다중율 샘플링과 가상질량을 포함한 햅틱 시스템의 안정성 분석

이경노(Kyungno Lee) 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.10

현실감이 높은 가상강체를 구현하려면 가상스프링의 강성을 최대한 크게 해야 한다. 그러나 가상스프링의 강성을 크게 하면 시스템이 불안정해질 수 있다. 따라서 시스템의 안정성을 유지하면서 가상스프링의 강성을 증가시킬 수 있는 방법이 연구 중이며, 최근 다중율 샘플링을 이용하는 방법이 제안되었다. 본 연구는 가상스프링의 안정성 영역을 크게 할 수 있도록 다중율 샘플링이 포함된 시스템에서 가상질량이 가상스프링의 안정성 영역에 미치는 영향을 분석한다. 다중율 샘플링이 포함된 시스템에서 가상질량의 크기가 작은 경우에는 안정적인 가상스프링의 영역을 영차홀드와 단일샘플링이 포함된 시스템의 경우보다 수십 배 더 크게 할 수 있다. 또한 적정한 가상질량의 크기와  값을 선정하면, 안정적인 가상스프링의 영역은 가상질량이 없는 경우보다 약 3배 ~ 200배 정도 더 커질 수 있다. 본 연구에서는 가상스프링의 안정성 영역을 보다 크게 만들 수 있도록 가상질량과 N값 선정 방향을 제안하며, 이는 보다 현실감높고 안정성이 보장된 가상강체 설계에 도움이 될 것으로 기대된다. To implement a virtual rigid body with high fidelity, the stiffness of a virtual spring is designed to be as large as possible. However, this may make a haptic system unstable, so methods to increase the stiffness of a virtual spring have been studied to maintain the stability. A method using multirate sampling was recently presented. In this study, the effect of a virtual mass on the stability region of a virtual spring was analyzed to enhance its stability in a haptic system with multirate sampling. If the virtual mass is small, the stability region of the virtual spring can be made many times larger than that of a system with zero-order hold and single sampling. In addition, if the values of a virtual mass and N are chosen appropriately, the stability region of the virtual spring can be made 3 to 200 times larger than that without a virtual mass. We propose a design guideline to determine the values of the virtual mass and N to enhance the stability of the virtual spring, which could be helpful in designing virtual bodies with stable interaction and high fidelity.

헌혈자 보관검체 보존방법 안정성 연구(1차년도)

오덕자,우경남,윤지연,김재석,박해준,황유성,윤경원,이재숙,강재원,서혜준,윤만정,서인범,하미나,권소영 대한수혈학회 2009 大韓輸血學會誌 Vol.20 No.2

Background: The Korean Red Cross (KRC) has stored blood donor samples for 10 years under −20℃ since 2004. These samples have been used for investigating transfusion related infections and for Look-back studies. We designed an experimental scheme to verify the stability of stored blood samples. Methods: We collected and prepared samples such as blood donor samples (HBV, HCV, HIV nucleic acid positive; n=90), the HIV infected patient samples (n=20), the WHO nucleic acid international standards serologic positive samples (HBsAg, anti-HCV, anti-HIV; n=120) and the negative samples (n=20). The samples were aliquoted in cryo tubes with volumes of 0.5∼5 mL and they were stored at −20∼−30℃ and −70∼−80℃. We used enzyme immunoassay, chemiluminescence immunoassay and quantitative PCR for the base line and the follow up studies. The linear mixed statistical model using SAS 9.1 for windows was used for statistical analysis. Results: The results of the baseline test of the stored samples showed a variable range of viral load (101∼107 IU/mL or copies/mL) and optical density (S/CO 3.0∼500). The results of the stored samples after 6 month (n=82) did not show any significant differences compared to the baseline data for the viral loads (P>0.05) and the qualitative serologic tests. Conclusion: We established an experimental scheme to verify the stability of the stored blood donor samples. From now on, the stability of the stored samples is going to be monitored by every 6 month for 10 years. 배경: 대한적십자사는 2004년 1월부터 헌혈자 검체를 −20℃ 이하에서 10년간 보존하고 있으며, 이 검체들은 수혈부작용이나 look back 조사를 위하여 사용되고 있다. 본 연구자들은 장기적으로 보관되고 있는 헌혈자 검체의 안정성을 검증하기 위한 실험적 방법을 구축하고자 하였다. 방법: 본 연구의 대상은 HBV, HCV, HIV 핵산 양성 헌혈자 검체(n=90), HIV 감염자로부터 확보된 HIV 핵산 양성 검체(n=20) WHO HBV, HCV, HIV 핵산 국제표준물질, 혈청학적 검사 양성 헌혈자 검체(n=120) 및 혈청학적 검사 음성 헌혈자 검체(n=20)로, 수집된 이후 동결튜브에 0.5∼5 ml씩 소분하여 −20∼−30℃ 및 −70∼−80℃에 보관하였다. 보관개시 및 추적검사에 사용된 검사는 효소면역검사법, 형광면역검사법 및 핵산정량검사법을 사용하였다. 검사 결과는 SAS® 9.1 프로그램을 이용한 Linear mixed statistical model을 사용하여 분석되었다. 결과: 연구대상 검체의 기본검사결과 핵산농도는 101∼107 IU/mL (copies/mL)의 분포를 보였고 혈청학적 검사의 흡광도 분포도 다양하였다(S/CO 3.0∼500). 본 연구의 1차년도 추적검사의 대상이 되는 82검체에 대한 추적검사결과는 기본검사결과와 비교하여 핵산농도나 정성적인 혈청학적 검사결과에서 유의한 차이를 보이지 않았다(P>0.05). 결론: 본 연구에서는 장기적인 보관 검체의 안정성에 대한 검증을 위한 실험 설계를 완료하였고 앞으로 10년간 6개월의 간격으로 추적검사를 실시하며 보관 검체의 안정성을 검증해갈 것이다.

Stability of Limiting Zeros of Sampled-data Systems with Backward Triangle Sample and Hold

Minghui Ou,Shan Liang,Cheng Zeng 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.8

The backward triangle sample and hold (BTSH) is a novel sample and hold function. This paper concentrated on the stability of zeros in the sampled-data system that arising from the case of a BTSH and a continuoustime system in cascade. The properties and stable conditions of the limiting zeros for sufficiently small or large sampling period in BTSH case are displayed. The framework of the limiting zeros is derived in the two different sampling rates. It is demonstrated that one can choose a suitable parameter value of BTSH, where the limiting zeros of the resulting sampled-data system can be located inside the stable region while the zero order hold (ZOH) fails to do. Finally, numerical examples are provided to better show proposed theories in this paper.

A Generalized Framework for Robust Stability Analysis of Discrete-Time Disturbance Observer for Sampled-Data Systems

Gyunghoon Park,Hyungbo Shim 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10

As a robust controller to compensate both model uncertainty and external disturbances, the disturbance observer (DOB) has been widely employed in a number of industrial applications, typically implemented in a discretetime fashion for sampled-data systems. Substantial research effort has gone into the study on how to design the discretetime DOB over the past decades, yet there is still no unified approach to robust stability analysis for the various types of DOBs. In this paper, by representing these variations into a general structure, we present a generalized framework for stability analysis that is available in whichever way the discrete-time DOB is designed and regardless of how large the model uncertainty is. As a consequence of the generalization, an almost necessary and sufficient stability condition under fast sampling is presented. Motivated by this new stability condition, a systematic design guideline for the discrete-time DOB is proposed in order to guarantee the robust stabilization against arbitrarily large (but bounded) model uncertainty. The validity of the presented analysis and design procedure is verified by an illustrative example.

Improving the Stability Behavior of Limiting Zeros for Multivariable Systems Based on Multirate Sampling

Cheng Zeng,Shan Liang,Shuwen Xiang 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.6

It is well-known that existence of unstable sampling zeros is recognized as a major barrier in many control problems, and stability of sampling zeros, in general, depends on the type of hold circuit used to generate the continuous-time system input. This paper is concerned with stability of limiting zeros, as the sampling period tends to zero, of multivariable sampled-data models composed of a generalized sample hold function (GSHF), a continuous-time plant with the relative degrees being two and three, and a sampler in cascade. In particular, the main focus of the paper is how to preserve the stability of limiting zeros when at least one of the relative degrees of a multivariable system is more than two. In this case, the asymptotic properties of the limiting zeros on the basis of normal form representation of continuous-time systems are analyzed and approximate expressions for their stability are discussed as power series expansions with respect to a sufficiently small sampling period. More importantly, unstable sampling zeros of the sampled-data models mentioned above can be avoided successfully through the contribution of this paper, whereas a zero-order hold (ZOH) or a fractional-order hold (FROH) fails to do so. It is a further extension of previous results for single-input single-output cases to multivariable systems.

An Investigation of Stability Criteria for Sampled-data Control System Using New Integral Inequality for Application to Electric Power Market

Arthit Hongsri,Wajaree Weera,Thongchai Botmart,Prem Junsawang 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.12

This article focuses on the stability problem of sampled-data systems, which is addressed using a new integral inequality. A method for systematic analysis is presented, then applied to the electric power market. The sampling point from tk to tk+1 assume to be a sampling interval but bounded. In addition, we develop a novel closed-loop Lyapunov functional that considers intervals from the sampling point t to tk and from t to tk+1. This new functional is utilized to derive a stability criterion that is less conservative than previous works based on novel integral inequalities for sampled-data systems. Numerical examples are proposed to demonstrate the efficacy and decreased conservatism of the suggested approach. Additionally, the method addresses the stability issue in electric power markets and explores the importance of reducing conservatism.

휘발성 유기화합물용 수동식 시료채취기 개발

장미연,이광용,전현진 한국산업보건학회 2022 한국산업보건학회지 Vol.32 No.4

Objective: This study is intended to design a commercially available passive sampler and conduct performance test on its use as a media for evaluating a working environment. Methods: This study was conducted to select adsorbents, design models, and evaluate storage stability and sampling rates for the development of new types of passive samplers. Results: The impurity detection, adsorbent capacity and breakthrough volume of five types of activated carbon were tested for selection of an adsorbent. One product was selected in consideration of the efficiency of purchase. A number of passive samplers were designed in a radial style and a badge style using plastic as a material. The final two prototypes were made using molds or 3D printing. For the storage stability evaluation, samples were stored at different temperature for 1~21 days and then analyzed. Most of the chemicals had excellent storage stability when refrigerated. However, some chemicals such as dichloromethane and methyl ethyl ketone need to be analyzed as soon as possible after sampling. Conclusion: In this study, new types of passive samplers for 66 chemical compounds were developed. The evaluation of storage stability and sampling rates showed different results depending on the properties of the chemical substance. For some chemicals such as methyl ethyl ketone and dimethylformamide, activated carbon is inappropriate as an absorbent. In future studies, additional experiments are required on chemicals that are difficult to collect with activated carbon.

Sampled-Data Modeling and Dynamic Behavior Analysis of Peak Current-Mode Controlled Flyback Converter with Ramp Compensation

Shuhan Zhou,Guohua Zhou,Shaohuan Zeng,Shungang Xu,Taiqiang Cao 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1

The flyback converter, which can be regarded as a nonlinear time-varying system, has complex dynamics and nonlinearbehaviors. These phenomena can affect the stability of the converter. To simplify the modeling process and retain theinformation of the output capacitor branch, a special sampled-data model of a peak current-mode (PCM) controlled flybackconverter is established in this paper. Based on this, its dynamic behaviors are analyzed, which provides guidance for designingthe circuit parameters of the converter. With the critical stability boundary equation derived by a Jacobian matrix, the stableoperation range with a varied output capacitor, proportional coefficient of error the amplifier, input voltage, reference voltageand slope of the compensation ramp of a PCM controlled flyback converter are investigated in detail. Research results show thatthe duty ratio should be less than 0.5 for a PCM controlled flyback converter without ramp compensation to operate in a stablestate. The stability regions in the parameter space between the output capacitor and the proportional coefficient of the erroramplifier are enlarged by increasing the input voltage or by decreasing the reference voltage. Furthermore, the rampcompensation also can extend to the stable region. Finally, time-domain simulations and experimental results are presented toverify the theoretical analysis results.

Stability of Aperiodic Sampled-data Systems - An Augmented Looped Lyapunov Functional with Wirtinger Inequality Approach

Min Zheng,Hainan Yang,Yang Song,Jing Deng,Minrui Fei 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.3

This paper is concerned with stability analysis of sampled-data systems with non-uniform sampling patterns. The stability problem is solved based on an augmented looped Lyapunov functional with Wirtinger inequality approach. The effectiveness of this approach depends on proper selecting looped Lyapunov functional parts and less conservative inequality techniques. The method developed here is an extension of previous results by using novel augmented functional and Wirtinger inequality. Numerical examples are given to illustrate the result.

Improved Stability and Stabilization for Sampled-data Control System via Augmented Lyapunov-Krasovskii Functional

Chang-Ho Lee(이창호),Seung-Hoon Lee(이승훈),Myeong-Jin Park(박명진),Oh-Min Kwon(권오민) 대한전기학회 2017 전기학회논문지 Vol.66 No.2

This paper investigates improved stability and stabilization criteria for sampled-data control systems. By using a suitable and newly constructed augmented Lyapunov-Krasovskii functional and some recent mathematic techniques such as auxiliary function-based integral inequalities, sufficient conditions for stability and stabilization conditions are derived within the framework of linear matrix inequalities(LMI) form. The superiority and validity of the proposed results are illustrated by three numerical examples.