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Adaptive feedforward control of ionic polymer metal composites with disturbance cancellation
Seonhyeok Kang,Woojin Kim,김현진,박재균 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1
Ionic polymer-metal composites (IPMCs) are promising candidates in various sensing and actuation applications due to their light weight, large bending, and low actuation voltage requirements. However, IPMCs are still in the early stage of development, and their bending response can vary widely depending on various factors such as fabrication process, water content, temperature, and contact with electrodes. To control IPMCs in a predictable manner and to minimize the effects of plant uncertainty and external disturbances, a precise and robust control scheme is required. In the present work, a three-part adaptive feedforward control architecture is employed for IPMC deflection control. First, adaptive identification is performed to identify changes in the dynamic behavior over time and in the input voltage using a gradient descent method. Second, an adaptive feedforward controller is implemented to control the dynamic response of the plant, where the IPMC displacement is observed and is used to adjust the parameters of the controller. Third, noise and disturbance cancelling is performed using an additional adaptive canceller, which does not affect the system dynamics. Our results show that the adaptive identification and feedforward controller with disturbance cancellation using the gradient descent method provides accurate tracking performance under plant variation and disturbance. Especially, the fast convergence speed of the proposed technique makes it practical for online control.
Online Learning Control of Hydraulic Excavators Based on Echo-State Networks
Park, Jaemann,Lee, Bongju,Kang, Seonhyeok,Kim, Pan Young,Kim, H. Jin IEEE 2017 IEEE transactions on automation science and engine Vol.14 No.1
<P>Note to Practitioners-Motivated by the fact that obtaining useful mathematical models of hydraulic excavators may be impractical or too costly, this paper proposes an online learning control technique for the position control of hydraulic excavators. The proposed control technique uses remote control valve (RCV) signals and measurements of the joint angles to learn the dynamics of the excavator in an online manner, and the RCV inputs required to track the desired trajectory are generated simultaneously. As a result of online learning, the controller compensates for the changes in the plant dynamics over time, caused by factors, such as fluid temperature change or component wear. In this paper, we have implemented and validated the proposed controller on a 21-ton class hydraulic excavator. The proposed online learning control framework can also be applied to a wide range of control applications, where a mathematical model of the plant is absent or impractical to obtain.</P>
Influence of smoking and fighter flight on the lung; low-dose computed tomography study
( Dong-ho Bang ),( Young-wook Jeon ),( Seong Hoon Park ),( Joon Beom Seo ),( Namkug Kim ),( Ok-man Jeong ),( Wi-sub Hwang ),( Seonhyeok Kang ) 국군의무사령부 2014 대한군진의학학술지 Vol.45 No.1
Objectives: to compare low-dose chest computed tomography (LDCT) findings between fighter pilots and nonflying personnel. Methods: A total of 235 participants without any fighter flight experience and 185 fighter pilots with > 1,000 flight hours who underwent LDCT imaging were included in our study. The subjects were further divided into a smoking group and a nonsmoking group. The prevalence of each LDCT finding was compared by univariate analysis. Logistic regression analysis was performed with variables suspected of being significant in the univariate analysis and controlled by age > 50 years, smoking status, and fighter flight. The diameters of the pulmonary artery (PA) and the ascending aorta (AA) were measured and the PA:AA ratio were calculated. Results: Among the nonsmokers, subsegmental atelectasis was rare in the fighter pilots. Among the smokers, bronchiectasis was rare in the fighter pilots, but paraseptal emphysema was common. Paraseptal emphysema was prevalent in the smokers. Fighter flight had no significant influence on the lung. The diameters of PA and AA and PA:AA ratio were not significantly different between the two groups. Conclusion: The results suggest that a combination of fighter flight and smoking may have effects on the chest, particularly regarding the development of paraseptal emphysema.
( Dong-ho Bang ),( Seong Hoon Park ),( Joon Beom Seo ),( Namkug Kim ),( Sang-min Lee ),( Young-wook Jeon ),( Ok-man Jeong ),( Wi-sub Hwang ),( Seonhyeok Kang ) 국군의무사령부 2014 대한군진의학학술지 Vol.45 No.1
Purpose: to compare pulmonary morphology between fighter pilots and nonflying personnel using low-dose chest CT (LDCT) quantification. Methods: A total of 36 military fighter pilots and 36 nonflying personnel who were non-smoker in our institute from April to July 2013 were included in our study. The LDCT images were reviewed and the prevalence of each LDCT finding was compared by univariate analysis. The diameters of the pulmonary artery (PA) and the ascending aorta (AA) were measured and the PA: AA ratio were calculated and they were compared between the military fighter pilots and nonflying personnel. Quantification with LDCT images using in-house software based on the fullwidth- half-maximum method was performed. Lung volume, emphysema index, mean lung density, airway diameter and airway luminal area of subsegmental bronchus were also obtained and compared between the two groups using paired-t-test. Results: There was no statistically significant difference in the prevalence of LDCT findings between the two groups. AA, PA, and PA:AA ratio of the subjects did not show any statistically significant difference between the two groups. The mean airway diameter (mm) and airway luminal area (mm2) were significantly larger than that of the nonflying personnel (3.50 0.34 vs 3.21 0.44 and 11.29 2.84 vs 9.26 2.93, respectively) but lung volume, emphysema index, and mean lung density were not significantly different between the two groups. Conclusion: The occupational exposure to fighter flight might have influence on the lung, especially, airway dilatation.