• 융합신호처리학회논문지
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• 제15권3호
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• pp.104-111
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• 2014

이 논문에서는 자동차의 제동장치에 사용되는 브레이크 모듈 조립 작업을 로봇을 사용하여 자동화한 사례를 소개한다. 브레이크 모듈은 하나의 토크 멤버에 두 개의 브레이크 패드와 두 개의 패드 라이너를 장착하여 조립을 완성한다. 이 조립 작업은 로봇의 방향을 자주 바꾸어 주어야하기 때문에 일반적인 산업용 로봇 핸드를 사용하면 조립 시간이 오래 걸린다. 이 논문에서는 두 가지 방법을 제안한다. 첫 번째 방법은 다섯 개의 그리퍼를 갖는 로봇 엔드 이펙터를 설계, 제작하여 기존의 산업용 6축 머니퓰레이터에 장착하여 조립 작업을 수행하는 방법이다. 이 방법에서는 두 개의 브레이크 패드와 두 개의 패드 라이너를 한꺼번에 파지하여 조립 작업을 수행하며 따라서 하나의 그리퍼 만을 가지고 있는 기존의 엔드 이펙터에 비해 조립 시간을 줄일 수 있었다. 두 번째 방법에서는 첫 번째 방법을 더욱 개선하여 엔드 이펙터가 하나의 부가적인 자유도를 가지도록 설계, 제작하여 기존의 산업용 6축 머니퓰레이터에 장착하였다. 이 방법에서는 전체 로봇 머니퓰레이터가 7 자유도를 갖는 여유자유도 머니퓰레이터가 되어 로봇의 동작을 최소화하면서 조립에 필요한 다양한 로봇 방향을 구현할 수 있었다.

• Journal of Power Electronics
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• 제17권4호
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• pp.933-941
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• 2017

In this paper an improved low frequency selective harmonic elimination-PWM (SHE-PWM) technique for Cascaded H-bridge (CHB) converters is proposed. The proposed method is able to eliminate low order harmonics from the output voltage of the converter for a wide range of modulation indices. To solve SHE-PWM equations, especially for low modulation indices, a modified method is used which employs either the positive or negative voltage polarities of H-bridge cells to increase the freedom degrees of each cell. Freedom degrees of the switching angles are also used to increase the range of available solutions for non-linear SHE equations. The proposed SHE methods can successfully eliminate up to $25^{th}$ harmonic from a 7-level output voltage by using just nine switching transitions or a 150 Hz switching frequency. To confirm the validity of the proposed method, simulation and experimental results have been presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권4호
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• pp.692-710
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• 2013

Conventional interference alignment (IA) for a MIMO interference channel (IFC) requires global and perfect channel state information at transmitter (CSIT) to achieve the optimal degrees of freedom (DoF), which prohibits practical implementation. In order to alleviate the global CSIT requirement caused by the coupled relation among all of IA equations, we propose an IA scheme with a single feedback link of each receiver in a limited feedback environment for a three-user MIMO IFC. The main feature of the proposed scheme is that one of users takes out a fraction of its maximum number of data streams to decouple IA equations for three-user MIMO IFC, which results in a single link feedback structure at each receiver. While for the conventional IA each receiver has to feed back to all transmitters for transmitting the maximum number of data streams. With the assumption of a random codebook, we analyze the upper bound of the average throughput loss caused by quantized channel knowledge as a function of feedback bits. Analytic results show that the proposed scheme outperforms the conventional IA scheme in term of the feedback overhead and the sum rate as well.

• 한국운동역학회지
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• 제32권3호
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• pp.87-93
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• 2022

Objective: The purpose of this research was to investigate the age-related changes in whole-body motor variability during sit-to-stand (STS) task. It has been reported that children perform motor tasks less accurately with greater variability as compared to adults. However, it is still unknown how they utilize the abundant degrees of freedom and accomplish voluntary actions. Uncontrolled manifold (UCM) analysis has been used to partition motor variabilities into two independent variability components, task-relevant variability (V_ORT) and task-irrelevant variability (V_UCM). We investigated what differences exist between children and adults with respect to these two motor variability components in relation to motor development stages. Method: Ten 6-year-old children (height: 116.2 ± 4.3 cm, weight: 23.1 ± 3.9 kg, motor development assessment percentile score: 77.5 ± 18.6%), ten 10-year-old children (height: 138.7 ± 7.2 cm, weight: 35.8 ± 10.3 kg, motor development assessment percentile score: 73.9 ± 12.7%), and ten young adults (age: 23 ± 1.6 year-old, height: 164.3 ± 11.4 cm, weight: 60.8 ± 12.0 kg) participated in this study. Each participant performed STS ten times, and a motion capture system was used to capture the whole-body kinematics. Each segment centers of mass and the whole-body center of mass were calculated, and UCM analysis was used to quantify motor variabilities, V_ORT and V_UCM. One-way ANOVA was used for statistical analysis. Results: We found that children produced more motor variabilities in V_ORT and V_UCM in all three dimensions, anterior-posterior, medial-lateral, and vertical. As age increased, both, V_ORT and V_UCM significantly decreased (p<.05). Conclusion: The greater V_ORT found in children compared to adults indicates that the repeatability over repetitions improves through development, while the greater V_UCM found in children suggests that children better utilize the abundant degrees of freedom during STS compared to adults.

• 소음진동
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• 제7권1호
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• pp.127-134
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• 1997

The dynamic stability of classical plates and Mindlin plates subjected to pulsating follower forces is investigated in this paper. Using the finite element method, the induced equation is reduced to that of one with finite degrees of freedom. Then, the multiple scales method is applied to analyze the dynamic instability region. The effects of aspect ratio, Poisson ratio, rotary inertia and shear deformation on the dynamic stability of plates are studied in this paper.

• 전기의세계
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• 제29권7호
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• pp.460-470
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• 1980

The design of a control unit for a playback-type industrial robot is studied. Implemented for the cylindrical-coordinate type industrial robot with 5 degrees of freedom, the control unit constructed for the study consists of (i) z-80 .mu.p-based .mu.-computer control system (ii) Teach-Box for work command, and (iii) various softwares for generating signals for servo driving unit and operating the robot as playback-type. Softwares are developed by using high level Basic Language and low level z-80 Assembly Language for ease of programming and speed of program execution. To show the effectiveness, and example is included.

• Journal of Advanced Marine Engineering and Technology
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• 제27권7호
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• pp.862-871
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• 2003

In this paper, we addressed a modeling for the magnetic levitation stage. This planar magnetic levitator employs four permanent magnet liner motors. Each motor generates vertical force for suspension against gravity, as well as horizontal force for propulsion. Therefore. this stage can generate six degrees of freedom motion by the combination of forces. We derived a mechanical dynamics equation using Lagrangian method and electromechanical dynamics equation by using Co-energy method. Based on the derived dynamics, we can analyze the stage motion that is subject to the input currents and forces.

• 소음진동
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• 제7권5호
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• pp.803-810
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• 1997

This paper is concerned with the vibration control of multi-layer structure for ultra-tall buildings and main tower of large bridge etc. We have modeled the multi-layer structure with the distributed mass system as the lumped mass system of two-degree-of-freedom structure and made experimental equipment. The $H_\infty$control theory was applied to the design of the control system. The designed control system was simulated by computer. As a result, the designed $H_\infty$controller showed the good vibration control performance to impulse response and frequency response.

• 한국통신학회논문지
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• 제40권7호
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• pp.1266-1275
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• 2015

본 리뷰 논문은 전이중 (Full-Duplex) 셀룰라 시스템의 간섭 제어에 관한 최근 연구동향을 소개한다. 먼저 전이중 셀룰라 시스템과 밀접한 연관이 있는 상향링크-하향링크 공존 환경에서의 간섭 제어에 대해 간략히 소개한다. 다음으로 전이중 셀룰라 시스템의 자기간섭 제어 기법과 이를 통한 전이중 셀룰라 시스템의 이론적 모델에 대해 소개한다. 전이중 셀룰라 시스템의 경우 자기간섭을 완벽히 제거하더라고 사용자간 간섭이라는 새로운 간섭현상이 존재한다. 따라서 전이중 통신을 통해 망의 용량을 획기적으로 증대하기 위해서는 이러한 사용자간 간섭을 효율적으로 제어하여야 한다. 최근 전이중 셀룰라 시스템에서 망의 최적 자유도를 달성하는 새로운 간섭 제어 기법이 제안되었다. 본 리뷰 논문은 이러한 최적 간섭 제어 기법에 대해 중점적으로 소개하고자 한다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.840-849
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• 1993

In this paper, it is reported that manipulator and hand-required for harvesting tomato were studied. At first, basic physical properties of tomato plant were investigated such as position of fruit, length of stems and leaves, width between ridges and son on . Secondly , basic mechanism of articulate manipulators with 5 to 7 degree of freedom were investigated by using evaluation indexes such as operational space, measure of manipulatability , posture diversity and so on. From the results, an articulate manipulator with 7 degrees of freedom was selected and the manipulator was manufactured as a trial according to the mechanism. Thirdly , physical properties about fruit and peduncle of tomato were also researched such as diameter, length , picking force and so on. Based on the properties , tomato harvesting hand with absorptive pad were also made as a trial. Finally, after the hand was attached to the manipulator, harvesting experiment was done in greenhouse . It was observed th t the robot could harvest satisfactorily , not only since the robot adapted to physical properties of tomato plant was manufactured but also since phyllotaxis of tomatoes was so methodical that all fruit clusters emerged in the same direction.