• 한국정밀공학회지
• /
• 제17권6호
• /
• pp.89-95
• /
• 2000

The engine idle speed mode becomes worse as one drives a vehicle for several years. This is due to ageing of engine and power-train parts. In this case, unstable idle conditions such as engine stall and droop are frequently experienced when the engine gets heavy torque loads due to power steering pump and air conditioning compressor. The objective of this paper is to study on the idle speed control using PID controller under load disturbances. The input of the PID controller is an error of rpm. The output of the PID controller is an ISCV duty cycle. The dSPACE Controller Boards are used to interface with engine. The on-vehicle test is realized using by SIMULINK and BLOCKSETS tools. The real time interface control panel supplied by Control Desk S/W is designed to have good results in engine idle speed control.

• 대한기계학회논문집B
• /
• 제39권9호
• /
• pp.713-718
• /
• 2015

본 연구의 목적은 자동차용 에어컨 시스템의 연비 개선을 위하여 압축기의 성능 향상을 도모하고자 하는데 있다. 압축기 성능은 자동차용 에어컨 압축기 전용 열량계를 이용하여 평가를 수행하였다. 압축기의 성능을 향상시키기 위하여 흡입 유량의 증대와 토출 사체적 축소를 검토하였으며, 각 개선 항목에 대한 평가를 진행하여 성능과 COP 의 개선을 확인하였다. 흡입 유량을 증대했을 경우 저속 구간보다 고속구간에서의 성능 효과가 컸으며, 토출 사체적을 축소했을 경우 상대적으로 저속 구간의 성능 개선효과가 컸다. 조합품의 경우 저속과 고속에서 전반적으로 균형 있게 개선되었으며, 토출측 온도가 가장 크게 개선되었다. 성능의 경우 저속에서 약 3.2%, 고속에서 약 8.3% 개선되었으며, COP 는 저속에서 약 5.8%, 고속에서 약 6.2% 개선되었고, 토출 온도는 저속에서 $3^{\circ}C$, 고속에서 $5^{\circ}C$ 개선되었다.

• 한국항행학회논문지
• /
• 제15권6호
• /
• pp.1187-1193
• /
• 2011

본 논문에서는 연료유량이 제어 수단인 터보제트 엔진에 대해 압축기의 서지를 방지하면서 가속시간을 줄일 수 있는 제어기를 제안하였다. 압축기 회전 속도를 추정하기위해 고이득 관측기를 사용하고 퍼지이론과 PID 제어 알고리즘을 적용하는 터보제트 엔진 제어기를 설계하였다. 퍼지추론의 결과는 터보제트 엔진의 가감속시 서지와 flame-out 현상을 방지하기 위한 연료 유량 제어 입력으로 사용되고, 신속하고 안전하게 원하는 속도로 수렴할 수 있도록 제어기를 설계한다. MATLAB을 사용한 컴퓨터 시뮬레이션을 수행하여 제안된 제어기의 성능을 입증하였다.

• 한국유체기계학회 논문집
• /
• 제7권3호
• /
• pp.23-31
• /
• 2004

An experimental study on the performance and instability development characteristics of a centrifugal compressor equipped with an adjustable inlet guide vane has been performed with varying guide vane angles. The test was conducted at the design speed of 20,800 rpm for 6 guide vane angles : $-30^{\circ},\;-20^{\circ},\;10^{\circ},\;0^{\circ},\;10^{\circ},\;20^{\circ},\;30^{\circ}$. Unsteady pressures were measured using high-frequency pressure transducers at the inducer to investigate the instability phenomena such as rotating stall and surge inside the compressor. From the unsteady measurements, it is found that the transient process from rotating stall to surge was mainly affected by inlet guide vane angles. The results of the present study can be applied to the instability control of the centrifugal compressors using a adjustable inlet guide vane.

• 설비공학논문집
• /
• 제28권12호
• /
• pp.502-508
• /
• 2016

An optimized PI controller design method is presented to promote the control performance of an oil cooler system for high precision machine tools. First, a transfer function model of the oil cooler system with a variable rotating speed compressor was obtained by the perturbation method as the first order system with a negligible dead time. Then, the closed-loop control system was described as the second order system with a zero. Its dynamic behaviors are mostly governed by characteristic parameters, the damping ratio, and the natural frequency which is incorporated in PI gains. Next, an optimum integral of the time-weighted absolute error (ITAE) criterion was applied to the second order system. The characteristic parameters can be determined by the given design specifications, percent overshoots and settling times and comparisons with the ITAE criterion. Hence, the PI gains were plainly identified in a deterministic way. Finally, the PI gains were fine-tuned to obtain desirable dynamics in real systems, considering the zero effect and parameter variations. The validity of the proposed method was proven by computer simulations and real experiments for selected cases.

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

• 설비공학논문집
• /
• 제25권3호
• /
• pp.137-142
• /
• 2013

A small air-conditioner or chiller for a constant temperature bath normally uses a constant speed compressor. The constant speed compressor is relatively inexpensive, but it uses on/off control for capacity modulation. The on/off control has several disadvantages, specifically energy loss and large temperature fluctuation. Continuous operation with a bypass system can be an alternative to on/off control, for capacity modulation. In this study, a heat pump system having a hot-gas bypass and a liquid bypass was adopted. The performance of the bypass-type heat pump was measured, by varying the bypass valve opening. The differences of the COP between the hot-gas bypass and the liquid bypass, in the cooling and heating operations, were within 2% and 1%, respectively. The liquid bypass showed a wider range of capacity control in the cooling operation but the hot-gas bypass showed a wider range of capacity control in the heating operation.

• 설비공학논문집
• /
• 제12권5호
• /
• pp.466-466
• /
• 2000

• 설비공학논문집
• /
• 제19권12호
• /
• pp.842-849
• /
• 2007

For a $CO_2$ two-stage twin rotary compressor used for heat pump water heater system, changes of $CO_2$ solubility in PAG oil were investigated along the gas passages from the first stage suction to final discharge. Only slight changes in solubility took place in suction chambers for both of the first and second stages, but for compression chambers, solubility variation ranged from 0.115 to 0.136, and from 0.133 to 0.182, respectively for the first and second stages. Calculation of gas flashing in parts of leakage oil flows and of oil contained in control volumes due to solubility changes was conducted and included in gas pressure calculation. For the second stage, gas flashing amounts to around $5%\sim6%$ for most leakage flows. Cooling capacity, compressor input, and COP obtained by calculation were well compared to the experimental results. Effects of operation speed on the compressor performance was also studied: as the shaft speed increased, adiabatic efficiency decreased rapidly due to increased over-compression loss.

• 한국공작기계학회논문집
• /
• 제13권4호
• /
• pp.87-94
• /
• 2004

Recently, technical trend in machine tools is focused on enhancing of speed, accuracy and reliability. The high speed usually results in thermal displacement and structural deformation. To minimize the thermal effect, precision machine tools adopt a high precision cooling system. This study proposes a temperature control for an oil cooler system using Pill control with fuzzy logic. In the cooler system, refrigerant flow rate is controlled by rotational speed of a compressor, and outlet oil temperature is selected as the control variable. The fuzzy control rules iteratively correct PID parameters to minimize the error and difference between the outlet temperature and the reference temperature. Here, ambient temperature is used as the reference one. To show the effectiveness of the proposed method, a series of experiments are conducted for an oil cooler system of machine tools, and the results are compared with the ones of a conventional Pill control. The experimental results show that the proposed method has advantages of faster response and smaller overshoot.