Kinematic analysis Harmonic Drive with pure involute profile pair

Anh_duc Pham,The_Linh Tran,Hyeong_Joon Ahn 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-

High Precision Reducers for Industrial Robots Driving 4th Industrial Revolution: State of Arts, Analysis, Design, Performance Evaluation and Perspective

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.

Opposition multiple objective symbiotic organisms search (OMOSOS) for time, cost, quality and work continuity tradeoff in repetitive projects

Duc-Hoc Tran,Long Luong-Duc,Minh-Tin Duong,Trong-Nhan Le,Anh-Duc Pham 한국CDE학회 2018 Journal of computational design and engineering Vol.5 No.2

Construction managers often face with projects containing multiple units wherein activities repeat from unit to unit. Therefore effective resource management is crucial in terms of project duration, cost and quality. Accordingly, researchers have developed several models to aid planners in developing practical and near-optimal schedules for repetitive projects. Despite their undeniable benefits, such models lack the ability of pure simultaneous optimization because existing methodologies optimize the schedule with respect to a single factor, to achieve minimum duration, total cost, resource work breaks or various combinations, respectively. This study introduces a novel approach called ‘‘opposition multiple objective symbiotic organisms search” (OMOSOS) for scheduling repetitive projects. The proposed algorithm used an opposition-based learning technique for population initialization and for generation jumping. Further, this study integrated a scheduling module (M1) to determine all project objectives including time, cost, quality and interruption. The proposed algorithm was implemented on two application examples in order to demonstrate its capabilities in optimizing the scheduling of repetitive construction projects. The results indicate that the OMOSOS approach is a powerful optimization technique and can assist project managers in selecting appropriate plan for project.

Kinematic analysis of a harmonic drive with involute tooth profiles

Anh-Duc Pham(팜안덕),The-Linh Tran(트란띠린),HyeongJoon Ahn(안형준) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.바이오공학 No.-

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.

Hysteresis Curve Analysis of a Cycloid Reducer Using Non-Linear Spring with a Dead Zone

Anh Duc Pham,The Linh Tran,안형준 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.3

Cycloid reducers are widely used for high-precision industrial instruments and robots because of many advantages: high efficiency, high stiffness and a high reduction ratio in a compact size. Nevertheless, the few studies that have investigated the hysteresis characteristics of a cycloid reducer used a time-consuming iterative procedure. This paper presents an efficient FE analysis procedure for the hysteresis characteristics of a cycloid reducer using a nonlinear spring with a dead zone. First, we introduced a cycloid reducer and performed a kinematic analysis of the cycloid disk with tolerance. Next, connecting elements of the cycloid reducer such as the input bearing, pin-roller and output roller were approximated as nonlinear springs with a dead zone. In particular, the dead zone for the nonlinear springs was introduced to represent the clearance of each connecting element. Then, a full FE model of the cycloid reducer was built incorporating the nonlinear springs, and the hysteresis characteristic of the cycloid reducer was directly evaluated at one time so as to significantly save its analysis effort and time. Results showed that tolerance had a great effect on torque and the torsional angle relationship of the cycloid reducer. such as lost motion, back lash and torsional rigidity.

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.

Efficient Forest Fire Detection using Rule-Based Multi-color Space and Correlation Coefficient for Application in Unmanned Aerial Vehicles

Nguyen Duc Anh,Pham Van Thanh,Doan Tu Lap,Nguyen Tuan Khai,Tran Van An,Tran Duc Tan,Nguyen Huu An,Dang Nhu Dinh 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.2

Forest fires inflict great losses of human lives and serious damages to ecological systems. Hence, numerous fire detection methods have been proposed, one of which is fire detection based on sensors. However, these methods reveal several limitations when applied in large spaces like forests such as high cost, high level of false alarm, limited battery capacity, and other problems. In this research, we propose a novel forest fire detection method based on image processing and correlation coefficient. Firstly, two fire detection conditions are applied in RGB color space to distinguish between fire pixels and the background. Secondly, the image is converted from RGB to YCbCr color space with two fire detection conditions being applied in this color space. Finally, the correlation coefficient is used to distinguish between fires and objects with fire-like colors. Our proposed algorithm is tested and evaluated on eleven fire and non-fire videos collected from the internet and achieves up to 95.87% and 97.89% of F-score and accuracy respectively in performance evaluation.

Evaluation of Input Shaping Methods for the Nonlinear Vibration System Using a Furuta Pendulum

팜안덕(Anh-Duc Pham),안형준(Hyeong-Joon Ahn) Korean Society for Precision Engineering 2020 한국정밀공학회지 Vol.37 No.11

There are many nonlinear vibration problems of mechanical structures because of various reasons such as geometric parameters, impact loads, or property of materials. One simple solution for the suppression of nonlinear structural vibration is input shaping that generates a command signal to cancel its vibration. However, a motion platform to evaluate the performance of input shapers for nonlinear vibration is rare. This paper presents the evaluation of input shaping methods for the nonlinear vibration system using a Furuta pendulum. First, the mathematical model of the Furuta pendulum is introduced and its nonlinear vibration characteristic is analyzed. Then, commands for canceling the nonlinear vibration of the Furuta pendulum are generated with various input shapers such as ZV, ZVD, and ZVDD. Finally, we illustrate the effects of input shapers on the nonlinear Furuta pendulum by comparing the pendulum overshoot, settling time, and vibration-reduction ratio. The Furuta pendulum is shown to be a good motion platform to evaluate input shaping methods for nonlinear vibration systems.

Impact of Motivational Factors on the Work Results of Lecturers at Vietnam National University, Hanoi

DO, Anh Duc,PHAM, Ngoc Thach,BUI, Hong Phuong,VU, Duc Thanh,NGUYEN, The Kien,NGUYEN, Thi Huyen Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.8

This paper aims to develop a conceptual framework for evaluating the impact of motivational factors on the work results of lecturers at Vietnam National University, Hanoi (VNU), one of two leading multidisciplinary and multi-sectoral national universities in Vietnam. This study has considered wages and other benefits (WB), training and development (TD), working environment (WE) and working motivation (WM) as motivational factors, and proposed a structural model of the impact of motivational factors on the work results of lecturers at VNU. The empirical analysis used data from the survey data of 321 university lecturers. Comprehensive, valid, and reliable tools (SPSS 26 and SmartPLS 3.0 software) are used to evaluate rigorous statistical tests including convergence validity, discriminatory validity, reliability, and average variance extracted to analyze and verify the gathered data, and the hypotheses developed. The result of path analysis shows that four motivational factors constitute a structured system with different degrees of influence on the work results of lecturers. There is also a positive relationship between the motivational factors and the work results of lecturers. As a result, it can be concluded that all hypotheses developed are supported. Several recommendations are further suggested to improve the performance of lecturers at VNU.