• 한국산학기술학회논문지
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• 제19권2호
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• pp.608-616
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• 2018

일반적으로 비선형 시스템은 1차와 2차 시스템의 곱의 형태로 선형화되며, 시스템의 근은 1차 시스템의 근과 2차 시스템의 중근, 서로 다른 두 실근, 복소근으로 구성된다. 그리고 LQ(Linear Quadratic) 제어는 성능지수함수를 최소화하는 제어법칙을 설계하는 방법으로 시스템의 안정성을 보장하는 장점과 가중행렬 조정으로 시스템의 근의 위치를 조정하는 극배치 기능이 있다. 가중행렬에 의해 LQ 제어는 시스템의 근의 위치를 임의로 이동시킬 수 있지만 시행착오 방법으로 가중행렬을 설정하는 어려움이 있다. 이것은 해밀토니안(Hamiltonian) 시스템의 특성방정식을 이용하여 해결 할 수 있다. 또한 제어가중행렬이 상수의 대칭행렬이면 제어법칙을 반복적으로 적용하여 시스템의 여러 근을 원하는 폐루프 근으로 이동시킬 수 있다. 이 논문은 해밀토니안 시스템의 특성방정식을 이용하여 조단 블록을 갖는 시스템의 중근을 두 실근으로 이동시키는 상태가중행렬과 제어법칙을 계산하는 방법을 제시한다. 삼각함수로 표현된 상태가중행렬로 해밀토니안 시스템의 특성방정식을 구한다. 그리고 이동된 두 실근이 특성방정식의 근이라는 조건에서 중근과 상태가중행렬의 관계식(${\rho},\;{\theta}$)을 유도한다. 상태가중행렬이 양의 반한정행렬이 될 조건에서 중근의 이동범위를 구한다. 그리하여 이동범위에서 선택한 두 실근을 관계식에 대입하여 상태가중행렬과 제어법칙을 계산한다. 제안한 방법을 간단한 3차 시스템의 예제에 적용해본다.

• 한국운동역학회지
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• 제17권3호
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• pp.209-215
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• 2007

The purpose of this study was to investigate gait factor and muscle activity depending on hiking poles-using. Eight healthy men volunteered for this experiment. Each of them performed down-hill walking with hiking poles-using and without poles at speed of 3.5km/h for 45 minutes on a treadmill. The treadmill was set 25% down-hill inclination. Kinematic data collected in 60Hz were recorded and analyzed by using 2D motion capture system to measure step time and step length so on. And the lower extremity muscle activities were simultaneously recorded in 1500Hz and assessed by using EMG. The statistical analysis was the paired t-test with repeated measures to compare between hiking poles-using and without poles. The level of statistical significance for all tests was .05. The results of this study were following : Step time was showed statistically different according to pole conditions. That is, the case of poles-using was longer than without poles in step time. Also, step length was showed statistically different between two conditions. Step length about trials with poles was longer than trials without poles. In the muscle activity, the case of all muscles was not showed statistical significance about pole conditions. However, in most muscles IEMG, there were some decreasing-trend relatively when hiking polesusing.

• International Journal of Control, Automation, and Systems
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• 제5권2호
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• pp.208-211
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• 2007

In a recently proposed method of model reduction for discrete interval systems, the denominator polynomial of a reduced model is computed by applying interval arithmetic to dominant poles of the original system. However, the denominator polynomial obtained via interval arithmetic usually has poles with larger intervals than desired ones. Hence an unstable polynomial can be derived from the stable polynomial. In this paper a simple technique is presented to partially overcome such a stability problem by accurately preserving desired real dominant poles.

• 조명전기설비학회논문지
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• 제28권9호
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• pp.35-44
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• 2014

This study was to secure the safety of poor appearance distribution concrete poles effectively and to reduce the replacement costs of them by developing a soundness evaluation index. The researcher of this study investigated poor appearance types of concrete pole, collected 53 of test samples, and tested pole strength. As a result of strength test, only 17 percent of poor appearance concrete poles were below 2.0 of safety factor spec. As results of multiple regression analysis, it is verified that surface air void, horizontal crack, net-shaped crack, elapsed year, vertical crack, and deterioration in concrete compressive strength have statistically negative effects on safety factor of concrete poles in a significant level. The researcher set up a soundness evaluation index by using multiple regression equation, and suggested that poor appearance concrete poles should be replaced or reinforced only in case of soundness evaluation score of 150 or above.

• 한국운동역학회지
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• 제17권2호
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• pp.1-9
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• 2007

Walking is not only an essential component of the human mobility, but also is a good exercise. Inability to walk freely can reduce an individual's quality of life and independence substantially. Being a relatively low impact activity, walking is particularly good for the elderly and research has shown that regular walking in the elderly reduces the chance of fall-related injuries and mental diseases as well. In spite of the documented benefits of regular walking, it is still difficult to walk without the aid of assistive devices for the frail elderly who have lower extremity problems. Assistive walking devices(AWD), such as crutches, canes, hiking-poles, T-Poles and walkers, are often prescribed to the elderly to make their walking be safe and efficient. Many researchers have demonstrated the effects of AWDs such as reducing lower extremity loading, improved dynamic/gait stability, yet, no study has been done for gait pattern when the elderly gait with AWDs. Therefore, the purpose of this study was to examine whether T-Poles, one of the AWDs, change the elderly gait pattern. Eight community-dwelling female elderly participated in this study. Laboratory kinematics during walking with T-Poles(PW) and with out T-Poles(NPW) was assessed. PW showed significant increase in step width, stride length, gait velocity and decrease in swing time. No significances were found in lower body joint angles but meaningful trend and pattern were found. Maybe the reason was due to the participants. Our participants were healthy enough so that the effect of T-Poles was minimum. PW also showed typical gait phases which are no single support phase during a gait cycle. It indicates that walking with T-Poles may guarantee safe and confident walking to the frail elderly.

• 전기학회논문지
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• 제66권2호
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• pp.315-322
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• 2017

This study presents a novel two­phase eight stator poles and six rotor poles (8/6) switched reluctance machine (SRM) that can compensate for the vibration and noise problems of two­phase 6/3 SRM and compare the characteristics of two SRMs. In the case of two­phase 6/3 SRM, the short flux path and the flux direction inside the stator are not reversed, so they have high efficiency characteristics. However, the use of three rotor poles causes problems of vibration and noise because the radial force applied to the rotor poles is not balance. The proposed two­phase 8/6 SRM has advantages of 6/3 SRM such as the flux­reversal­free stator and it can improve vibration and noise by using six rotor poles due to balanced radial force acting on the rotor poles. In order to make a reasonable comparison between two SRMs, the electromagnetic field structure of 8/6 SRM is designed to have equivalent torque characteristic to 6/3 SRM and then the copper loss and core loss are compared and analyzed. Finally, we compare the effieicney of two SRMs using finite element analysis and compare the distribution of radial force acting on the rotor poles based on Maxwell's stress method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.125-127
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• 1996

This paper deals with the fabrication of 4 poles anisotropic Sr·ferrite plastic magnets. After Polyamide6 and polyamlde12 are kneaded respectively with Sr·ferrite powder, silane coupling and calcium stearate of lwt% are added for coating and pelleting. The pelleted specimen are injection-moulded under the magnetic field using 4 poles mould. For 4 poles anisotropic Sr·ferrite plastic magnets with polyamide6 as a binder, the surface magnetic flux density distribution is +943.8∼-943.87kG and the deviation is 5.2%, where as with polyamide12, the distribution is +1040.9∼-1040.9kG and the deviation is 5.4%. It shows that both of the magnet distributions are stable. As the results of the experiments, we find 4 poles anisotropic Sr·ferrite magnets have good properties as the materials appropriate for manufacturing magnet type synchronous motors.

• 한국산학기술학회논문지
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• 제22권6호
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• pp.566-572
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• 2021

본 논문에서는 도시환경과 모래가 많은 토양 아래에 구 형태의 빈 공간이 있을 경우를 가정하고, 해당 목표물의 고유 pole과 고유 공진주파수를 활용하여 목표물을 식별 및 위치를 추정하는 방안을 제시하였으며 가능성을 분석하였다. EM(Electromagnetic) 시뮬레이터를 활용하여 다양한 형태와 크기를 가진 완전도체(PEC: Perfect Electric Conductor)들을 모델링하였고, 이를 통해 획득한 EM 산란응답에 Cauchy 방법을 적용하여 물체의 고유 특성에 해당하는 고유 pole을 축적하여 pole 라이브러리를 생성하였다. 생성된 pole 라이브러리는 목표물에서 추출한 고유 pole과의 비교를 통해 목표물을 식별할 수 있는 가능성을 제공해 준다. 도시환경과 모래가 많은 토양 아래에 구 형태의 빈 공간이 있음을 가정하고 EM 시뮬레이션 모델링을 통해 얻은 전자파 산란 데이터로부터 관심 목표물의 응답을 추출하였으며, 시간영역에서 임펄스 응답의 시간 지연을 이용하여 목표물의 위치를 추정할 수 있었다. 또한 MP(Matrix Pencil) 방법을 적용하여 목표물의 고유 pole을 추출하였다. 최종적으로 계산된 고유 pole과 고유 공진주파수를 pole 라이브러리와 비교하여 탐지된 목표물을 구 형태의 빈 공간(직경 0.2m)으로 추정할 수 있었으며, 계산된 목표물의 위치(깊이)는 약 84 ~ 93%의 정확도를 보였다.

• 한국운동역학회지
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• 제19권2호
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• pp.227-235
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• 2009

본 연구는 등산 폴 사용 여부와 걷는 지속시간 경과가 오르막 걷기에 미치는 영향을 규명하는 것이었다. 이러한 연구목적을 달성하기 위해 7명의 피험자가 동원되었고, 각 피험자들은 45분 동안 오르막 25%로 세팅된 트레드밀 위에서 3.5km/h의 속도로 폴 사용 여부에 따른 2회의 실험을 각각 수행하였다. 대퇴직근, 전경골근, 비복근, 대퇴이두근 등을 포함한 하지의 대표적인 4개 근육들에 대한 활동량이 EMG를 통해 획득되었고, 피험자의 심박수와 주관적 운동자각도가 15분 간격으로 기록되었다. 등산 폴 사용 여부와 걷는 지속시간이 경과됨에 따른 이러한 변인들의 통계적 유의성을 검증하기 위해 이원 급내 분산분석이 사용되었고, 이 때 통계적 유의수준은 P<.05로 설정하였다. 본 연구의 결과를 요약하면 다음과 같다 : 첫째, 4개의 개별 근육에 대한 적분근전도는 조건에 따라 통계적 차이가 나타나지 않았지만, 4개 근육을 합한 적분근전도는 폴을 사용한 경우가 사용하지 않은 경우보다 더 작게 나타났고, 시간 경과에 따른 차이점은 나타나지 않았다. 둘째, 심박수는 폴 사용 여부에 의한 차이는 없었지만, 걷는 지속시간이 경과됨에 따라 더 크게 나타났다. 셋째, 운동자각도의 경우, 폴을 사용했을 때가 그렇지 않았을 때보다 더 적게 나타났고, 걷는 지속시간이 경과됨에 따라 증가하는 것으로 나타났다.

• 조명전기설비학회논문지
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• 제28권5호
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• pp.92-97
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• 2014

The SRM is a doubly salient, singly excited machine. The torque is developed by the tendency for the magnetic circuit to adopt a configuration of minimum reluctance, i.e. for the rotor to move into in line with the stator poles and to maximize the inductance of the coils excited. It is common practice to combine them into groups of poles which are excited simultaneously; for example, 8/6 SRM (8 stator poles and 6 rotor poles) for 4 phases, 6/4, 12/8 SRM for 3 phases, 4/2, 6/3 SRM for 2 phases. Small number of phases in two-phase SRMs allows more cost savings with regards to the switching devices in the converter. The stator back irons of two phase 6/3 SRM and C-core 4/3 SRM does not experience any flux reversal as the flux is in the same direction whether phase A or B is excited. In this study, the similarities, the differences, and structural characteristics between the two SRMs was studied, The magnetic analysis also has been carried out by the finite element method analysis (FEM).