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arXiv 2022年

作者： Jiang, Chaokang Wang, Guangming Miao, Yanzi Wang, Hesheng Engineering Research Center of Intelligent Control for Underground Space Ministry of Education School of Information and Control Engineering Advanced Robotics Research Center China University of Mining and Technology Xuzhou221116 China Department of Automation Key Laboratory of System Control and Information Processing Ministry of Education Key Laboratory of Marine Intelligent Equipment and System of Ministry of Education Shanghai Engineering Research Center of Intelligent Control and Management Shanghai Jiao Tong University Shanghai200240 China

3D scene flow characterizes how the points at the current time flow to the next time in the 3D Euclidean space, which possesses the capacity to infer autonomously the non-rigid motion of all objects in the scene. The previous methods for estimating scene flow from images have limitations, which split the holistic nature of 3D scene flow by estimating optical flow and disparity separately. Learning 3D scene flow from point clouds also faces the difficulties of the gap between synthesized and real data and the sparsity of LiDAR point clouds. In this paper, the generated dense depth map is utilized to obtain explicit 3D coordinates, which achieves direct learning of 3D scene flow from 2D images. The stability of the predicted scene flow is improved by introducing the dense nature of 2D pixels into the 3D space. Outliers in the generated 3D point cloud are removed by statistical methods to weaken the impact of noisy points on the 3D scene flow estimation task. Disparity consistency loss is proposed to achieve more effective unsupervised learning of 3D scene flow. The proposed method of self-supervised learning of 3D scene flow on real-world images is compared with a variety of methods for learning on the synthesized dataset and learning on LiDAR point clouds. The comparisons of multiple scene flow metrics are shown to demonstrate the effectiveness and superiority of introducing pseudo-LiDAR point cloud to scene flow estimation. © 2022, CC BY.

关键词： Three dimensional computer graphics

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Soft-Landing Dynamics of a Type of Four-Legged Space Lander

SSRN

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SSRN 2024年

作者： Shi, Tengfei Shi, Tengfei Yang, Yinping Zhang, Zhijuan Liu, Cuicui Liu, Caishan Ma, Daolin Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace Engineering Southwest Jiaotong University Chengdu610031 China State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing100871 China Institute of Dynamics and Control College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing100871 China China Academy of Space Technology Beijing100094 China School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai200240 China Key Laboratory of Marine Intelligent Equipment and System Ministry of Education Shanghai200240 China

Analyzing the landing dynamics response is essential for enhancing the success rate of surface explorations on Mars, the moon, or asteroids. This paper develops a comprehensive dynamics model for a space lander equipped with four sets of buffer legs, each consisting of a primary strut, two secondary struts, and a footpad, during its soft landing process. The degrees of freedom of the main body and the footpads are defined as generalized coordinates to describe the motion of the space lander. The compression force of the buffer struts is obtained by interpolating real experimental data, and the contact force between the footpad and the ground is calculated using Archimedes law for granular media. Then, the dynamical model for the lander in terms of minimal degrees of freedom can be constructed by applying the Lagrange equations of the second kind. The proposed dynamics model is validated by the experiments of a single-legged lander vertical touchdown and a four-legged lander free touchdown. Moreover, histories of buffer force, acceleration of the main body, and other key physical quantities are computed to investigate the landing process. This highly efficient and accurate dynamics model provides a method to perform extensive simulations to design and optimize a soft landing process. © 2024, The Authors. All rights reserved.

关键词： Landing

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Unsupervised Learning of 3D Scene Flow with 3D Odometry Assistance

arXiv

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arXiv 2022年

作者： Wang, Guangming Feng, Zhiheng Jiang, Chaokang Wang, Hesheng Department of Automation Key Laboratory of System Control and Information Processing of Ministry of Education Key Laboratory of Marine Intelligent Equipment and System of Ministry of Education Shanghai Engineering Research Center of Intelligent Control and Management Shanghai Jiao Tong University Shanghai200240 China Engineering Research Center of Intelligent Control for Underground Space Ministry of Education School of Information and Control Engineering Advanced Robotics Research Center China University of Mining and Technology Xuzhou221116 China

Scene flow represents the 3D motion of each point in the scene, which explicitly describes the distance and the direction of each point’s movement. Scene flow estimation is used in various applications such as autonomous driving fields, activity recognition, and virtual reality fields. As it is challenging to annotate scene flow with ground truth for real-world data, this leaves no real-world dataset available to provide a large amount of data with ground truth for scene flow estimation. Therefore, many works use synthesized data to pre-train their network and real-world LiDAR data to finetune. Unlike the previous unsupervised learning of scene flow in point clouds, we propose to use odometry information to assist the unsupervised learning of scene flow and use real-world LiDAR data to train our network. Supervised odometry provides more accurate shared cost volume for scene flow. In addition, the proposed network has mask-weighted warp layers to get a more accurate predicted point cloud. The warp operation means applying an estimated pose transformation or scene flow to a source point cloud to obtain a predicted point cloud and is the key to refining scene flow from coarse to fine. When performing warp operations, the points in different states use different weights for the pose transformation and scene flow transformation. We classify the states of points as static, dynamic, and occluded, where the static masks are used to divide static and dynamic points, and the occlusion masks are used to divide occluded points. The mask-weighted warp layer indicates that static masks and occlusion masks are used as weights when performing warp operations. Our designs are proved to be effective in ablation experiments. The experiment results show the promising prospect of an odometry-assisted unsupervised learning method for 3D scene flow in real-world data. Copyright © 2022, The Authors. All rights reserved.

关键词： Deep learning

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Line Spectrum Estimation and Detection with Few-bit ADCs: Theoretical Analysis and Generalized NOMP Algorithm

arXiv

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arXiv 2023年

作者： Zhu, Jiang Zhang, Hansheng Zhang, Ning Fang, Jun Qu, Fengzhong The Ocean College Zhejiang University China The engineering research center of oceanic sensing technology and equipment Ministry of Education No.1 Zheda Road Zhoushan316021 China The Nanjing Marine Radar Institute Nanjing China The National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China Chengdu611731 China

As radar systems will be equipped with thousands of antenna elements and wide bandwidth, the associated costs and power consumption become exceedingly high, and a potential solution is to adopt low-resolution quantization technology, which not only reduces data storage needs but also lowers power and hardware costs. This paper focuses on line spectral estimation and detection (LSE&D) with few-bit ADCs (typically 1-4 bits) by investigating the signal-to-noise ratio (SNR) loss, establishing a framework to understand the impact of intersinusoidal interference, the bit-depth of the quantizer, and the noise variance on weak signal detection in scenarios involving multiple sinusoids under low-resolution quantization. Additionally, a low-complexity, super-resolution, and constant false alarm rate (CFAR) algorithm, named generalized Newtonized orthogonal matching pursuit (GNOMP), is proposed. Extensive numerical simulations are conducted to validate the theoretical findings, particularly in terms of the detection probability bound. The effectiveness of GNOMP is demonstrated through comparisons with state-of-the-art algorithms, the Cramér Rao bound, and the detection probability bound. Real data acquired by mmWave radar further substantiates the effectiveness of GNOMP in practical applications. © 2023, CC BY.

关键词： Signal to noise ratio

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Typhoon-Induced Stormwater Drives Nutrient Dynamics and Triggers Phytoplankton Blooms in Laizhou Bay, China

SSRN

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SSRN 2023年

作者： Li, Hongguan Li, Shanshan Zhang, Mingzheng Li, Xiuren Xu, Zehao Ma, Haoyang Liang, Shengkang Song, Dehai Li, Junlong Ma, Yuanqing Qin, Huawei Ji, Diansheng Frontiers Science Center for Deep Ocean Multispheres and Earth System Key Laboratory of Marine Chemistry Theory and Technology Ministry of Education Ocean University of China Qingdao266100 China College of Chemistry and Chemical Engineering Ocean University of China Qingdao266100 China College of Oceanic and Atmospheric Sciences Ocean University of China Qingdao266100 China Laboratory for Marine Ecology and Environmental Science Qingdao National Laboratory for Marine Science and Technology Qingdao266237 China Key Laboratory of Physical Oceanography Ocean University of China Ministry of Education Qingdao National Laboratory for Marine Science and Technology Qingdao China State Environmental Protection Key Laboratory of Quality Control in Environmental Monitoring China National Environmental Monitoring Center Beijing100012 China Shandong Marine Resources and Environment Research Institute Yantai264000 China National Marine Environmental Monitoring Center China

The heavy rainfall brought by typhoons result in pulsed inputs of freshwater and nutrients, causing drastic changes in the offshore hydrographic and biogeochemical conditions in a short time. In this study, we evaluated the heavy rainfall impact of Typhoons Rumbia and Lekima on Laizhou Bay (LZB). We found that torrential rainfall significantly modified riverine nutrient concentrations, component ratios, and fluxes. Our results demonstrated that 9% and 16% of the annual riverine total nitrogen (TN) and total phosphorus (TP) fluxes were transported to the LZB within two weeks in Rumbia, and the proportions were 17% and 35% in Lekima, respectively. Influenced by terrestrial inputs, the sea surface temperature (SST) and sea surface salinity (SSS) decreased postRumbia, while the dissolved inorganic nitrogen (DIN) increased from 0.13 ± 0.13 mg/L to 0.47 ± 0.32 mg/L. Furthermore, the SST and SSS decreased by approximately 2.5 ℃ and 2.3 psu postLekima, and the concentration of DIN increased from 0.13 ± 0.08 mg/L to 0.58 ± 0.48 mg/L, which induced subsequent diatom blooms. However, rapid luxury uptake of dissolved inorganic phosphorus (DIP) by phytoplankton resulted in the LZB remaining under P-limited conditions. Freshwater and nutrient pulse input accelerated the growth of highly adaptable and small diatoms in coastal waters, and the dominant species transitioned to Skeletonema costatum after Lekima. We suggest that excess freshwater inputs alter the hydrodynamic structure and residence time, combined with other suitable factors, resulting in a dramatic increase in Noctiluca scintillans and the formation of harmful algal blooms (HABs) after a decline in diatom blooms. © 2023, The Authors. All rights reserved.

关键词： Nutrients

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Automated Assembly by Two-Fingered Microhand for Fabrication of Soft Magnetic Microrobots

Automated Assembly by Two-Fingered Microhand for Fabrication...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Yue Zhao Xiaoming Liu Ruixi Wang Dan Liu Masaru Kojima Qiang Huang Tatsuo Arai Key Laboratory of Biomimetic Robots and Systems Ministry of Education State Key Laboratory of Intelligent Control and Decision of Complex System Beijing Advanced Innovation Center for Intelligent Robots and Systems Beijing China School of Mechatronical Engineering Beijing Institute of Technology Beijing China Department of Intelligent Manufacturing Shenzhen International Graduate School Tsinghua University Shenzhen China Department of Materials Engineering Science Osaka University Osaka Japan Center for Neuroscience and Biomedical Engineering The University of Electro-Communications Tokyo Japan

ISBN: (数字)9798350384574

ISBN: (纸本)9798350384581

Micro-assembly is an emerging method to fabricate microrobots with multiple modules or particles. However, there is always a lack of a flexible and efficient method to freely create the desired magnetic soft microrobots. In this paper, an automated assembly system based on a two-fingered microhand is presented for fabricating magnetic soft microrobots. Our proposed system can automatically pick and place components to assemble microrobots with a two-fingered micromanipulator, and orient these components through an external magnetic field. The automated assembly has the advantages of high accuracy, high speed, and high success rate. It can endow magnetic microrobots with flexible material selection, arbitrary geometry design, and programable magnetization profile. We can make full use of this system to fabricate multiple magnetic soft microrobots. The experiment results demonstrate that this system can efficiently fabricate microrobots with excellent mechanical properties, which have application potential in robotics, biomedical engineering, and environmental governance.

关键词： Three-dimensional displays Shape Micromanipulators Magnetization Manuals Three-dimensional printing Soft magnetic materials

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Effect of soaking time on tribological Properties of Thordon bearing Materials in High Temperature Water Bath

Effect of soaking time on tribological Properties of Thordon...

引用

International Conference on Transportation Information and Safety (ICTIS)

作者： Xincong Zhou Peng Wang Jian Huang Xueshen Liu Chaozhen Yang Da Zhong Shaopeng Xing Key Laboratory of Marine Power Engineering &#x0026 Technology (Ministry of Communications) Wuhan University of Technology Wuhan China Reliability Engineering Institute Wuhan University of Technology Wuhan China

ISBN: (纸本)9781665497145

In view of the fact that its tribological performance will be changed by the Thordon bearing being soaked in the high temperature water environment when working. Thordon bearing samples was soaked in high temperature water bath at 80°C for 0h, 24h, 48h and 72h to study the effect of soaking time on the tribological properties of water lubrication of Thordon. The ring - block friction and wear tests were carried out by SSB-100V ship stern bearing testing machine. The results showed that under the same load and rotational speed, the friction coefficient of Thordon decreased at first and then increased from the increase in soaking time, and the friction coefficient was the minimum when soaked for 24 hours. The main wear mechanism of Thordon material is adhesive wear and furrow wear. With the increase in soaking time, the wear volume of Thordon decreased at first and then increased, and the wear volume was the minimum when the soaking time was 24 hours. This indicates that the soaking time will have an impact on the wear volume of Thordon material.

关键词： Water Temperature Friction Velocity control Transportation Safety Lubrication

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Experimental Investigation on Shear Strength between Ultra-High-Performance Concrete and Normal Concrete Substrates

引用

Advances in Materials Science and engineering 2023年第1期2023卷

作者： Jiang, Xinghong Song, Hengxiang Li, Ke Qiang, Jing Tian, Jing State Key Laboratory of Coal Mine Dynamics and Control Chongqing University Chongqing400044 China China Merchants Chongqing Communications Technology Research Design Institute CO. LTD. Chongqing4000467 China School of Civil Engineering Chongqing Jiaotong University Chongqing400074 China Hong Kong-Zhuhai-Macao Bridge Authority Guangdong Zhuhai519060 China Key Laboratory of Road and Traffic Engineering the Ministry of Education Tongji University Shanghai201804 China

Tunnel engineering in China has developed to the stage of both construction and maintenance, and the problem of structural defect is widespread. The cast-in-situ jacketed arch treatment takes a long time and has a great impact on traffic. It is urgent to develop prefabricated treatment technology, and the guarantee of mechanical properties of the prefabricated UHPC-post-cast NC interface is the key problem. Through the oblique shear test, combined with the XTDIC full-field strain monitoring system, the failure process and failure mode of UHPC-NC specimens were studied and analyzed under different interface keyway numbers (0, 1, 2, and 3), interface agents (meshless interface agent, cement slurry, silica fume modified cement slurry, modified cement slurry mesh, cement slurry, and expansion agent), and NC pouring grades (C30, C35, C40, and C50), as well as the influencing factors of shear strength, shear stiffness, and the slip model of the bonding interface. The results show that there are four typical failure modes in UHPC-NC under compression and shear, including complete interface failure (Class A), interface failure + NC shear failure (Class B), NC compression failure (Class C), and interface failure + NC compression failure + NC slip failure in the keyway (Class D). The complete interface failure type (Type A) without keyway treatment has sudden failure, and the keyway has the ability to disperse load and limit interface slip. The principal strain decreases along the normal sides of the interface, and the influence range of UHPC and NC sides is about 16.2 mm and 17.5 mm, respectively. In practice, the thinnest part of the treatment structure should not be less than 2 cm. The shear strength of the prefabricated UHPC-post-pouring NC interface is generally low, and the maximum shear strength of 13.9 MPa obtained by the test is still lower than the recommended value of 14-21 MPa of ACI 546.3R-14. In treatment design, the interface shear reinforcement can be introduc

关键词： keyways

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Adaptive Backstepping Sliding Mode control for Underwater Glider Trajectory Tracking Based on Nonlinear Disturbance Observer

Adaptive Backstepping Sliding Mode Control for Underwater Gl...

引用

Chinese Automation Congress (CAC)

作者： Zhenjia Li Weihua Cao Chao Gan Mingming Wen School of Automation China University of Geosciences Wuhan China Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems Wuhan China Engineering Research Center of Intelligent Technology for Geo-Exploration Ministry of Education Wuhan China Guangzhou Marine Geological Survey Guangzhou China

An adaptive backstepping dynamic surface sliding mode controller based on nonlinear disturbance observer (NDOABSMC) is designed to track zigzag motion of underwater glider (UG). Firstly, a nonlinear disturbance observer is devised to observe ocean current. Then, the backstepping sliding mode control is used to devise motion attitude controller of UG to ensure that UG can track the target trajectory quickly. Additionally, the stability of UG's control system is analyzed. In the end, the proposed control strategy is compared with other approaches.

关键词：

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A Trajectory Tracking Method using Dynamic Sliding Mode control with Parameter Optimization for Autonomous Underwater Vehicles

A Trajectory Tracking Method using Dynamic Sliding Mode Cont...

引用

Industrial Cyber-Physical Systems (ICPS)

作者： Weiliang Li Xuzhi Lai Sheng Du Chengda Lu Yawu Wang Zonghuan Chen Min Wu School of Automation China University of Geosciences Wuhan China Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems Wuhan China Ministry of Education Engineering Research Center of Intelligent Technology for Geo-Exploration Wuhan China Guangzhou Marine Geological Survey Guangzhou China

Autonomous underwater vehicles (AUVs) must be able to track a particular trajectory when performing various tasks. Sometimes, the widely used control method in actual marine engineering, the proportional integral derivative (PID) control method cannot meet the accuracy requirements of AUVs' trajectory tracking. In this paper, a dynamic surface sliding mode controller for trajectory tracking is designed. A nonlinear disturbance observer is used to compensate for environmental interference, and an improved particle swarm optimization with dynamic inertia weight is applied to optimize the control parameter. Simulation experiments are based on the mathematical model of an underwater robot BLUEROV2, and the control and optimization algorithms are designed.

关键词： Autonomous underwater vehicles Trajectory tracking Heuristic algorithms Mathematical models Trajectory Vehicle dynamics Particle swarm optimization

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