• 한국초전도ㆍ저온공학회논문지
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• 제21권4호
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• pp.59-63
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• 2019

To reduce the fault current below the current capacity of a circuit breaker, researches on HTS (High Temperature Superconductor) power cables with fault current limiting (FCL) function are increasing. An FCL HTS power cable transports current with low a impedance during normal operation. Yet, it limits the fault current by an increased inductive or resistive impedance of conducting layer when quench occurs at the FCL HTS power cable by the large fault current. An inductive type FCL HTS power cable uses increased inductive impendence caused by leakage magnetic flux outside the cable core when the quench occurs at a shield layer losing the magnetic shielding effect. Therefore, it has an advantage of less resistive heating than resistive type FCL HTS power cable and temperature increase is suppressed. This paper describes an ideal circuit model for the FCL HTS power cable to investigate the effectiveness of increased inductive impedance when quench occurs at the shield layer. Then, FEM analysis is presented with a simplified model cable composed of various iron yokes to investigate the effect of the shape of yoke on the generation of the inductive impedance.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권3호
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• pp.105-113
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• 2003

This study developed a practical two-microphone impedance tube method to measure the sound transmission loss of sound isolation materials without the use of an expensive reverberation room or an acoustic intensity probe. In order to evaluate the validation and applicability of the two-microphone impedance tube method, sound transmission losses for several sound isolation materials with different surface density and bending stiffness were measured, and the measured values were compared with the results from the reverberation room method and the theory. From the experimental results, it was found that the accuracy of sound transmission loss obtained by the impedance tube method depends upon the diameter size of the impedance tube (i.e., tested sample size). For sound isolation materials having relatively large bending stiffness such as acryl, wood, and aluminum plates, it was found that the impedance tube method proposed by this study was not valid to measure the sound transmission loss. On the other hand, for sound isolation materials having relatively small bending stiffness such as rubber, polyvinyl, and asphalt sheets, the comparisons of transmission loss between the results from the impedance tube method and the theory showed a good agreement within the range of the frequencies satisfying the normal incidence mass law. Therefore, the two-microphone impedance tube method proposed by this study can be an effective measurement method to evaluate the sound transmission loss for soft sound isolation sheets having relatively small bending stiffness.

• 대한기계학회논문집
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• 제16권11호
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• pp.2059-2071
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• 1992

본 연구에서는 물리적 상황을 구체적으로 표현하기 위하여 카테너리를 연속적 인 임피던스를 갖는 동력학계로 모델링하고 팬터그래프를 1자유도를 갖는 진동계로 간 주하여 카테너리의 시간 공간적 운동 및 카테너리에 작용하는 압상력의 변화를 예측하 고자 한다.

• 로봇학회논문지
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• 제14권4호
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• pp.348-356
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• 2019

The backdrivable servovalve is a desirable component for force and interaction control of hydraulic actuation systems because it provides direct force generation mechanical impedance reduction by its own inherent backdrivability. However, high parametric uncertainty and friction effects inside the hydraulic actuation system significantly degrade its advantage. To solve this problem, this letter presents a disturbance-adaptive robust internal-loop compensator (DA-RIC) to generate ideal interactive control performance from the backdrivable-servovalve-based system. The proposed control combines a robust internal-loop compensator structure (RIC) with an explicit disturbance estimator designed for asymptotic disturbance tracking, such that the controlled system provide stable and ideal dynamic behavior for impedance control, while completely compensating the disturbance effects. With the aid of a backdrivable servovalve, we show that the proposed control structure can be implemented based on a simplified nominal model, and the controller enables implementation without accurate knowledge of the target system parameters and disturbances. The performance and properties of the proposed controller are verified by simulation and experiments.

• 대한전자공학회논문지
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• 제12권4호
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• pp.41-45
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• 1975

기계계와 전기계 사이의 두 analogy로부터 mobility 회로와 impedamice회로를 얻었다. 이 두 기계기로에서 Ipedance와 nobility관계를 회로망리론을 근거로 비교 검토 하였고 이로부터 mobility 회로가 더 자연스럽고 기본적인 기계회로임을 구명하였다. 또한 impedance측정이 관찰점과 수에 따라서 가변성인데 비하여 mobility 측정은 불변성임을 보였다. Two mechanical networks, mobility network, and impedance network, are proposed md the relations between a mechanical system n4 their two mechanical networks are examined briefly. The mobility network is founed to be more natural of two networks. This paper also shows the invariant property of mobility elements in the measurement procedure.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 1999년도 추계학술대회 논문집
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• pp.97-100
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• 1999

Human feels kinesthetic sense in response to the force acted on him. In order to represent kinesthetic sense, a force is analyzed as mechanical impedance (i.e., stiffness or damping) and implemented by active impedance control. In this research, a 3-dimensional arm motion generator is developed to present various mechanical impedance characteristics to an operator. An introduction of virtual reality provides not only a visual effect in virtual environment but also the change in force synchronized with the visual effect in real time.

• 대한기계학회논문집A
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• 제21권2호
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• pp.252-260
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• 1997

In this paper, a friction compensation method using a disturbance observer is proposed for an impedance control of pneumatic manipulator. It is assumed that the generated torque by a pneumatic actuator can be estimated based on the pressure signals and the discharge volume. In order to improve the dynamic characteristics of the pneumatic actuator driven by meter out method, we construct the inner torque control system by feeding back the generated torque. In order to reduce the influence of disturbances comprising friction torque and parameter variations of plant, the impedance control system is constructed with a disturbance observer which estimates the disturbances based on the generated torque of pneumatic actuator, the angular velocity and the reaction torque. From some experiments, it is confirmed that the proposed control system is effective to improve the robustness for the friction torque in the impedance control of a pneumatic manipulator.

• Smart Structures and Systems
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• 제15권4호
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• pp.1159-1175
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• 2015

In this study, the effect of temperature variation on the wireless impedance monitoring is analyzed for the tendon-anchorage connection of the prestressed concrete girder. Firstly, three impedance features, which are peak frequency, root mean square deviation (RMSD) index, and correlation coefficient (CC) index, are selected to estimate the effects of temperature variation and prestress-loss on impedance signatures. Secondly, wireless impedance tests are performed on the tendon-anchorage connection for which a series of temperature variation and prestress-loss events are simulated. Thirdly, the effect of temperature variation on impedance signatures measured from the tendon-anchorage connection is estimated by the three impedance features. Finally, the effect of prestress-loss on impedance signatures is also estimated by the three impedance features. The relative effects of temperature variation and prestress-loss are comparatively examined.

• 대한의용생체공학회:의공학회지
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• 제32권3호
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• pp.207-217
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• 2011

Electrode impedances are measured to quantitatively characterize the electrode-electrolyte or cell-electrode interfaces. In the case of high-density microelectrode arrays(MEAs) that have been developed for brainmachine interface applications, the characterization process becomes a repeating and time-consuming task; a system that can perform the measurement and analysis in an automated fashion with accuracy and speed is required. However, due to the large number of channels, parasitic capacitance and off-capacitance components of the switching system become the major factors that decreased the accuracy for the measurement of high impedance microelectrodes. Here we investigated the implementation of automatic impedance measurement system with analyzing the causes of possible measurement-related problems in multichannel switching configuration. Based on our multi-channel measurement circuit model, we suggest solutions to the problems and introduce a novel impedance measurement scheme using electro-mechanical relays. The implemented measurement system could measure |Z| < 700 $k{\Omega}$ of impedance in - 10% errors, which can be widely applicable to high density neural recording MEAs.

• International Journal of Precision Engineering and Manufacturing
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• 제5권2호
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• pp.46-52
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• 2004

Numerous connectors are used in automobiles for transmission of electrical signals across various electro-mechanical components. The connectors must operate with high reliability in order to minimize failures due to signal degradation. In this work, the effects of contamination at the contact interface of connectors used fur automobile crankshaft position sensor on the impedance change were investigated. An experimental set-up was built to simulate the electrical signal transmitted from the sensor to the engine control unit through a connector. Output from the connector was investigated using connectors contaminated with engine block residues and water droplets. It was found that slight contamination of the connectors could lead to significant signal degradation which can lead to engine failure. Also, the effect of water in the connector altered the signal severely. However, the signal gradually regained the original state as the water evaporated from the interface.