• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.179-184
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• 1993

In this paper, an optimal motion control scheme is proposed for robot manipulators. A simple explicit solution to the Hamilton-Jacobi equation is presented. The optimization of motion control is based on the mininization of the torque term affecting the kinetic energy and the augmented error which has the first-order stable dynamics for the position and velocity tracking error. In the presence of parametric uncertainty, an adaptive control scheme using the optimal principle is proposed. The global stability of the closed-loop system is guaranteed by the Lyapunov stability approach, The effectiveness and feasibility of the proposed control schemes are shown by simulation results.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1712-1719
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• 2003

This paper concerns on application of active magnetic bearing(AMB) system to levitate the elevation axis of an electro-optical sight mounted on moving vehicles. In such a system, it is desirable to retain the elevation axis within the predetermined air-gap while the vehicle is moving. An optimal base acceleration feedforward control is proposed to reduce the base motion response. In the consideration of the uncertainty of the system model, a filtered-x least-mean-square(FXLMS) algorithm is used to estimate the frequency response function of the feedforward control which cancels base motions. The frequency response function is fitted to an optimal feedforward control. Experimental results demonstrate that the proposed control reduces the air-gap deviation to 27.7% that by feedback control alone.

• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1834-1847
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• 2006

A robust minimum-time control (RMTC) strategy is addressed and it is extended to the dual-stage servo design. Rather than conventional switching type sub-optimal controls, it is a reference following control approach where the predetermined minimum-time trajectory (MTT) is tracked by the perturbation compensator based feedback controller. First, the minimum-time trajectory for a mass-damper system is derived. Then, the perturbation compensator to achieve robust tracking performance in spite of model uncertainty and external disturbance is suggested. The RMTC is also applied to the dual-stage positioner which consists of coarse actuator and fine one. To best utilize the actuation redundancy of the dual-stage mechanism, a null-motion controller to actively regulate the relative motion between the two stages is formulated. The performance of RMTC is validated through simulation and experiment.

• 한국군사과학기술학회지
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• 제10권3호
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• pp.161-172
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• 2007

This article suggests an inverse kinematics analysis of a two degree of freedom spatial parallel motion simulator and design methodology of the robust PID controller. The parallel motion simulator consists of a fixed base and a moving frame connected by two serial chains, with each serial chain containing one revolute joint and two passive spherical joint. First, an inverse kinematics problems are solved in order to find the joint variable necessary to bring the end effector to track the desired trajectory. Second, an inverse optimal PID controller is proposed to track trajectories in the face of uncertainty. And the $H_{\infty}$ optimality and robust stability of the closed-loop system is acquired through the PID controller. Finally numerical results show the effectiveness of the PID controller that is designed by square/linear tuning laws.

• Wind and Structures
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• 제14권2호
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• pp.113-131
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• 2011

Excessive wind-induced motion in tall buildings can cause discomfort, affect health, and disrupt the daily activities of the occupants of a building. Dynamic vibration absorbers such as the tuned mass dampers (TMDs) can be used to reduce the wind-induced motion below a specified tolerable serviceability limit state (SLS) criterion. This study investigates whether the same probability of not exceeding specified wind-induced motion levels can be achieved by torsionally sensitive structures without/with linear/nonlinear TMDs subjected to partially correlated wind forces, if they are designed to just meet the same SLS criterion. For the analyses, different structures and the uncertainty in the response, wind load and perception of motion is considered. Numerical results indicate that for structures that are designed or retrofitted without or with optimum linear TMDs and satisfying the same SLS criterion, their probability of exceeding the considered criterion is very consistent, if the inherent correlation between the wind forces is considered in design. However, this consistency deteriorates if nonlinear TMDs are employed. Furthermore, if the correlation is ignored in the design, in many cases a slightly unconservative design, as compared to the designed by considering correlation, is achieved.

• 한국전산구조공학회논문집
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• 제28권4호
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• pp.351-359
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• 2015

구조물의 붕괴성능을 정확하게 평가하기 위해서는 구조물과 관련된 구조부재 및 지반운동의 불확실성을 고려한 확률적 접근방식이 요구된다. 불확실성의 종류에 상관없이 불확실성은 구조물의 응답에 영향을 미치게 되는데, 구조물의 성능목표를 설정함에 있어 이러한 불확실성 전파를 예측할 필요가 있다. 최근 들어, 구조물의 붕괴성능을 평가하는 방법으로 사용되고 있는 증분동적해석은 지반운동과 관련된 임의적 불확실성을 해석과정에서 고려할 수 있다는 장점이 있으나, 확률론적 평가를 위한 또 다른 중요 요인인 인식론적 불확실성을 직접적으로 평가할 수 없다는 제한사항이 있다. 본 연구에서는 철골모멘트골조를 표본 건물로 선정하여 인식론적 불확실 요인으로 정의한 구조물의 고유감쇠, 지진중량, 구조부재의 항복강도 및 탄성계수가 구조물의 붕괴성능에 미치는 영향을 확률적으로 평가하였다. 이를 위하여 라틴 방격 추출법을 사용한 몬테카를로 시뮬레이션을 통해 증분동적해석을 수행하여 구조시스템 붕괴성능의 변동성을 정량적으로 예측하였다. 해석결과, 붕괴성능의 변동성에 인식론적 불확실성을 대표하는 변수 중에서 구조물 고유감쇠의 영향이 가장 두드러지는 것으로 나타났다.

• 한국정보통신학회논문지
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• 제20권3호
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• pp.527-535
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• 2016

3차원 형상과 모션을 추정하기 위한 통계학적 최적화 알고리즘들이 다양하게 개발되고 있다. 그렇지만 통계적 접근은 카메라의 기하학적 위치나 관측시야각 등의 설정에 따른 SfM(Shape form Motion)의 민감한 영향을 분석하는데는 한계가 있다. 본 논문은 SfM의 모호성을 예측하기 위해 카메라 촬영 구성 요소를 이용하여 관측행렬의 불확실성을 정량적으로 추정할 수 있는 방법을 제안한다. 제안한 방법은 SfM 알고리즘의 최종적인 복원 성능을 예측하는데도 매우 효과적인 방법이다. 또한 합리적인 복원 결과를 기대할 수 있도록 카메라 촬영 구성을 설정하기 위한 직접적인 가이드라인을 제공할 수 있다는 점에서 중요하다. 실험결과는 이러한 카메라 촬영 구성을 이용하여 관측행렬의 불확실성에 대한 정량적 추정을 실험적으로 검증하고 본 알고리즘의 효율성을 확인한다.

• 한국실내디자인학회논문집
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• 제22권1호
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• pp.115-123
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• 2013

Today, the views on Temporality of space have been changed not only to be based on the concept of time, but also to identify the space with a body adapted to the new circumstances. The study suggests that the actions of performers in space have been important by changes of views and are connected to the music phenomenology mixed with music whose tempo is the phenomenology related with of human consciousness itself, and derives the temporal property by putting them into Rem Koolhaas space with the fluid quality. According to Clifton's Phenomenology of Music, an understanding of music is made in both human body and consciousness as two ways to listen to sounds and enjoy music. Though a correlation between the characteristics of Clifton's Phenomenology of Music and one of resulted from uncertainty and immateriality of modern space Temporality, we could work out four kinds of characters which are the continuity of the fluidity from temporal programs, contrasting changes or synchronicity, the multidimensionality from synesthesia of line and face, ventilation by quality of the material and immaterial circumstances of sound effects, the implication in events resulted from cognition for information and unexpected actions, and the autonomy of the route of a variety of experiences including intimate connection of inter-related events and temporary and diverse external conditions. Hereby Temporality of musical phenomenology in Rem Koolhaas's space can be experienced by systems base oh the importance of host's motion, changes of programs according to the motion as well as uncertainty and immaterial changes. Due to the changes user's emotion and motion is undergone as Temporality that changes automatically.

• Radiation Oncology Journal
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• 제36권2호
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• pp.122-128
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• 2018

Purpose: To investigate positional uncertainty and its correlation with clinical parameters in spine stereotactic body radiotherapy (SBRT) using thermoplastic mask (TM) immobilization. Materials and Methods: A total of 21 patients who underwent spine SBRT for cervical or upper thoracic spinal lesions were retrospectively analyzed. All patients were treated with image guidance using cone beam computed tomography (CBCT) and 4 degrees-of-freedom (DoF) positional correction. Initial, pre-treatment, and post-treatment CBCTs were analyzed. Setup error (SE), pre-treatment residual error (preRE), post-treatment residual error (postRE), intrafraction motion before treatment (IM1), and intrafraction motion during treatment (IM2) were determined from 6 DoF manual rigid registration. Results: The three-dimensional (3D) magnitudes of translational uncertainties (mean ${\pm}$ 2 standard deviation) were $3.7{\pm}3.5mm$ (SE), $0.9{\pm}0.9mm$ (preRE), $1.2{\pm}1.5mm$ (postRE), $1.4{\pm}2.4mm$ (IM1), and $0.9{\pm}1.0mm$ (IM2), and average angular differences were $1.1^{\circ}{\pm}1.2^{\circ}$ (SE), $0.9^{\circ}{\pm}1.1^{\circ}$ (preRE), $0.9^{\circ}{\pm}1.1^{\circ}$ (postRE), $0.6^{\circ}{\pm}0.9^{\circ}$ (IM1), and $0.5^{\circ}{\pm}0.5^{\circ}$ (IM2). The 3D magnitude of SE, preRE, postRE, IM1, and IM2 exceeded 2 mm in 18, 0, 3, 3, and 1 patients, respectively. No association were found between all positional uncertainties and body mass index, pain score, and treatment location (p > 0.05, Mann-Whitney test). There was a tendency of intrafraction motion to increase with overall treatment time; however, the correlation was not statistically significant (p > 0.05, Spearman rank correlation test). Conclusion: In spine SBRT using TM immobilization, CBCT and 4 DoF alignment correction, a minimum residual translational uncertainty was 2 mm. Shortening overall treatment time and 6 DoF positional correction may further reduce positional uncertainties.

• 한국지능시스템학회논문지
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• 제25권4호
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• pp.361-368
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• 2015

본 논문은 실내 환경에서 이동로봇의 위치추정을 위해 무향 칼만 필터(UKF, Unscented Kalman Filter)를 적용하는 방법을 기술한다. 위치 추정을 위해 적용한 무향 칼만 필터 방법은 측정 거리에 따라 오차 공분산 값을 조절하는 새로운 측정 불확실성 모델을 제안한다. 또한 이 방법은 속도정보의 불확실성 및 측정 불확실성에 관한 오차 공분산 행렬의 비 대각 성분을 '0'이 아닌 값으로 설정한다. 이 방법은 100*40m 의 실내 작업환경에서 외수용성 센서로서 레이저영역측정기(Laser range finder)를 가진 차륜형 이동로봇을 이용한 실험을 통하여 평가한다. 이 실험에서는 적응적 불확실성 모델을 사용하지 않는 보통의 방법과 제안된 방법의 추정성능을 비교한다. 또한 이 실험은 오차 공분산의 비 대각성분을 '0'이 아닌 값으로 설정하여 추정 성능이 개선되는 것을 확인한다. 이 논문은 이동로봇의 위치추정을 위한 실용적인 UKF 방법을 구현하고 그 성능을 평가 하는 것을 주요 내용으로 한다.