• 대한기계학회논문집A
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• 제25권10호
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• pp.1501-1513
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• 2001

Disturbance observer, adaptive robust control, and enhanced internal model control are model based disturbance attenuation methods famous for robust motion controller which can satisfy desired performance and robustness of high-speed/high-accuracy positioning systems. In this paper, these are shown to be the same scheme with different parameterizations. To do this, a generalized framework, called as RIC(robust internal-loop compensator) is proposed and the conventional schemes are analyzed in the RIC framework. Through this analysis, it can be shown that there are inherent similarities between the schemes and advantages of the RIC in the viewpoint of controller design. This is verified through simulations and experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.381-385
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• 1992

In this paper, dynamic modeling and adaptive control problems for a space robot system are discussed. The space robot consist of a robot manipulator mounted on a free-floating base where no attitude control is applied. Using an extended robot model, the entire space robot can be viewed as an under-actuated robot system. Based on nonlinear control theory, the extended space robot model can then be decomposed into two subsystems: one is input-output exactly linearizable, and the other is unlinearizable and represents an internal dynamics. With this decomposition, a normal form-augmentation approach and an augmented state-feedback control are proposed to facilitate the design of adaptive control for the space robot system against parameter uncertainty, unknown dynamics and unmodeled payload in space applications. We demonstrate that under certain conditions, the entire space robot can be represented as a full-actuated robot system to avoid the inclusion of internal dynamics. Based on the dynamic model, we propose an adaptive control scheme using Cartesian space representation and demonstrate its validity and design procedure by a simulation study.

• 반도체디스플레이기술학회지
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• 제23권2호
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• pp.92-99
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• 2024

As semiconductor processes require several nanometers precision, the importance of motor control is increasing in semiconductor equipment. Due to unpredictable uncertainties such as friction and mechanical vibrations achieving precise position control in semiconductor processes is challenging. The internal model principle-based controller is a control technique that ensures robust steady-state performance by incorporating a model of the reference and disturbance. The disturbance observer-based controller is a prominent robust control technique implemented to cope with various nonlinearities and uncertainties. Provided that the two controllers can be designed to exhibit equivalent performance under certain conditions, this paper demonstrates through experiments that they yield identical results for the case of a BLDC position control problem. The experimental results also indicate that they can offer enhanced robustness compared with the conventional PID controller in the presence of a time-varying disturbance.

• 한국융합학회논문지
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• 제9권11호
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• pp.307-313
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• 2018

본 연구는 급변하는 비즈니스 환경에서 기업의 내부통제시스템의 도입과 운영이 기업의 회계정보에 미치는 영향을 분석하였다. 본 연구를 수행하기 위해 내부통제와 회계정보의 유용성에 관한 선행연구를 종합적으로 분석하여 본 연구 목적에 맞게 연구모델을 적용하여 실증분석을 실시하였다. 본 연구는 중국기업을 대상으로 내부통제시스템의 구성 요소를 중심으로 내부통제평가지수를 이용하여 수정된 존스(Jones) 모형의 재량적 발생액을 기본으로 변수간의 관계정도를 분석하였다. 실증분석에서는 내부통제의 운영이 회계정보의 유용성 대용변수인 재량적 발생액에 음의 영향관계가 있는 것으로 분석되었다. 또한 내부통제시스템의 위험관리 요인도 회계정보의 유용성에 음의 상관관계가 있는 것으로 분석되었다. 이러한 결과는 재량적 발생액이 적정하고 유의적으로 조정되어 회계정보의 유용성에 긍정적인 영향을 주고 있는 주요 요인으로 추정 할 수 있다. 본 연구 결과는 내부통제의 도입과 운용이 중요해지고 있는 많은 기업에 내부통제시스템의 긍정적인 기능을 제시할 수 있으며, 외국계 기업의 내부통제의 운용과 재량적 발생액과의 관계연구에도 유용한 지침을 제공할 수 있을 것으로 기대된다.

• 디지털융복합연구
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• 제10권6호
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• pp.341-347
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• 2012

시스템 및 네트워크에 설치/운용되는 의료자산보호 솔루션 중 네트워크 접근통제 시스템은 내부 네트워크에 접근하는 정보통신 디바이스의 안전성을 검증한 후 자원을 사용하게 하는 프로세스를 제공한다. 그러나 인가된 정보통신 디바이스의 위장 및 허가된 사용자의 이석 시간을 이용한 비인가 사용 등으로 내부 네트워크에 대한 의료 정보절취 위협은 여전히 존재하고 있고, 장시간 운영되는 정보통신 디바이스의 경우는 사용자가 인지하지 못하는 시간대에 악성코드 감염에 의한 외부 네트워크 임의 접속 및 의료 정보유출도 발생할 수 있기 때문에 이러한 위협을 차단하기 위한 보안 대책이 필요하다. 따라서 본 논문에서는 의료 정보유출 방지를 위해 현행 네트워크 접근통제 시스템을 개선하여 적용한 네트워크 이중 접근통제 모델을 제시한다. 제안한 네트워크 이중 접근통제 모델은 사용자가 실제 조직 내부에 위치하고 있어 인가된 정보통신 디바이스를 활용하는 때에만 내부 네트워크 접속을 허용한다. 그러므로 비인가자의 내부 네트워크 접근을 차단하고, 허가된 사용자 부재 시의 불필요한 외부 인터넷 접속을 차단함으로써 의료 정보를 보호할 수 있는 안전한 의료자산 환경을 제공한다.

• Journal of Korea Trade
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• 제23권7호
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• pp.128-146
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• 2019

Purpose - The purpose of this paper is to investigate the relationship between internal control, economic policy uncertainty, and performance of cross-border merger and acquisition (M&A) based on the panel data of Chinese listed firms. The authors expected that internal control has a positive moderating effect on the performance of cross-border M&A and that it mainly occurs during periods when economic policies are relatively stable. In addition, the authors tried to find out the mechanism of internal control affecting cross-border M&A and the corporate performance. Design/methodology - The authors tested the hypotheses by a multivariate regression model based on the panel data of Chinese listed firms from 2009 to 2017. The dependent variable is the change value of business performance (DROA_1,2,3) and the explanatory variables are cross-border M&A (MA), China's uncertainty of economic policy (EPU), and internal control level (IC) respectively. Findings - The authors find that internal control has a positive moderating effect on the relationship between cross-border M&A and corporate performance. Further, the authors find that the moderating effect is more significant in state-owned enterprises and that it mainly occurs during periods when economic policies are relatively stable. Originality/value - This paper is the leading study that tries to analyze empirically the relationship between internal control, economic policy uncertainty, and performance of cross-border M&A. It provides a new avenue through which internal control might reasonably mitigate the risks of cross-border M&A and correspondingly improve the performance of cross-border M&A. It also confirms the moderating effect of internal control on the performance of cross-border M&A under the uncertainty of economic policy.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.422-425
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• 1997

We consider the robust control problem for nonminimum phase(NMP) systems with parametric uncertainty which appear often in aircraft and missile control. First, a new method that makes such an uncertain NMP system to be factored as a interval minimum phase(MP) transfer function and a time delay term in the Pade approximation form has been presented. The controller to be proposed consists of a compensator $C_{Q}$(s) with Smith predictor in the internal model control(IMC) structure, so that it can have good robustness and performance against the structured uncertainty and the time delay behaviour due to NMP plant the $C_{Q}$(s) is designed on the MP model by using QFT. The stability and performance of overall system has been evaluated by the generalized Kharitonov theorem.rem.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1681-1686
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• 1991

In robotics and other fields of engineering, techniques for artificial reality or virtual reality are focused on and studied extensively, e.g., virtual existence for tele-operator systems in robotics, and virtual reality of designed objects in architecture. In order to realize the system we should create physical stimulations according to internal models created by experiences in a human brain. The internal model does not have to have direct connections to the real world, however, the stimulation must be signals such that the internal model are retrieved in a human brain. In this paper we propose a technique for tele-virtual reality of dynamic mechanical models, which means that one dynamic mechanical model can be shared by peoples in distant places. Since a stability issue due to time delays arises in the system, we employed a scattering technique developed for a tele-operator system and a kind of passive adaptive controllers. Furthermore, restrictions due to a simple digital implementation of the scattering transformation are discussed and some conditions for stability are shown. The proposed method is applied to a remote tug of war system and the effectiveness is verified.

• Steel and Composite Structures
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• 제18권1호
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• pp.29-50
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• 2015

With a quasi-three point bending apparatus, ratcheting deformation is studied experimentally on a pressurized austenitic stainless steel Z2CND18.12N pipe under bending load and vertical displacement control, respectively. The characteristic of ratcheting behavior of straight pipe under both control methods is achieved and compared. The cyclic bending loading and internal pressure influence ratcheting behavior of pressurized straight pipe significantly under loading control and the ratcheting characteristics are also highly associated with the cyclic displacement and internal pressure under displacement control. They all affect not only the saturation of the ratcheting strain but the ratcheting strain rate. In addition, ratcheting simulation is performed by elastic-plastic finite element analysis with ANSYS in which the bilinear model, Chaboche model, Ohno-Wang model and modified Ohno-Wang model are applied. By comparison with the experimental data, it is found that the CJK model gives reasonable simulation. Ratcheting boundaries under two control modes are almost same.

• 제어로봇시스템학회논문지
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• 제20권2호
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• pp.180-185
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• 2014

DC motor is a representative electric motor commonly utilized in various motion control fields. However, DC motor-based motion control systems suffer from degradation of position precision due to nonlinear static friction. In order to enhance control precision, friction model-based compensators have been introduced in previous researches, where friction models are identified and counter inputs are added to control inputs for cancelling out the identified friction forces. In this paper, a static friction compensator is proposed without use of a friction model. The proposed compensation algorithm utilizes internal state manipulation to generate compensation pulses, and related parameters are easily tuned experimentally. The proposed friction compensator is applied to a DC motor-based motion control system, and results are presented in comparison with those without a friction compensator.