• Smart Structures and Systems
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• 제28권6호
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• pp.761-777
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• 2021

This study presents a numerical investigation on the sensitivity of electromechanical (EM) impedance responses to inner damaged concrete of a prestressed anchorage zone. Firstly, the Ottosen yield criterion is selected to simulate the plasticity behavior of the concrete anchorage zone under the compressive loading. Secondly, several overloading cases are selected to analyze inner damage formations in the concrete of the anchorage zone. Using a finite element (FE) model of the anchorage zone, the relationship between applied forces and stresses is analyzed to illustrate inner plasticity regions in concrete induced by the overloading. Thirdly, EM impedance responses of surface-mounted PZT (lead-zirconate-titanate) sensors are numerically acquired before and after concrete damage occurrence in the anchorage zone. The variation of impedance responses is estimated using the RMSD (root-mean-square-deviation) damage metric to quantify the sensitivity of the signals to inner damaged concrete. Lastly, a novel PZT skin, which can measure impedance signatures in predetermined frequency ranges, is designed for the anchorage zone to sensitively monitor the EM impedance signals of the inner damaged concrete. The feasibility of the proposed method is numerically evaluated for a series of damage cases of the anchorage zone. The results reveal that the proposed impedance-based method is promising for monitoring inner damaged concrete in anchorage zones.

• 반도체디스플레이기술학회지
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• 제5권4호
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• pp.17-22
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• 2006

In the manufacturing processes of semiconductor, test process is important for quality of products. In the manufacturing process of dynamic memory, memory test is more important. So, automatic test equipment(ATE) is used necessarily. But, according to increase of speed of dynamic memory operation, the rapid test equipment is needed. Impedance matching between ATE and dynamic memory is expected to be an important problem for making a rapid test equipment over 1Gbps. According to increase of speed, inner impedance of ATE also works on important parameter for test. This paper is about the method that is for impedance matching of inner impedance and coaxial cable occurring in manufacturing of ATE. We proved effects of inner impedance by electric theory and verified the method of impedance matching using computer simulation.

• 대한토목학회논문집
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• 제26권5D호
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• pp.763-769
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• 2006

중력모형은 출발 존의 유출통행량과 도착존의 유입통행량, 그리고 출발존 중심에서 도착존 중심까지의 교통저항을 이용하여 장래 분포통행을 예측한다. 중력모형에서 존내통행 예측의 경우 교통저항이 "0"로 산정되기 때문에 중력모형에 의해 예측하지 못하고 성장율법과 같은 타 방법에 의해 예측을 행해야 하는 어려움이 존재했다. 본 연구에서는 중력모형에 의한 분포통행 예측시 구축된 중력모형을 이용하여 존내 분포통행을 예측하는 방법을 제안하였는데, 제안한 방법은 기준연도의 존내 분포통행량과 유출, 유입통행량을 존간통행에서 구축된 중력모형식에 대입하여 존내 교통저항을 산출하고 이를 다시 중력 모형에 대입하여 장래 존내 분포통행 예측을 행하는 것이다. 1988년 O-D표를 기준연도 O-D로 하고, 본 연구에서 제안한 방법과 기존의 방법인 성장률법과 회귀모형법의 1992년과 2004년 예측결과들을 실제 O-D와 $x^2$, RMSE, 상관계수 등으로 비교 분석해 본 결과, 본 연구에서 제안한 방법이 우수한 결과를 나타내었다.

• 한국멀티미디어학회논문지
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• 제19권7호
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• pp.1146-1153
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• 2016

The bioelectrical impedance (BI) at the inner forearms was measured using bioelectrical impedance measurement system (BIMS), which employs the multi-frequency and the two-electrode method. Experiments were performed as follows. First, while applying a constant alternating current of 800A to the inner region of the forearms, BI (Z) was measured at nineteen frequencies ranging from 5 to 500 kHz. The prediction marker (PM) was calculated for right and left forearm. The resistance (R) and the reactance (X_c) were simultaneously measured during impedance measurement. Second, a Cole-Cole plot (relationship between reactance and resistance) was obtained for left and right forearm, indicating the different characteristic frequencies (f_c). Third, the phase angle was obtained, indicating strong dependence on the applied frequency.

• 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.

• 로봇학회논문지
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• 제15권1호
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• pp.77-89
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• 2020

This paper proposes a simple and intuitive model-free torque-tracking control for rotary electro-hydraulic actuators. The undesirable natural-velocity-feedback effect is discussed by introducing mechanical impedance into the electro-hydraulic actuation system. The proposed model-free torque control comprises inner- and outer-loop control to achieve two control objectives. Inner-loop control reduces the mechanical impedance passively and optimally. To improve the tracking accuracy, a certain form of proportional-integral-derivative control is applied to the outer loop. The robustness of the proposed closed-loop system against external disturbances is demonstrated by transforming the two-loop control structure into a disturbance observer form. The proposed method is validated on a single joint electro-hydraulic actuator.

• Journal of Power Electronics
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• 제17권5호
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• pp.1278-1287
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• 2017

Inverters are widely used in distributed power generation and other applications. However, their lack of inertia and variable impedance may cause system instability and power transfer inaccuracy. This paper proposes a control scheme for a single phase voltage-controlled inverter with some grid-friendly characteristics. The proposed control algorithm enables the inverter to function as a voltage source with an inner output impedance in both the islanded and grid-connected modes. Virtual inertia and rotor equations are embedded in the PLL part. Thus, the frequency stability can remain. The inner output impedance can be adjusted freely, which helps to accurately decouple and transmit the output active and reactive power. The proposed inverter operates like a traditional synchronous generator. Simulations and experiments are designed and carried out to verify the proposed control strategy.

• 전기학회논문지
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• 제61권2호
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• pp.342-346
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• 2012

This paper presents a loop impedance(inner loop impedance & external impedance) measurement method in TN system. When the measurement of a loop impedance then the measurement result have a some error by load condition. In this paper suggest the loop impedance measurement on actual loading condition by two experiment. one was laboratory condition and the other was the actual measurement on site. Analysis result, measuring error by load condition has not effect on measuring loop impedance.

• 전기학회논문지
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• 제62권8호
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• pp.1163-1168
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• 2013

The maximum allowable value of loop impedance($Z_s$) to secure the operation of overcurrent protective devices and the safety for indirect contact is a very important in TN-C-S system. The loop impedance is divided into inner loop impedance which consumer can adjust and external loop impedance($Z_e$) which only electric operator can adjust. Thus, an external loop impedance which limits to less than a certain value is a very important factor for human body protection against electric shock in TN-C-S system. The concept of loop impedance($Z_s$) is recently introduced to the domestic, the study about external loop impedance is yet insufficient. However, the study about the reference impedance as specified by the IEC 60725 standard to improve the quality and reliability of the power supply is being made. In this paper, reference value of external loop impedance($Z_e$) to meet domestic environment will be proposed by the nationwide measurement and statistical analysis.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.73-76
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• 1996

An impedance control approach based on an extended task space formulation is addressed to control the kinematically redundant manipulators. Defining a weighted inner product in joint space, a minimal parametrization of the null space can be achieved and we can visualize the null space motion explicitly. Based on this formulation, we propose a control method called inertially decoupled impedance controller to control the motion of the end-effector as well as the internal motion expanding the conventional impedance control. Some numerical simulations are given to demonstrate the performance of the proposed control method.