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World Electr. Veh. J., Volume 10, Issue 3 (September 2019)

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Open AccessArticle
Multi-Level Deceleration Planning Based on Reinforcement Learning Algorithm for Autonomous Regenerative Braking of EV
World Electr. Veh. J. 2019, 10(3), 57; https://doi.org/10.3390/wevj10030057 (registering DOI) - 16 Sep 2019
Abstract
A smart regenerative braking system, which is an advanced driver assistance system of electric vehicles, automatically controls the regeneration torque of the electric motor to brake the vehicle by recognizing the deceleration conditions. Thus, this autonomous braking system can provide driver convenience and [...] Read more.
A smart regenerative braking system, which is an advanced driver assistance system of electric vehicles, automatically controls the regeneration torque of the electric motor to brake the vehicle by recognizing the deceleration conditions. Thus, this autonomous braking system can provide driver convenience and energy efficiency by suppressing the frequent braking of the driver brake pedaling. In order to apply this assistance system, a deceleration planning algorithm should guarantee the safety deceleration under diverse driving situations. Furthermore, the planning algorithm suppresses a sense of heterogeneity by autonomous braking. To ensuring these requirements for deceleration planning, this study proposes a multi-level deceleration planning algorithm which consists of the two representative planning algorithms and one planning management. Two planning algorithms, which are the driver model-based planning and optimization-based planning, generate the deceleration profiles. Then, the planning management determines the optimal planning result among the deceleration profiles. To obtain an optimal result, planning management is updated based on the reinforcement learning algorithm. The proposed algorithm was learned and validated under a simulation environment using the real vehicle experimental data. As a result, the algorithm determines the optimal deceleration vehicle trajectory to autonomous regenerative braking. Full article
(This article belongs to the Special Issue Autonomous Driving of EVs)
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Open AccessArticle
Exploration of Optimal Powertrain Design Using Realistic Load Profiles
World Electr. Veh. J. 2019, 10(3), 56; https://doi.org/10.3390/wevj10030056 - 15 Sep 2019
Viewed by 169
Abstract
The electrification of bus-based public transportation contributes to the goal of reducing the adverse environmental impacts caused by urban transportation. However, the penetration of electric vehicles has been slow due to their lower vehicle range and total costs in comparison to vehicles driven [...] Read more.
The electrification of bus-based public transportation contributes to the goal of reducing the adverse environmental impacts caused by urban transportation. However, the penetration of electric vehicles has been slow due to their lower vehicle range and total costs in comparison to vehicles driven by internal combustion engines. By improving the powertrain efficiency, the total costs can be reduced for the same vehicle range. Therefore, this paper proposes a holistic design exploration approach to investigate and identify the optimal powertrain concept for electric city buses based on the component costs and energy consumption costs. The load profiles of speed, slope, and passenger occupancy profiles are derived for a selected bus route in Singapore, which is used in a powertrain design exploration for a 30-passenger vehicle. Six different powertrain architectures are analyzed, together with single and multi-speed gearbox configurations, to identify the optimal powertrain architecture and the resulting component sizes. The powertrain configurations are further analyzed in terms of their influence on the vehicle characteristics and total costs. Multi-motor configurations were found to have better vehicle characteristics and lower total costs in comparison to single rear motor configurations. Concepts with motors on the front and a rear axle could shift the load points to a higher efficiency region, resulting in lower energy consumption and energy costs. The optimal powertrain concept was a fixed-speed two-motor configuration, with a booster motor on the front axle and a motor on the rear axle. Full article
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Open AccessArticle
Comparison of Tab-To-Busbar Ultrasonic Joints for Electric Vehicle Li-Ion Battery Applications
World Electr. Veh. J. 2019, 10(3), 55; https://doi.org/10.3390/wevj10030055 - 14 Sep 2019
Viewed by 147
Abstract
Recent uptake in the use of lithium-ion battery packs within electric vehicles has drawn significant attention to the selection of busbar material and corresponding thickness, which are usually based on mechanical, electrical and thermal characteristics of the welded joints, material availability and cost. [...] Read more.
Recent uptake in the use of lithium-ion battery packs within electric vehicles has drawn significant attention to the selection of busbar material and corresponding thickness, which are usually based on mechanical, electrical and thermal characteristics of the welded joints, material availability and cost. To determine joint behaviour corresponding to critical-to-quality criteria, this study uses one of the widely used joining technologies, ultrasonic metal welding (UMW), to produce tab-to-busbar joints using copper and aluminium busbars of varying thicknesses. Joints for electrical and thermal characterisation were selected based on the satisfactory mechanical strength determined from the T-peel tests. Electrical contact resistance and corresponding temperature rise at the joints were compared for different tab-to-busbar joints by passing current through the joints. The average resistance or temperature increase from the 0.3 mm Al tab was 0.6 times higher than the 0.3 mm Cu[Ni] tab, irrespective of busbar selection. Full article
Open AccessArticle
A Consideration on Maximum Efficiency of Resonant Circuit of Inductive Power Transfer System with Soft-Switching Operation
World Electr. Veh. J. 2019, 10(3), 54; https://doi.org/10.3390/wevj10030054 - 11 Sep 2019
Viewed by 104
Abstract
By using bi-directional inductive power transfer (IPT) systems as battery chargers for electric vehicles (EVs), battery charging operations become convenient and safe. However, IPT systems have problems such as occurrences of much electromagnetic noise and power loss because the converters of IPT systems [...] Read more.
By using bi-directional inductive power transfer (IPT) systems as battery chargers for electric vehicles (EVs), battery charging operations become convenient and safe. However, IPT systems have problems such as occurrences of much electromagnetic noise and power loss because the converters of IPT systems are driven in high frequency by tens of kHz. To solve these problems, there is a case where the soft-switching technique needs to be applied to the converters of IPT systems. However, in soft-switching operation, the power factor of the resonant circuit becomes lower, resulting in a lower resonant circuit efficiency. In previous works, when the soft-switching technique was applied to the converters, the resonant circuit had not always been able to be operated with high efficiency because the influence caused by soft-switching operation had not been considered. For this reason, there was a case where the efficiency of the overall system with soft-switching operation became lower than the efficiency in hard-switching operation. Therefore, in this paper, the influence on the efficiency of the resonant circuit caused by the soft-switching operation is clarified by the theoretical analysis and experiments; then, the guideline for improving the efficiency of IPT systems is shown. As a result, in the experiments, it could be understood that the efficiency of the overall system with soft-switching operation becomes higher than the efficiency in hard-switching operation when the operating point of the resonant circuit was close to the requirement guideline, which is shown by using the primary-side voltage and the secondary-side voltage of the resonant circuit. Therefore, it is suggested that the efficiency of IPT systems could be improved by properly regulating the primary-side direct current (DC) voltage. Full article
(This article belongs to the Special Issue Power Electronics Subsystems)
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Open AccessArticle
Modeling and Optimal Shift Control of a Planetary Two-Speed Transmission
World Electr. Veh. J. 2019, 10(3), 53; https://doi.org/10.3390/wevj10030053 - 09 Sep 2019
Viewed by 155
Abstract
To improve the efficiency of electric vehicles (EVs), a planetary two-speed transmission is proposed, which consists of a brushless direct current (BLDC) motor, a turbo-worm reducer, two multi-disc wet brakes, and a Simpson planetary gearset. Based on the devised electronic actuator for shifting, [...] Read more.
To improve the efficiency of electric vehicles (EVs), a planetary two-speed transmission is proposed, which consists of a brushless direct current (BLDC) motor, a turbo-worm reducer, two multi-disc wet brakes, and a Simpson planetary gearset. Based on the devised electronic actuator for shifting, the rotation direction of the BLDC shaft determines the gear ratio of the transmission. For acquiring smooth shift, the state-space equations with control variables of transmission are derived, and a three-stage algorithm is suggested. During the brake engagement process, the optimal control strategy has been developed using linear quadratic regulator control, considering the jerk and friction work of the brake. The simulation results show that the proposed optimal control strategy could reduce the slipping friction work of the brake and improve the shifting quality of EVs. The optimal control trajectory of the BLDC motor was conducted on the electronic shifting actuator bench test. Full article
Open AccessArticle
Automated Longitudinal Control Based on Nonlinear Recursive B-Spline Approximation for Battery Electric Vehicles
World Electr. Veh. J. 2019, 10(3), 52; https://doi.org/10.3390/wevj10030052 - 05 Sep 2019
Viewed by 143
Abstract
This works presents a driver assistance system for energy-efficient ALC of a BEV. The ALC calculates a temporal velocity trajectory from map data. The trajectory is represented by a cubic B-spline function and results from an optimization problem with respect to travel time, [...] Read more.
This works presents a driver assistance system for energy-efficient ALC of a BEV. The ALC calculates a temporal velocity trajectory from map data. The trajectory is represented by a cubic B-spline function and results from an optimization problem with respect to travel time, driving comfort and energy consumption. For the energetic optimization we propose an adaptive model of the required electrical traction power. The simple power train of a BEV allows the formulation of constraints as soft constraints. This leads to an unconstrained optimization problem that can be solved with iterative filter-based data approximation algorithms. The result is a direct trajectory optimization method of which the effort grows linearly with the trajectory length, as opposed to exponentially as with most other direct methods. We evaluate ALC in real test drives with a BEV. We also investigate the energy-saving potential in driving simulations with ALC compared to MLC. On the chosen reference route the ALC saves up to 3.4% energy compared to MLC at same average velocity, and achieves a 2.6% higher average velocity than MLC at the same energy consumption. Full article
(This article belongs to the Special Issue Autonomous Driving of EVs)
Open AccessArticle
Diesel or Electric Jeepney? A Case Study of Transport Investment in the Philippines Using the Real Options Approach
World Electr. Veh. J. 2019, 10(3), 51; https://doi.org/10.3390/wevj10030051 - 22 Aug 2019
Viewed by 381
Abstract
The Philippines is moving towards a more sustainable public transport system by introducing a public utility vehicle (PUV) modernization program with electric jeepneys (e-jeepneys) and modernized diesel jeepneys. Despite its potential to address problems related to air pollution, traffic congestion, dependence on fuel [...] Read more.
The Philippines is moving towards a more sustainable public transport system by introducing a public utility vehicle (PUV) modernization program with electric jeepneys (e-jeepneys) and modernized diesel jeepneys. Despite its potential to address problems related to air pollution, traffic congestion, dependence on fuel imports, and carbon emissions, transport groups show resistance to the adoption of the government program due to costs and investment risk issues. This study aims to guide transport operators in making investment decisions between the modernized diesel jeepney and the e-jeepney fleet. Applying the real options approach (ROA), this research evaluates option values and optimal investment strategies under uncertainties in diesel prices, jeepney base fare price, electricity prices, and government subsidy. The optimization results reveal a better opportunity to invest in the e-jeepney fleet in all scenarios analyzed. Results also show a more optimal decision strategy to invest in the e-jeepney immediately in the current business environment, as delaying or postponing investment may incur opportunity losses. To make the adoption of the e-jeepney more attractive to transport operators, this study further suggests government actions to increase the amount of subsidy and base fares, establish public charging stations, and continue efforts to rely on cleaner, cheaper, and renewable sources of electricity. Full article
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Open AccessArticle
Under Pressure—Users’ Perception of Range Stress in the Context of Charging and Traditional Refueling
World Electr. Veh. J. 2019, 10(3), 50; https://doi.org/10.3390/wevj10030050 - 01 Aug 2019
Viewed by 585
Abstract
Although electric drives can locally reduce the environmental impact of traffic, the penetration rates of battery electric vehicles (BEV) are far below expectations, not least because the charging infrastructure network is still considered insufficient by potential users. Therefore, the planning of charging infrastructure [...] Read more.
Although electric drives can locally reduce the environmental impact of traffic, the penetration rates of battery electric vehicles (BEV) are far below expectations, not least because the charging infrastructure network is still considered insufficient by potential users. Therefore, the planning of charging infrastructure that considers both needs and user requirements is essential to remove an important barrier to widespread adaptation of e-vehicles, but it is also a challenge. A better understanding of the charging behavior and the underlying usage motivation is therefore needed. A frequently mentioned factor is the so-called range stress. While there are many studies on this subject with new BEV users, there is a lack of approaches that also include experienced e-vehicle users and at the same time allow a comparison with drivers of cars with internal combustion engines (ICE). In this paper, this is realized with the help of a questionnaire study ( n = 204 ). The results show that ICE and BEV users at different experience levels hardly differ regarding the perceived range stress; BEV users even perceive less stress. BEV users also showed more trust in the vehicle and in the tank/battery indicators, while this trust depends only marginally on the type of information provided by the car. Furthermore, there is a correlation between users’ technology commitment and risk-taking, on the one hand, and range stress, on the other. However, for the prediction of range stress, gender, experience with e-cars, and the question of whether cars are privately owned, or car-sharing is used, are more relevant. Full article
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Open AccessArticle
A Real-Car Experiment of a Dynamic Wireless Power Transfer System Based on Parallel-Series Resonant Topology
World Electr. Veh. J. 2019, 10(3), 49; https://doi.org/10.3390/wevj10030049 - 20 Jul 2019
Viewed by 457
Abstract
A short mileage and long charging times are problems facing electric vehicles (EVs), and dynamic wireless power transfer (WPT) systems are one of the most effective solutions to overcome these shortcomings. This paper proposes a dynamic WPT system consisting of several stationary primary [...] Read more.
A short mileage and long charging times are problems facing electric vehicles (EVs), and dynamic wireless power transfer (WPT) systems are one of the most effective solutions to overcome these shortcomings. This paper proposes a dynamic WPT system consisting of several stationary primary underground coils and a secondary coil on an EV. The dynamic WPT system employed solenoid coils that were superior to circular coils in terms of misalignment to the traveling direction. A dynamic WPT system rated at 25 kW was designed, constructed, and tested to verify the principles of operation; that is, the capability of supplying electric power continuously. Full article
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Open AccessArticle
Development of Technical Regulations for Fuel Cell Motorcycles in Japan—Hydrogen Safety
World Electr. Veh. J. 2019, 10(3), 48; https://doi.org/10.3390/wevj10030048 - 09 Jul 2019
Viewed by 483
Abstract
Hydrogen fuel cell vehicles are expected to play an important role in the future and thus have improved significantly over the past years. Hydrogen fuel cell motorcycles with a small container for compressed hydrogen gas have been developed in Japan along with related [...] Read more.
Hydrogen fuel cell vehicles are expected to play an important role in the future and thus have improved significantly over the past years. Hydrogen fuel cell motorcycles with a small container for compressed hydrogen gas have been developed in Japan along with related regulations. As a result, national regulations have been established in Japan after discussions with Japanese motorcycle companies, stakeholders, and experts. The concept of Japanese regulations was proposed internationally, and a new international regulation on hydrogen-fueled motorcycles incorporating compressed hydrogen storage systems based on this concept are also established as United Nations Regulation No. 146. In this paper, several technical regulations on hydrogen safety specific to fuel cell motorcycles incorporating compressed hydrogen storage systems are summarized. The unique characteristics of these motorcycles, e.g., small body, light weight, and tendency to overturn easily, are considered in these regulations. Full article
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