sign up

Export Citation Format

Share Document