Four Wheel Independent Drive Electric Vehicle Lateral Stability Control Strategy

In this paper,a kind of lateral stability control strategy is put forward about the four wheel independent drive electric vehicle.The design of control system adopts hierarchical structure.Unlike the previous control strategy,this paper introduces a method which is the combination of sliding mode control and optimal allocation algorithm.According to the driver’s operation commands(steering angle and speed),the steady state responses of the sideslip angle and yaw rate are obtained.Based on this,the reference model is built.Upper controller adopts the sliding mode control principle to obtain the desired yawing moment demand.Lower controller is designed to satisfy the desired yawing moment demand by optimal allocation of the tire longitudinal forces.Firstly,the optimization goal is built to minimize the actuator cost.Secondly,the weighted least-square method is used to design the tire longitudinal forces optimization distribution strategy under the constraint conditions of actuator and the friction oval.Beyond that,when the optimal allocation algorithm is not applied,a method of axial load ratio distribution is adopted.Finally,Car Sim associated with Simulink simulation experiments are designed under the conditions of different velocities and different pavements.The simulation results show that the control strategy designed in this paper has a good following effect comparing with the reference model and the sideslip angle is controlled within a small rang at the same time.Beyond that,based on the optimal distribution mode,the electromagnetic torque phase of each wheel can follow the trend of the vertical force of the tire,which shows the effectiveness of the optimal distribution algorithm.

Torque Distribution of Electric Vehicle with Four In-Wheel Motors Based on Road Adhesion Margin

With the worsening of energy crisis and environmental pollution,electric vehicles with four in?wheel motors have been paid more and more attention. The main research subject is how to reasonably distribute the driving torque of each wheel. Considering the longitudinal motion,lateral motion,yaw movement and rotation of the four wheels,the tire model and the seven DOF dynamic model of the vehicle are established in this paper. Then,the torque distribution method is proposed based on road adhesion margin,which can be divided into anti ? slip control layer and torque distribution layer. The anti?slip control layer is built based on sliding mode variable structure control,whose main function is to avoid the excessive slip of wheels caused by road conditions. The torque distribution layer is responsible for selecting the torque distribution method based on road adhesion margin. The simulation results show that the proposed torque distribution method can ensure the vehicle quickly adapt to current road adhesion conditions,and improve the handling stability and dynamic performance of the vehicle in the driving process.

Electromagnetic analysis and design of in-wheel motor of micro-electric vehicle based on Maxwell

To obtain a good drivability and high efficiency of the micro-electric vehicle, a new driving in-wheel motor design was analyzed and optimized. Maxwell software was used to build finite element simulation model of the driving in-wheel motor. The basic features and starting process were analyzed by field-circuit coupled finite element method. The internal complicated magnetic field distribution and dynamic performance simulation were obtained in different positions. No-load and load characteristics of the driving in-wheel motor was simulated, and the power consumption of materials was computed. The conformity of the final simulation results with the experimental data indicates that this method can be used to provide a theoretical basis to make further optimal design of this new driving in-wheel motor and its control system, so as to improve the starting torque and reduce torque ripple of the motor. This method can shorten the development cycle of in-wheel motors and save development costs, which has a wide range of engineering application value.

Multi-objective Optimization of Differential Steering System of Electric Vehicle with Motorized Wheels

A differential steering system is presented for electric vehicle with motorized wheels and a dynamic model of three-freedom car is built.Based on these models,the quantitative expressions of the road feel,sensitivity,and operation stability of the steering are derived.Then,according to the features of multi-constrained optimization of multi-objective function,a multi-island genetic algorithm(MIGA)is designed.Taking the road feel and the sensitivity of the steering as optimization objectives and the operation stability of the steering as a constraint,the system parameters are optimized.The simulation results show that the system optimized with MIGA can improve the steering road feel,and guarantee the operation stability and steering sensibility.

The Summary of the Research on the Compound Braking Strategy of Four Wheel Hub Motor Drive Electric Vehicle

This paper describes in detail three kinds of typical compound braking strategy of wheel motor drive electric vehicle and summarizes the current commonly used strategies based on the three typical strategies developed. In the end, a new compound braking strategy is proposed;that is, we take braking mode classify, ECE regulations and SOC value of the battery as an important reference of braking force that joins the motor braking force, as well as we join the different identification models;according to the different braking modes, the purpose is that we can apply the different braking program.

A new braking force distribution strategy for electric vehicle based on regenerative braking strength continuity

Regenerative braking was the process of converting the kinetic energy and potential energy, which were stored in the vehicle body when vehicle braked or went downhill, into electrical energy and storing it into battery. The problem on how to distribute braking forces of front wheel and rear wheel for electric vehicles with four-wheel drive was more complex than that for electric vehicles with front-wheel drive or rear-wheel drive. In this work, the frictional braking forces distribution curve of front wheel and rear wheel is determined by optimizing the braking force distribution curve of hydraulic proportional-adjustable valve, and then the safety brake range is obtained correspondingly. A new braking force distribution strategy based on regenerative braking strength continuity is proposed to solve the braking force distribution problem for electric vehicles with four-wheel drive. Highway fuel economy test(HWFET) driving condition is used to provide the speed signals, the braking force equations of front wheel and rear wheel are expressed with linear equations. The feasibility, effectiveness, and practicality of the new braking force distribution strategy based on regenerative braking strength continuity are verified by regenerative braking strength simulation curve and braking force distribution simulation curves of front wheel and rear wheel. The proposed strategy is simple in structure, easy to be implemented and worthy being spread.

四轮转向干预下电动助力转向控制策略研究

四轮转向(4WS)车辆相较于前轮转向(FWS)车辆具有更高的灵活性,其后轮转向在提高车辆操稳性的同时转向阻力矩也发生变化,使得原电动助力转向系统助力策略与四轮转向车辆不匹配,对行车安全产生影响.本文以线性二自由度车辆模型为基础,对比分析了前轮转向车辆与四轮转向车辆的转向特性,提出电动助力转向修正控制策略.仿真结果表明,角阶跃工况下,有助力修正的四轮转向车辆,驾驶员操纵方向盘力矩与驾驶前轮转向车辆基本一致,既保证了四轮转向车辆低速时的操纵轻便性,也兼顾了高速时的操纵稳定性.

考虑道路识别的四驱电动汽车再生制动策略

为了充分利用路面附着条件分配再生制动力,提高制动能量回收率,根据双电动机四驱结构电动汽车复合制动系统的特点,对其制动能量回收控制策略进行了研究.分析了驱动轮与地面附着特性,设计了道路识别器来计算每个轮胎与当前路面之间的峰值附着系数,并使用模糊控制策略确定每个车轮与8种道路的滑移率和附着利用率的相似输入.根据双电动机外部特性的制动力分配关系,提出了使更多制动能量回馈给电池的策略.结果表明:制动强度为0.3时,能量回收率为65.55%,具有较高的回收效率.

基于路面影响因子的轮毂电机驱动车辆自适应转矩控制

为实现轮毂电机驱动越野车辆在附着条件多变、路面起伏不定的复杂环境中动力性和稳定性的多目标优化,提出一种基于路面影响因子的自适应转矩控制策略。以滚动阻力差异、空气阻力归一化比例、坡度阻力归一化比例、路面附着差异方差以及最小路面附着系数5个特征参数作为输入,并基于模糊理论方法搭建路面影响因子五参数辨识模型。基于辨识出的路面影响因子,开发整车动力性和稳定性多目标优化自适应转矩控制策略,构建了三层式控制架构:顶层引入路面影响因子对加速度紧迫程度进行判定,采用模型预测控制算法得到期望总驱动力;中层为目标决策层,以最优滑转率为目标决策驱动防滑力矩,并基于路面行驶阻力,决策期望前馈补偿力矩;下层为转矩分配层,以需求总驱动力及轮胎利用率作为控制目标,引入路面影响因子优化两者权重系数,以多约束条件的混合优化算法对转矩进行自适应控制。利用Matlab/Simulink-CarSim联合仿真平台进行仿真,基于实车进行验证。结果表明,在低附着路面,在0.2s内快速完成滑转率抑制;在对开路面,侧向位移接近0;在大扭曲路面,避免腾空车轮出现大滑转率,滑转率最高0.2。

永磁轮毂电机技术发展综述

电传动技术是车辆实现全电化的重要基础,电驱动系统是电动车辆的动力核心,而轮毂电驱系统是电驱动系统的终极驱动形式,轮毂电机的性能在轮毂电驱系统中具有决定性作用。首先,该文介绍了轮毂电驱系统的结构形式,对不同磁场类型的轮毂电机的优缺点进行了分析;其次,调研了目前市场主流轮毂电机产品的性能参数,为轮毂电机的研发提供参考目标;然后,针对轮毂电机高功率/转矩密度、宽转速运行范围、高运行效率和高可靠性等需求,分别调研了径向磁场、轴向磁场和横向磁场等不同类型的永磁轮毂电机的研究现状;最后,展望了不同磁场类型的永磁轮毂电机的发展方向。

小曲率路面车辆差动转向与横摆稳定性集成控制研究

为减小车辆在前轮转向系统失效的负面影响,保证转向系统的瞬态控制性能,本文提出差动转向控制与横向稳定性控制相结合的控制方法,通过调节左右轮毂电机转矩形成横摆力矩,实现对系统完全失效车辆的转向控制与横向稳定性控制。首先设计基于LQR差动转向控制器跟踪参考前轮转角与参考横摆角速度,保证车辆轨迹跟踪能力,然后设计基于模糊PID横向稳定性控制器跟踪参考质心侧偏角,保证车辆横摆稳定性,两者构成双闭环控制系统将控制量最终转化为横摆力矩,实现车辆的集成控制。最后通过Simulink-Carsim联合仿真验证,仿真结果表明差动转向系统能够在前轮转向系统失效情况下实现车辆转向控制,并在横向稳定性控制系统的作用下有效地提高了车辆瞬态控制性能。

分布式驱动系统用轮毂电机及其技术综述

应用轮毂电机的分布式驱动型电动汽车在系统效率、车身控制、平台开发等方面具有突出优势,是新一代电动汽车领域的研究热点和重要发展方向。该文对比分析电动汽车集中式驱动与分布式驱动的技术优缺点,指出分布式驱动系统用轮毂电机具有巨大的发展潜力;介绍国内外学者在轮毂电机拓扑创新方面做的工作,总结该领域的研究特点以及面向高转矩密度的技术发展方向;阐述振动分析与抑制、温升计算与冷却、多目标优化与算法加速这三大轮毂电机优化设计研究领域的技术进展,提出全局性多物理场分析优化理论的技术空白;阐明驱动控制领域的研究主要围绕单电机层的高性能控制与容错控制、整车层的多电机协同控制展开;最后,该文总结分布式驱动轮毂电机的研究进展,展望该领域的技术研究方向。

基于多胞体系统的FWID EV鲁棒加权增益调度轨迹跟踪控制

为了提高四轮独立驱动电动汽车(FWID EV)轨迹跟踪控制性能,针对车辆横向运动系统的不确定性与非线性问题,考虑转向执行机构的动态特性,提出了基于线性变参数(LPV)的鲁棒加权增益调度轨迹跟踪控制策略。首先利用凸分解技术将LPV系统转化为有限多胞顶点凸组合的多胞体系统,然后基于离线设计的每个多胞顶点控制器和线性组合在线计算任意时变参数对应的系统控制器参数,并利用MATLAB和CarSim进行联合仿真。结果表明:在加速变道场景下,所设计的控制器可以保证横向偏移误差不超过2 cm,横向偏移平均绝对误差不超过0.9 cm的较高跟踪精度及行驶稳定性和鲁棒性。

中国语境下纯电动微型车全生命周期碳排放

为回答中国语境下纯电动微型车能够减碳多少,建立了针对中国语境下的纯电动微型车的全生命周期碳排放的评估模型。基于一组1030车·天的纯电动微型车的典型出行数据,使用了与交通有关的温室气体、排放及能耗的全生命周期碳排放核算模型—GREET,该模型包括:制造环节(CTG)、能源周期(WTW)和回收环节(GTC)。结果表明:中国内地纯电动微型车的日均出行里程37.2 km,73.1%的日出行里程低于50.0 km;在2021年平均电网、采用新欧洲驾驶循环(NEDC)的条件下,纯电动微型车全生命周期CO_(2)当量碳排放为26.8 t,比同级别内燃机汽车低约33%。其中的72%的排放来自纯电动微型车WTW环节,其CO_(2)当量碳排放为19.3 t。电网清洁化程度的提升和动力电池回收比例的增加,将有助于进一步降低纯电动微型车的碳排放。

四驱电动汽车变附着路面行驶操稳性控制研究

针对四轮驱动电动汽车行驶时路面峰值附着系数和附着利用率变化的问题,提出利用直接横摆力矩控制提高操纵稳定性的控制策略。该策略采用分层控制,上层控制器负责目标车速的追踪、滑移率调整力矩的计算、以及根据行驶危险程度实现对质心侧偏角和横摆角速度的协调控制,下层控制器包括以轮胎利用率最优为目标的分配算法及集成滑移率控制的分配算法,根据滑移率大小实时切换。Carsim-Simulink联合仿真结果表明,在对开路面行驶时,相比于转矩平均分配控制策略,该控制策略能够使车辆具有良好操稳性的同时保持各车轮处于最佳滑移率区间内,有效改善了车辆性能。

基于计算流体力学冷却风机性能参数设计分析

冷却风机作为电动轮车辆轮边牵引电机冷却系统最重要的部件,其性能优劣对冷却系统的效果有直接的影响。针对强制冷却系统的结构特点,结合牵引电机的冷却需求,对影响风机冷却风量和压差的关键参数进行设计;在此基础上,基于CFD搭建风机的流场分析模型;采用差异化网格划分技术,对不同区域选取不同网格尺寸;对整机和叶片静压场进行分析,并对整机全压场和流道区域速度场进行分析,获取关键参数值,并与设计值进行对比。结果可知:风机内部的流场十分复杂,多处存在二次流和尾流-射流现象,但是流动趋势符合流体力学原理;模拟所得流量结果为3.86m^(3)/s与设计流量4m^(3)/s误差为3.63%,模拟功率结果为29.4kW与设计功率29.92kW的误差为1.77%,二者结果一致,表明设计和分析结果是合理的。参数设计计算和流场分析结果一致性,为同类型冷却风机设计提供参考。

低附着路面条件下四轮独立驱动转向电动车稳定性控制研究

针对四轮独立驱动转向车辆在低附着路面的稳定性问题,提出了一种协调稳定性控制器。首先,基于模糊理论设计了主动后轮转向(active rear wheel steering,ARS)控制器,实现减小质心侧偏角的效果;然后,基于等效滑模变结构设计了直接横摆力矩控制(direct yaw moment control,DYC)控制器,以控制横摆角速度为目标;最后,基于Carsim/Simulink仿真平台搭建稳定性算法模型,进行了低附着系数双移线工况仿真对比。结果表明,所提出ARS和DYC协调控制算法能有效改善车辆在低附着路面上的行驶稳定性。

基于CAN通信的矿用纯电动无轨胶轮车故障诊断技术研究

以WLL5型矿用防爆纯电动无轨胶轮车为例,在分析胶轮车故障监测对象的基础上,深入研究了相关的故障诊断技术和方法,通过对整车局域网架构的解析,设计了集仪表盘和故障诊断仪功能于一体的车载复用显示器。经车辆运行试验,车辆的在线故障诊断和监测效果良好,具有一定的借鉴意义。

GIS设备搬运升降一体化自动控制系统设计

电网GIS设备通常被分段安装在钢型材框架上,一般没有专用顶升点,抬升、搬运、移位、落位效率低,作业安全性差。针对现有钢型材框架结构,设计了集搬运和抬升一体的U形搬运车,每台U形车上包含一个转向轮和两个舵轮,搬运时双U形车抱夹GIS设备两端,双车协调联动可实现小场地灵活万向运动;同时车上配备液压抬升装置,可实现设备抬升、保持、落地功能;开发了基于STM32的控制系统,经超带宽定位模块实现了车体实时定位;设计了车体位姿调节方法,可实现双U形车系统对GIS设备的自动搬运功能。与现有搬运方式相比,GIS设备的搬运效率和稳定性均有较大提升。

四驱纯电动车型加速性能优化分析

文章基于量产状态纯电动四驱车型,进行加速性能提升,以达到赛道版本车型加速目标。在整车架构基本固定的情况下,通过优化电机可用的电流上限、实际场地测试标定起步前电机扭矩上限阈值、更换半热熔轮胎、轮毂轻量化、以及热胎改善起步打滑时间的方法。在提出方案的初期通过仿真软件计算各个方案对百公里加速时间减少量,再由实车场地现场标定确认标定值,最终测试百公里加速时间缩短0.4s,可达到3.5s,在同级别纯电动车型百公里加速性能方面,达到领先水平。同时在后续开发中,为加速性能提升积累了整车子系统开发方案,并且完善了轮胎-地面模型的实测数据积累,对整车动力性能开发具有一定的借鉴意义。