Mild Hybrid Electric Vehicle Research Articles

마일드 하이브리드 전기 차량용 2.5kW급 8상 양방향 컨버터에 관한 연구

마일드 하이브리드 전기 차량용 2.5kW급 8상 양방향 컨버터에 관한 연구

Multimode combustion in a mild hybrid electric vehicle. Part 2: Three-way catalyst considerations

This is the second of a two-part study that discusses multimode combustion in a mild hybrid electric vehicle. Homogeneous charge compression ignition (HCCI) combustion oxidizes the oxygen storage capacity (OSC) of the three-way catalyst (TWC), thereby removing the TWC's ability to convert NOx under lean conditions. Despite prolonged operation in HCCI mode, enabled by the electric motor, the depletion of the OSC causes significant penalties in fuel economy and the amounts of tailpipe NOx are substantial. Counter-intuitively, it is seen that decreasing the sizes of both HCCI regime and OSC results in reduced tailpipe NOx while maintaining fuel economy benefits.

Multimode combustion in a mild hybrid electric vehicle. Part 1: Supervisory control

This is the first of a two-part simulation study that discusses the application of a multimode combustion engine in a mild hybrid electric vehicle (HEV). The torque assist, offered by the electric motor, can be used to extend the residence time in the homogeneous charge compression ignition (HCCI) regime, before returning to spark-ignition (SI) combustion. To enable multimode operation in the HEV, the supervisory control strategy has to maintain the battery's state-of-charge while accounting for the SI/HCCI combustion mode switch. In this study four supervisors are discussed which extend the baseline equivalent consumption minimization strategy by the mode switching decision.

Perspectives of electric mobility: Total cost of ownership of electric vehicles in Germany

The transport sector is a major source of greenhouse gas emissions worldwide as well as in Germany and is therefore able to contribute significantly to the achievement of climate protection goals. With this in mind and the steadily increasing electricity generation from renewable energy sources in Germany, electrically driven vehicles can be an attractive option to reach the climate targets of the EU and the German government. The target of the German government to have at least one million electric vehicles registered by 2020 seems currently far from realisation. For this reason, this article analyses the total cost of ownership (TCO) of electric passenger vehicles in Germany on a component-based approach and gives an estimation about the further development until 2050. To represent the German market, we investigate different vehicle sizes, user types and drive technologies. Furthermore, we show the CO2 abatement potential offered by different types of electric vehicles. Finally, we analyse buyer's premiums as an incentive to accelerate the uptake of electric vehicles on German roads.In result, even without governmental subsidies, full and mild hybrid electric vehicles are already an economic option for a wide range of vehicle sizes and user types. To achieve nowadays cost competitiveness for full electric vehicle powertrains, considerable buyer's premiums are necessary. For plug-in hybrid electric vehicles and battery electric vehicles, the premiums range from about 8,600 to 32,400 EUR2010/vehicle depending on the vehicle size and user type. Eventually, following the future cost estimations, full electric vehicles can reach economic viability from 2030 onwards for many of the investigated vehicles and users.

Application of a modified thermostatic control strategy to parallel mild HEV for improving fuel economy in urban driving conditions

A modified thermostatic control strategy is applied to the powertrain control of a parallel mild hybrid electric vehicle (HEV) to improve fuel economy. This strategy can improve the fuel economy of a parallel mild HEV by operating internal combustion engine (ICE) in a high-efficiency region. Thus, in this study, experiments of a parallel mild HEV were conducted to analyze the characteristics of the hybrid electric powertrain and a numerical model is developed for the vehicle. Based on the results, the thermostatic control strategy was modified and applied to the vehicle model. Also, battery protection logic by using electrochemical battery model is applied because the active usage of battery by thermostatic control strategy can damage the battery. The simulation results of the vehicle under urban driving conditions show that the thermostatic control strategy can improve the vehicle’s fuel economy by 3.7 % compared with that of the conventional strategy. The results also suggest that the trade-off between the fuel economy improvement by efficient ICE operation and the battery life reduction by active battery usage should be carefully investigated when a thermostatic control strategy is applied to a parallel mild HEV.

Mild HEV with Multimode Combustion: Benefits of a Small Oxygen Storage

This simulation study discusses the application of a multimode combustion engine in a mild hybrid electric vehicle (HEV) with three-way catalytic converter (TWC). Operation in the lean combustion mode homogeneous charge compression ignition (HCCI) results in oxidation of the oxygen storage capacity (OSC) of the TWC. Thereby, the TWC’s ability to convert NOx under lean conditions is removed. Succeeding depletion of the OSC under rich spark-ignition (SI) conditions is required, which results in significant fuel efficiency penalties. In case of a mild HEV the torque assist from the electric motor is able to extend the residence time in HCCI, thereby reducing the number OSC depletion events. The applied supervisory controller, which decides when to switch between SI and HCCI, is based on the equivalent consumption minimization strategy (ECMS) and incorporates the fuel penalties associated with mode switching and OSC depletion. It is shown that, while the impact of the OSC depletion on drive cycle fuel economy of the mild HEV is still significant, it is much smaller than in case of the vehicle without electric motor. The prolonged operation in lean HCCI mode leads to substantial amounts of tailpipe NOx for all drive cycles tested. In a case study two modifications to the system hardware are introduced with counterintuitive results. First, the HCCI regime is further constrained to conditions where engine-out NOx levels are extremely low. Second, the size of the OSC is significantly reduced, allowing a much faster and less inefficient depletion. Associated drive cycle results show a substantial reduction in tailpipe NOx while fuel economy benefits can be maintained.

Integrated Starter–Alternator With Sensorless Ringed-Pole PM Synchronous Motor Drive

The so-called integrated starter–alternator (ISA) is a high-efficiency electrical machine that is connected to an internal combustion engine obtaining mild hybrid electric vehicles. The ISA has a twofold task: starting up the engine and generating electrical energy to be stored into a battery. This paper is focused on the first task. Two different motors are investigated: an external rotor surface permanent magnet (SPM) machine and an interior permanent magnet (IPM) machine. For drive control, both motors require knowledge of their rotor position; then, a sensorless technique based on the high-frequency (HF) voltage injection for rotor position detection has been implemented. In order to create an HF anisotropy in the SPM rotor configuration, a ringed-pole solution has been adopted. Experimental tests have highlighted that the first machine has a clear capability of starting up the engine with good speed and position estimation in spite of the particular nonconstant load torque. As regard the IPM machine, the sensorless engine startup appears not possible because the anisotropy disappears at a high current level due to saturation effects.

Optimal torque control of an integrated starter–generator using genetic algorithms

A mild hybrid electric vehicle is a type of hybrid electric vehicle with a simplified hybrid drivetrain mechanism. These mild hybrid electric vehicles use an integrated starter–generator to assist the internal-combustion engine simply rather than to drive the vehicle independently of the internal-combustion engine. In a previous study, a lookup- table-based control scheme was proposed for optimal control of the integrated starter–generator and the internal-combustion engine on a mild hybrid vehicle. In order to investigate further the optimality of the integrated starter–generator control lookup table, a widely used global optimization technique called a genetic algorithm is utilized in this study. The constructed optimal lookup tables are implemented in MATLAB/Simulink together with a mild hybrid vehicle model, which is based on an US Environmental Protection Agency light-duty vehicle model. The simulation results show that the genetic algorithm can construct an optimal lookup table with better performance characteristics than the weighted cost function method.

Integration of a Dual-Mode SI-HCCI Engine Into Various Vehicle Architectures

A simulation study was performed to evaluate the potential fuel economy benefits of integrating a dual-mode SI-HCCI engine into various vehicle architectures. The vehicle configurations that were considered include a conventional vehicle and a mild parallel hybrid electric vehicle. The two configurations were modeled and compared in detail for a given engine size (2.0 L) over the EPA UDDS (city) and highway cycles. The results show that the dual-mode engine in the conventional vehicle offers a modest gain in vehicle fuel economy of approximately 5–7%. The gains were modest because the baseline (the SI engine in the conventional vehicle) is relatively advanced with a six-speed automated manual transmission. The mild parallel hybrid with the SI engine achieved 32% better fuel economy than the conventional vehicle in the city, but only 6% on the highway. For the dual-mode engine in the mild parallel hybrid, a specific control strategy was used to manipulate engine operation in an attempt to minimize the number of engine mode transitions and maximize the time spent in HCCI. The parallel hybrid with the dual-mode engine and modified control strategy provides dramatic improvements of up to 48% for city driving, demonstrating that the addition of HCCI has a more significant impact with mild parallel hybrids than with conventional vehicles. Finally, a systematic study of engine sizing provides guidelines for selecting the best option for a given vehicle application.

An Economic and In-Service Emissions Analysis of Conventional, Hybrid and Electric Vehicles for Australian Driving Conditions

Hybrid and fully electric vehicles are becoming more common as a response to rising fuel prices and greenhouse considerations. While the benefits of electrification on urban air quality have been studied quite widely, financial assessments of the various alternative vehicle forms are less common, particularly for Australian driving conditions. The aim of this paper is therefore to identify the scenarios under which different vehicle configurations are attractive to the vehicle owner. A Class-E conventional vehicle is compared with full-electric, plug-in hybrid, parallel hybrid, series hybrid and mild hybrid electric vehicle configurations. A simulation model of a conventional internal combustion engine based large sized car is developed and validated against experimental data. The conventional vehicle model is then systematically altered to obtain its increasingly electric variants. The fuel consumption and greenhouse gas emissions are simulated on the legislative NEDC drive cycle and the more representative Australian Urban Drive Cycle (AUDC). The outcomes of these tests are used to estimate the total cost of ownership and in-service emissions, thus allowing the cost of emissions mitigation to be approximated for the different vehicles. Different scenarios are considered for the pricing of energy and major powertrain components. This provides a baseline assessment based on current prices and projections, as well as ‘electrification favorable’ and ‘electrification unfavorable’ scenarios. The impact on vehicle emissions of significant penetration of renewable energy into the Australian electricity grid is also considered.

Advanced hybrid energy storage system for mild hybrid electric vehicles

Hybrid electric vehicles (HEV) utilize electric power and a mechanical engine for propulsion; therefore, the performance of HEVs is directly influenced by the characteristics of the energy storage system (ESS). The ESS for an HEV generally requires high power performance, long cycle life, reliability and cost effectiveness; thus, a hybrid energy storage system (HESS) that combines different types of storage devices has been considered to fulfill both performance and cost requirements. To improve the operating efficiency and cycle life of a HESS, an advanced dynamic control regime in which pertinent storage devices in the HESS can be selectively operated based on their status is presented. Verification tests were performed to confirm the degree of improvement in energy efficiency. In this paper, an advanced HESS with a battery management system (BMS) that includes an optimal switching control function based on the estimated state of charge (SOC) is presented and verified.

Simulation on the Control Strategy of a New Super-mild Hybrid Transmission System

In order to reduce production cost,improve control effect of saving fuel and reducing emission,a new super-mild hybrid transmission system is developed to over the limitation of the existing mild hybrid electric vehicle (HEV) which has not the working condition as the pure electric drive. The new one is based on continuously variable transmission (CVT) with reflux power,which features wide speed ratio range,high transmission efficiency and big loading ability. Through adoption of the new transmission mode and match control strategy,the match design theory and control method of hybrid transmission system based on large speed range are researched. The test results show that the super-mild HEV saves fuel by 13.02%,in which 1.88% is contributed by the continuously variable transmission (CVT) with reflux power.

Preface to special issue on electrical energy storage for future transportation and renewable energy

Energy storage technology helps make possible many of the freedoms and personal mobility enjoyed by today's society. In consumer electronics for example, devices such as cell phones and laptops have experienced a great surge in popularity in large-part thanks to advances in battery energy density. In addition to providing convenience, energy storage technology is also a critical enabler on the pathway to the low carbon lifestyle required for future sustainable societies. For these reasons, worldwide interest in energy storage research continues to grow. In conventional vehicle applications, lead acid batteries remain the preferred low-cost solution, providing good cranking power capability to start internal combustion engines at low temperatures. But for electric traction applications, more energy and power-dense chemistries are required. The nickel-metal hydride chemistry, with roughly double the power and energy of the lead acid chemistry, has functioned for some years as the battery of choice for mild and medium hybrid electric vehicles. But to effectively transition our vehicles to run on electricity rather than fossil-based fuels requires substantial further advancement in energy dense, long life, low cost energy storage. The lithium ion chemistry is presently poised to enter transportation markets. Lithium ion battery safety remains a concern, however, given the energetic nature of the chemistry. Another compelling technology for power and cycling-intensive transportation applications are electrochemical ultracapacitors that function based on a double layer charge separation, rather than faradic mechanism. Given the intermittency of sun and wind availability, widespread penetration of renewable energy also requires some means to store it, often for many hours. Today's lithium ion chemistries are too expensive for such large-scale applications. Less-expensive traditional technologies such as lead acid suffer from short life. In certain geographic locations, compressed air and pumped hydraulic power may have a role in renewable energy storage. Novel electrochemical technologies, such as the vanadium redox flow battery, readily scalable and with promising life, may also have a role. Battery science and engineering spans diverse subject areas ranging from electrochemistry to materials science, mechanical and electrical engineering. Battery research, by definition, is a multidisciplinary endeavor. Taking lithium ion safety as an example, safety improvements are sought on multiple fronts. Good design and selection of stable materials, careful quality control during manufacture, proper thermal and electrical design of battery packs under normal and abusive conditions, and sound design of monitoring electronics, algorithms and controls are all needed to produce a safe, high-energy battery. For all storage chemistries, breakthrough advances will no doubt come from research groups that merge the boundaries of several of these traditional science and engineering disciplines. In the theme of multidisciplinary energy storage research, this special issue of International Journal of Energy Research compiles overview and research articles from a broad array of leading researchers in industry, government laboratories and academia. We trust that the findings compiled herein will motivate further investigation in the rapidly evolving field of energy storage.

Shift Performance Control for Mild Hybrid Electric Vehicle Equipped with Automatic Manual Transmission

Transmission ratio will change as a step after shifting for an automatic manual transmission (AMT) vehicle. Input speed and output speed of clutch are different due to ratio change and jerk occurs. By using the auxiliary dynamic action of ISG motor, the power source can be quickly controlled in shifting process, and shift performance can be improved for mild hybrid electric vehicle equipped with AMT. On the basis of analysis of shifting process on traditional AMT vehicles, and by combining the features of mild hybrid electric vehicle, a control model of power source is built up, and an advanced shift control strategy in which the control is realized jointly by integrated starter generator (ISG) motor, engine and clutch are proposed. Power source is well controlled and shift shock and power interrupt time are reduced. The bench test results show that the proposed control strategy can more effectively improve the shift performance in comparison to the traditional control strategy.

Optimization of System Efficiency for the Mild Hybrid Electric Vehicle with Continuously Variable Transmission under the Motor and Engine Combined Working Conditions

The experimental numerical molel for the efficiency of key components of a mild hybrid electric vehicle with continuously variable transmission(CVT)is built.Based on the efficiency model and the longitudinal dynamics equations of the mild hybrid power system,the formulas for calculating the system efficiency under different driving conditions of hybrid electric vehicle are derived and the model for system efficiency optimization is obtained.The sequential quadratic programming(SQP)algorithm is applied to calculating the optimization of system efficiency of the mild hybrid electric vehicle under different driving conditions,so the electrical motor/generators power and the optimal CVT speed ratio under the different driving conditions.The research provides a method for optimizing the control strategy to improve the system efficiency of the CVT mild hybrid electric vehicle.

Optimization and Analysis of System Efficiency for the Mild Hybrid Electric Vehicle under the Cruise Conditions

When the hybrid electrical vehicle is cruising,in order to reduce the fuel consumption of the engine and improve the service life of the battery,the work areas optimization of the engine and motor is considered in the energy management strategy of hybrid electrical vehicle.At the same time,the work areas optimization of the battery is considered too.Aiming at this problem,the longitudinal dynamics of a mild hybrid electric vehicle with continuously variable transmission(CVT)is firstly analyzed.And then, the efficiency of total system under different cruise conditions is studied by comprehensively considering the efficiencies of the engine,motor,battery and transmission system.After the objective function and constraints are obtained,the sequential quadratic programming (SQP) algorithm is applied to the optimization of system efficiency for the mild hybrid electric vehicle.At last the optimal battery power and optimal speed reduction ratio are found for different cruise conditions.The optimization results show the characteristics of the drive system,and these results can lay a foundation for the optimization of the drive system.

Fuel Economy Benefits of Look-ahead Capability in a Mild Hybrid Configuration

Mild hybrid electric vehicles (HEVs) take some benefits of full HEVs while having lower initial cost and weight, making them a more viable proposition for OEMs looking to enter the hybrid market. The popularization of mild hybrid electric vehicles (HEV) has exposed a new research potential in hybrid energy management. The optimal control of fuel economy in such a configuration is hard to achieve due to its multi-dimensional nature and the absence of future information. The blossoming telematics industry offers the potential to gather future information at relatively low cost through on-board sensing and vehicle-to-vehicle communication systems. In this paper, a novel approach to further fuel consumption minimization of a mild HEV is proposed. The approach is focused on adjusting the by-wire throttle in the vehicle in order to modify forward velocity, as well as controlling the power split between two sources. We show that on a realistic urban drive cycle, the telematic-enabled mild hybrid vehicle with preview of 150 meters can achieve up to 20% fuel saving compared to a comparable baseline conventional powertrain vehicle, and a further 1% fuel saving relative to previously published algorithms. The potential for further improvement in fuel economy through optimizing the use of the electric motor is also discussed.

Regenerative braking control strategy in mild hybrid electric vehicles equipped with automatic manual transmission

The actual regenerative braking force of an integrated starter/generator (ISG), which is varied with desired braking deceleration and vehicle speed, is calculated based on an analysis of the required deceleration, maximum braking force of ISG, engine braking force and state of charge (SOC) of battery. Braking force distribution strategies are presented according to the actual regenerative braking force of ISG. To recover the vehicle’s kinetic energy maximally, braking shift rules for a mild hybrid electric vehicle (HEV) equipped with automatic manual transmission (AMT) are brought forward and effects of transmission ratios are considered. A test-bed is built up and regenerative braking tests are carried out. The results show that power recovered by the braking shift rules is more than that recovered by the normal braking control rules.

Batteries and Ultracapacitors for Electric, Hybrid, and Fuel Cell Vehicles

The application of batteries and ultracapacitors in electric energy storage units for battery powered (EV) and charge sustaining and plug-in hybrid-electric (HEV and PHEV) vehicles have been studied in detail. The use of IC engines and hydrogen fuel cells as the primary energy converters for the hybrid vehicles was considered. The study focused on the use of lithium-ion batteries and carbon/carbon ultracapacitors as the energy storage technologies most likely to be used in future vehicles. The key findings of the study are as follows. 1) The energy density and power density characteristics of both battery and ultracapacitor technologies are sufficient for the design of attractive EVs, HEVs, and PHEVs. 2) Charge sustaining, engine powered hybrid-electric vehicles (HEVs) can be designed using either batteries or ultracapacitors with fuel economy improvements of 50% and greater. 3) Plug-in hybrids (PHEVs) can be designed with effective all-electric ranges of 30-60 km using lithium-ion batteries that are relatively small. The effective fuel economy of the PHEVs can be very high (greater than 100 mpg) for long daily driving ranges (80-150 km) resulting in a large fraction (greater than 75%) of the energy to power the vehicle being grid electricity. 4) Mild hybrid-electric vehicles (MHEVs) can be designed using ultracapacitors having an energy storage capacity of 75-150 Wh. The fuel economy improvement with the ultracapacitors is 10%-15% higher than with the same weight of batteries due to the higher efficiency of the ultracapacitors and more efficient engine operation. 5) Hybrid-electric vehicles powered by hydrogen fuel cells can use either batteries or ultracapacitors for energy storage. Simulation results indicate the equivalent fuel economy of the fuel cell powered vehicles is 2-3 times higher than that of a gasoline fueled IC vehicle of the same weight and road load. Compared to an engine-powered HEV, the equivalent fuel economy of the hydrogen fuel cell vehicle would be 1.66-2.0 times higher

Design and Analysis of a Stator-Doubly-Fed Doubly-Salient Permanent-Magnet Machine for Automotive Engines

This paper presents a new outer-rotor stator-doubly-fed doubly-salient permanent-magnet (SDF-DSPM) machine, which can be used as the integrated starter-generator for modern automobiles and mild hybrid electric vehicles. The key of the proposed machine is to incorporate both dc field windings and PMs in the inner stator, hence, offering a compact arrangement of hybrid field excitations. While armature windings are located in salient poles of the outer stator, the outer rotor is simply composed of salient poles without windings or PMs. In addition, an air bridge is purposely created in shunt with each PM in the inner stator, hence, providing an amplification effect for flux regulation. With this idea, the air-gap flux can be strengthened or weakened with a small dc field current so that the electromagnetic torque and induced electromotive force (EMF) can be effectively regulated. The newly designed SDF-DSPM machine is analyzed by using both the magnetic circuit model and finite element method, and assessed by performance simulation.