• 한국산학기술학회논문지
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• 제18권3호
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• pp.666-672
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• 2017

본 연구팀은 프레스 성형 공정에서 버텀 섀시 (bottom chassis)에 팸너트 (pem nut)를 고정하는 것과 같은 협소 공간 작업을 위한 6축 다관절 로봇을 개발하고 있다. 본 논문에서는 6축 다관절 로봇의 위치 제어를 위한 기구학 해석과 가반하중에 따른 위치 정밀도 파악을 위한 구조해석을 수행하였다. 먼저, 로봇의 Denavit-Hatenberg 파라미터를 정의하고, 정기구학과 역기구학 모델을 제시하였다. 기구학 모델은 Coppelia Robotics 사의 virtual robot experimentation platform (V-REP)을 이용하여 시각적인 시뮬레이션을 통해 검증하였다. 위치 정밀도 분석은 완전 펼침 상태와 완전 접힘 상태에서 자중에 의한 처짐량과 가반하중에 의한 처짐량에 대한 구조해석을 통해 수행하였다. 해석 결과, 최대 변형량은 완전 펼침 상태에서 자체 하중만 있는 경우 0.339 mm로 나타났으며, 5kgf의 하중이 장착된 경우에는 0.667 mm로 나타났고, 설계 조건 1 mm 내에 있음을 확인하였다. 또한, 최대 발생 응력은 축 2와 3을 연결하는 링크에서 22.05 MPa로 나타났고, 부품 재질을 고려할 때 이 값은 구조적으로 안전함을 확인하였다.

• Structural Engineering and Mechanics
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• 제29권5호
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• pp.505-530
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• 2008

This paper proposes the application of active multiple tuned mass dampers (AMTMD) for translational and torsional response control of a simplified two-degree-of-freedom (2DOF) structure, able to represent the dynamic characteristics of general asymmetric structures, under the ground acceleration. This 2DOF structure is a generalized 2DOF system of an asymmetric structure with predominant translational and torsional responses under earthquake excitations using the mode reduced-order method. Depending on the ratio of the torsional to the translational eigenfrequency, i.e. the torsional to translational frequency ratio (TTFR), of asymmetric structures, the following three cases can be distinguished: (1) torsionally flexible structures (TTFR < 1.0), (2) torsionally intermediate stiff structures (TTFR = 1.0), and (3) torsionally stiff structures (TTFR > 1.0). The even distribution of the AMTMD within the whole width and half width of the asymmetric structure, thus leading to three cases of installing the AMTMD (referred to as the AMTMD of case 1, AMTMD of case 2, AMTMD of case 3, respectively), is taken into account. In the present study, the criterion for searching the optimum parameters of the AMTMD is defined as the minimization of the minimum values of the maximum translational and torsional displacement dynamic magnification factors (DMF) of an asymmetric structure with the AMTMD. The criterion used for assessing the effectiveness of the AMTMD is selected as the ratio of the minimization of the minimum values of the maximum translational and torsional displacement DMF of the asymmetric structure with the AMTMD to the maximum translational and torsional displacement DMF of the asymmetric structure without the AMTMD. By resorting to these two criteria, a careful examination of the effects of the normalized eccentricity ratio (NER) on the effectiveness and robustness of the AMTMD are carried out in the mitigation of both the translational and torsional responses of the asymmetric structure. Likewise, the effectiveness of a single ATMD with the optimum positions is presented and compared with that of the AMTMD.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.138-145
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• 1998

Recently, TCS(Traction Control System) is attracting attention, because it maintains traction ability and steerability of vehicles on low-$\mu$ surface roads by controlling the slip rate between tire and road surface. The development of TCS control law is difficult due to the highly nonlinearity and uncertainty involved in TCS. A fuzzy logic approach is appealing for TCS. In this paper, fuzzy logic controller for TCS is introduced and evaluated by the computer simulation with 8 DOF vehicle model. The result indicate that the fuzzy logic TCS improves vehicle's stability and steerability.

• 한국정밀공학회지
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• 제17권12호
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• pp.47-53
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• 2000

The casing oscillator is a construction equipment to clamp, oscillate and push a casing for foundation work. In case that the casing oscillator is operated on the slant ground, if another construction heavy equipment is not used, it is impossible to insert the casing in ground using only casing oscillator. So in this paper, we present the new casing oscillator that need not to level the ground for work of casing insertion. This mechanism can execute 4 DOF motion by actuating 5 single - rod hydraulic cylinders. The inverse kinematics analysis of the casing oscillator is performed and we verify the validity of kinematics analysis through the experiment.

• Smart Structures and Systems
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• 제25권4호
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• pp.393-399
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• 2020

In this paper, the design method and experimental validation for the two-degree-of-freedom (2DOF) electromagnetic energy harvester are presented. The harvester consists of the rigid body suspended by four tension springs and electromagnetic transducers. Once the two resonant frequencies and the mass properties are specified, both the constant and the positions for the springs can be determined in the closed form. The designed harvester can locate two resonant peaks close to each other and forms the extended frequency bandwidth for power harvesting. Halbach magnet array is also introduced to enhance the output power. In the experiment, two resonant frequencies are measured at 34.9 and 37.6 Hz and the frequency bandwidth improves to 5 Hz at the voltage level of 207.9 mV. The normalized peak power of 4.587 mW/G² is obtained at the optimal load resistor of 367 Ω.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.237-240
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• 1997

The casing oscillator is a construction equipment to clamp, oscillate and push a casing for foundation work. In case that the casing oscillator is operated on the slant ground, if another construction heavy equipment is not used, it is impossible to insert the casing in ground using only casing oscillator. So in this paper, we present the new casing oscillator that need not to level the ground for work of casing insertion. This mechanism can execute 4 DOF motion by actuating 5 single - rod hydraulic cylinders. The forward kinematics analysis of the casrng oscillator by tetrahedron geometry is performed so predict workspace, direction and poison of casing oscillatoer.

• 제어로봇시스템학회논문지
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• 제5권6호
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• pp.683-690
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• 1999

This paper deals with a fault-tolerant control method for robust control of RPV(Remotely Piloted Vehicle). To design the flight control system, the 6-DOF simulation program has been developed based on the dynamic model of RPV. A robust fault detection and diagnosis method proposed by Kwon et al. [8]-[10] is adopted to detect the actuator fault of RPV and to make the controller reconfiguration. The Hoo control method is applied to the flight control system. An integrated simulation for performance evaluation of the fault-tolerat\nt control system designed is performed via 6 DOF simulation and shows that the control system works even under the actuator fault.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.II
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• pp.354-362
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• 2000

In Korea, researches on year-round leaf vegetables production system are in progress, most of them focused on environmental control. Therefore, automation technologies for harvesting, transporting, and grading are in great demand. A robot system for harvesting lettuces, composed of a 3-DOF (degree of freedom) manipulator, an end-effector, a lettuce feeding conveyor, an air blower, a machine vision system, six photoelectric sensors, and a fuzzy logic controller, was developed. A fuzzy logic control was applied to determine appropriate grip force on lettuce. Leaf area index and height were used as input variables and voltage as an output variable for the fuzzy logic controller. Success rate of the lettuce harvesting was 94.12%, and average harvesting time was approximately 5 seconds per lettuce.

• Journal of Biosystems Engineering
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• 제25권1호
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• pp.63-70
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• 2000

In Korea, researches for year-round leaf vegetables production system are in progress and the most of them are focused on environment control. Automation technologies for harvesting , transporting and grading need to be developed. This study was conducted to develop harvesting process automation system profitable to a competitive price. 1. Manipulator and end-effector are to be designed and fabricated , and fuzzy logic controller for controlling these are to be composed. 2. The entire system constructed is to be evaluated through a performance test. A robot system for harvesting a lettuce was developed. It was composed of a manipulator with 20DOF (degrees of freedom) an end-effector, a lettuce feeding conveyor , an air blower , a machine vision device, 6 photoelectric sensors and a fuzzy logic controller. A fuzzy logic control was applied to determined appropriate grip force on lettuce. Leaf area index and height index were used as input parameters, and voltage was used as output parameter for the fuzzy logic controller . Success rate of the lettuce harvesting system was 93.06% , and average harvesting time was about 5 seconds per lettuce.

• 로봇학회논문지
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• 제5권3호
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• pp.216-223
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• 2010

Most lamp units at ceilings, walls, and streets are static and no automatic motion capabilities are available at all to adjust lamp tilting angles and its zooming position. This paper proposes a new robotic lamp that creates three degrees of freedom (DOF) motion by using a spherical-type parallel mechanism with a unique forward kinematic position. In the robotic lamp, three motors are placed at the base frame to control two tilting angles and one zoom in-and-out motion for a localized light. The kinematic model of this device is derived and the proto type has been developed. The performance of this device was verified through experiment.