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Summary The estimation of state-of-charge (SOC) is crucial to determine the remaining capacity of the Lithium-Ion battery, and thus plays an important role in many electric vehicle control and energy storage management problems. The accuracy of the estimated SOC depends mostly on the accuracy of the battery model, which is mainly affected by factors like temperature, State of Health (SOH), and chemical reactions. Also many characteristic parameters of the battery cell, such as the output voltage, the internal resistance and so on, have close relations with SOC. Battery models are often identified by a large amount of experiments under different SOCs and temperatures. To resolve this difficulty and also improve modeling accuracy, a multiple input parameter fitting model of the Lithium-Ion battery and the factors that would affect the accuracy of the battery model are derived from the Nernst equation in this paper. Statistics theory is applied to obtain a more accurate battery model while using less measurement data. The relevant parameters can be calculated by data fitting through measurement on factors like continuously changing temperatures. From the obtained battery model, Extended Kalman Filter algorithm is applied to estimate the SOC. Finally, simulation and experimental results are given to illustrate the advantage of the proposed SOC estimation method. It is found that the proposed SOC estimation method always satisfies the precision requirement in the relevant Standards under different environmental temperatures. Particularly, the SOC estimation accuracy can be improved by 14% under low temperatures below 0 °C compared with existing methods. Copyright © 2017 John Wiley & Sons, Ltd.

Summary State of Health (SOH) is one of the most important parameters of lead-acid batteries. Most of the existing SOH estimation methods only take the influence of charge cycles into consideration, and the estimation accuracy is limited. Batteries in the substations have two typical states: one is the check-discharge state, in which the batteries are discharged for 8 h at 0.1 C (Capacity) to determine whether the battery pack has certain reliability. The other is the floating charge state, in which the batteries are connected to the charger to maintain full power. This paper proposes a novel SOH estimation method based on the two states. In the check-discharge state, the relationship between the voltage and the age of battery is analysed. The health index, which is introduced in this model, is affected by the age of battery. In the floating state, the relationship between the internal resistance and the age of battery is discussed. Another SOH model is established based on the change of the internal resistance. By combining the two models, the estimation method can achieve real-time estimation and high accuracy for substation application. An accelerated life test is applied to verify the theoretical analysis. The experimental results demonstrate that the SOH estimation error is less than 3% which is very satisfactory for practical applications. Copyright © 2016 John Wiley & Sons, Ltd.

© 2017 by the authors. Battery equalization can increase batteries' life cycle, utilization, and reliability. Compared with battery equalization topologies based on resistance or energy storage components, the topologies based on transformers have the advantages of high balancing current and efficiency. However, the existence of switching losses will reduce the reliability and service life span of the equalization circuit. Aiming at resolving this problem, a new battery equalization topology by fly-back transformer with an absorbing circuit is proposed in this paper. Compared with other transformer-based topologies, it can decrease switching losses because the voltage/current spike is solved by the absorbing circuit which is composed of inductance, capacitance and diode (LCD), and it can also maintain a high balancing current of about 1.8 A and high efficiency of about 89%, while the balancing current and efficiency of other topologies were usually 1.725 A/1.5 A and 80%/80.4%. The working principle of the balancing topology and the process of soft switching are analyzed and calculated in the frequency domain. Due to the addition of the LCD absorbing circuit, soft switching can be realized to reduce the switching losses while the high equalization speed and efficiency are still maintained. The corresponding control strategy of the balancing topology is also proposed and the timely balancing is achieved. The theoretical analysis is verified by simulation and experimental results.

With the increasing environmental concerns, plug-in electric vehicles will eventually become the main transportation tools in future smart cities. As a key component and the main power source, lithium-ion batteries have been an important object of research studies. In order to efficiently control electric vehicle powertrains, the state of charge (SOC) of lithium-ion batteries must be accurately estimated by the battery management system. This paper aims to provide a more accurate dynamic SOC estimation method for lithium-ion batteries. A dynamic Thevenin model with variable parameters affected by the temperature and SOC is established to model the battery. An unscented Kalman particle filter (UPF) algorithm is proposed based on the unscented Kalman filter (UKF) algorithm and the particle filter (PF) algorithm to generate nonlinear particle filter according to the advantages and disadvantages of various commonly used filtering algorithms. The simulation results show that the unscented Kalman particle filter algorithm based on the dynamic Thevenin model can predict the SOC in real time and it also has strong robustness against noises.

Series battery equalization can improve battery charge and discharge reliability and extend battery life. It requires a higher requirement in battery management system (BMS). This paper introduces the high speed inductor-based battery equalization schemes. It can realize energy transfer between the cells and batteries by charging and discharging of the inductors. Thus the equalization time can be improved. Finally the simulation and experimental results verify the theoretical analysis.

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Series battery equalisation can improve battery charge and discharge reliability and extend battery life. Inductor-based battery equalisation schemes have the advantages of simple topologies and control strategies. According to the energy transfer pathway, inductor-based battery equalisation schemes can be divided into cell-to-cell and cell-to-pack equalisation schemes. The control strategies of the cell-to-cell schemes are simple; the inductor can only transfer energy between the neighbouring cells, so the equalisation speed is low. The cell-to-pack schemes are able to accomplish energy transfer between the cells and pack by charging and discharging the inductors. The equalisation speed is high, but the control strategies may be complex. In this paper, different equalisation topologies are reviewed, then a unified control strategy which is applicable to all of the inductor-based equalisation topologies is proposed. The equalisation speeds and efficiencies of these different schemes, including the newly-proposed unified control strategy, are analysed and compared. Based on the theoretical analysis, simulations, and experimental verifications, it is concluded that this unified control strategy can perform the battery equalisation process quickly and efficiently.

Designing products for recyclability is driven by environmental and economic goals. To obtain good recyclability, two measures can be adopted. One is better recycling strategy and technology; whilst the other is design for recycling (DFR). Recyclability assessment is one of the most important contents in DFR. First, this paper discusses the content of DFR, and strategies and types related to product recycling, and points out that whether recyclability is easy or difficult depends on the product design. Then the methods and the procedure of recyclability assessment based on artificial neural network are explored in detail. Finally, a case study shows that this method is simple and operable.

Multi-link independent suspension is built according to the hard point parameters of a car. Using multi-body dynamics and suspension kinematics theory, the suspension performance were analyzed under the simulation test of parallel wheel travel, loading brake force after the outer rubber bushing stiffness of the under control arm is changed. The conclusion is drawn that axial stiffness of rubber bushing has almost no effect on the suspension performance, but radical stiffness has a little effect and torsion stiffness has the biggest effect on the suspension performance of these three parameters.

as the most important assembly affecting passengers' safe, automobile seat must meet the requirements of the national standard GB 15083-2006 and even stricter company standards. Seat recliner, which is the major subassembly contributes to the strength of seat, should have strong strength to balance the torque transferred from the backrest. In this paper, a finite element analysis of seat recliner was carried on, and an accurate modeling method was put forward according to the results bench test. The results of FEA show that this method rightly reveals the position and tendency of plastic deformation when a high torque was exerted on to the recliner. Applying FEA method in the design process of seat recliner can evidently reduce the time and cost.

Based on the finite element method (FEM), this paper presented a technique for analyzing the vibro-acoustic coupling characteristics of bus passenger compartments. In view of sound quality of vehicle interior noises in the low frequency range, the acoustical, structural and coupled acoustic-structural FEM models of the passenger compartment of a sample bus are respectively established for modal, harmonic response analysis. The correlation of the resonance frequencies from 0Hz to 200Hz of the structural vibration, cavity acoustic modals and the coupled vibro-acoustic modals of the bus body is revealed. The harmonic response results suggest that the sound pressure levels at any observed point in the interior cavity have a similar curve pattern in frequencies, but different in their amplitudes. In the low frequency range, the main resonance frequency of the sample bus is 80Hz, which is mainly due to the cavity acoustic modals and the vibro-acoustic coupling relationship of the bus body system. The newly proposed technique can be extended to other types of vehicle for interior noise prediction and sound source recognition and further reduction.

Front double wishbone independent suspension is built according to hard point parameters of a car. After the rubber bushing stiffness of under arm is changed, the suspension performance is analyzed and discussed with multi-body dynamics and Suspension Kinematics theory. The conclusion is drawn that axial and torsion stiffness of rubber bushing has a little effect on the suspension performance, but radical stiffness of rubber bushing has heavy on the suspension performance.

This paper presents a battery-equalization circuit and its control strategy. Energy storage inductors are applied in the circuit and their number is less than that of the switches. The topology is simple and easy to control. The antiparallel diode of the power switches can provide freewheeling path of the inductance current, and the energy can be transferred by switching. Battery charging and discharging has constant-voltage and constant-current mode. The corresponding control strategies of the equalization circuit are different. The working principle is discussed and the control strategies in the conditions of constant-voltage and constant-current modes are analyzed. The simulation model of the active battery-equalization scheme and an equalization circuit combined with the battery management system are established. Also a comparison is made to the existing inductor-based equalization schemes. The simulation and experimental results verify the theoretical analysis. The proposed battery-equalization scheme can realize the expected effect.