Daeheung Lee

Comparison of the Fuel Economy of Series and Parallel Hybrid Bus System Using Dynamic Programming

There are lots of studies about hybrid electric vehicles (HEVs) because of the global warming and energy problems. Series and parallel HEVs are the common types of many developing hybrid vehicle types. Series HEV uses engine only as the generator for the battery but parallel HEV utilizes engine for driving and generating of the vehicle. In this paper, backward simulations based on dynamic programming were conducted for the fuel economy analysis of two different types of hybrid transit buses depending on driving cycles. It is shown that there is a relation between the type of HEV and the characteristics of driving cycles. Regarding the aggressiveness, the series hybrid bus is more efficient than the parallel system on highly aggressive driving cycle. On the other hand, the parallel hybrid bus is more efficient than the series system on low aggressive driving cycle. Based on this results of the paper, it is expected to choose more efficient type of the hybrid buses according to the driving cycle.

The Component Sizing Process and Performance Analysis of Extended-Range Electric Vehicles (E-REV) Considering Required Vehicle Performance

It is very important to determine specifications of components included in the drive-train of vehicles at the initial design stage. In this study, component sizing process and performance analysis for Extended-Range Electric Vehicles (E-REV) are discussed based on the foundation of determined system configuration and performance target. This process shows sizing results of an electric driving motor, a final drive gear ratio and a battery capacity for target performance including All Electric Range (AER) limit. For E-REV driving mode, the constant output power of a Gen-set (Engine+Generator) is analyzed in order to sustain State of Charge (SOC) of the battery system.

Designing and manufacturing of Formula SAE-Hybrid racecar for a new engineering education program

This paper addresses the preparation and participation of new collegiate design series “Formula SAE-hybrid (FSAE-Hybrid)” under society of automotive engineers (SAE). These participation processes of FSAE-Hybrid are required various engineering knowledge as well as practical skills in terms of the design engineering education in university. The car is built in an open-wheel, single seat, plug-in hybrid racecar. The design issues of FSAE-Hybrid emphasize powertrain innovation and fuel efficiency in high hybrid power management. It is next generation vehicle, even though base model of FSAE-Hybrid is based on FSAE regulations and rules. Also, the several processes of competition, design, cost, and sale presentation, required the team management and team-work for university students. Students would utilize the software (CATIA and Pro-E) of computer-aided design in order to design chassis and suspension, including especially upright. Based on a design part and a frame, they should analyze stress distribution of each part and flow visualization of intake as well as exhaust. Also, the integrated vehicle is simulated by estimating the estimation of fuel-economy of hybrid management (supervisory control logic) via Matlab/Simulink and vehicle dynamics via Adams program.

Development of Integrated Control Logic of Wheel Motor Drive Electric Bus considering Stability and Driving Performance

Abstract : Recently, many types of electric vehicles including a heavy duty vehicle have been developed and released because of the better fuel economy and less gas products. In this study, research about an electric bus which utilizes the wheel motor drive system was conducted. The wheel motor is a motor connected to the wheel directly only with a simple gear so that the developer can utilize the space efficiently and the whole system efficiency will be better because of simple structure. However, because it is different from former types of vehicles which use the differential gear, the development of the integrated control logic is required in order to meet the vehicle stability and driving performance. The developed control logic is composed with direct yaw moment control, regenerative braking control and slip control logics. It is compared to the control logics which does not consist of direct yaw moment control and slip control when the vehicle is exposed in tough situations. For the unification of the control logic, a few maps were developed and applied to determine the output torque of each motor according to the driving status. As a result, it is shown that the developed control logic is more safe and well follow the target speed than the other control logic applied simulations.

Fuel economy analysis of a parallel hybrid bus using the optimal control theory

Distribution of the power between engine and motor is an important issue for parallel hybrid electric vehicles. A lot of studies have been carried out for the conventional passenger hybrid cars control logic. However, it still needs more studies for the parallel hybrid bus control logic. In this study, we developed a control logic based on the optimal control theory for the parallel hybrid bus. To verify the control logic, a forward simulator was developed. The control logic was applied to the forward simulator and the simulation was conducted. Backward simulation of which result is the global optimal was conducted for the comparisons of results from simulations. Consequently, similarity of forward and backward simulations was found.

Analysis of Abnormal Vibration by a Damper Clutch Operation in Low Speed Ranges of A/T Vehicles

A damper clutch in automatic transmission systems has some advantages of fuel economy and dynamic performance. Although a damper clutch operation improves a fuel economy of the vehicles, a positive operation of a damper clutch in a low vehicle speed induces abnormal vibration. This paper analyzed one of reasons for abnormal vibration by a damper clutch operation in low engine speed ranges. A simulation model was designed to confirm the effects of a damper clutch operation under unstable regions of an engine. A theoretical analysis was carried out about an engine operation stability. Simulation was conducted to depict abnormal vibration by a damper clutch operation in unstable regions of an engine performance curve. The effects of an engine operation region for abnormal vibration by a damper clutch was investigated according to the range and the slope of unstable regions. As a result of simulations, a damper clutch operation would be better to avoid an engine unstable regions.

Enhanced Diffusion in Polymer Electrolyte Membrane Fuel Cell using Pulsating Flow

초록: 본연구에서는진동자를이용하여채널내공기중산소의확산을증대시키는방법을고안하였다. 왕복유동시물질전달을지배하는두가지요소인왕복유동주파수와왕복유동거리가채널내의길이방향확산에어떤영향을미치는지에대해선행연구결과를이용한이론적해석을통하여보여주었으며, 이러한채널내의길이방향확산량의증가가스택성능에미치는영향에대해알수있었다. 스택의채널내의길이방향확산량은연료전지가반응하는반응량에비례하게되며, 따라서스택내의길이방향확산량을늘려주는만큼연료전지의최고파워밀도가늘어나게된다. 이러한길이방향확산량을증가시키기위해서는왕복유동이좋은방법이되며, 연료전지운전시왕복유동의주파수를증가시키게되거나왕복유동의거리를증가시킬수록채널내의길이방향으로확산량이증대되게된다.Abstract: This study considered the feasibility of controlling the air concentration by oscillating flow in fuel cellchannels. The fuel cell stack performance is largely influenced by the air concentration. If the air concentration islower than 2.5 times the stoichiometric of the inlet air, the fuel cell stack performance seriously deteriorates becauseof air starvation. In this respect, optimizing the air concentration is crucially important to maximizing the fuel cellstack performance. In this work, the effects of oscillating actuation were studied to control the concentration.Studies have shown that there are two non-dimensional key parameters related to the frequency and oscillatingamplitude. This paper presents how those parameters affect the performance of the stack.