International Journal of Electric and Hybrid Vehicles (16 papers in press)
State of health estimation for 18650-type lithium battery based on D-UKF
by Qiuting Wang, Yinzhu Jiang
Abstract: This paper considers an accurate estimation method of State of Health (SOH) for the 18650-type lithium battery. An improved battery model combined with electrochemical characteristics and equivalent circuit model is established. In our study, Double Unscented Kalman Filtering (D-UKF) algorithm is proposed to calculate the internal resistances and battery SOH in the same time. The features of our new method are the derivation of an SOH estimation model based on the Ohmic resistance, and the Ohmic resistance is identified online based on the UKF algorithm. The experimental results indicate that our new battery model considers the different values of the battery internal resistances under different working condition (such as different voltages, different currents and different temperatures). Besides, our study verifies the performance and feasibility of new estimation method based on D-UKF. This new algorithm has a practical value for further study of other electrical vehicle systems.
Keywords: 18650-type lithium battery; D-UKF; Ohmic resistance; state of health; SOH;
Research on indirect detection of rotor position for switched reluctance motor starting operation
by Yongqin Zhou, Hang Wang, Ningzhi Jin
Abstract: The initial rotor position information of the Switched Reluctance Motor (SRM) is the most critical problem to be solved for motor starting operation. The initial turn-on phase can be determined by pulse injection method, but cannot realise the accurate positioning of the initial angle. In this paper, a method combining the pulse injection method with the inductance model is proposed to estimate the rotor position angle. The method is to inject a high frequency excitation pulse into the phase winding and indirectly calculate phase inductance by response current. Based on the inherent relationship between phase inductance and rotor position, the initial position angle is accurately located by the phase inductance model, and the continuous rotor position information can be estimated when the motor runs at low speed. Finally, the feasibility of the method is proved by theoretical analysis and experimental study, which can effectively improve the starting effect of SRM.
Keywords: SRM; starting operation; rotor position; indirect detection; inductance model; pulse injection.
Study on the vertical and lateral coupling dynamics control of the in-wheel motor driven electric vehicles under multi-excitation
by Di Tan, Yanshou Wu, Fan Song
Abstract: To study the coupling dynamics control in the vertical and lateral direction of the in-wheel motor driven electric vehicles under the steering input, road and electromagnetic excitation, a 16-degree of freedom coupling dynamic model is given, which has been verified in previous work. To achieve the improvement of the vehicle coupling dynamics, a dynamics controller is designed subsequently based on the active suspension, active front steering and direct yaw control system. The dynamics controller includes a supervisory coordination layer controller and the above subsystem controller with different control algorithm, respectively. Finally, comparative analysis with or without control is carried out to verify the validity of the controller designed in this paper under certain combined excitation conditions. The results show whether the road with high or low adhesion coefficient, the controller developed in this paper is highly effective for the vertical and lateral coupling dynamics of the in-wheel motor driven vehicle. Especially, under the road with low adhesion coefficient, the control effect on the vehicle running stability and path track capacity is more obvious.
Keywords: in-wheel motor; coupling dynamics control; steering; road excitation; electromagnetic force.
Design and simulations of dual clutch transmission for hybrid electric vehicles
by Vu Trieu Minh, Abouelkheir Moustafa, Mart Tamre
Abstract: Dual clutch transmissions (DCTs) refer to double friction clutches; they are designed and operated fully automated in the vehicle shift gearbox. The best advantage of the DCTs is the improvement of the fuel economy because the power flow from the engine to the transmission is always kept in very high friction coefficient and not interrupted. The current six-speed DCTs can provide more than 10% of fuel economy compared with the conventional six-speed automatic gearbox. Therefore, the use of DCTs for hybrid vehicles has drawn attraction for researchers in automotive industries because of the higher energy efficiency and the environmental benefits. This paper develops the concept design of three vehicle models: conventional dual clutch transmission (DCT); conventional hybrid electric vehicle (HEV); and a combined hybrid dual clutch transition (HDCT). Then, three models DCT, HEV, and HDCT are simulated on different standard drive-cycles in city, extra city, and highway. HEV and HDCT proved the superiority on fuel savings in low speeds. HDCT showed a little bit higher energy saving over HEV owing to the higher efficiency of clutches to torque converters. Conclusions and recommendations for the development of DCT, HEV, and HDCT are also drawn.
Keywords: hybrid electric vehicle; dual clutch transmission; hybrid dual clutch vehicle; Matlab simulations.
Analysis of effect of driving motor on electric vehicle dynamic performance
by Wanyou Huang, Guangcan Wang, Mingjin Yu
Abstract: Dynamic performance is the most essential and important performance for vehicles. In order to find influencing rules on Electric Vehicle (EV) dynamic performance, this paper tests and analyses the effect of the driving motor system and transmission gear selection on EV dynamic performance. By taking an AC asynchronous motor with rated power of 32 kW as the research object, tests are performed to analyse the effect of motor torque in a high-speed flux-weakening range, as well as the effect of motor temperature and bus voltage on motor driving torque. Tests are performed to analyse the effect of motor driving torque limit on dynamic performance. Additionally, real vehicle tests are taken to analyse the influence of transmission gear selection on EV dynamic performance. The above research could provide the basis for the matching among EV powertrain key parts, and the basis for the optimised control of EV dynamic performance.
Keywords: electric vehicle; dynamic performance; influencing factor; driving motor system.
Research on the energy management of a composite energy storage system in electric vehicles
by Meilan Zhou, Zhanhua Liu, Jifeng Feng
Abstract: To solve the problem of power allocation of battery and supercapacitor in the composite energy storage system of electric vehicles, we propose a logic threshold and fuzzy control strategy to arrange battery and supercapacitor to supply the average and peak power to the load, respectively. Based on the simulation software of electric vehicles, we perform simulation modelling to analyse the current of battery, the SOC of battery and the current of supercapacitor. For verifying the feasibility of the control strategy, we set up an experimental platform to study pure electric vehicles during driving and braking. Simulation and experimental results indicate that the composite energy storage system can reduce the charging and discharging times and the current amplitude of the battery, and improve the usage ratio of regenerative braking energy and the mileage of electric vehicles.
Keywords: electric vehicles; composite energy storage; control strategy; test platform.
Factors affecting the intention to buy electric vehicles: empirical evidence from Thailand
by Trin Thananusak, Sirisuhk Rakthin, Thiti Tavewatanaphan, Prattana Punnakitikashem
Abstract: This study used Partial Least Squares Structural Equation Modelling (PLS-SEM) to test the relationships between the five factors (financial factors, infrastructure, performance, environmental concern, and price-premium) and intention to buy electric vehicles (EVs) in Thailand. Our findings suggest that the Thai car buyers pay attention to the performance factor of EVs (e.g., driving range, speed, safety) whilst not being concerned much with the infrastructure (e.g., charging facilities) and the financial factors (purchase price, operation and maintenance costs, resale price) of EVs. Moreover, the individuals environmental concerns affect the decision to own EVs, and Thai customers are willing to pay a price-premium for EVs. However, the price-premium factor could negatively moderate the relationship between the environmental concern and intention to buy EVs. That is, if the price-premium of EVs becomes too high, people with a pro-environmental ethos may be less likely to adopt EVs.
Keywords: intentions to buy; electric vehicles; EV; Thailand; financial factors; purchase price; maintenance cost; infrastructure; car buyers; charging facilities; performance; driving range; environmental concern; conspicuous conservation; price-premium; moderating factors;.
Matching and optimisation of an in-wheel tri-motor powertrain for electric vehicles
by Hongyu Shu, Xingpeng Diao, Yexing Liao, Qiping Chen
Abstract: As an important development direction of electric vehicles (EVs), the in-wheel motor powertrain has advantages of compact structure and flexible control, although there are some serious problems, such as high performance requirements to the drive motor and complex control strategies. To address these problems, a novel in-wheel tri-motor powertrain (IWTMP) is proposed at first, followed by the introduction of configuration and operating principles. Afterwards, vehicle power demand is calculated based on vehicle parameters and dynamic performance requirements, and a statistical analysis for typical driving cycles is carried out before conducting parameters matching for the IWTMP. Next, an optimisation for original parameters is achieved with an objective function of minimum total power of the IWTMP. Finally, a detailed IWTMP EV model is developed in CRUISE, and simulation results indicate that the IWTMP meets the dynamic performance requirements and efficiently reduces the energy consumption compared with an in-wheel single motor powertrain (IWSMP).
Keywords: electric vehicles; in-wheel motor; driving cycles; statistical analysis; parameters matching; optimisation; simulation; CRUISE; dynamic performance; economic performance.
Research on battery data compression method for electric vehicles
by Xiaogang Wu, Xiaoyu Li, Chunbo Zhu
Abstract: The transmission and storage of electric vehicle battery management system data is time-consuming and infeasible, which reduces the efficiency of data transmission and storage. For this problem, this paper presents a method of battery data compression, the pre-compression is to reduce the amount of data and improve the data redundancy and repeatability, and a strategy was formulated that two universal compression methods, Huffman coding and run-length coding, were applied to different battery data. Experimental results show the method of battery data compression can achieve a good compressibility. The battery data compressibility was about 21%.
Keywords: battery data; data compression; pre-compression; Huffman coding; run-length coding.
State estimation method for power lithium-ion battery based on dynamic equilibrium voltage
by Qiuting Wang, Wei Qi, Duo Xiao
Abstract: The state parameters of power lithium-ion battery include the State of Charge (SOC), the State of Health (SOH) and the State of Power (SOP). These three parameters are used to indicate the current remaining mileage, the maximum endurance mileage, and the acceleration performance, respectively. The dynamic equilibrium voltage (DEV) based on electrical characteristics is studied in this paper. The online state estimation problems for battery cells under dynamic working conditions is discussed in depth. We chose the DEV value as the characteristic parameter to estimate the SOC and SOH values online. The main results of our researches are (1) the mathematical model of power lithium-ion battery is established based on the dynamic behaviour;(2) the state space equations are derived to describe the model parameters and the working performance; (3) the SOC and SOH values are estimated accurately, according to only the DEV curve results under all-new state. Our experiments were processed under different temperatures and different ageing degrees to investigate the new model and new estimation method.
Keywords: lithium-ion battery; dynamic equilibrium voltage; SOC; SOH; SOP; online estimation.
Simulation and analysis of heat losses of in-wheel motor for micro-electric vehicles
by Qiping Chen, Qiang Xiao, Sheng Kang, Liping Zeng, Chuanjie Liao, Xiangqin Li
Abstract: Heat losses of in-wheel motor for micro-electric vehicles are computed and analysed, which can enhance the dependability, efficiency, safety and lifetime for in-wheel motors. The theory-practice combination method is adopted in this paper. The computational mathematical model of heat losses is set up, which is regarded as the study goal, and the field-circuit coupling and the electromagnetic-thermal coupling model are regarded as the breakthrough point, and electromagnetic structures of in-wheel motor are systematically optimised. In order to settle the coupled calculation equations of electromagnetic field, temperature field, open circuit and in-wheel motor motion, control equations of incremental steps alternating solving multiple fields are calculated and analysed. A more comprehensive electromagnetic-thermal coupling calculation model is established. Calculation results are verified to illustrate the heat losses principle and uncover the internal mechanism of electromagnetic-thermal coupling field for in-wheel motors. This paper will put forward a complete set of integrated modelling method and coupling algorithm of electromagnetic-thermal coupling field, which can provide theoretical and technical support for improving in-wheel motor quality and property of micro-electric vehicles.
Keywords: heat losses; simulation; coupled solution; in-wheel motor of micro-electric vehicles.
Control of a hybrid electric vehicle with dual clutch transmission configurations during mode transition
by Walid Elzaghir, Yi Zhang, Narasimhamurthi Natarajan, Frank Massey, Chris Mi, Hafiz Malik
Abstract: Mode transitions are significant events in the operation of a hybrid electric vehicle with dual clutch transmission (HDCT). Owing to the friction-induced discontinuity of the clutch torque, seamless transition is difficult to achieve. First, this paper presents mathematical equations for the nonlinear system. Then it presents the linearised model for the proposed system. The control objective of the Model Reference Adaptive Controller (MRAC) considered in this paper is to minimise fuel consumption and reduce torque interruption in a hybrid electric vehicle. The simulation and experimental results from an HDCT demonstrate that the MRAC achieves reduced torque interruption and less vehicle jerk compared with the conventional operation method, in addition to smooth and fast transition from pure electrical driving to hybrid driving.
Keywords: hybrid electric vehicle; dual clutch transmission; mode transition; model reference adaptive control.
Power factor correction and load demand peak shaving in residential town using electric vehicle fleet in smart parking
by Chia Lailypour, Dariush Nazarpour
Abstract: This paper presents an algorithm for compensating the active and reactive power simultaneously in a real residential distribution household system using the amount of energy saved in plug-in hybrid electric vehicles (PHEVs) or in electric vehicles (EVs) parked in smart parking. The system and vehicle's specifications are discussed in separate sections. Moreover, the effects of the algorithm on active power peak shaving, reactive power compensation, and power factor correction are discussed as well. The economic effect of the algorithm on costumer energy payment bills in Iran's distribution market is depicted in section VІ. Reactive power compensation leads to correction of the power factor and power loss reduction. The main reason for connecting vehicles to the grid is to charge them in their departure time to the desired state of charge (SOC). This algorithm guarantees that all vehicles will reach their desired state of charge at least a half-hour before departure. Finally, the positive effect of algorithm on all items is demonstrated.
Keywords: charging vehicles; distributed systems; electric vehicle; plug-in hybrid electric vehicle; peak shaving; power factor correction; residential grids; smart grid; smart building; smart home; smart parking.
Smart accelerating and braking achieving higher energy efficiencies in electric vehicles
by Guido Wäger, Jonathan Whale, Thomas Bräunl
Abstract: To maximise the use of the relatively small energy storage in mainstream electric vehicles (EV), an efficient operation is critical. Regardless of the traction power or energy regeneration capabilities (recuperation), each EV motor controller operates more efficiently under certain motor rotational speeds (rpm) and loads than others. Unlike internal combustion engine (ICE) cars or hybrid cars, EVs do not have variable gearboxes that allows the rpm to be adapted to adjust the engine speed towards more efficient regions. However, the driver can actively influence the load by changing acceleration or deceleration rates. This can lead to a more efficient operation of the EV's motor and controller. Although EV efficiency tests, modelling, and multi gearbox efficiency tests have been conducted, many of these studies focused on following a speed profile with relatively small changes in acceleration and deceleration rates. This study exposes an EV to a series of high load variations in acceleration and deceleration, in order to investigate the impact on energy consumption. The results show significant improvements in efficiency and a reduction in energy consumption by applying high loads at low vehicle speeds. However, the study also found increased losses under certain high acceleration rates, which outweighed the benefits of loading an EV so that its engine speed is in its most efficient region.
Keywords: electric vehicle efficiency; motor controller efficiency; smart acceleration.
Research status of structure optimisation design for in-wheel motor-driven system
by Di Tan, Haitao Wang, Fan Song, Lidong Miao
Abstract: As one of the key technologies of the next generation 'pure electric drive' electric vehicle, the in-wheel motor-driven electric vehicle has been paid great attention by the auto industry, because of its obvious technical advantages in the overall arrangement of the vehicle, the chassis active control and the convenience of control. Domestic and international automobile group companies, scientific research institutes and automobile components suppliers have invested considerable research and development efforts on these vehicles. The in-wheel motor-driven system integrates the motor, the speed reducer, the brake and so on into a narrow space and its integrated structure and performance directly affect the driving/braking performance of the driving wheels and the driving performance of the vehicle. Therefore, as one of the core technologies of these vehicles, the optimisation design of the integrated structure has always been a difficult and hot spot in the research institutes. In this paper, the development status of the optimisation design technology for the integrated structure of the in-wheel motor driven system at home and abroad is analysed and summarised, and on the basis of this, the future research directions are discussed.
Keywords: in-wheel motor-driven system; optimisation design; electromagnetic design; thermal design; lightweight design.
Power optimisation of electric coaster
by Ataur Rahman, Mizanur Rahman, Sany Ihsan Izan, Ahmed Faris
Abstract: Sustainability is the capacity to endure and ensure that the advanced technology for electric vehicles (EVs) remains diverse and productive over time. The power optimisation of the battery pack has been maintained by enhancing the lifespan of the battery by keeping the battery temperature 35-40
Keywords: electric vehicle sustainability; wireless battery management system; battery thermal management; cell charge balancing management.