Kim M.-H.,Republic of Korea Army Headquarters |
Baik H.,GM Korea Company |
Lee S.,Purdue University
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2014
This paper addresses a task allocation problem for a team of UAVs that cooperatively performs a search and attack mission in an unknown region. The UAVs are heterogeneous carrying different types and amounts of munition resources, and limited in communications and sensing capabilities. The environment is highly uncertain and dynamic where no prior information is available and dynamic events such as UAV failures unpredictably occur. The objective of the mission is to maximize total reward obtained by destroying targets within a given mission horizon. A group of UAVs may need to be formed to attack a target because individual UAVs may not have sufficient resources for the execution of attack tasks. Instantaneous task allocation approaches that seek for optimal solution for current tasks cannot effectively account for the unpredictability of future tasks in the uncertain dynamic environment. In this paper, we propose a distributed task allocation scheme based on resource welfare of which concept is adopted from economics. The approach we present enables the UAV team to effectively utilize resources by balancing resource depletions and consequently be capable of smoothly responding to dynamic events by retaining more UAVs available. Simulation experiments were conducted in various conditions to evaluate the performance of the proposed approach in comparison with the instantaneous task allocation method. The results show that our approach improves the performance by up to 29.3 % with respect to the instantaneous task allocation method. © 2014, Springer Science+Business Media Dordrecht.
Jeon B.J.,Seoul National University of Science and Technology |
Kim Y.S.,GM Korea Company |
Choi H.G.,Seoul National University of Science and Technology
Journal of Mechanical Science and Technology | Year: 2012
Conjugate heat transfer around a circular cylinder with heat source was numerically investigated. Both the forced convection of water and conduction of carbon-steel were involved in the present simulation. A finite element formulation based on SIMPLE type algorithm was adopted for solving the incompressible Navier-Stokes equations coupled with energy equation. A conduction heat transfer problem inside the cylinder was trivially coupled with forced convection around the cylinder by using the Galerkin formulation of energy equation. The proposed algorithm was verified by solving the benchmark problem of conjugate heat transfer inside a cavity having a centered body. The effect of the Reynolds number on the temperature distribution on the cylinder surface and the maximum temperature inside the cyl-inder was examined. It was shown that the maximum temperature decreased as Reynolds number increased and that the position of the maximum temperature moved from the center to the rear part of the cylinder till Re = 20 and then moved back toward the center beyond Re = 20 since the reverse flow around the rear part of the cylinder became stronger as the Reynolds number further increased. Lastly, the maximum temperature of the cylinder with rotation was higher than that of the fixed one and the position of the maximum temperature inside the cylinder depended on the position and the strength of the dead zone. © KSME & Springer 2012.
Lee J.,GM Korea Company |
Song S.,Yonsei University |
Chun K.M.,Yonsei University
International Journal of Automotive Technology | Year: 2012
In lean-DeNOX catalysis reactions, hydrogen is a good reducing agent in PGM catalysts as well as an effective promoter in selective catalytic reduction reactions over base metal oxide catalysts. However, such a lean-DeNOX system, which uses hydrogen, requires an on-board fuel reforming system applicable to internal combustion engines. In this study, catalytic partial oxidation (CPOx) performance was tested in a laboratory for various reactants and hydrocarbon conditions. Volume concentrations of 5-10% oxygen and 0-5% water vapor were used to simulate diesel exhaust, and n-C12H26 was used as the feedstock for the reforming reaction. In the CPOx of n-C12H26, the highest hydrogen selectivity was 64% and was achieved at 100,000 h-1 GHSV. Additionally, the C/O ratio was less than unity in the absence of water vapor. However, as the water concentration was increased to 2. 5 and 5. 0 vol. % in the n-C12H26 CPOx reactions, the maximum hydrogen selectivity was increased from 64% in the absence of water to 70% and 75%, respectively. This effect is a consequence of the water-gas shift reaction over the catalyst bed. Regarding oxygen concentration effects, hydrogen selectivity slightly increased with increasing oxygen concentration from 10% to 15%. It was also found that the CPOx reaction of n-C12H26 can be ignited at temperatures below 300 C. Accordingly, it can be concluded that CPOx is a useful and feasible device for promoting diesel DeNOx catalysis in terms of hydrogen productivity and reaction initiation. © 2012 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.
Ge J.C.,Chonbuk National University |
Kim M.S.,Chonbuk National University |
Yoon S.K.,GM Korea Company |
Choi N.J.,Chonbuk National University
Energies | Year: 2015
Biodiesel as a clean energy source could reduce environmental pollution compared to fossil fuel, so it is becoming increasingly important. In this study, we investigated the effects of different pilot injection timings from before top dead center (BTDC) and exhaust gas recirculation (EGR) on combustion, engine performance, and exhaust emission characteristics in a common rail diesel engine fueled with canola oil biodiesel-diesel (BD) blend. The pilot injection timing and EGR rate were changed at an engine speed of 2000 rpm fueled with BD20 (20 vol % canola oil and 80 vol % diesel fuel blend). As the injection timing advanced, the combustion pressure, brake specific fuel consumption (BSFC), and peak combustion pressure (Pmax) changed slightly. Carbon monoxide (CO) and particulate matter (PM) emissions clearly decreased at BTDC 20° compared with BTDC 5°, but nitrogen oxide (NOx) emissions increased slightly. With an increasing EGR rate, the combustion pressure and indicated mean effective pressure (IMEP) decreased slightly at BTDC 20° compared to other injection timings. However, the Pmax showed a remarkable decrease. The BSFC and PM emissions increased slightly, but the NOx emission decreased considerably.
Yu M.,GM Korea Company |
Kim Y.,GM Korea Company
Lecture Notes in Electrical Engineering | Year: 2013
Vehicles can lead to the environmental impact throughout their whole life cycle - from production, use, to disposal. Therefore, analyzing the whole life's environmental profile and setting up advanced environmental performance target for each vehicle within vehicle development process is the basis of 'Eco-design'. In this respect, Life Cycle Assessment (LCA) is a useful tool for analyzing the environmental profile. However, it is very time and manpower consuming work to collect and process the huge amounts of data related to material and energy flows during whole life cycle of a vehicle in the LCA process, due the number of components that a vehicle is made from. Therefore, environmental assessment system of vehicle is developed by GM Korea Company to help manage this problem based on automated and standardized data management and processing methods. © Springer-Verlag 2013.
Meinert F.,General Motors |
Johannessen K.,GM Holden Ltd. |
Saito F.,GM do Brazil |
Song B.,GM Korea Co. |
And 4 more authors.
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2016
Wind tunnel testing of reduced-scale models is a valuable tool for aerodynamic development during the early stages of a new vehicle program, when basic design themes are being evaluated. Both full-and reduced-scale testing have been conducted for many years at the General Motors Aerodynamics Laboratory (GMAL), but with increased emphasis on aerodynamic drag reduction, it was necessary to identify additional facilities to provide increased test capacity. With vehicle development distributed among engineering teams around the world, it was also necessary to identify facilities local to those teams, to support their work. This paper describes a cooperative effort to determine the correlation among five wind tunnels: GMAL, the Glenn L. Martin Wind Tunnel (GLMWT) at the University of Maryland, the Institute of Aeronautics and Space (IAE/ALA) TA-2 Wind Tunnel in Brazil, the Monash University Wind Tunnel in Australia, and the Korea Aerospace Research Institute Low Speed Wind Tunnel (KARI LSWT). Correlation tests were conducted using a vehicle model with interchangeable body modules and additional parts, to determine the relationships of measured aerodynamic force and moment coefficients among the tunnels. Despite the significant differences among facilities, the correlation results were satisfactory for reduced-scale wind tunnel development of future General Motors Co. (GM) vehicles. Correlation equations were defined, allowing conversion of data from one tunnel to equivalent values at another. This paper will present the physical descriptions and airflow characteristics of the wind tunnels, the test equipment and procedures, and the correlation results. Copyright © 2016 SAE International.
Kim K.,GM Korea Co. |
Mital R.,General Motors |
Higuchi T.,IBIDEN |
Chan S.,GM Korea Co. |
Kim C.H.,General Motors
SAE Technical Papers | Year: 2014
Diesel particulate filter (DPF) is a widely used emission control device on diesel vehicles. The DPF captures the particulate matter coming from the engine exhaust and periodically burns the collected soot via the regeneration process. There are various trigger mechanisms for this regeneration, such as distance, time, fuel and simulation. Another method widely used in the industry is the pressure drop across the filter. During calibration, relation between the pressure sensor reading and soot mass in the filter is established. This methodology is highly effective in successful DPF operation as pressure sensor is a live signal that can account for any changes in engine performance over time or any unforeseen hardware failures. On the other hand, any erroneous feedback from the sensor can lead to inaccurate soot mass prediction causing unnecessary regenerations or even needless DPF plugging concerns. A similar phenomenon was observed on certain vehicles where the DPF pressure reading jumped inexplicably leading to DPF plugging concerns. Extensive research and testing was carried out to understand this mysterious phenomenon starting with the usual hardware suspects such as pressure sensor, pressure lines, DPF substrate and washcoat etc. When none of these could be identified as the root cause, same drive cycles that caused this occurrence were tested on vehicles and dynamometer along with the environmental conditions and destructive testing was conducted on the filters. Results indicated a remarkable phenomenon was occurring inside the DPF channels. Under certain driving conditions the soot inside the DPF channels collapsed causing sudden restriction and an abrupt increase in pressure across the DPF. This paper discusses the fascinating journey of how the conditions necessary for this pressure jump to occur were discovered and how some of the hardware design changes could mitigate the sudden pressure increase phenomenon, increasing the DPF robustness. Copyright © 2014 SAE International.
Nguyen L.D.K.,Sungkyunkwan University |
Sung N.W.,Sungkyunkwan University |
Lee S.S.,GM Korea Company |
Kim H.S.,Korea Institute of Machinery and Materials
International Journal of Automotive Technology | Year: 2011
The effects of split injection, oxygen enriched air, and heavy exhaust gas recirculation (EGR) on soot emissions in a direct injection diesel engine were studied using the KIVA-3V code. When split injection is applied, the second injection of fuel into a cylinder results in two separate stoichiometric zones, which helps soot oxidation. As a result, soot emissions are decreased. When oxygen enriched air is applied together with split injection, a higher concentration of oxygen causes higher temperatures in the cylinder. The increase in temperature promotes the growth reaction of acetylene with soot. However, it does not improve acetylene formation during the second injection of fuel. As more acetylene is consumed in the growth reaction with soot, the concentration of acetylene in the cylinder is decreased, which leads to a decrease in soot formation and thus soot emissions. A combination of split injection, a high concentration of oxygen, and a high EGR ratio shows the best results in terms of diesel emissions. In this paper, the split injection scheme of 75.8.25, in which 75% of total fuel is injected in the first pulse, followed by 8°CA of dwell time, and 25% of fuel is injected in the second pulse, with an oxygen concentration of 23% in volume and an EGR ratio of 30% shows a 45% reduction in soot emissions, with the same NOx emissions as in single injection. © 2011 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.
Kim J.,Delphi Corporation |
Ryu N.,GM Korea Company |
Kim Y.,Delphi Corporation
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2012
Limiting residual drag torque and fluid displacement is a major requirement of a caliper brake as they are related to the fuel efficiency and the safety of a vehicle. However, it is difficult to simultaneously reduce both the drag torque and the fluid displacement since improving one tends to degrade the other. This paper investigates a caliper with a high residual drag torque. DFSS (Design for Six Sigma) method was implemented to identify all major factors and the design optimization was performed to achieve a low drag caliper. The prototype was created with the desirable design factors identified in the study and the dynamometer tests confirmed that it is possible to achieve a low drag caliper without sacrificing the fluid displacement. © 2012 SAE International.
Yoon S.K.,GM Korea Company |
Kim M.S.,Chonbuk National University |
Kim H.J.,Chonbuk National University |
Choi N.J.,Chonbuk National University
Energies | Year: 2014
In this study, we investigated the effects of canola oil biodiesel (BD) to improve combustion and exhaust emissions in a common rail direct injection (DI) diesel engine using BD fuel blended with diesel. Experiments were conducted with BD blend amounts of 10%, 20%, and 30% on a volume basis under various engine speeds. As the BD blend ratio increased, the combustion pressure and indicated mean effective pressure (IMEP) decreased slightly at the low engine speed of 1500 rpm, while they increased at the middle engine speed of 2500 rpm. The brake specific fuel consumption (BSFC) increased at all engine speeds while the carbon monoxide (CO) and particulate matter (PM) emissions were considerably reduced. On the other hand, the nitrogen oxide (NOx) emissions only increased slightly. When increasing the BD blend ratio at an engine speed of 2000 rpm with exhaust gas recirculation (EGR) rates of 0%, 10%, 20%, and 30%, the combustion pressure and IMEP tended to decrease. The CO and PM emissions decreased in proportion to the BD blend ratio. Also, the NOx emissions decreased considerably as the EGR rate increased whereas the BD blend ratio only slightly influenced the NOx emissions. © 2014 by the authors.