• 한국자동차공학회논문집
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• 제8권4호
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• pp.1-9
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• 2000

To understand the thermal characteristics around the piston ring gap ring gap positions and piston temperatures are measured simultaneously. The locations of piston ring gap are measured by the radio-tracer method and piston temperature are measured by a K-type thermocouple and scissors type linkage system. From these experiments following facts are clarified. Piston temperatures fluctuate according to the piston ring rotation. And the temperature fluctuation is mainly affected by top ring gap position irrelevant to the second ring fop position. If the top ring gap position increases and the temperature of top ring groove shows maximum value when top rin gap position coincide with temperature measuring point. The maximum amplitude of temperature fluctuation which is proportional to the blow by gas rate is around 12-15$^{\circ}C$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.243-245
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• 2006

A closed-loop sensorless stroke control system for a linear compressor has been designed. The motor parameters are identified as a function of the piston position and the motor current. They are stored in ROM table and used later for the accurate estimation of piston position. Also it was attempted to approximate the identified motor parameters to the 2nd-order surface functions. Some experimental results are given in order to show the feasibility of the proposed control schemes for linear compressors.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.697-702
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• 2004

LG Electronics developed linear compressors for a household refrigerator which can reduce energy consumption up to $24\%$ by only Drop-ln instead of a conventional reciprocating compressor. The linear compressor is composed of a linear oscillating motor, a piston directly coupled with the linear motor, a cylinder and the specific discharge system of LG. Because of this free-piston structure, the position of the piston can be changeable according to the voltage variation, load variation and so on. By this reason, LG linear compressor has been in need of an additional unit to control the position of the free-piston stably. In this paper we will introduce the innovative technology which is able to operate the linear compressor without controlling the piston position like a conventional reciprocating compressor.

• 한국정밀공학회지
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• 제18권7호
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• pp.40-45
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• 2001

This paper proposes a methodology for the small-displacement-movement of a piston and develops a hybrid control algorithm for the precision position control of a pneumatic rodless cylinder. The pneumatic system uses the voltage-proportional solenoid valves to minimum valve switching since the on/off type valves are create diffculties for accurate position control and induce a lot of valve switching. For the accurate position control a methodology for the small-displacement-movement of the piston is developed and identified experimentally. The main consideration on the development of the hybrid control law is to eliminate a stick-slip phenomenon in the pneumatic control system. This paper addresses these critical issues and presents experimental results for the pneumatic control system.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.509-512
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• 2015

본 논문에서는 유압 실린더내의 피스톤 위치를 측정하기 위한 정전용량 센서(Capacitive Sensor) 구조를 연구하였다. 기존에 유압 실린더 내 피스톤 위치 측정을 위해 인덕티브(Inductive) 방식을 응용한 LVDT(Linear Variable Differential Transformer) 센서가 사용되고 있으며, 높은 정확도를 갖지만, 고가이며 구조적으로 복잡하다는 단점이 있다. 본 논문에서는 이러한 단점을 극복하기 위한 방법으로 유압실린더 내 최적화된 구조를 바탕으로 여러 가지 비접촉 정전용량 센서 구조 방식을 연구하였다. 실험을 통하여 본 논문의 제안구조를 사용하면 유압 실린더 내 피스톤 위치측정이 가능함을 확인하였다.

• 전기학회논문지
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• 제56권3호
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• pp.594-599
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• 2007

A dosed-loop sensorless stroke control system for a linear compressor has been designed. The motor parameters are identified as a function of the piston position and the motor current. They are stored in ROM table and used later for the accurate estimation of piston position. Also it was attempted to approximate the identified motor parameters to the 2nd-order surface functions. The 2nd-order surface functions are divided into 2 or 4 sub-sections for more precise identification of motor parameters. Some experimental results are given in order to show the feasibility of the proposed control schemes for linear compressors.

• 전력전자학회논문지
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• 제10권5호
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• pp.421-427
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• 2005

리니어 컴프레서를 위한 폐루우프 센서리스 스트로크 제어시스템이 구성되었다. 피스톤 위치를 정확히 알아내기 위해 모터 매개변수를 피스톤 위치와 모터 전류의 함수로 추정하였다. 이 매개변수 데이터는 ROM 테이블에 저장한 뒤 차 후 피스톤 위치를 정확히 알아내는데 사용된다. 또한, 추정된 모터 매개변수의 데이터 크기를 줄이기 위해 2차원 곡면 함수로 근사화 하는 작업을 수행하였다. 실험을 통해 본 제어 방식이 리니어 컴프레서에 유용하게 사용될 수 있음을 보였다.

• Journal of Power Electronics
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• 제10권1호
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• pp.58-64
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• 2010

In this paper, the dynamic performance of oscillating linear motors, which are used in household refrigerators, is improved by means of efficient parameter identification. Oscillating linear motor parameters are identified as a function of the piston position and the motor current. They are stored in a ROM table and used later for an accurate estimation of piston position. The identified motor parameters are also approximated to the $2^{nd}$-order surface functions, which are divided into 2 or 4 subsections in order to decrease identification errors. Experimental results are given to show that the proposed control scheme can provide oscillating linear motors with high dynamic performance.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1700-1711
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• 2004

Piston friction is one of the important but complicated sources of energy loss of a hydraulic axial piston machine. In this paper, two formulas are derived for estimating instantaneous piston friction force and average piston friction moment loss. The derived formula can be applicable for piston guides with or without bushing as well as for axial piston machines of motoring and pumping operations. Through the formula derivation, a typical curve shape of friction force found from several experimental measurements during one revolution of a machine is clearly explained in this paper that it is mainly due to the equivalent friction coefficient dependent on its angular position. Stribeck curve effect can easily be incorporated into the formula by replacing outer and inner friction coefficients at both edges of a piston with the coefficient given by Manring (1999) considering mixed/boundary lubrication effects. Novel feature of the derived formula is that it is represented only by physical dimensions of a machine, hence it allows to estimate the piston friction force and loss moment of a machine without hardworking experimental test.

• 전자공학회논문지
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• 제50권8호
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• pp.274-282
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• 2013

본 논문에서는 위상지연필터를 이용한 전류제어 루프를 갖는 선형압축기의 스트로크 제어기를 구현하였다. 선형압축기가 적용된 냉장고나 에어컨의 냉각능력을 제어하기 위해서는 단위시간동안 피스톤의 움직인 거리, 즉 피스톤의 속도를 제어해야 하는데 이때 리니어 모터의 주파수나 스트로크를 조정함으로써 가능하다. 이때, 주파수를 고정하고 스트로크를 변화시키는 것이 일반적이다. 인가된 전류를 정밀하게 제어하는 것이 선형압축기의 동특성을 좌우하는데, 본 연구에서는 전류제어 루프를 갖는 피스톤 진폭 제어기를 제안하고 성능이 우수함을 모의실험을 통해 확인하였다.