• 한국항공우주학회지
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• 제35권4호
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• pp.316-322
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• 2007

정유압 방식 EHA는 종래의 밸브 제어 방식 전기유압 구동장치와 전혀 다른 특성을 나타낸다. 본 논문에서는 EHA의 비선형 요소를 포함한 수학적 모델을 유도하고 실험적으로 검증하였다. 이 수학적 모델을 근거로 전기 모터로 구동되는 유압 펌프, 파이프 배관 그리고 유압 실린더로 구성되는 EHA의 시물레이션 모델을 개발하여 주요 설계 인자인 모터 토크의 피크치, 펌프의 관성 모멘트 등이 제어 성능에 미치는 영향을 분석하였다. 여기에서 실험 조건은 의도적으로 과도기에서 모터 토크가 포화되도록 선정하였다. 그 결과로서 최대 속도로 동작하는 EHA의 제어 정밀도를 개선하기 위한 설계 조건을 조사하였다.

• 드라이브 ㆍ 컨트롤
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• 제12권2호
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• pp.21-26
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• 2015

In order to design a swash plate type pump for electro-hydrostatic actuators the performance of the hydrostatic piston shoe bearings in the low speed range needs to be examined, since the pump operates frequently at low speeds, compensating for position control errors as a control element. As a common practice, piston shoes are equipped with inner rings as an auxiliary element to enhance their tribological performance. In this paper, the effects of the inner rings of the piston shoes on the frictional loss and leakage flow rate were investigated, where three piston shoe models, with different inner ring shapes and different inlet orifice sizes, were integrated. The test results showed that a large inner ring and small inlet orifice were advantageous for reducing both the frictional loss and leakage flow rate; this could also be confirmed by computational analyses.

• 드라이브 ㆍ 컨트롤
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• 제11권4호
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• pp.25-31
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• 2014

This paper details application of a DLC(Diamond Like Carbon)-coating to the swash plate and the ball joint of pistons that make sliding contact with the piston shoes of an axial piston pump. This process, aimed to reduce the frictional and leakage power losses of the hydrostatic piston shoe bearings at the low speed range. At lower speeds than 100rpm, the positive effects of the DLC-coating on the power loss reduction of the hydrostatic piston shoe bearings could be confirmed. These effects resulted in little improvement in volumetric efficiency of the test pump, but the mechanical efficiency could be raised by up to 5% at 100rpm; here, the DLC-coated swash plate played a more dominant role than the DLC-coated ball joint.

• 드라이브 ㆍ 컨트롤
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• 제11권2호
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• pp.30-35
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• 2014

The pumps of electro-hydrostatic actuators operate most frequently in boundary lubrication speed range, as they compensate for the position control errors as a control element. When conventional swash plate type piston pumps are applied to electro-hydrostatic actuators, the frictional power losses as well as the wear rate of sliding components, such as piston shoes can increase drastically under the boundary friction condition. In this paper, the power losses of the piston shoes were investigated which were engendered by a frictional solid-to-solid contact and leakage flow rate of their hydrostatic bearing. In order to reduce them, DLC-coating was applied to the swash plate and the ball joint of pistons along with its effects were demonstrated. In addition, it was also shown that the wear rate of the piston shoes could be markedly reduced using the DLC-coated swash plate.