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Negative Stiffness Mechanism on An Asymmetric Wave Energy Converter by Using A Weakly Nonlinear Potential Model

China Ocean engineering 2024年第4期38卷 689-700页

作者： Sunny Kumar POGULURI Dongeun KIM Yoon Hyeok BAE Department of Ocean Engineering IIT MadrasChennaiIndia Multidisciplinary Graduate School Program for Wind Energy Jeju National UniversityJejuRepublic of Korea Mechanical and System Design Engineering Hongik UniversitySeoulRepublic of Korea

Salter's duck,an asymmetrical wave energy converter(WEC)device,showed high efficiency in extracting energy from 2D regular waves in the past;yet,challenges remain for fluctuating wave *** can potentially be addressed by adopting a negative stiffness mechanism(NSM)in WEC devices to enhance system efficiency,even in highly nonlinear and steep 3D waves.A weakly nonlinear model was developed which incorporated a nonlinear restoring moment and NSM into the linear formulations and was applied to an asymmetric WEC using a time domain potential flow *** model was initially validated by comparing it with published experimental and numerical computational fluid dynamics *** current results were in good agreement with the published *** was found that the energy extraction increased in the range of 6%to 17%during the evaluation of the effectiveness of the NSM in regular *** irregular wave conditions,specifically at the design wave conditions for the selected test site,the energy extraction increased by 2.4%,with annual energy production increments of approximately *** findings highlight the potential of NSM in enhancing the performance of asymmetric WEC devices,indicating more efficient energy extraction under various wave conditions.

关键词： asymmetric wave energy converter negative stiffness mechanism weakly nonlinear potential flow power

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Ultrafast Miniature Robotic Swimmers with Upstream Motility

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Cyborg and Bionic Systems 2023年第1期4卷 452-459页

作者： Yibin Wang Hui Chen Junhui Law Xingzhou Du Jiangfan Yu School of Science and Engineering The Chinese University of Hong KongShenzhenChina ShenzhenInstitute of Artificial Intelligence and Robotics for Society ShenzhenChina Department of Mechanical and Industrial Engineering University of TorontoTorontoCanada

With the development of materials science and micro-nano fabrication techniques,miniature soft robots at millimeter or submillimeter size can be manufactured and actuated *** small-scaled robots have the unique capability to access hard-to-reach regions in the human body in a noninvasive *** date,it is still challenging for miniature robots to accurately move in the diverse and dynamic environments in the human body(e.g.,in blood flow).To effectively locomote in the vascular system,miniature swimmers with upstream swimming capability are ***,we design and fabricate a miniature robotic swimmer capable of performing ultrafast swimming in a fluidic *** maximum velocity of the swimmer in water is 30 cm/s,which is 60 body ***,in a tubular environment,the swimmer can still obtain a swimming velocity of 17 cm/*** swimmer can also perform upstream swimming in a tubular environment with a velocity of 5 cm/s when the flow speed is 10 cm/*** ultrasound-guided navigation of the swimmer in a phantom mimicking a blood vessel is also *** work gives insight into the design of agile undulatory milliswimmers for future biomedical applications.

关键词： millimeter upstream environments

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Development of Video Stabilization Technology in Extreme Environments Using Lidar-inertial Odometry

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Journal of Institute of Control, robotics and Systems 2025年第1期31卷 61-67页

作者： Yoon, Yeong-In Suh, Hyeong-Seok Shin, Gwan-Jun Lim, Jong-Woo Department of Mechanical Engineering Seoul National University Korea Republic of Interdisciplinary Program in Artificial Intelligence Seoul National University Korea Republic of

This study proposes designing and applying a video stabilization algorithm using LIDAR-inertial odometry (LIO). The performance of the video stabilization function was validated in narrow, low-light environments using a small robot. A unique camera pose estimation method based on LIO has been introduced and integrated with the camera system in this work to not only overcome the limitations of image feature-based camera pose estimation but also address the issues arising from camera sensors. Thus, this strategy allows the practical implementation of a robust camera stabilization algorithm even in extreme environments. The proposed approach is resilient to the differing scan rates of the LIDAR system and the camera, and it enhances usability by filtering noise from the LIO. Furthermore, it requires less computational resources compared to traditional image feature extraction-based methods. This technology can substantially improve the operational convenience for robot operators, especially in scenarios where robots equipped with various sensors are deployed in extreme environments. © ICROS 2025.

关键词： image perspective transformation lidar-inertial odometry video stabilization

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Fabrication of Microchannels on Aluminium-Coated Polymethyl Methacrylate (PMMA) Using a Low Power CO2 Laser

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Lasers in Manufacturing and Materials Processing 2024年第4期11卷 868-886页

作者： Okello, Job Lazarus El-Bab, Ahmed M. R. Fath Yoshino, Masahiko El-Hofy, Hassan A. Industrial and Manufacturing Engineering Department Egypt-Japan University of Science and Technology New Borg El-Arab City Egypt Mechatronics and Robotics Engineering Department Egypt-Japan University of Science and Technology New Borg El-Arab City Egypt Department of Mechanical Engineering Tokyo Institute of Technology Tokyo Japan Department of Production Engineering Faculty of Engineering Alexandria University Alexandria Egypt

The emergence of microfluidics as one of the most viable technologies for making various microfluidic devices has greatly enhanced miniaturization in several areas. The utilization of polymethyl methacrylate (PMMA) for making such devices using CO2 lasers has significantly increased due to the flexibility, time, and cost-effectiveness involved. However, attaining microchannels with accurate dimensions is a challenge because of the resulting defects like bulges, high heat-affected zone (HAZ), and surface roughness (Ra). This paper presents a novel attempt to engrave rectangular microchannels on PMMA substrates using a CO2 laser by coating the substrates with a thin layer of 1 μm thickness of 99.95% pure aluminium. The study investigated the effects of power, and speed on the quality of the microchannels. The fabrication was done on both coated and uncoated substrates under the same conditions and the results were compared. Power and speed ranged from 1.5 to 7.5 W and 5 to 17.5 mm/s, respectively. At 1.5 W and 17.5 mm/s, the aspect ratio increased by 37.16%. However, the microchannel depth, width, HAZ, and Ra all reduced by 44.66%, 59.68%, 29.44%, and 64.74% respectively. At 7.5 W and 5 mm/s, the aspect ratio increased by 81.46%. However, the microchannel depth, width, HAZ, and Ra all reduced by 21.84%, 54.64%, 32.36%, and 72.70% respectively. The coated substrates produced better microchannels than the uncoated ones. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.

关键词： Carbon dioxide lasers

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A Multi-party Asymmetric Self-play Algorithm and Its Application in Multi-USV Adversarial Game Simulations 24

A Multi-party Asymmetric Self-play Algorithm and Its Applica...

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2024 International Conference on Machine Learning, Pattern Recognition and Automation engineering, MLPRAE 2024

作者： Rao, Jinjun Wang, Cong Liu, Mei Lei, Jingtao Giernacki, Wojciech Department of Precision Mechanical Engineering School of Mechatronic Engineering and Automation Shanghai University China Institute of Robotics and Machine Intelligence Faculty of Automatic Control Robotics and Electrical Engineering Poznan University of Technology Poland

ISBN: (纸本)9798400709876

Aiming at the problem that the combination of self-play (SP) and deep reinforcement learning (DRL) only involves two-party games and the policy learning of each party is limited, a multi-party asymmetric self-play algorithm (MASP) is proposed. Firstly, by improving the ELO scoring system, the ELO scoring takes into account each party of the unmanned surface vehicle (USV) clusters, and the imbalance of the number of USV clusters, so that the frequency of exchanging strategies of all USV clusters in the confrontation process is equal. Secondly, it ensures that USV clusters have a balanced combat ability, and at the same time ensures that the combat ability of all parties is strong and weak and the gap is not too wide. In addition, the parameters are dynamically set to reduce the update frequency of the policy of the stronger party. The experimental results show that the MASP can make the USV clusters learn more effective policies, have a shorter game time, and obtain higher rewards and ELO scores in the simple 2v2 adversarial game scenario and the three-party game scenario of a warship escort mission. © 2024 ACM.

关键词： Deep reinforcement learning

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Effect of Brass Content and Speed of Cut on Machining Outcomes of Copper–2% Silver Alloy

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Journal of The Institution of Engineers (India): Series D 2024年 1-7页

作者： Prashanth, Mrudula Prasad, N. J. Krishna Kumar, B. S. Ajay Satish, N. Department of Industrial Engineering and Management Bangalore Institute of Technology Bengaluru Visveswaraya Technological University Belgaum India Department of Mechanical Engineering Amrita School of Engineering Amrita Vishwa Vidyapeetham Bengaluru India Department of Mechanical Engineering Bangalore Institute of Technology Bengaluru Visveswaraya Technological University Belagavi Karnataka India Department of Robotics and Artificial Intelligence Bangalore Institute of Technology Bengaluru Visveswaraya Technological University Belagavi India

Copper is one of the ductile materials which is difficult to machine, but extensively used in variety of applications such as electrical, thermal and nuclear. Turning is one of the predominantly used lathe operation, and the current work focuses on turning different alloys of copper at various compositions of alloying elements to investigate the effect of the machining parameter, i.e. speed of cut on cutting force, thrust force, unit power consumption and machinability which marks the effect as machining outcomes. The work also focuses on the effect of the alloys formed out of varying compositions of brass on the machining outcomes of copper–2wt% silver alloy. The work concludes on, the forces exerted on tool, unit power consumption and machinability to be least at 9% brass addition to copper silver alloy. © The Institution of Engineers (India) 2024.

关键词： Brass

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Enhanced Optimal Control of a Magnetically Actuated Capsule Endoscope Using Electromagnetic Coils Considering Small Intestine Dynamics 12

Enhanced Optimal Control of a Magnetically Actuated Capsule ...

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12th RSI International Conference on robotics and Mechatronics, ICRoM 2024

作者： Jamali, Mahdi Zarifi Khameneh, Mohammadreza Sarkhosh, Mohammadhossein Pishkenari, Hossein Nejat Sharif University of Technology Micro/Nano Robotics Laboratory Department of Mechanical Engineering Tehran Iran

ISBN: (纸本)9798331529734

Active locomotion of capsule endoscopes has become a prominent progress in minimally invasive diagnostic procedures. Utilizing external magnetic fields for this purpose enables contactless actuation and enhanced maneuverability. This study presents an optimal control technique for magnetically actuated capsule endoscopes (MACE) within the small intestine, using a modified OCTAMAG setup. The objective is to minimize input currents while ensuring accurate path tracking, thereby preventing coil overheating and avoiding actuation inaccuracies. A correction force is also incorporated into the controller to stabilize it against external disturbances. The proposed method is evaluated using a path inspired by the small intestine and compared to conventional PID control. Results show that the optimal controller achieves superior path tracking while maintaining input currents within safe limits. Additionally, the disturbance rejection capabilities of the optimal controller are comparable to those of the PID. © 2024 IEEE.

关键词： Disturbance rejection

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Enhancing the Versatility and Performance of Soft Robotic Grippers, Hands, and Crawling Robots Through Three-Dimensional-Printed Multifunctional Buckling Joints

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Soft robotics 2024年第5期11卷 741-754页

作者： Yang, Chih-Wen Ou Yu, Shao-Yi Chan, Che-Wei Tseng, Chien-Yao Cai, Jing-Fang Huang, Han-Pang Juang, Jia-Yang Department of Mechanical Engineering National Taiwan University Taipei Taiwan Department of Mechanical Engineering University of California at Berkeley BerkeleyCA United States Program in Nanoengineering and Nanoscience Graduate School of Advanced Technology National Taiwan University Taipei Taiwan

Soft robotic grippers and hands offer adaptability, lightweight construction, and enhanced safety in human–robot interactions. In this study, we introduce vacuum-actuated soft robotic finger joints to overcome their limitations in stiffness, response, and load-carrying capability. Our design—optimized through parametric design and three-dimensional (3D) printing—achieves high stiffness using vacuum pressure and a buckling mechanism for large bending angles (>90◦) and rapid response times (0.24 s). We develop a theoretical model and nonlinear finite-element simulations to validate the experimental results and provide valuable insights into the underlying mechanics and visualization of the deformation and stress field. We showcase versatile applications of the buckling joints: a three-finger gripper with a large lifting ratio (*96), a five-finger robotic hand capable of replicating human gestures and adeptly grasping objects of various characteristics in static and dynamic scenarios, and a planar-crawling robot carrying loads 30 times its weight at 0.89 body length per second (BL/s). In addition, a jellyfish-inspired robot crawls in circular pipes at 0.47 BL/s. By enhancing soft robotic grippers’ functionality and performance, our study expands their applications and paves the way for innovation through 3D-printed multifunctional buckling joints. © Mary Ann Liebert, Inc.

关键词： Grippers

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A Comparative Analysis of Electric Vehicles Charging-Discharging Topologies for Sustainable Energy 3

A Comparative Analysis of Electric Vehicles Charging-Dischar...

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3rd International Conference on Communication, Control, and Intelligent Systems, CCIS 2024

作者： Sinha, Ashish Kumar Pushkarna, Mukesh Kumar, Prashant Gla University Institute of Engineering and Technology Department of Electrical Engineering Mathura India Dongguk University Department of Mechanical Robotics and Energy Engineering Seoul04620 Korea Republic of

ISBN: (纸本)9798331528201

Electric vehicles (EVs) have gained immense popularity in recent times owing to the decrease in conventional energy resource reserves and the concurrent threat to the environment caused from the harmful discharge of IC engine vehicles. EVs are mainly divided into the following three categories: pure electrical vehicles or battery electric vehicles, hybrid electrical vehicles, and fuel cell electrical vehicles. All these classifications have certain advantages and drawbacks associated with them. Based on the associated advantages and disadvantages, various aspects of EV performance have been scrutinized namely, design optimization, transmission performance optimization, battery management system (BMS) and charging technology to name a few. While all the abovementioned aspects affect the EV performance critically, BMS and charging technology have been the main area of concern for design engineers and researchers. Herein, two major charging topologies are prevalent, i.e. vehicle-to-grid (V2G) and grid-to-vehicle (G2V). Moreover, a third and fourth scheme of operation, namely, vehicle-to-home (V2H) and vehicle-to-vehicle (V2V) topology respectively, is also gaining importance off-late. With this view, the present manuscript aims to categorize, engulf and encapsulate the different EVs along with the existing charging technologies in EVs and BMS. This shall make the topic at hand easier to comprehend for the prospective future researchers. © 2024 IEEE.

关键词： Vehicle-to-grid

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Development of a Lightweight Real-Time Application for Dynamic Hand Gesture Recognition 20

Development of a Lightweight Real-Time Application for Dynam...

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20th IEEE International Conference on Mechatronics and Automation, ICMA 2023

作者： Yusuf, Oluwaleke Habib, Maki Program Department of Mechanical Engineering Cairo Egypt

ISBN: (纸本)9798350320831

Hand Gesture Recognition (HGR) is a form of perceptual computing with applications in human-machine interaction, virtual/augmented reality, and human behavior analysis. Within the HGR domain, several frameworks have been developed with different combinations of input modalities and network architectures with varying levels of efficacy. Such frameworks maximized performance at the expense of increased hardware and computational requirements. These drawbacks can be tackled by transforming the relatively complex dynamic hand gesture recognition task into a simpler image classification task. This paper presents a skeleton-based HGR framework that implements data-level fusion for encoding spatiotemporal information from dynamic gestures into static representational images. Said static images are subsequently processed by a custom, end-to-end trainable multi-stream CNN architecture for gesture classification. Our framework reduces the hardware and computational requirements of the HGR task while remaining competitive with the state-of-the-art on the CNR, FPHA, LMDHG, SHREC2017, and DHG142S benchmark datasets. We demonstrated the practical utility of our framework by creating a lightweight real-time application that makes use of skeleton data extracted from RGB video streams captured by a standard inbuilt PC webcam. The application operates successfully with minimal CPU and RAM footprint while achieving 93.46% classification accuracy with approximately 2s latency at 15 frames per second. © 2023 IEEE.

关键词： Network architecture

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