• 제어로봇시스템학회논문지
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• 제11권2호
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• pp.103-108
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• 2005

Loading/Unloading task in the real industry is performed by crane, but most of the loading/unloading task with the weight of 5kg∼30kg is done by human workers and this kind of work causes industrial disaster of workers. Therefore it is necessary to develop low cost loading/unloading manipulator system to prevent this kind of industrial accidents. This paper is concerned with the design and fabrication of 2 axis pneumatic manipulators using on/off solenoid valves and accurate position control without respect to the external load and low damping in the pneumatic rotary actuator. To overcome the change of external load, switching of control parameter using LVQNN (Learning Vector Quantization Neural Network) is newly applied, which estimates the external loads in the pneumatic cylinder. As an underlying controller, a state feedback controller using position, velocity and acceleration is applied to the switching control system. The effectiveness of the proposed control algorithms are demonstrated through experiments of pneumatic cylinder with various loads.

• 한국화재소방학회논문지
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• 제30권2호
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• pp.106-113
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• 2016

초고압 용적형 펌프는 로터의 회전에 의한 주기적인 용적의 변화를 이용하는 펌프로 고압, 고유량을 동시에 만족하며 로터의 저속 및 고속 회전에 따라 변화 없이 일정하게 상대적으로 높은 펌프 효율을 유지할 수 있는 장점을 가진다. 많이 사용되고 있는 원심펌프와는 달리 별도의 진공펌프가 없이도 자흡 성능을 가지고 있으며, 비교적 단순한 구조로 인하여 경량화, 소형화가 가능한 특성을 자기고 있다. 유체를 높은 압력으로 이송할 수 있으며, 압력의 변동에 따라 유량의 변동이 적은 정량 토출이 가능하다. 이러한 용적형 펌프를 사용하는 이유는 흡입된 유체가 유량의 변화 없이 토출되는 장점이 있기 때문이다. 본 연구에서는 유량의 변화가 없다는 장점이 있는 용적형 펌프의 체절시스템을 개발하여 펌프의 고압 운전시의 안전성을 확보하고자 하였다. 체절시스템은 컨트롤러 프로그램, 전자클러치, 릴리프밸브의 3가지로 이루어져, 한 가지 시스템이 작동하지 않아도 다른 시스템이 작동하는 시스템으로 이루어져 있다. 컨트롤러 프로그램과 전자 클러치의 작동을 확인하기 위한 과속도 시험과 릴리프 밸브의 유체유동해석, venting 실험을 통해 현재 개발한 초고압 용적형 펌프의 체절시스템이 작동됨을 확인하였다.

• 드라이브 ㆍ 컨트롤
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• 제13권4호
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• pp.1-6
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• 2016

Typically, the seat of an automotive vehicle generally includes a horizontal seat-cushion portion and a vertical seat-back portion that is operatively connected to the seat-cushion portion. The seat may include a recliner for the reclining of the seat-back portion relative to the seat-cushion portion by the seat occupant. An energy absorber or damper can also be provided for the seat-back portion. Because the recliner is configured to be released at a relatively high speed, and it results in an impact at the end of a folding stroke, the damper needs to dissipate energy as the seat back moves with respect to the seat cushion; therefore, the role of the seat damper in the automotive-seat design is important. In this paper, the mechanism of an hydraulic-type automotive-seat damper is investigated, and the torque characteristic is simulated according to the design-parameter variations such as the orifice area and the working-fluid properties.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.151-158
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• 1998

The screw compressor is first invented by a Swedish engineer, Alf Lysholm in 1934. Since then, the development of the screw compressor idea for industrial applications has been continued by the Swedish research organization Svenska Rotor Maskiner, often identified by its initials SRM. The first industrial application of the machine was marketed as an air compressor in the 1950s. The screw compressor which is a positive displacement type compressor compresses gases by the rotation of a pair of mating rotors. The operation of this compressor is entirely rotary and dynamically in balance. Also there is no need for any valve mechanism and there exists less mechanical wear between the parts compared to the conventional reciprocating compressors. Due to these prominent features, the screw compressor has been rapidly spread into the air compressor market replacing the conventional reciprocating compressors and begun to be applied as a refrigerant compressor since the 1960s. In this work, the operation principle of the screw compressor is described in brief and the major design parameters affecting the compressor performance are classified. The international research trend in screw compressor development is introduced and the current situation in our country is described.

• 한국자동차공학회논문집
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• 제16권4호
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• pp.135-142
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• 2008

Hydraulic power steering system has been adopted in seniority passenger and commercial vehicle system for an easy maneuverability and a smoother ride. In this study, hydraulic power steering system analysis model which includes hydraulics and mechanical sub-systems was developed using commercial software, AMESim in order to predict characteristics for various steering components. Each component which constructs system was modeled and verified by experimentally obtained characteristics curves of each components. The parameter sensitivity analysis such as valve opening area, torsional stiffness of torsion bar for system design are carried out by the analysis and experimental method. The predicted results by the development model were a good agreement with experimentally obtained results. The sensitivity investigation results rotary torque when changing an input shaft edge width, was most sensitive, to change in angle and slot width and supply flow of input shaft edge is not a lot sensitively.

• 한국유체기계학회 논문집
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• 제19권5호
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• pp.28-34
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• 2016

Though a peristaltic pump is a crucial element in miniaturized drug delivery systems, it has some intrinsic disadvantages such as backflow and flow fluctuation. To overcome these limitation, we have developed valve-less peristaltic pump system including orifice and stagnation chamber. we measured flow rate to investigate the performance of rotary peristaltic pump with three rollers and an elastomeric tube pumping a viscous fluid. The flow fluctuations and the backflow happen as a result from the disengagement of the contact interaction between the rollers and the tubes. Stagnation chamber installed in front of orifice plate was composed of rubber tube and gas chamber. By changing orifice hole diameter with stagnation chamber flow rate and pressure in the tube was regulated. The obtained maximum reduction ratio of flow fluctuation is 96.79%.

• 설비공학논문집
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• 제21권8호
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• pp.425-432
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• 2009

In this study, the improvement of cooling capacity by applying gas injection technique in a two-stage heat pump using R410A was experimentally investigated. A twin rotary type compressor with gas injection was applied to the heat pump system. The optimum refrigerant charge for the injection and the non-injection cycles was selected to achieve the maximum COP at the cooling standard condition. The injection cycle showed less optimum refrigerant charge than that of the non-injection cycle. The cooling performances of the injection and the non-injection cycles were measured and compared by varying compressor frequency from 40 to 90 Hz. The cooling capacity of the gas injection cycle was 1.6% -11.3% higher than that of the non-injection cycle. The COP of the gas injection cycle was 13.7% to 28.9% higher than that of the non-injection cycle at the same cooling capacity. The heat pump system showed stable operation after 30% of the injection valve opening.

• 대한기계학회논문집B
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• 제32권6호
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• pp.454-462
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• 2008

Since operating conditions are significantly different for heating and cooling mode operations in a $CO_2$ heat pump system, it is difficult to optimize the performance of the $CO_2$ cycle. In addition, the performance of a $CO_2$ heat pump is very sensitive to outdoor temperature and gascooler pressure. In this study, the cooling and heating performances of a variable speed $CO_2$ heat pump with a twin-rotary compressor were measured and analyzed with the variations of EEV opening and compressor frequency. As a result, the cooling and heating COPs were 2.3 and 3.0, respectively, when the EEV opening was 22%. When the optimal EEV openings for heating and cooling were 28% and 16%, the cooling and heating COPs increased by 3.3% and 3.9%, respectively, over the COPs at the EEV opening of 22%. Beside, the heating performance was more sensitive to EEV opening than the cooling performance. As the compressor speed decreased by 5 Hz, the cooling COP increased by 2%, while the heating COP decreased by 8%.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.277-282
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• 2006

With the aim of achieving half the regulated value of EURO-3 Emission Regulations, an ultra low emission motorcycle has been developed based on a motorcycle with an 1800 $cm^3$, horizontal opposed 6-cylinder engine. For the fuel supply system, an electronically controlled fuel injection system was applied. For the emission purification system, three-way catalysts, a feedback control system with a LAF(Linear Air-Fuel ratio) sensor, and a secondary air induction system were applied. To reduce CO and HC emissions during cold starting, an early catalyst activation method combining RACV(Rotary Air Control Valve) and retarded ignition timing was applied. After the catalyst activation, air-fuel ratio was controlled to maximize the purification ratio of the catalyst according to vehicle speed. For the air-fuel ratio control system, the LAF sensor was used. Furthermore, fine adjustment by the LAF feedback control reduced torque fluctuation due to the air-fuel ratio change. As a result, smooth ride feeling was maintained. Owing to these technologies, half the regulated value of EURO-3 has been achieved without any negative impact to the large-scaled motorcycles' drivability. This paper presents the developed ultra low emission technologies including the control method using an LAF sensor.

• Tribology and Lubricants
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• 제30권6호
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• pp.370-377
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• 2014

The basic elements in a rotary-type scroll compressor are two identical spiral scrolls containing refrigerant gas. The pressure variations in the compression pockets of a scroll compressor change the forces acting on the orbiting scroll, and these forces affect the dynamic behavior of the compression mechanism parts. To achieve high efficiency, using a self-sealing mechanism as a tip seal mechanism is very effective. Tip seals, which are placed on top of the scroll wraps, accomplish thrust sealing. This study calculates the friction force between the tip seal and the side plate of a scroll compressor using the numerical model considered in the Reynolds equation. The calculated friction force is verified by an experiment using a pin-on-disk apparatus. A hydraulic servo valve that controls the pressure of the oil hydraulic cylinder applies the normal load for the test, and a DC servo motor controls the sliding velocity of the disk. The friction force and normal load are measured by the force sensors attached to the supporting parts. The results show that the theoretical and experimental results are similar and that the friction is influenced by the viscosity of the oil and the sliding velocity of the scroll.