승용 디젤엔진의 배기압력 추정기 기반 VGT 및 EGR 고장진단

Abstract

점차 강화되고 있는 디젤 엔진의 배기 및 에너지 규제를 만족시키기 위해서는 고장진단을 통해 디젤엔진에 장착된 장치들의 신뢰성을 확보하는 것이 중요하다. 본 연구에서는 승용 디젤엔진에 장착된 가변 용량 터보차져(VGT) 와 배기 재순환 장치(EGR)의 모델기반 고장진단 알고리즘을 제안하였다. 제안된 고장진단 알고리즘은 VGT vane의 위치 센서 고장, VGT vane의 액추에이터 고장, EGR 밸브의 위치 센서 고장, 그리고 EGR 밸브 액추에이터 고장을 진단할 수 있었다. 고장진단에 필요한 디젤엔진 흡배기 시스템의 상태량을 추정하기 위해 슬라이딩 모드 추정기를 설계하였으며 양산엔진에서 사용 가능한 센서만을 이용하여 배기 압력, EGR 율, 터빈 질량유량 등의 상태량을 추정하였다. 또한 제안된 추정기의 수렴성은 Lyapunov stability 조건을 통해 검증되었다. 추정기로부터 추정된 상태량을 기반으로 VGT와 EGR 시스템의 모델기반 고장진단 알고리즘을 제안하였으며, 시스템의 외란이나 센서의 노이즈로부터 강인한 고장진단을 위하여 cumulative summation (CUSUM) 알고리즘을 개선하여 고장진단 알고리즘에 적용하였다. 제안된 고장진단 알고리즘은 실시간 임베디드 시스템에 구현되어 엔진 실험을 통해 성능을 검증하였다. 그 결과 추정된 상태량을 이용하여 VGT와 EGR 시스템의 고장을 정확히 진단하였다.|In this study, a model based fault diagnosis algorithm was proposed to detect and isolate the four types of faults in the variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) systems including the VGT vane position sensor fault, VGT vane stuck fault, EGR valve position sensor fault, and EGR valve stuck fault. Accurate fault diagnosis is important for the reliability of devices in diesel engines in order to satisfy stringent emission and energy regulations. The sliding mode observer was designed in order to estimate the system states of the air system in diesel engines such as the exhaust pressure, EGR rate, and turbine mass flow rate using only the sensors available in mass-produced engines. The convergence of the proposed observer was guaranteed by the Lyapunov stability criterion. Based on the estimated physical states, the model based fault diagnosis algorithm of the VGT and EGR systems was proposed. In addition, the cumulative summation (CUSUM) algorithm was modified to obtain a robust algorithm for the system disturbance and sensor noise. The proposed algorithm was implemented on a real-time embedded system and validated with engine experiments. The experimental results indicate that the proposed algorithm could accurately detect and isolate the faults of the VGT and EGR systems with estimated states from the observer.; In this study, a model based fault diagnosis algorithm was proposed to detect and isolate the four types of faults in the variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) systems including the VGT vane position sensor fault, VGT vane stuck fault, EGR valve position sensor fault, and EGR valve stuck fault. Accurate fault diagnosis is important for the reliability of devices in diesel engines in order to satisfy stringent emission and energy regulations. The sliding mode observer was designed in order to estimate the system states of the air system in diesel engines such as the exhaust pressure, EGR rate, and turbine mass flow rate using only the sensors available in mass-produced engines. The convergence of the proposed observer was guaranteed by the Lyapunov stability criterion. Based on the estimated physical states, the model based fault diagnosis algorithm of the VGT and EGR systems was proposed. In addition, the cumulative summation (CUSUM) algorithm was modified to obtain a robust algorithm for the system disturbance and sensor noise. The proposed algorithm was implemented on a real-time embedded system and validated with engine experiments. The experimental results indicate that the proposed algorithm could accurately detect and isolate the faults of the VGT and EGR systems with estimated states from the observer.