Quantitative Stability Analysis of an Unmanned Tethered Quadrotor

Dong Liang,Li Ding,Mingyue Lu,Rui Ma,Jie Cao 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.3

Tethered quadrotors, unmanned aerial quadrotors connected to a fixed point via tether cables, have been widely applied in numerous aerial tasks. However, their structural parameters and external disturbances give rise to dynamic stability issues, resulting in uncontrolled autonomous flight, shaking, and vibrating. Thus, this article investigates the quantitative stability of a tethered quadrotor using the Lyapunov exponent approach. First, a mathematical model of the tethered quadrotor is developed, and its dynamic stability is quantified to verify the rationality of the designed physical prototype and enhance the aerial system’s stability. Both simulation and experimental results show that the dynamic stability during the landing phase is better than that during takeoff. Finally, optimizing the structural parameters enhances the dynamic stability, which is sensitive to cable length, wind gusts, and yaw angle.

Mathematical model and meshing analysis of internal meshing gear transmission with curve element

Dong Liang,Weibin Li,Bingkui Chen 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12

A new internal meshing gear transmission with curve element is put forward in this paper. The mathematical principle of tooth profile generation is described based on conjugate curves theory. For a given spatial curve, the meshing equation and its conjugated spatial curve under the motion law were derived. Considering the equidistant kinematic method, general internal tooth profiles models were established by the conjugate-curve pair. Numerical example of the internal gear pair was developed according to gear parameters and gear solid models were established by MATLAB and UG software. Motion simulation result shows that the gear pair satisfies point contact condition and design requirements. Meshing analysis of tooth profiles using FEA method was carried out. Stress analysis results of tooth profiles with single point contact and two points contact were, respectively, obtained. The conclusions lay the foundation for multi-point contact generation and tooth profile design. Also, further studies on transmission characteristics and manufacturing technology of the new gear drive will be carried out.

Hobbing Manufacturing of New Type of Involute-Helix Gears for Wind Turbine Gearbox

Dong Liang,Bingkui Chen,Yane Gao 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.6 No.2

The involute gears are widely used in the gearbox for wind turbine. To satisfy the requirements of reduction of noise and increase of the endurance of the gear drive, the new type of involute-helix gears, which have the advantages of involute gears and circular arc gears, had been proposed. In this paper, the hobbing cutters of involute-helix gears are designed utilizing the normal section of convex and concave tooth profiles, respectively. Mathematical models of hobbing cutters are established and general products are also manufactured. Using the developed hobbing cutters, the proposed gear pair is manufactured based on the numerical control technology. Combining with the measure method of gear measuring center and the characteristic of the investigated gears, the method of error measurement of special tooth profiles is provided. The further development of special detection software for the gears will be carried out. The results will lay the foundations for the large-scale industrial practice and production applications of gear drive.

Deviation Calculation and Analysis of Tooth Surfaces of Conjugate-Curve Gear Drive

Dong Liang,Bingkui Chen,Shuai Peng,Chengli Hua,Ruijin Liao 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.5

Conjugate-curve gears are point contact gears and the locus curves of contact points are conjugate curves. For conjugate-curve gear drive, the application of rack cutters may result in geometrical deviation between the theoretical tooth profiles and the generated tooth profiles. To discuss the deviation conditions between two tooth surfaces, generation of theoretical tooth profiles is described and the tooth profiles generated by the rack cutters are derived. General calculation method for the deviation is provided and the analysis of tooth surfaces is also carried out. Numerical examples utilizing the circular-arc curve and parabolic curve are performed, respectively. The obtained results are discussed and the influences of design parameters including the design parameter, helix angle and the radius of pitch circle on the deviation are shown. The summarized contents of this paper are finally present.

Analysis of Differences in Fun, Flow, and Self-Directed Learning According to the Background Variables and Characteristics of the Senior Citizens Participating in the HEALTH QIGONG Program

Dong Liang,Jaebum Lee,Hyunwoo Kim J-INSTITUTE 2021 Protection Convergence Vol.6 No.3

Purpose: This study has analyzed the differences between fun, flow, and self-directed learning according to the background variables and the characteristics of senior citizens participating in the Health Qigong program with a view to use them as the basic data for the senior citizens’ health education. Method: Participants in this study were 241 elderly people participating in the Health Qigong program at sen-ior welfare centers, senior centers, and public health centers located in Seoul and Gyeonggi-do, Korea. As an anal-ysis method, MANOVA was conducted to examine the differences in fun, flow, and self-directed learning accord-ing to background characteristics such as age, education, training experience, number of training sessions, and residence type, which are background variables of the elderly. Results: As a result of study, the fun variable, flow variable, and the self-directed learning variable demon-strated differences each according to the demographic background variable. In particular, it was evident that the demographic characteristics of age, training experience, and number of training sessions demonstrated the statis-tically significant differences for fun, flow, and self-directed learning. Conclusion: The results of this study demonstrate the possibility that very active physical activities and related experiences for the senior citizens for health intervention would bring about the self-directed learning through the experiences of fun and flow, which in turn might impact the improvement of the quality of life for the old age. It confirmed that in terms of the operation of the Health Qigong program, it is necessary to accommodate the needs by age, experience, and number of training sessions, and also induce the senior citizens participating in the exer-cises to participate in the program positively through the development of the Health Qigong program towards that end.

Theoretical and Experimental Investigations on Parallel- Axis Gear Transmission with Tubular Meshing Surfaces

Dong Liang,Bingkui Chen,Yane Gao 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Theoretical and experimental investigations on parallel-axis gears with tubular meshing surfaces are performed in this study. Based on theory of conjugate curves, the parametric design for tubular tooth profiles is provided and solid models are established for motion simulation. Tubular meshing surfaces are evaluated according to geometric and meshing characteristics including undercutting condition, interference with engagement and curvature, calculation of sliding ratios, and successive meshing property. The meshing essence of tubular tooth surfaces is determined. The mechanics properties of tooth surfaces are analyzed using the finite element method. The contact stress, meshing law and deformation analysis of tooth surfaces are presented. The transmission efficiency experiment is based on the developed gear prototype, and a comparison of the prototype with an involute gear drive is provided. Further research on the dynamics analysis and key manufacturing technology will be conducted, and this gear drive is expected to exhibit excellent transmission performance.

Characterization of proteinase A excretion from Saccharomyces cerevisiae in high sugar stress conditions

Dong, Liang,Li, Feng,Piao, Yongzhe,Sun, Dong,Zhao, Rui,Li, Cheng,Cong, Lina,Zhao, Changxin The Korean Society for Applied Biological Chemistr 2015 Applied Biological Chemistry (Appl Biol Chem) Vol.58 No.2

High sugar concentration culturing was commonly used in modern fermentation industry. However, it leads to the reduction of the foam stability in beer brewing due to the excess secretion of proteinase A. To better understand the characterization of proteinase A excretion from Saccharomyces cerevisiae in high sugar stress conditions, the cultures were grown by using YNB medium with a high concentration of glucose. Pro-PrA isolated from the medium was purified by gel exclusion chromatography, and the PrA activity was detected using fluorescent substrate analysis. The relative molecular weight of the purified PrA and pro-PrA was estimated at 42 and 54 kDa, respectively, by SDS-PAGE. It indicated that the metabolic behavior of PrA in the high glucose culturing was quite different from the normal conditions, and glucose concentration may have a big influence on its secreted process. Further study showed that PrA was released at the logarithmic growth phase of the culturing, and the amount of PrA was 11 times higher compared with the normal culturing. PrA was considered to be activated by itself under acidic conditions. And it was also confirmed in this work that the step-wise pathway for the autoactivation known as a pseudo-PrA has a major contribution to the autoactivation process of PrA zymogen outside the cell.

Coupled Inductor Design Method for 2-Phase Interleaved Boost Converters

Dong Liang,신휘범 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.2

To achieve high efficiency and reliability, multiphase interleaved converters with coupled inductors have been widely applied. In this paper, a coupled inductor design method for 2-phase interleaved boost converters is presented. A new area product equation is derived to select the proper core size. The wire size, number of turns and air gap length are also determined by using the proposed coupled inductor design method. Finally, the validity of the proposed coupled inductor design method is confirmed by simulation and experimental results obtained from a design example.

A method for inductor design to improve efficiency in PFC boost converter

Dong Liang,Woong-Jae Kang,Hwi-Beom Shin 전력전자학회 2017 전력전자학술대회 논문집 Vol.2017 No.7

Research on Concrete Cracks Recognition based on Dual Convolutional Neural Network

Dong Liang,Xue-Feng Zhou,Song Wang,Chen-Jing Liu 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.7

Cracks are the most common and important diseases of concrete bridges. A dual convolutional neural network (DCN) model which is composed of one convolutional neural network (CNN) model and one fully convolutional network (FCN) model is proposed to recognize the cracks in image. Firstly, the CNN model is used to identify the crack area. The interfering factors such as spot, shadow, water stain, and graffiti in the non-crack area will be excluded by CNN model. Then, the CNN results will be segmented by the FCN model with the structure of merging layer-by-layer to extract crack features such as length and width. The DCN model is trained to recognize the actual concrete bridge cracks in this paper. The recognition results show that the DCN model has a good balance between high accuracy and low noise in the process of crack recognition compared with the current image recognition method. The reliability and accuracy of recognition are both greatly improved. The DCN model is helpful for automatic identification of cracks in concrete bridges.