• Journal of Mechanical Science and Technology
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• 제15권6호
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• pp.699-708
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• 2001

This paper presents a new approach to the AFR (Air-to-Fuel Ratio) control problem, which is based on the wide-band oxygen sensor output. The dedicated nonlinear controller is based on the feedback lineaization technique. It is well known that the feedback linearizing control technique requires an exact model of the plant for the cancellation of plant nonlinearities. A sliding mode control scheme is applied which can effectively compensate the modeling uncertainties. The measurement time delay of an oxygen sensor limits the gain of the feedback controller. Hence, time delay compensation procedure is necessary for the improvement of control performance. The Smith predictor is adopted to compensate the effects of time delay. The simulation and experimental results show that the proposed controllers can effectively reduce the transient peaks of AFR in spite of fast tip-in and tip-out maneuvers of the throttle.

• 로봇학회논문지
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• 제17권2호
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• pp.159-163
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• 2022

A linearly moving structure in the area where the friction force is dominant - such as ducts filled with grease in the nuclear power plant - experiences increase in friction since the contact surface gets larger as the structure proceeds. To solve this problem is critical for the pipe inspection robot to investigate further area and this makes the system more energy-efficient. In this paper, we propose a passively growing sheath that can be added to linearly moving structures using zipper mechanism. The mechanism enables the linearly moving structures to maintain rolling contact condition against external environment, which provides substantial reduction in kinetic friction. To analyze the effect of the mechanism's head shape, we establish a physical model and compare to the experimental results. Finally, we have shown that the passively growing sheath can be successfully applied to the pipe inspection robot for the nuclear power plant.

• 한국자동차공학회논문집
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• 제21권3호
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• pp.88-97
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• 2013

This paper presents a robust air-to-fuel ratio (AFR) control algorithm for managing exhaust gas recirculation (EGR) systems. In order to handle production tolerance, deterioration and parameter-varying characteristics of the EGR system, quantitative feedback theory (QFT) is applied for designing the robust AFR control algorithm. A plant model of EGR system is approximated by the first order transfer function plus time-delay (FOPTD) model. EGR valve position and AFR of exhaust gas are used as input/output variables of the plant model. Through engine experiments, parameter uncertainty of the plant model is identified in a fixed engine operating point. Requirement specifications of robust stability and reference tracking performance are defined and these are fulfilled by the following steps: during loop shaping process, a PID controller is designed by using a nominal loop transmission function represented on Nichols chart. Then, the frequency response of closed-loop transfer function is used for designing a prefilter. It is validated that the proposed QFT-based AFR control algorithm successfully satisfy the requirements through experiments of various engine operating points.

• 한국CDE학회논문집
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• 제21권2호
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• pp.170-176
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• 2016

PLM system has been widely used in whole industry. Specially, in case of the company that constructs the engineering plant, PLM can be a key success tool for the innovation with ERP and Enterprise IT Systems. This paper describes the innovation strategy for engineering plant PLM including Master Data management, EPC project management, full 3D modeling and quality management.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.351-359
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• 2007

In this study, a hierarchical switching control scheme based on robust control theory is proposed for tracking control of vehicle longitudinal acceleration in the presence of large uncertainties. A model set consisting of four multiplicative-uncertainty models is set up, and its corresponding controller set is designed by the LMI approach, which can ensures the robust performance of the closed loop system under arbitray switching. Based on the model set and the controller set, a switching index function by estimating the system gain of the uncertainties between the plant and the nominal model is designed to determine when and which controller should be switched into the closed loop. After theoretical analyses, experiments have also been carried out to validate the proposed control algorithm. The results show that the control system has good performance of robust stability and tracking ability in the presence of large uncertainties. The response time is smaller than 1.5s and the max tracking error is about $0.05\;m/S^2$ with the step input.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.182-189
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• 2014

This paper proposes a decoupler design method to reduce interaction between exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems in passenger car diesel engines. The EGR valve and VGT vane are respectively used to control air-to-fuel ratio (AFR) of exhaust gas and intake pressure. A plant model for EGR and VGT systems is defined by a first order transfer function plus time-delay model, and the loop interaction between these systems is analyzed using a relative normalized gain array (RNGA) method. In order to deal with the loop interaction, a design method for simplified decoupler is applied to this study. Feedback control algorithms for AFR and intake pressure are composed of a compensator using PID control method and a prefilter. The proposed decoupler is evaluated through engine experiment, and the results successfully showed that the loop interaction between EGR and VGT systems can be reduced by using the proposed decoupler. Furthermore, it presents stable performance even off from the designed operating point.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.106-113
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• 2002

A procedure to model and simulate control systems is presented using CADyna and MATLAB/Simulink computer codes. For the plant modeling, a technique for obtaining the state matrices from CADyna is presented. To obtain state matrices from CADyna models, perturbation theory is used. These state matrices are then used in NATLAB to design a controller for the plant. The controller design can subsequently be incorporated into the CADyna model and its closed loop performance is evaluated. Examples are presented to verify the developed methodology.

• 한국정밀공학회지
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• 제19권10호
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• pp.130-138
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• 2002

This paper presents the modeling and analysis of dynamic characteristics of hydraulic snubber in electric power plant. The nonlinear state-space model of 14th order to describe the dynamics of the snubber was established by Simulink. The simulation results show that the hydraulic snubber reacts as like the conventional shock absorbers against the high pulse shock load. The snubber also shows the peculiar characteristics to the small step load, which temporarily lock the control valves up, however maintain same steady-state pressures of all internal chambers in the long run. Two case studies for the analysis of the snubber were addressed. Practical pulse testing method was also proposed to identify the frequency response characteristics of the snubber.

• 한국수소및신에너지학회논문집
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• 제29권2호
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• pp.181-189
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• 2018

Polymer electrolyte membrane fuel cell (PEMFC) system receives great attention as a promising power device for automotive applications. For the wide commercialization, the efficiency and performance of automotive PEMFC system should be further improved in terms of total system (stack and balance of plant [BOP]). Air supply module, which is a major part of the BOP, greatly affects the efficiency of automotive PEMFC system. In this paper, a systematic study on the low-pressure automotive PEMFC system was made in an attempt to enhance the net system efficiency. This study mainly presents an investigation of the effect of blower configuration (1-blower and 2-blower) on the net system efficiency of automotive PEMFC system. For this purpose, the effect of operating pressure and cathode stoichiometry on the system efficiency was investigated with stack temperature under the fixed net system power condition. Results indicate that 1-blower system is better in system efficiency over 2-blower system under an air stoichiometry of 2. However, 2-blower system is better in system efficiency under an air stoichiometry of 3. The simulation results show that the optimum operating strategy needs to be established for various blower system configurations considering blower performance maps.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1474-1479
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• 2012

회전형 스마트 조명 제어시스템은 작물 재식판에 위치한 작물들에게 필요한 광을 회전하며 공급하는 시스템이다. 기존 식물공장은 무수히 많이 설치되는 LED와 형광등과 같은 조명장치에 따라 고가의 초기 조명 시스템 설치비용이 발생 된다. 이에 본 논문은 비교적 적은 양으로 설치된 조명장치를 회전시키는 시스템을 개발하였으며, 식물이 생장하는데 필요한 광량과 광속, 광양자속 밀도(PPFD)를 계산하였다. 조명 시뮬레이션 프로그램 Relux와 시제품을 이용한 실험을 통하여 조명 모듈의 각도 변화와 블레이드의 회전속도 변화에 따른 측정 영역에서의 광량의 차이를 비교하고 분석하였다.