Yeong-il Park

Performance analysis and parametric design of the dual-mode planetary gear hybrid powertrain

Abstract The multimode electrically variable transmissions (EVTs) are an advancement of the conventional planetary gear hybrid powertrains (PGHPs). Using the analytical methodologies once applied to the single-mode PGHP, the dual-mode PGHP was investigated. The transmission efficiency and the system optimal operation point maximizing the system overall efficiency were analysed. With the system optimal operation points, the fuel economies of the dual-mode PGHP vehicle were calculated assuming constant-velocity cruising and NEDC mode driving. The top velocity and the acceleration performance were also estimated. To assign appropriate parameters for the new system, the design space and the optimization problem were defined using the vehicle performances from the analyses. An approach with various optimization techniques is proposed, and the optimal parametric design is obtained. The dual-mode PGHP showed improvements in efficiency and dynamic performances compared with the single-mode PGHP. In particular, the powertrain is expected to have advantages because it uses a smaller-sized motor/generator (MG) or two identical machines as two MGs.

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.

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.

The Analysis of Energy Consumption for an Electric Vehicle under Various Driving Circumstance

This paper discusses the energy consumption for a mid-size electric vehicle(EV) under various conditions. In order to analyze which driving style is more efficient in terms of the system of the EV, we develop the electric vehicle model and apply several types of speed profiles such as different steady speeds, acceleration/deceleration, and a real world driving cycle including the elevation profile obtained from a GPS device. The results show that the energy consumption of the EV is affected by the operating efficiency of components when driving at low speed, while it depends on required power at wheels when driving at high speed. Also this paper investigates the effect of the elevation of a road and the rate of electrical braking on the energy consumption as well as the fuel economy of a conventional vehicle model under the same conditions.

A Study on Battery SOC Estimation by Regenerative Braking in Electric Vehicles

In traditional vehicles, a great amount of energy is dissipated by braking. In electric vehicles (EVs), however, electric motors can be controlled to operate as generators to convert kinetic and potential energy of vehicles into electrical energy and store it in batteries. In this paper, the relationship between regenerative braking factor and battery final SOC is derived and the final SOC from the relationship is compared to that from simulation. Two types of braking algorithms are introduced and applied to an EV, and the final SOC derived from simulation is compared to that derived from the relationship.

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 Fuel Economy for Series Plug-in Hybrid Electric Bus according to Engine Operation Strategy Based on Simulation

Abstract : Because of high oil prices and emission gas problems, many governments tighten regulation of fuel economy and emission gas. For Passenger car, there are many researches for plug-in hybrid electric vehicles and they are being manufactured. On the other hand, there are few researches for plug-in hybrid electric bus that is heavy commercial vehicle. In this study, analysis of fuel economy for series plug-in hybrid electric bus according to engine operation strategy based on simulation is conducted. Forward simulator is developed using Autonomie. Engine operation strategies consist on constant engine operation strategy and engine on/off operation strategy. Considering the engine operation strategy, results of vehicle speed, engine operating points and fuel economy are obtained and analyzed. As a result, engine on/off operation strategy has more advantage than constant engine operation strategy in terms of fuel economy. Key words : Series plug-in hybrid electric vehicle(직렬형 플러그인 하이브리드 전기 자동차), Forward simulation(전방향 시뮬레이션), Engine operation strategy(엔진 구동 전략), Fuel economy(연비)

Strategies and evaluation of fuel economy in fuel cell hybrid vehicles

The operating points of a fuel cell system (FCS) in a fuel cell hybrid vehicle (FCHV) can be shifted to its high-efficiency region by using a battery. In FCHVs, power management strategies directly affect the total fuel consumption. Two types of power management strategies are presented in this paper and the concept of equivalent fuel consumption is applied to this study due to the difference between the initial and final SOC of the battery. The equivalent fuel consumption of each strategy is evaluated and compared to each other.

Analysis on the Squeal Noise of Wheel Brake System for Tilting Train

Squeal, a kind of self-excited vibration, is generated by the friction between the disc and the friction materials. It occurs at the ending stage of the braking process, and radiates and audible frequency range of 1 kHz to 10 kHz. Squeal is generated from unstability because of the coupling between the translation and rotation of the system. This instability is caused by the follower force and follower force is normal component of the friction force. In this paper modal analysis of wheel brake system was performed in order to predict the squeal phenomenon. It was shown that the prediction of system instability is possible by FEM. A finite element model of that brake system was made. Some parts of a real brake was selected and modeled. Modal analysis method performs analyses of each brake system component. Experimental modal analysis was performed for each brake components and experimental results were compared with analytical results from FEM. To predict the dynamic unstability of a whole system, the complex eigenvalue analysis for assembly modeling of components confirmed by modal analysis is performed. The finite element models of the disk brake assembly have been constructed, and the squeal noise problems have been solved by complex eigenvalue analysis. The complex eigenvalue analysis results compared with real train test.