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Anh Duc Pham,안형준 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.5 No.4
New industrial revolution - “The 4th industrial revolution” must be a remarkable milestone for the second decade of the twenty-first century. Many countries are competing to innovate their manufacturing chains for eco-friendly and energy-efficient productions. Although this green or sustainable manufacturing system evolves under the support of cyber-physical system (or digital twin) based on ICT technology, industrial robots also play important roles in this speedy, flexible and effective manufacturing chains. Recently, low-cost industrial robots or collaborative robots, are rising in a highly interactive environment with humans. Although an industrial robot consists of many important components such as mechanical parts (kinematic structure and reducer) and electric parts (servo motor, driver, sensors, and controller), precision reducer takes approximately 25% of material-cost and governs important performance indices of industrial robots. This paper presents review of high precision reducers (HPRs) for industrial robots driving 4th industrial revolution. First, we provide HPRs market along with industrial robots. According to previous studies, HPRs for industrial robots can be classified based on their principles: planetary reducer, cycloid reducer, and harmonic drive (HD). Then, principle, characteristics, and three main performances (hysteresis, rotational transmission error (RTE) and efficiency) of HPRs are discussed. In addition, compensation methods overcoming accuracy limits of HPRs are summarized. Finally, other applications of HPRs except industrial robots are presented.
Rigid Precision Reducers for Machining Industrial Robots
Anh-Duc Pham,Hyeong-Joon Ahn 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.8
Machining robots are expected to significantly change existing production systems in the near future. The quality of the machining process with robots is mainly governed by the accuracy and stiff ness of the robots. Therefore, a precision reducer for the robot joint is an important component that governs the accuracy of machining robots. This paper presents a review of rigid precision reducers for machining robots. Initially, an overview of the machining robots and their features is introduced. The importance of a precision reducer as a component of a robot for machining is explored. A cycloid reducer is the best candidate among precision reducers, considering both the structural compliance and kinematic accuracy of the machining robots. This is followed by reviews of various cycloid reducers and their operating principles. The design issues of the cycloid reducer for performance improvement are then presented. Additionally, the methodology and analysis to assess the performance of the cycloid reducers are discussed. The machining and fault detection of a cycloid reducer are briefly addressed. Finally, other applications of cycloid reducers are introduced.
Machine learning for predicting long-term deflections in reinforce concrete flexural structures
Anh-Duc Pham,Ngoc-Tri Ngo,Thi-Kha Nguyen 한국CDE학회 2020 Journal of computational design and engineering Vol.7 No.1
Prediction of deflections of reinforced concrete (RC) flexural structures is vital to evaluate the workability and safety of structures during its life cycle. Empirical methods are limited to predict a long-term deflection of RC structures because they are difficult to consider all influencing factors. This study presents data-driven machine learning (ML) models to early predict the long-term deflections in RC structures. An experimental dataset was used to build and evaluate single and ensemble ML models. The models were trained and tested using the stratified 10-fold cross-validation algorithm. Analytical results revealed that the ML model is effective in predicting the deflection of RC structures with good accuracy of 0.972 in correlation coefficient (R), 8.190 mm in root mean square error (RMSE), 4.597 mm in mean absolute error (MAE), and 16.749% in mean absolute percentage error (MAPE). In performance comparison against with empirical methods, the prediction accuracy of the ML model improved significantly up to 66.41% in the RMSE and up to 82.04% in the MAE. As a contribution, this study proposed the effective ML model to facilitate designers in early forecasting long-term deflections in RC structures and evaluating their long-term serviceability and safety.
Anh Duc Truong,Yeojin Hong,Janggeun Lee,Kyungbaek Lee,Hyun S. Lillehoj,Yeong Ho Hong 한국가금학회 2017 韓國家禽學會誌 Vol.44 No.3
Mitogen-activated protein kinase (MAPK) signaling pathways play a key role in innate immunity, inflammation, cell proliferation, cell differentiation, and cell death. The main objective of this study was to investigate the expression level of candidate MAPK pathway genes in the intestinal mucosal layer of two genetically disparate chicken lines (Marek’s diseaseresistant line 6.3 and Marek’s disease-susceptible line 7.2) induced with necrotic enteritis (NE). Using high-throughput RNA sequencing, we investigated 178 MAPK signaling pathway related genes that were significantly and differentially expressed between the intestinal mucosal layers of the NE-afflicted and control chickens. In total, 15 MAPK pathway genes were further measured by quantitative real-time PCR(qRT-PCR) and the results were consistent with the RNA-sequencing data. All 178 identified genes were annotated through Gene Ontology and mapped onto the KEGG chicken MAPK signaling pathway. Several key genes of the MAPK pathway, ERK1/2, JNK1-3, p38 MAPK, MAP2K1-4, NF-κB1/2, c-Fos, AP-1, Jun-D, and Jun, were differentially expressed in the two chicken lines. Therefore, we believe that RNA sequencing and qRT-PCR analysis provide resourceful information for future studies on MAPK signaling of genetically disparate chicken lines in response to pathogens.