Jaesung Chung

Control of the air system of a diesel engine using the intake oxygen concentration and the manifold absolute pressure with nitrogen oxide feedback

In production-type engine control systems for passenger car diesel engines, the mass air flow is commonly used as a feedback variable for control of the exhaust gas recirculation system. However, the mass air flow is not appropriate as a feedback variable for control of the exhaust gas recirculation system because the mass air flow has a weak correlation with the formation of the nitrogen oxide emissions. Another defect of production-type engine control systems is that the emissions-relevant systems are controlled without emissions feedback. In order to address these problems, this study proposes air system control using the intake oxygen concentration as it has a strong correlation with the formation of the nitrogen oxide emissions with nitrogen oxide feedback. The intake oxygen concentration is estimated using a closed-loop observer, and the estimated intake oxygen concentration is used as a feedback variable for control of the exhaust gas recirculation system. The measured nitrogen oxide concentration is used as emissions feedback control. When the measured nitrogen oxide concentration exceeds the reference nitrogen oxide value, emissions feedback control is activated and causes the set value of the intake oxygen concentration to decrease in order to reduce the nitrogen oxide emissions when the measured nitrogen oxide concentration exceeds the typical value. The proposed air system control method is validated with engine experiments, and the nitrogen oxide emissions are reduced by 11.5–39.8% using nitrogen oxide feedback control in various test cases which cause the drift of the nitrogen oxide emissions.

Modelling of the exhaust gas recirculation rate based on the in-cylinder pressure measurement for a passenger car diesel engine

This paper proposes a modelling of the exhaust gas recirculation rate using the in-cylinder pressure sensor for a passenger car diesel engine. Traditional modelling approaches for the exhaust gas recirculation rate normally use variables which are measured for a long intake–exhaust air path so that a time delay is inevitable. In addition, the model structure is complex, since many non-linear or unmeasurable variables such as the volumetric efficiency and the efficiency of the exhaust gas recirculation cooler have to be considered in the model. The proposed exhaust gas recirculation rate model is based on the in-cylinder pressure measurement which provides instantaneous information about combustion. Therefore, when this information is used, it is able to model the exhaust gas recirculation rate with a fast response compared with traditional modelling approaches. Furthermore, the proposed model can have a simple model structure since the model does not require consideration of the non-linear or unmeasurable parameters of the air path. The proposed exhaust gas recirculation rate model was integrated into an engine control unit and validated through engine experiments on various operating conditions.

Development of IMEP Estimation and Control Algorithm Using In-Cylinder Difference Pressure for Passenger Diesel Engines

이 연구에서는 실린더 압력과 모터링 압력의 차이인 차이 압력(difference pressure)을 이용하여 IMEP 를 추정하는 방법을 제안하고, 추정된 IMEP 를 IMEP diff 로 정의하였다. IMEP diff 는 차이 압력이 연소 시작 시점에서 연소 종료 시점까지만 존재하는 압력이라는 사실에 기반하여 이론적인 IMEP 계산식의 연산 구간을 최적화한 것으로 IMEP 와 비교 시 R 2 0.9955 의 높은 선형관계를 보였다. 또한 이론적인 IMEP 계산 방법과 비교하여 21 %의 실린더 압력 데이터 및 31 %의 계산량만으로 IMEP 획득이 가능하여 실시간 제어에 용이하다. IMEP diff 추정 및 제어 성능은 엔진 실험을 통하여 검증하였으며, IMEP diff 제어를 통하여 실린더 간 토크 편차 감소를 확인하였다.In this study, we propose a new method for estimating the IMEP using difference pressure, which is the pressure difference between the cylinder pressure and the motoring pressure. The estimated IMEP, denoted as , optimizes the theoretical IMEP calculation range based on the fact that the difference pressure exists between the start and the end of combustion. is verified to have a high linear correlation with IMEP with of 0.9955. The proposed method can estimate the IMEP with 21% of the cylinder pressure data and 31% of the calculation effort compared to the theoretical IMEP calculation method, and therefore, it has great potential for real-time implementations. The estimation and control performance of is validated by engine experiments, and by controlling , the torque variation between the cylinders was reduced.

An Alternative Method to MFB50 for Combustion Phase Detection and Control in Common Rail Diesel Engines

Although injection timing does not change at every cycle in compression ignition engines, the variations in combustion phase may occur. The variations in combustion phase are directly related to emission dispersion, torque variation, and fuel economy; therefore, the variations should be minimized by combustion phase detection and control. In this study, we propose a novel combustion indicator: location of 20% of initial heat release after the peak (IHRap20) that is an alternative to MFB50 to detect and control combustion phase in real time. IHRap20 is extracted from IHR, which is a simplified heat release model derived by the product of in-cylinder volume and the gradient of difference pressure between firing pressure and motoring pressure. IHRap20 is confirmed with engine experiment that it is highly correlated to MFB50 with RMSE of 0.2790° crank angle and R 2 of 0.9873 under various operating conditions such as injection timing, mass air flow, boost pressure, and rail pressure changes. In addition, IHRap20 is able to detect combustion phase in real time with fewer number of in-cylinder pressure data and computational load compared to MFB50. Furthermore, IHRap20 is more robust to in-cylinder pressure sensor noise than MFB50. Consequently, IHRap20 is promising for real-time combustion phase detection.

3D map generation algorithm for energy management system on electric vehicles

This paper proposes a three-dimensional (3D) map generation algorithm for energy management systems on electric vehicles (EV) or hybrid electric vehicles (HEV). The 3D road geometry of the predefined driving path can be crucial information for energy management systems to design an optimal driving strategy. A single GPS receiver can provide the 3D position of a road profile; however, it is not accurate and reliable enough to use for an energy management system. An information fusion algorithm based on the optimal smoother is applied for map generation to improve the accuracy and integrity of the 3D map database. The algorithm developed in this study is verified and evaluated through experimentation using a probe vehicle equipped with GPS and several on-board sensors. The experimental results show that the map generation algorithm performance is sufficiently accurate and reliable for an energy management system.