Jongryeol Jeong

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.

Modeling of Generation and Growth of Non-Spherical Nanoparticles in a Co-Flow Flame

Generation and growth of polydisperse non-spherical silica nanoparticles in an oxy-hydrogen co-flow diffusion flame have been simulated for the first time. A complete set of Navier–Stokes equations describing multi-component chemically-reacting fluid flows was first solved considering the detailed H2/O2 chemistry and oxidation/hydrolysis reactions of SiCl4. A recently developed aggregate sectional model (Jeong & Choi, 2001) was employed to solve the dynamics of particles undergoing generation, convection, diffusion, coagulation and coalescence in a spatially two-dimensional flame system. Non-uniform spatial distributions of flame temperatures and non-spherical particle sizes were successfully simulated. Comparison on flame temperature and particle size between the numerical simulation and the experimental data has also been done. Performance of a simple monodisperse model was also studied by comparing with the detailed sectional model.

Sufficient Conditions for Optimal Energy Management Strategies of Fuel Cell Hybrid Electric Vehicles Based on Pontryagin’s Minimum Principle

Although an onboard fuel cell system is able to provide sufficient electricity to power a vehicle, a secondary energy storage system such as an electrical battery is desirable because the fuel cell system is generally not capable of braking energy recuperation, and the efficiency of the fuel cell system can be improved by using the secondary energy system. In this paper, sufficient conditions are obtained for an optimal control idea for fuel cell hybrid electric vehicles when the fuel cell system is combined with a rechargeable battery. The optimal control is based on Pontryagin’s minimum principle, and this study demonstrates that it results in total hydrogen consumptions if the properties of the fuel cell hybrid system satisfy two assumptions: first, the hydrogen consumption rate of the fuel cell system is convex and, second, the time derivative of the state of charge is concave. In order to validate optimality of the control concept, a vehicle simulation model is developed for a fuel cell hybrid electric vehicle, and control based on Pontryagin’s minimum principle is applied in a backward-looking simulator. In the simulation results, control based on Pontryagin’s minimum principle produces an optimal solution, which is very close to the global optimal solution obtained by dynamic programming. In addition, control based on Pontryagin’s minimum principle simplifies the control organization; the control concept should be considered as a promising solution for fuel cell hybrid electric vehicles because it really achieves results which are near the global optimal results.

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.

A Power Management Strategy for Hybrid Buses Using Measured Driving Route Information

Pontryagins Minimum Principle (PMP)-based power management strategy is known as one of the promising candidates for hybrid vehicles. The point of this strategy in the real-world driving condition is the determination of the costate value. This research deals with hybrid buses. The characteristic of the specified driving route of the buses makes the realization of the PMP-based strategy easier compared to the case of passenger cars. This research proposes a realization methodology of the PMP-based power management strategy for hybrid buses by presenting a case study of a fuel cell hybrid bus. Several points on the proposed methodology are also discussed.

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.

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 Vehicle Status in Various Driving Situations for a Separated Axle Torque Combination Parallel Hybrid System Using Forward Simulator

The paper presents closed-loop electric vehicle (EV) drive with 5-phase induction motor operating with switched-autotransformer (LCCAt) inverter. Electrical drives with five-phase induction motors are considered for application in electric vehicles. Space vector modulation (SVM) is the most common options for controlling a five-phase inverter. However, if the battery level cannot ensure the controllability over a wide speed range of EV drive, the supply voltage has to be elevated. Bidirectional impedance source inverters (e.g. Z- source inverter, qZ-source inverter) have been presented suitable for EVs. The concept of Z-source inverters has been recently extended to transformer-based inverters (e.g. Trans-Z-source inverter, T - source inverter) which use coupled inductors with an appropriate turns ratio. Unfortunately, coupled inductors store significant portion of the energy during boost operation which tends their cores to saturate at higher currents. The use of four element LCCAt-source (inductor-capacitor-capacitor- autotransformer) network allows proposed switched- autotransformer inverter for obtaining high voltage gain while ensuring high modulation index and reduced volume of inductive elements. Simulation and experimental results using the laboratory model of switched-autotransformer inverter with designed 4.3 kW, 30V five-phase induction motor are shown to verify the effectiveness of the proposed system.

Analysis of Regenerative Braking Effect for E-REV Bus According to Driving Cycle Based on Simulation

Among eco-friendly vehicles, extended range electric vehicle (E-REV) is concept for electric vehicle that has light engine for extended range driving. One of the most important features of these vehicles based electricity is their ability to recover significant amounts of braking energy. Recovering the braking energy and reusing it can significantly improve the fuel economy of the vehicle which is subject to frequent braking events such as a city bus. To develop the E-REV bus, the regenerative braking effect should be checked in advance. However, because of many technical constraints, regenerative braking should consider some conditions like vehicle speed, accelerator pedal signal, brake pedal signal, battery voltage and so on. Hence, regenerative braking torque is assumed as 2D and 3D maps with these conditions based on simulation. Fuel economy simulations are conducted to analyze regenerative braking effect according to driving cycle. They consist of E-REV bus without regenerative braking and with regenerative braking torque maps. Fuel economy difference between two cases was calculated and driving cycles were analyzed. Among the characteristic analyzed, the aggressiveness means harshness of driving cycle. And the inclination between the aggressiveness and the fuel economy difference is verified. The smaller absolute value of the aggressiveness is, the smaller fuel economy difference is. In short, the aggressiveness and the regenerative braking effect have direct proportion. According to the obvious tendency, proper regenerative braking should be determined.