• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.593-598
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• 2009

In this study we present results for the design of ground test system for 4 degree of freedom(DOF) control test is one of the smart UAV ground test. This system is equipped with real smart UAV and Z direction DOF and 3 direction rotation DOF, Ensuring safe operation of the Smart UAV is a top priority. To this end, it is required to do structure analysis and test verification to confirm the design margin and safety. Based on the analysis, the ground test system has been redesigned to meet the structural conditions.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 춘계종합학술대회
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• pp.395-398
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• 2001

본 논문에서는 직류 서보 전동기를 구동원으로 하는 위치 제어계에서 부하변동에 따른 파라메타 변화, 외란 둥에 강인한 2자유도 PID 제어기의 설계법을 제시하여 신경망으로 2자유도 PID 제어기를 구성하였다. 이 제어기의 계수들이 기동시나 계 응답의 변동시 신경망 역전파 알고리즘(Back-Propagation Algorithm)에 의해서도 수성 되도록 하였다. 그리고 이것을 실제의 위치 제어계에 적용하여 실험을 통해 그 성능을 검증하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.1430-1435
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• 2006

This study deals with the problem of balance beam system to stabilize about static and sinusoidal disturbance. wherein the design objectives are to keep the gap deviation from static and sinusoidal disturbance. In this paper propose the 2-Degree of Freedom(DOF) structure and a simple first-order controller which is designed by Characteristic ratio assignment (CRA) method. Matlab simulation result verify stabilization of balance beam system despite of disturbance. Hybrid simulation between digital controller and analog plant is presented by Matlab Simulink.

• 한국정밀공학회지
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• 제29권8호
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• pp.906-912
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• 2012

This paper presents the new method for a six-degree-of-freedom (DOF) motion measurement and those dynamic characterizations in an ultraprecision linear stage using angle sensor-implemented grating interferometry. It consists of a diffractive optical element, a corner cube, four separate two-dimensional position sensitive detectors, four photodiodes and auxiliary optics components. From the previous study, it was confirmed that the proposed optical system could measure a six-DOF motion error in a linear stage. In this article, six-DOF motion dynamic characteristics of the stage were investigated through the step response and with respect to the conditions with a different speed of a slide table. As a result, the natural frequency and damping ratio according to a six-DOF direction was obtained. Also, it was seen that the speed of slide table had an significant effect on a six-DOF displacement motion, especially, X, which was considered as the effect of friction mechanism and local elastic mechanical deformation in a slide guide.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.232-237
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• 2004

In many application of DC-DC converters, loads cannot be specified in advance, i.e., their amplitudes are suddenly changed from the zero to the maximum rating. Generally, design conditions are changed for each load and then each controller is re-designed. Then, a so-called robust DC-DC converter which can cover such extensive load changes and also input voltage changes with one controller is needed. Analog control IC is used usually for the controller of DC-DC converter. Simple integral control etc. are performed with the analog control IC. However it is difficult to retain sufficient robustness of DC-DC converter by these techniques. The authors proposed the method of designing an approximate 2-degree-of-freedom (2DOF) controller of DC-AC converter. This controller has an ability to attain sufficient robustness against extensive load and DC power supply changes. For applying this approximate 2DOF controller to DC-DC converter, it is necessary to improve the degree of approximation for better robustness. In this paper, we propose a method of designing good approximate 2DOF digital controller which makes the control bandwidth wider, and at the same time makes a variation of the output voltage very small at a sudden change of resistive load. The proposed good approximate 2DOF digital controller is actually implemented on a DSP and is connected to a DC-DC converter. Experimental studies demonstrate that this type digital controller can satisfy given specifications.

• Wind and Structures
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• 제26권2호
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• pp.57-68
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• 2018

Wind tunnel tests are conducted to investigate wake-induced vibrations of two circular cylinders with a center-to-center spacing of 4 diameters and attack angle varying from $0^{\circ}$ to $20^{\circ}$ for Reynolds numbers between 18,000 and 168,800. Effects of structural damping, Reynolds number, attack angle and reduced velocity on dynamic responses are examined. Results show that wake-induced vortex vibrations of the downstream cylinder occur in a wider range of the reduced velocity and have higher amplitudes in comparison to the vortex-induced vibration of a single circular cylinder. Two types of wake-induced instability phenomena with distinct dynamic characteristics are observed, which may be due to different generation mechanisms. For small attack angles like $5^{\circ}$ and $10^{\circ}$, the instability of the downstream cylinder characterizes a one-degree-of-freedom (1-DOF) oscillation moving in the across-wind direction. For a large attack angle like $20^{\circ}$, the instability characterizes a two-degree-of-freedom (2-DOF) oscillation with elliptical trajectories. For an attack angle of $15^{\circ}$, the instability can transform from the 1-DOF pattern to the 2-DOF one with the increase of the Reynolds number. Furthermore, the two instabilities show different sensitivity to the structural damping. The 1-DOF instability can be either completely suppressed or reduced to an unsteady oscillation, while the 2-DOF one is relatively less sensitive to the damping level. Reynolds number has important effects on the wake-induced instabilities.

• 로봇학회논문지
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• 제13권2호
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• pp.92-96
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• 2018

In this paper, a soft robotic arm which can prevent impact injury during human-robot interaction is introduced. Two degrees of freedom joint are required to realize free movement of the robotic arm. A robotic joint concept with a single degree of freedom is presented using simple inflatable elements, and then extended to form a robotic joint with two degrees of freedom joint using similar manufacturing methods. The robotic joint with a single degree of freedom has a joint angle of $0^{\circ}$ bending angle when both chamber are inflated at equal pressures and maximum bending angles of $28.4^{\circ}$ and $27.1^{\circ}$ when a single chamber if inflated. The robotic joint with two degrees of freedom also has a bending angle of $0^{\circ}$ in both direction when all three chambers are inflated at equal pressures. When either one or two chambers were pressurized, the robotic joint performed bending towards the uninflated chambers.

• 융합신호처리학회논문지
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• 제5권1호
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• pp.66-72
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• 2004

PID제어는 수십년간 잘 사용이 되어 왔다. PID알고리즘은 적당한 튜닝법을 사용하여 파라미터를 구하여 제어시스템을 설계한다. 그러나 어떤 경우에는 다양한 평가지표가 필요하고, 따라서 이들 다양한 평가지표를 사용하여 설계할 제어시스템이 필요로 하는 조건들을 만족되게 해야 한다. 본 논문에서는 오차, 제어입력의 에너지 및 제어입력의 변화율 등의 시간영역지표들은 물론이고 견실성을 확보하기 위해서 견실성 지표 예들 들면 가중치를 부과한 상보감도함수의 무한대놈을 포함한 선형조합형태의 평가지표를 사용하여 2 자유도 PID제어기를 설계한다. 수치해석을 통하여 최적의 2 자유도 PID파라미터들을 구한다. 이들 I-PD형 등의 2자유도 형은 PID를 변형한 형태로서 단일의 PID제어기들에 비해 더 개선된 출력특성을 얻을 수 있음을 보인다. 시뮬레이션은 MATLAB m 및 mdl파일을 통하여 실행한다.

• 제어로봇시스템학회논문지
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• 제3권1호
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• pp.9-16
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• 1997

The method of designing robust two degree of freedom(2 DOF) controllers for linear systems with parameter uncertainties and unmodeled dynamics is presented in this paper. Robust performance condition that accounts for robust model matching of closed loop system and disturbance rejection is derived. Using the robust performance condition, the feedback controller is designed to meet robust stability and disturbance rejection specifications, while prefilter is used to improve the robust model matching properties. The $H^{\infty}$ and $\mu$ controller for six degree of freedom vehicle with parameter variations are designed and compared. Simulations for hydrodynamic parameter variations and disturbance are presented to demonstrate the achievement of good robust performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.621-626
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• 2002

Two problems in the measurement of 6-DOF head vibration in very low frequency range were investigated in this study. One is how much error was involved in the estimation of three rotational and three translational motion at any specified point from measured 6 translational accelerations. The other is quantitative and qualitative influence of gravity on DC and AC component of the estimated accelerations in 6 degree of freedom, which were derived from pick-ups fixed on a helmet. In the study the effect of nonlinear terms on the estimation of 6 degree of freedom accelerations was negligible but gravity effect must be considered carefully.