Electronic stability control for electric vehicle with four in-wheel motors

The electric vehicle with four direct-driven in-wheel motors is an over actuated system. A three-level control strategy of electronic stability control (ESC) is proposed to achieve optimal torque distribution for four in-wheel motors. The first level is a gain-scheduled linear quadratic regulator which is designed to generate the desired yaw moment command for ESC. Control allocation is the second level which is used to distribute the desired longitudinal tire forces according to the yaw moment command while satisfying the driver’s intent for acceleration and deceleration. The associated weighting matrix is designed using the work load ratio at each wheel to prevent saturating the tire. The third level is slip ratio control (SRC) which is employed at each wheel to generate the desired longitudinal tire force based on a combined-slip tire model. Simulation results show that the proposed method can enhance the ESC performance for the test maneuvers. Since the tire model is often unknown for practical implementation, the effectiveness of the SRC is studied using the sine with dwell test. It is found that the SRC is not crucial for achieving performance similar to the proposed method with SRC, if the slip ratio can be maintained in the stable region using traction control system/anti-lock braking system.     

Energy efficiency optimization of electric vehicle driven by in-wheel motors

Electric vehicle is considered to be the solution for energy and environment crisis, but it’s still not competitive enough with conventional vehicles because of the limited energy density and high cost of the power battery. So the energy efficiency is of the most importance for the control of electric vehicles. This paper looks into the energy efficiency optimization problem of electric vehicle driven by four in-wheel motors by developing a comprehensive energy efficiency model of the permanent magnet synchronous motor including the inverter. The calculated efficiency agrees with the measured data quite well. Based on the power loss analysis, the conclusion is drawn that in all driving or braking conditions the total torque requirement should be distributed evenly to all the motors in order to maximize the energy efficiency for electric vehicles driven by permanent magnet synchronous in-wheel motors. Vehicle test results show that the energy efficiency of the evenly distributed torque control is higher than the control strategy proposed by control allocation in literature.     

Cooperative control of the motor and the electric booster brake to improve the stability of an in-wheel electric vehicle

A cooperative control algorithm for an in-wheel motor and an electric booster brake is proposed to improve the stability of an in-wheel electric vehicle. The in-wheel system was modeled by dividing it into motor and mechanical parts, and the electric booster brake was modeled through tests. In addition, the response characteristics of the in-wheel system and the electric booster brake were compared through a frequency response analysis. In the cooperative control, the road friction coefficient was estimated using the wheel speed, motor torque, and braking torque of each wheel, and the torque limit of the wheel to the road was determined using the estimated road friction coefficient. Based on the estimated road friction coefficient and torque limit, a cooperative algorithm to control the motor and the electric booster brake was proposed to improve the stability of the in-wheel electric vehicle. The performance of the proposed cooperative control algorithm was evaluated through a hardware-in-the-loop simulation (HILS). Furthermore, to verify the performance of the proposed cooperative control algorithm, a test environment was constructed for the anti-lock braking system (ABS) hydraulic module hardware, and the performance of the cooperative control algorithm was compared with that of the ABS by means of a HILS test.     

Vehicle dynamics control of an electric-all-wheel-drive hybrid electric vehicle using tyre force optimisation and allocation

ABSTRACT

Hybrid Electric Vehicles (HEV) offer improved fuel efficiency compared to conventional vehicles at the expense of adding complexity and at times, reduced total power. As a result, HEV generally lack the dynamic performance that customers enjoy. To address this issue, the paper presents a HEV with electric All-Wheel-Drive capabilities via the use of torque vectoring electric rear axle drive (TVeRAD) to power the rear axle. The addition of TVeRAD to a front wheel drive HEV improves the total power output. To improve the handling characteristics of the vehicle, the TVeRAD provides torque vectoring at the rear axle. A bond graph model of the drivetrain is developed and used in co-simulation with CarSim. The paper proposes a control system which utilises control allocation to optimise tyre forces. The proposed control system is tested in the simulation environment with a high fidelity CarSim vehicle model. Simulation results show the control system is able to maximise vehicle longitudinal performance while avoiding tyre saturation on low mu surfaces. More importantly, the control system is able to track the desired yaw moment request on a high speed double lane change manoeuvre through the use of the TVeRAD to improve the handling characteristic of the vehicle.     

Development of the performance simulator for electric scooters with an in-wheel motor

Due to the increasing use of fossil fuel, carbon dioxide emission also increased and environmental problems have emerged as social issues. Accordingly, the research about electric vehicles as personal transportation has been actively performed. An electric scooter is not as complex as an automobile, but it takes a lot of time and costs to design and develop a new vehicle due to trial and error in selecting the specifications of core components according to consumer’s requirements. In this paper, a performance simulator for an electric scooter with an in-wheel motor at the rear wheel was developed and the simulation results were verified through experiments. For a longer travelling distance with the same energy source, the regenerative braking algorithm that converts kinetic energy into electric energy during braking was applied. The usefulness of the regenerative braking control algorithm was verified through various simulation results.     

Vehicle longitudinal velocity estimation during the braking process using unknown input Kalman filter

In this paper, vehicle longitudinal velocity during the braking process is estimated by measuring the wheels speed. Here, a new algorithm based on the unknown input Kalman filter is developed to estimate the vehicle longitudinal velocity with a minimum mean square error and without using the value of braking torque in the estimation procedure. The stability and convergence of the filter are analysed and proved. Effectiveness of the method is shown by designing a real experiment and comparing the estimation result with actual longitudinal velocity computing from a three-axis accelerometer output.     

Cooling performance of 25 kW in-wheel motor for electric vehicles

The in-wheel motor used in electric vehicles was designed and constructed for an electric direct-drive traction system. It is difficult to connect cooling water piping to the in-wheel motor because the in-wheel motor is located within the wheel structure. In the air cooling structure for the in-wheel motor, an outer surface on the housing is provided with cooling grooves to increase the heat transfer area. In this study, we carried out the analysis on the fluid flow and thermal characteristics of the in-wheel motor for various motor speeds and heat generations. In order to resolve heat release, the analysis has been performed using conjugate heat transfer (conduction and convection). As a result, flow fields and temperature distribution inside the in-wheel motor were obtained for base speed condition (1250 rpm) and maximum speed condition (5000 rpm). The thermo-flow analysis of the in-wheel motor for vehicles was performed in consideration of ram air effect. Also, in order to improve cooling effect of the motor, we variously changed geometries of housing. Therefore, we confirmed the feasibility of the air cooling for the motors of 25 kW capacity with housing geometry having cooling grooves and investigated the cooling performance enhancement. We found that the cooling effect was most excellent, in case that cooling groove direction was same with air flow direction and arranged densely.     

Active approach to Electronic Stability Control for front-wheel drive in-wheel motor electric vehicles

Recently, motion control for electric vehicles has gradually gained respect in automotive society due to increased strictness of vehicle safety evaluation over time. Electronic Stability Control (ESC) is the kernel technology, which refers to two-dimensional motion stabilization. Many investigations have demonstrated that Direct Yaw-moment Control (DYC) is an effective and practical way to carry out the ESC of electric vehicles. However, based on the drive train of conventional steering, conventional approaches are using braking to achieve the DYC. This paper proposes a new ESC based on the construction of DYC. The presented approach is based on a core of individual traction control measures for propulsion wheels. This approach not only constrain the longitudinal slip, but also ensure the performance and the effectiveness of two-dimensional motion control. With a proper control, the vehicle can be maintained to a nearly neutral-steering under high speed turning. Hence, the vehicle’s dynamic stability can be enhanced under aggressive driving by yaw-moment control. Evaluation of the entire control system is performed by well-acknowledged software, which demonstrates that the vehicle’s dynamic stability can be enhanced under aggressive driving by the proposed approach.     

电动汽车的新动力

技术专家们正在绞尽脑汁用各种各样方法让电池更新换代,一场电子设备的革命正悄悄来临。在不远的将来,可乐或许就可以帮助汽车行驶几百公里的路程。     

一种电动汽车车载高频智能充电机的设计研究

采用单片机和充电集成电路进行充电机的设计,不但能够实现对一般的蓄电池进行充电,而且还能够实现相应的过压、温度等保护功能,从而可以充分发挥蓄电池的性能,延长电池的使用寿命,并避免简易充电器在充电时可能对电池造成损害的情况发生。     

Vehicle distance estimation using a mono-camera for FCW/AEB systems

For robust vision-based forward collision warning (FCW) and autonomous emergency braking (AEB) systems, not only reliable detection performance including high detection rate and low false positives but also accurate measurement output of a target vehicle is required. Especially, in order to reduce false alarm or activation of FCW/AEB systems, the systems require the precise measurement output of a target object, such as position, velocity, acceleration, and time-to-collision (TTC). In this study, we developed a measurement estimation algorithm of a target vehicle using a monocular camera. This method estimates two cases of vehicle widths for a target vehicle by using the detected lane information and a pin-hole camera model. After that, the position, velocity, acceleration, and TTC of a target vehicle are estimated by using a Kalman filter for the each estimated vehicle width. To improve robustness, the both estimation results using the detected lane information and the pinhole camera model are fused. This estimation algorithm was evaluated and compared with the state-of-the-art technology. As a result, the proposed measurement output estimation method can improve the performance of the FCW/AEB systems.     

后轮轮毂电机驱动电动汽车的液压复合制动系统匹配方法

根据某电动汽车的总体设计要求,提出了该类型电动汽车的液压复合制动系统前、后制动力分配和匹配原则,分析了后轮轮毂电机特性对液压复合制动系统设计的影响.以满足理想制动力分配为目标,利用非线性最小二乘法优化方法对该液压复合制动系统前、后制动力分配和匹配进行了优化设计,并在不同循环工况、整车质量及电机外特性情况下评估了优化结果.     

A vehicle ABS adaptive sliding-mode control algorithm based on the vehicle velocity estimation and tyre/road friction coefficient estimations

A sliding-mode observer is designed to estimate the vehicle velocity with the measured vehicle acceleration, the wheel speeds and the braking torques. Based on the Burckhardt tyre model, the extended Kalman filter is designed to estimate the parameters of the Burckhardt model with the estimated vehicle velocity, the measured wheel speeds and the vehicle acceleration. According to the estimated parameters of the Burckhardt tyre model, the tyre/road friction coefficients and the optimal slip ratios are calculated. A vehicle adaptive sliding-mode control (SMC) algorithm is presented with the estimated vehicle velocity, the tyre/road friction coefficients and the optimal slip ratios. And the adjustment method of the sliding-mode gain factors is discussed. Based on the adaptive SMC algorithm, a vehicle's antilock braking system (ABS) control system model is built with the Simulink Toolbox. Under the single-road condition as well as the different road conditions, the performance of the vehicle ABS system is simulated with the vehicle velocity observer, the tyre/road friction coefficient estimator and the adaptive SMC algorithm. The results indicate that the estimated errors of the vehicle velocity and the tyre/road friction coefficients are acceptable and the vehicle ABS adaptive SMC algorithm is effective. So the proposed adaptive SMC algorithm can be used to control the vehicle ABS without the information of the vehicle velocity and the road conditions.     

电动汽车的动力电池技术

当前节能和环保正日益受到重视，因此，电动汽车已经成为各国政府和汽车企业关注的热点，正在初步形成朝阳产业。动力电池技术是电动汽车开发中需要解决的关键技术。分析国内外动力电池技术及其发展；在比较了各类动力电池的优缺点和综合性能的基础上，指出全密封铅酸蓄电池、MH-Ni蓄电池、锂离子蓄电池、锌空气蓄电池、质子交换膜燃料电池超大容量电容器和飞轮蓄电池将是21世纪动力电池技术发展的目标。     

A method for estimation of vehicle inertial parameters

In this paper, a new method is presented for estimating the current sprung mass inertial parameters of a vehicle, such as the mass, pitch and roll mass moments of inertia, and lateral and longitudinal centre of gravity locations. The method measures the sprung mass response when the vehicle is driven over an unknown and unmeasured random road profile. From these measurements, the equivalent free-decay responses are extracted and modal analysis techniques used to estimate the sprung mass natural frequencies, damping ratios and mode shapes. This information is combined with a simplified vehicle estimation model, least squares analysis and known equivalent stiffness parameters to estimate the vehicles’ inertial parameters. The results obtained from several simulation examples show that estimates of the inertial parameters generally have small relative errors.     

汽车铅酸蓄电池SOC的实时估计方法

为应对汽车铅酸蓄电池荷电状态在线估计的需求,分析了现有SOC估计方法不足;在给出Thevenin电路模型基础上,结合铅酸电池的开路电压与SOC关系曲线,获得SOC估计线性化的输出方程,进而提出采一种基于卡尔曼滤波的铅酸电池SOC在线估计方法。通过卷绕式铅酸电池实验和计算结果表明,该算法能够实时估计电池SOC状态,最大误差小于5%,相比于传统的安时积分法更适合用于在线检测。     

混合动力电动汽车控制策略的研究

主要讨论了并联式混合动力电动汽车的控制策略,详细阐述了控制策略的依据以及控制过程,并给出了控制策略的仿真结果。     

Design of 2-speed transmission for electric commercial vehicle

As environmental and economic interests increase, the need for eco-friendly vehicle such as an electric vehicle (EV) has increased rapidly. Various research of enhancing EV powertrain efficiency and relibility have been studied. In this study, 2-speed shift gears mechanism is designed by using simpson type planetary gear train. This transmission has two planetary gear unit. Gear position is determinded by which ring gear is fixed. Internal components of the transmission are designed for satisfying the required specification of EV. We analyze gear strength, gear mesh efficiency, and transmission efficiency. By manufacturing the transmission prototype and performing some experiments, we verify the application suitability of this transmission.     

氢电混合动力车动力系统结构布置研究

随着能源危机和环境恶化,汽车工业的进一步发展受到极大的挑战,发展新能源汽车成为未来汽车工业的发展方向。氢电混合动力车是一种新能源车,其动力系统的性能对汽车的整体性能起着至关重要的作用,为了更好地实现其性能,对其结构布置进行研究很有必要。通过与传统汽车、油电混合动力车以及纯燃料电池车的动力系统进行对比,研究了氢电混合动力车动力系统的组成与特点;并详细研究了动力系统的结构布置及其特点和各自适合的工况条件。通过以上的研究,为后续动力系统结构布置的选择提供了参考,并指出了其未来发展的方向。     

Robust control for four-wheel-independent-steering electric vehicle with steer-by-wire system

A four-wheel-independent-steering (4WIS) electric vehicle (EV) with steer-by-wire (SBW) system is proposed in this paper. The fast terminal sliding mode controller (FTSMC) is designed for the SBW system to suppress external disturbances. Taking unstructured and structured uncertainties into consideration, a robust controller is designed for the 4WIS EV utilizing μ synthesis approach and the controller order reduction is implemented based on Hankel-Norm approximation. Since sideslip angle is the feedback signal of robust controller and it is hard to measure, the extended Kalman filter (EKF) is employed to estimate sideslip angle. To evaluate the vehicle performance with the designed control system, step and sinusoidal steering maneuvers are simulated and analyzed. Simulation results show that the designed control system have good tracking ability, strong robust stability and good robust performance to improve vehicle stability and handing performance.