Design, Simulation and Experiment for a Vortex-Induced Vibration Energy Harvester for Low-Velocity Water Flow

Dongxing Cao,Xiangdong Ding,Xiangying Guo,Minghui Yao 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4

Piezoelectric vibration energy harvesting has attracted considerable attention because of its prospects in self-powered electronic applications. There are a many low-velocity waters in nature, such as rivers, seas and oceans, which contain abundant hydrokinetic energy. In this paper, an optimal geometric piezoelectric beam combining magnetic excitation is identified and applied to a vortex-induced vibration energy harvester (ViVEH) for low velocity water flow, which is composed of a continuous variable-width piezoelectric beam carrying a cylindrical bluff body. The finite element simulation and experiment are first carried out to study the harvesting characteristics of the designed variable-width beam ViVEH without considering the magnetic excitation. The influence of the width-ratio and flow velocity on the harvesting voltage is studied in detail. The optimal structure, a ViVEH equipped with triangular piezoelectric beam, is then obtained by the superior energy harvesting performance for low velocity water flow. From the experimental results, at a flow velocity of 0.6 m/s, the highest root mean square (RMS) voltage and RMS voltage per unit area are 19.9 V and 0.07 V/mm 2 , respectively. Furthermore, magnetic excitation is introduced to improve the scavenging performance of the optimal triangular beam ViVEH, different polarity arrangements are compared, and the optimal case, the arrangement of horizontal repulsion and vertical attraction (HR-VA), is obtained. This case can scavenge the highest power of 173 μW at a flow velocity of 0.5 m/s, which is increased by 127% compared to a conventional constant-width beam ViVEH with no magnetic excitation.

Augmented Reality Annotation for Real-Time Collaboration System

Dongxing Cao,Sangwook Kim 한국멀티미디어학회 2020 멀티미디어학회논문지 Vol.23 No.3

Design and modeling of a cable-driven articulated robot intended to conduct lower limb recovery training

Dongxing Cao,Xiangxu Qu,Chunlei Wang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

The proposed cable-driven articulated robot (CDAR) is composed mainly of an articulated-multibody system which is connected to three cables, and can perform sitting type rehabilitation therapies for lower extremity. Adding torsion springs to the rotary joints of CDAR ensures that all cables are always in tension. The arrangement of kinematics in the sagittal plane is presented for motion control and the corresponding optimization problems with strongly nonlinear characteristics are developed. After, the particle swarm optimization method is used to determine the dimensions of the mechanism and the optimum attachment position of the cable. Further, the system dynamics is derived based on Newton-Euler method to help analyze the force profiles and the stiffness of the robot is described when considering compliant impacts of the structural joints. Finally, experimental results demonstrated that the designed robot can fulfill lower limb rehabilitation with advantages such as being lightweight, low-cost, and having simple transmission.

Improved Flow-Induced Vibration Energy Harvester by Using Magnetic Force: An Experimental Study

Dongxing Cao,Xiangdong Ding,Xiangying Guo,Minghui Yao 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.3

Vibration energy harvesting has attracted considerable attention because of its application prospects for charging or powering micro-electro-mechanical system. Abundant hydrokinetic energy of water at low velocity is contained in the fluid environment, such as rivers and oceans, which are widely existing in nature. In this paper, a flow-induced piezoelectric vibration energy harvester (PVEH) with magnetic force enhancement, which is integrated by piezoelectric beam, circular cylinder bluff body and magnets, is proposed and experimental investigated. It could transfer the hydrokinetic energy, both the vortex-induced vibration and magnetic force excitation underwater, into electricity. First, the frequency sweep experiment of the piezoelectric cantilever beam is carried out to determine the resonance frequency where the effect of magnetic force on the vibration characteristic is obtained. Furthermore, the flow-induced vibration experiment platform is setup and the energy harvesting performance of the PVEH is investigated in detail. The effects of the magnet property, flow velocity and the magnetic poles distance on the vibration frequency and the acquisition voltage are demonstrated and discussed. The results show that it could improve the harvesting performance by introducing magnetic force. It has advantages in higher output voltage for the flow-induced PVEH, especially in low velocity water flow, when the flow velocity is 0.35 m/s, the PVEH under attractive magnetic force with magnetic distance of 20 mm scavenges the higher acquisition voltage of 5.2 V, which is increased by 225% than the PVEH with non-magnetic. The results can be applied to guide further fabrication process and optimized design of the proposed flow-induced PVEH underwater with low flow velocity.

Augmented Reality Annotation for Real-Time Collaboration System

Cao, Dongxing,Kim, Sangwook Korea Multimedia Society 2020 멀티미디어학회논문지 Vol.23 No.3

Advancements in mobile phone hardware and network connectivity made communication becoming more and more convenient. Compared to pictures or texts, people prefer to share videos to convey information. For intentions clearer, the way to annotating comments directly on the video are quite important issues. Recently there have been many attempts to make annotations on video. These previous works have many limitations that do not support user-defined handwritten annotations or annotating on local video. In this sense, we propose an augmented reality based real-time video annotation system which allowed users to make any annotations directly on the video freely. The contribution of this work is the development of a real-time video annotation system based on recent augmented reality platforms that not only enables annotating drawing geometry shape on video in real-time but also drastically reduces the production costs. For practical use, we proposed a real-time collaboration system based on the proposed annotation method. Experimental results show that the proposed annotation method meets the requirements of real-time, accuracy and robustness of the collaboration system.

Research on the workspace and analytical stiffness method of a cable-driven robot intended to conduct lower limb rehabilitation therapies

Xiangxu Qu,Dongxing Cao,Mengying Song,Yuting Zhang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.10

This paper proposed a cable-driven robot for performing lower limb rehabilitation therapies. Based on important requirements intended to confirm positive tensions within a redundant number of cables, a simple way of examining the operational area for cable-driven structures is discussed and implemented for a rehabilitation device. In contrast, a more suitable scheme is to add torsion springs at the robot joints. These springs can create resistance torque, potentially reducing the number of cables and solving issues of interference. An examination approach using the virtual joint method is suggested to describe the stiffness of the robot amidst rehabilitation development when considering mass, external force, and compliant impacts of the structural joints. Simulated and experimental results demonstrated that the proposed method was effective and the designed robot can fulfil lower limb rehabilitation with advantages such as being lightweight, low-cost, and having simple transmission.

Quantitative validation of the analytical mode shapes of a beam-like structure with a Z-shaped configuration

Wenhua Hu,Fengxiang Wang,Dongxing Cao,Jianen Chen,Jingjing Feng 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

Beam-like structures are widely used in engineering. The accuracy of the analytical mode shapes of these structures is important for studying their dynamic characteristics. A method is presented in this study to theoretically obtain and quantitatively validate the analytical mode shapes of a beam-like structure with a Z-shaped configuration. The governing equations and boundary conditions of the structure’s planar motion are derived using Hamilton’s principle. Frequencies and analytical mode shapes of the structure are theoretically obtained and compared with the numerical results from finite element method. The comparison of frequencies and modal assurance criterion is used to quantitatively validate the analytical mode shapes. Examples are presented to show the analytical mode shapes of Zshaped beams with different fold angles. The proposed method is useful for improving the accuracy of analytical mode shapes, which is beneficial to the design and control of beam-like structures in engineering fields.

실시간 상황 인지 동적 그래프에 의한 대피로 탐색 및 예측

김선형(Seonhyeong Kim),류신혜(Shinhye Ryu),차오동싱(Dongxing Cao),권영우(Youngwoo Kwon),김상욱(Sangwook Kim) 한국HCI학회 2020 한국HCI학회 학술대회 Vol.2020 No.2