International Journal of Electric and Hybrid Vehicles (12 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;
Battery electric vehicle energy consumption modelling for range estimation
by Jiquan Wang, Igo Besselink, Henk Nijmeijer
Abstract: Range anxiety is considered as one of the major barriers to the mass adoption of battery electric vehicles. One method to solve this problem is to provide accurate range estimation to the driver. This paper describes a vehicle energy consumption model considering the influence of weather conditions and road surface dependent rolling resistance, which includes a road load, a powertrain, a regenerative braking, an auxiliary system and a battery model. The parameters of these models are obtained by different types of experiments. The energy consumption model is verified by 20 driving tests, including highway, rural and city driving. The results show that the proposed model can predict the energy consumption under different circumstances with a maximum error of 5%, which is a clear improvement over the 10% error from a simple energy consumption model. The proposed energy consumption model will be used to build a range estimator in future research.
Keywords: battery electric vehicle; energy consumption; modelling; weather influence; coast down test; dynamometer test.
Cycle life estimation method for parallel lithium battery pack based on double Kalman filtering algorithm
by Qiuting Wang, Wei Qi
Abstract: The lithium-iron phosphate battery cell and parallel battery pack are studied in this paper. The characteristics of three parameters, defined as Ohmic resistance, open circuit voltage (OCV) and State of Charge (SOC), are analysed based on the equivalent circuit model. The double Kalman filtering(D-KF) algorithm is presented to estimate the cycle life of the lithium battery pack, which is defined as battery State of Health (SOH). The aims of our study are: firstly, the equivalent model of battery pack is established and the model parameters are estimated based on the robust unscented Kalman filtering algorithm (R-UKF); secondly, the SOH estimation model is proposed and validated; thirdly, the SOH value of the battery pack is calculated using extended Kalman filter (EKF) as the auxiliary filter, according to the real-time value of model parameters. The experimental results indicate that the proposed parameters and SOH estimation method has better accuracy, robustness and convergence behaviour.
Keywords: lithium-iron phosphate; battery state of health; double Kalman filter; cycle life; parallel battery pack; robust unscented Kalman filter.
Advances in the study of heating and cooling issues for in-wheel-motor-driven systems
by Di Tan, Fan Song
Abstract: For in-wheel-motor-driven electric vehicles, the brakes, transmission system and driving motor are highly integrated in the wheel. This structure has obvious technical advantages in the vehicle layout structure, the active control of the chassis and the convenience of the operation. But at the same time, when the in-wheel motor installed in the wheels, its working environment is even worse, which will not only make the installation space narrow and close and the air circulation not smooth, but also be affected by the heat radiation and heat conduction of other surrounding mechanical components. If the large amount of heat generated during the operation of the in-wheel motor cannot be dissipated in time, it will not only damage the winding insulation and reduce the life, but also cause irreversible demagnetisation of the permanent magnet and threaten the safety and stability of the in-wheel motor. Consequently, it is vitally important to calculate and analyse the heat source and temperature field distribution of in-wheel-motor-driven system and design an efficient cooling system. In this paper, based on the domestic and overseas research status of in-wheel-motor-driven systems, the heating and cooling problems of the in-wheel-motor-driven system are analysed and summarised, and the future research direction is discussed.
Keywords: in-wheel-motor-driven systems; heating issue; cooling issue; research status ;development trend.
Design and parameter matching of a new electro-hydraulic hybrid transmission system
by Yang Yang, Luo Chang, L.I. Pengxi
Abstract: In order to avoid the impact of large charge and discharge current on the cycle life of the battery in the process of driving or braking of pure electric vehicles, a new electro-hydraulic hybrid power transmission system was designed. Taking the ChangAn prototype as a reference, a method based on driving cyclic condition was used to match parameters and develop a novel control strategy. The model of this new electro-hydraulic system and the dynamic model of the whole vehicle were established. The co-simulation results verified the effectiveness of the new hybrid power transmission system and the parameter matching method. The results show that the new electro-hydraulic hybrid power transmission system effectively avoids the impact of large charging and discharging current on the battery cycle life, and can improve the economy of the vehicle to a significant extent while also displaying satisfactory power performance.
Keywords: automotive engineering; electric vehicle; electro-hydraulic hybrid power transmission system; combine simulation; parameter matching.
Magnetic flux analysis and performance test of permanent magnet and claw-pole electromagnetic hybrid excitation generator for electric vehicle range extender
by Xueyi Zhang, Qinjun Du, Shilun Ma, Wenjing Hu, Huihui Geng
Abstract: The hybrid excitation generator (HEG) has a tangential permanent magnet (PM) and claw-pole electromagnetic parallel combined rotor and a fractional-slot winding stator, which reduces the stator core eddy-loss and the armature winding copper-loss. By establishing the equivalent magnetic circuit model of each part of the HEG and analysing permeance influence factors, magnetic isolation measures are taken to reduce flux leakage and improve output efficiency. The designed electromagnetic coupling regulator controller can ensure stable voltage export from the HEG in a wide range of speed and load state by changing quantity and direction of excitation current to adjust the size of the air gap magnetic flux density. A performance test is done and results show that the output voltage is relatively stable. So the HEG can provide electric energy to battery and electrical equipment of vehicles.
Keywords: tangential permanent magnet; claw-pole electromagnetic; parallel magnetic circuit; hybrid excitation; generator; electric vehicles; range extender; electromagnetic coupling regulator controller; magnetic flux analysis; magnetic field simulation.
State estimation of four-wheel-independent-drive electric eehicle based on adaptive unscented Kalman filter
by Bin Huang, Sen Wu, Xiang Fu, Jie Luo
Abstract: In this paper, an algorithm using adaptive unscented Kalman filter (AUKF) to estimate key states of a four-wheel-independent-drive (4WID) electric vehicle is proposed. The algorithm estimates unknown noise by use of the modified Sage-Husa noise statistic estimator. Its recursive form is combined with unscented Kalman filter (UKF) algorithm for real time estimation and correction of noise statistic property in filtering process so as to reduce the error in state estimation. The nonlinear vehicle dynamics system, which contained constant/time-variable noise and four degrees of freedom, including longitudinal, lateral, yaw and rolling motion, is established. The estimator based on AUKF is compared with that based on UKF. The results of virtual experiments by using both Simulink and Carsim software and real vehicle experiments demonstrate that the AUKF based algorithm can estimate quite accurately the key driving state parameters of the 4WID electric vehicle.
Keywords: state estimation; four-wheel-independent-drive; electric vehicle; adaptive unscented Kalman filter; noise statistic property.
'Journey mapping', a redefined drive cycle: an accurate vehicle performance prediction tool
by Kavya Prabha Divakarla, Ali Emadi, Saiedeh N. Razavi
Abstract: With the increasing popularity of hybrid electric vehicles, updating their testing procedures to have more accurate vehicle performance prediction has become very important. Traditionally, vehicles are tested using certain standardised drive cycles or velocity over time profiles. These drive cycles, however, are not able to represent real-life driving scenarios for the different conditions that a vehicle might encounter during its life-cycle across all users. This results in high discrepancies between the predicted and the actual vehicle performance. As such, this study highlights the application of a novel concept called Journey Mapping, which redefines drive cycles in order to provide more realistic and accurate vehicle performance prediction. In contrast to the existing standard drive cycles, Journey Mapping incorporates real-life conditions that influence a vehicle during its journey from an origin to a destination. The Journey Mapping model was able to predict the test hybrid vehicles performance with only about 2% error, on average, when the predicted performance values were compared with the true values.
Keywords: automotive drive cycles; data acquisition hybrid and electric vehicles; predictive models and simulations.
Research on torque distribution of distributed driving electric vehicle based on fuzzy control
by Wu Xiaogang, Zheng Dianyu
Abstract: For a distributed drive electric vehicle power system based on the wheel hub motor, on the basis of its mathematical model, this paper proposes a torque distribution strategy based on a fuzzy control algorithm, in order to improve the driving wheel hub motor work efficiency and reduce energy consumption to distribute drive and brake torque. The simulation results show that, compared with the rule-based torque averaging method, the fuzzy control torque distribution optimisation algorithm is applied to the Chinese passenger vehicle urban road driving condition and NEDC driving conditions. Compared with the rule-based method of torque average assignment, the energy efficiency of the dynamic system is respectively increased by 16.61% and 19.31%, and the 100 km power consumption is reduced by 1.27 kWh and 2.7kWh by using fuzzy control for torque distribution optimisation.
Keywords: electric vehicle; distributed drive; fuzzy control; torque distribution.
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.
What works? An ANFIS-based policy evaluation framework for electric vehicle technology development
by Fatih M. Özel, Huw Davies, Peter Wells
Abstract: The application of socio-technical transitions analysis into realms such as future sustainable mobility has revealed the requirement to understand the efficacy of policy measures ex ante. Electrification of the vehicle drivetrain has been promoted as one possible solution to achieve carbon emission and air quality targets. National governments are increasingly forming suites of policy measures to encourage electric vehicle technologies in the transport sector. To evaluate multiple policy measures, a framework based on adaptive neuro-fuzzy inference systems (ANFIS) has been developed and is described here. For data generation, the electric vehicle innovation policies of the European Union, the USA, Japan, Germany, France and the UK were analysed and compared with the actual technology development that was measured with patent filings in those regions. The training and validation of the proposed ANFIS framework shows that the model is able to predict the development of electric vehicle technologies in terms of patent filings. The model is subsequently applied to Austria in a predictive capacity to evaluate three proposed policy scenarios. This paper concludes that the developed framework might play a significant role for assisting EV innovation policy-making by enabling ex-ante assessment the effects of different policy-mixes on the technical change.
Keywords: battery electric vehicles; policy evaluation; socio-technical transitions; ANFIS-based modelling; Austria; sustainable mobility.
Public procurement of electric vehicles as a way to support a market: examples from Sweden
by Jenny Palm, Fredrik Backman
Abstract: Electric vehicles (EV) are increasingly seen as a desirable sustainable solution for the transport sector, and public procurement is often highlighted as one tool to stimulate a market. In this article, we analyse the role of Swedish municipalities in relation to public procurement and especially whether and in such cases how municipalities in Sweden use public procurement as an instrument to enhance a market for EVs. The strategy in both municipalities was to let the municipal organisation act as role models, create buying power and develop a second-hand market for EVs. The strategy to speed up diffusion within the municipal organisation was through information and test-driving and in dialogue with the administration to solve problems that arise. A potential improvement of the diffusion process would be to find ways to share the extra cost of an EV.
Keywords: electric vehicle; public procurement; sustainable public procurement; municipalities; barriers.