Elastodynamic modeling of spatial parallel manipulators contain subclosed loops

Chao Yang,Yang Wang,Junbin Lou,Wei Ye,Fengli Huang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

In this work, the delta parallel manipulator (PM) was considered as a case study to present a system elastodynamic modeling of spatial PMs contain subclosed loops. The mechanism consisted of major substructures including proximal, short, and distal links. Each link was divided into elements to establish the body-to-body and body-to-ground constraint equations. The global independent generalized displacement coordinates (IGDC) of the mechanism were extracted with the theory of multi-point constraint elements. Besides, the global IGDC and substructure synthesis approach was used to obtain the complete elastodynamic modeling of the mechanism without supplementing constraint equations. The resulting configuration-dependent elastodynamic modeling had fewer degrees of freedom, different from thousands used in finite element model (FEM). The natural frequencies could be predicted at any configuration of the mechanism, and were compared against the values of FEM to assess the correctness of the modeling. The proposed modeling could predict the distribution of natural frequencies of the mechanism in the workspace with computational efficiency. Therefore, it could be used as a numerical twin to simulate the elastodynamic performance of PMs in the pre-design stage.

Transcatheter Embolization of a Ruptured Internal Pudendal Artery Pseudoaneurysm in a Patient with Neurofibromatosis Type 1

Chang-Wei Zhang,Zhi-Gang Yang,Xiao-Dong Xie,Chao-Hua Wang,Chao You,Wei Li 대한의학회 2010 Journal of Korean medical science Vol.25 No.4

Neurofibromatosis type 1 (NF-1) is an autosomal dominant disorder. Pseudoaneurysms formation and rupture is an unusual complication of neurofibromatosis. To date, pseudoaneurysm of the internal pudendal artery associated with NF-1 has not been reported. In this article, we present a 62-yr-old man with NF-1 suffering from spontaneous hematoma of the perinea and scrotum. A digital substraction angiography disclosed a ruptured pseudoaneurysm of the right internal pudendal artery, which was successfully managed with transcatheter embolization.

Delay of Surgery for Spinal Metastasis due to the COVID-19 Outbreak Affected Patient Outcomes

Chia-Jung Hsieh,Chun-Yu Wu,Yen-Heng Lin,Yu-Cheng Huang,Wen-Chi Yang,Tom Wei-Wu Chen,Wei-Li Ma,Wei-Hsin Lin,Feng-Ming Hsu,Furen Xiao,Shih-Hung Yang,Dar-Ming Lai,Chang-Mu Chen,Shin-Yi Chao,Fon-Yih Tsuan 대한척추신경외과학회 2023 Neurospine Vol.20 No.4

Objective: The present study is to analyze the effects of the coronavirus disease 2019 (COVID 2019) outbreak and the subsequent lockdown on the outcomes of spinal metastasis patients. Methods: The study was a retrospective analysis of data from a prospective cohort study. All patients underwent surgical intervention for spinal metastases between January 2019 and December 2021 and had at least 3 months of postoperative follow-up. The primary outcome was overall mortality during the 4 different stages (pre-COVID-19 era, COVID-19 pandemic except in Taiwan, national lockdown, lifting of the lockdown). The secondary outcomes were the oncological severity scores, medical/surgical accessibility, and patient functional outcome during the 4 periods as well as survival/mortality. Results: A total of 233 patients were included. The overall mortality rate was 41.20%. During the Taiwan lockdown, more patients received palliative surgery than other surgical methods, and no total en bloc spondylectomy was performed. The time from surgeon visit to operation was approximately doubled after the COVID-19 outbreak in Taiwan (75.97, 86.63, 168.79, and 166.91 hours in the 4 periods, respectively). The estimated survival probability was highest after the national lockdown was lifted and lowest during the lockdown. In the multivariate analysis, increased risk of mortality was observed with delay of surgery, with emergency surgery having a higher risk with delays above 33 hours, urgent surgery (below 59 and above 111 hours), and elective surgery (above 332 hours). Conclusion: The COVID-19 pandemic and related policies have altered daily clinical practice and negatively impacted the survival of patients with spinal metastases.

Pin-Slot Clearance Joints in Multibody Systems

Wei Li,Chao Wang,Chao-lian Sheng,Hai Yang,En Lu 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.12

The pin-slot joint is one of the most commonly used form of kinematic pairs, which with clearance will have a significant effect on the motion and dynamic response of multibody systems. In this study, the multibody system with a pin-slot clearance joint is modeled and the kinematic and dynamic effects are studied. Firstly, the generalized coordinate systems were established and the motion constraint equations of the pin-slot clearance joint were derived. Then, the theories of kinematics and dynamics were used to deduce equations of motion and dynamics. Finally, using slider-crank mechanism as the application example, the simulation study of the multibody system with a pin-slot clearance joint was carried out. The results show that there is an impact phenomenon in the moving process of the end slider, and with the increase of the slot angle, the impact phenomenon is earlier and the impact strength is weaker, however, with the increase of the slot value, the time when the impact phenomenon appearing doesn't change while the impact strength increasing. Furthermore, the maximum displacement of the end slider reduces with the increase of the slot value while the maximum value of driving torque doesn't change and the fluctuation of driving torque increased.

A Three-Terminal Hybrid HVDC System Based on LCC and Hybrid MMC with DC Fault Clearance Capability

Wei Han,Ruizhang Yang,Wang Xiang,Chao Liu,Weidong Ma,Jinyu Wen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

In this paper, a three-terminal hybrid HVDC system based on LCC and hybrid MMC is proposed, which has the ability of DC fault clearance. The system combines the merits of hybrid HVDC system and multi-terminal HVDC system, which is able to deliver bulk renewable power to multiple receiving power grids at a relatively lower cost. By utilizing hybrid MMC as the inverters, the system has the capability to ride through DC faults. The topology and the operating characteristics of the system are introduced in detail. The design of the hybrid MMC is analyzed. The control strategy and the DC fault ride through strategy are proposed. Finally, the model of three-terminal HVDC system is built in PSCAD / EMTDC. The simulation verifies the effectiveness of the control strategy and the DC fault ride through strategy. The results indicate that this kind of HVDC system has a good application prospect in bulk power transmission to the multiple remote receiving regional power grids and the DC fault ride through ability proposed for the system operates well.

AR model-based crosstalk cancellation method for operational transfer path analysis

Wei Cheng,Yan Zhu,Xuefeng Chen,Chao Song,Le Zhang,Lin Gao,Yilong Liu,Zelin Nie,Hongrui Cao,Yang Yang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.3

To reduce the crosstalk effects between the signals at reference points in operational transfer path analysis (OTPA) and improve the reliability of solutions, a novel OTPA method based on auto-regressive (AR) model is proposed in this paper. The key to this method is to obtain the power spectrum by AR model for estimating the prior transmissibility function matrix. Firstly, in view of the lack of noise reduction process in conventional crosstalk cancellation method, singular value decomposition (SVD) is applied to reduce the noise of original signals. Secondly, Burg algorithm is used to calculate AR model parameters. Thirdly, auto-power spectrum and cross-power spectrum are obtained by AR model and the periodogram method respectively. Fourthly, the transmissibility function matrix is obtained by Landweber iterative method based on corrected signals at reference points. Finally, the proposed method can significantly reduce the crosstalk effects, resulting in more accurate evaluation of transfer path contributions. Generally, this study can provide accurate and reliable evidences for vibration & noise monitoring and reduction for mechanical systems, and thus benefit for the active control of vibration & noise.

Effects of operational parameters on performance of the air-powered needle-free injector

Yang Zhu,Can Kang,Wei Cai,Jing Liu,Chao Huang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

The needle-free injection is a new technique for treating subcutaneous drug delivery through penetrating the skin with a high-speed liquid drug jet. The present study aims to reveal fluid dynamics characteristics of the needle-free injection. The operational parameters such as the driving pressure, the nozzle diameter and the liquid volume were investigated for an air-powered needle-free injection system using experimental techniques. The results show that the peak stagnation pressure determines the penetration performance of the jet and is significantly affected by the driving pressure, nozzle diameter and liquid volume. Furthermore, the entire injection process of fluid in the gel can be defined as two phases of penetration and diffusion. Thus, the dispersion characteristics of fluid in different phases could be controlled by an effective combination of the nozzle diameter and liquid volume. Overall, the obtained conclusions provide a sound support for understanding the operation of the needle-free injector.

Bandwidth-Related Optimization in High-Speed Frequency Dividers using SiGe Technology

Chao-Zhou Nan,Xiao-Peng Yu,Wei-Meng Lim,Bo-Yu Hu,Zheng-Hao Lu,Yang Liu,Kiat-Seng Yeo 대한전자공학회 2012 Journal of semiconductor technology and science Vol.12 No.1

In this paper, the trade-off related to bandwidth of high-speed common-mode logic frequency divider is analyzed in detail. A method to optimize the operating frequency, band-width as well as power consumption is proposed. This method is based on bipolar device characteristics, whereby a negative resistance model can be used to estimate the optimal normalized upper frequency and lower frequency of frequency dividers under different conditions, which is conventionally ignored in literatures. This method provides a simple but efficient procedure in designing high performance frequency dividers for different applications. To verify the proposed method, a static divide-by-2 at millimeter wave ranges is implemented in 180 ㎚ SiGe technology. Measurement results of the divider demonstrate significant improvement in the figure of merit as compared with literatures.

Mathematical modeling of a six-axis force/moment sensor

Chao Yuan,Gang Xue,Mei-Zhi Yang,Lu-Ping Luo,Kyoo-Sik Shin,Xue-Wei Zhang 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10

In controlling the robot interacting with the external environment, an important role is played by the force/moment sensors. To design a good force sensor, we need to make a good model first. This paper presents a systematic modeling method of one type of force/moment sensor. A model of a previously designed sensor has been built on the basis of static and kinematic equations and a block form of the strain compliance matrix is obtained using the model.

The IC Design of A High Speed RSA Processor

Yang, Ching Chao,Jen, Chein Wei,Chang, Tian Sheuan 대한전자공학회 1996 APCCAS:Asia Pacific Conference on Circuits And Sys Vol.1 No.1

In this paper, we proposed a new algorithm based on Montgomery's algorithm[I] to calculate modular multiplication that is the core arithmetic operation in RSA cryptosystem. Since the critical path delay in modular multiplication operation is reduced, the new design yields a very fast implementation. We have implemented a 512-bit single chip RSA processor based on our modified algorithm with Compass 0.6㎛ SPDM cell library. By our modified modular exponentiation algorithm, it takes about 1.5n² clock cycles to finish one n-bit RSA modular exponentiation operation in our architecture. The simulation results show that we can operate up to 125Mhz, therefore the baud rate of our 512-bit RSA processor is about 164k bits/sec.