基于预测滑转率的转矩分配策略研究

为解决后轮双电机驱动电动汽车的动态非线性转矩分配问题,提出一种预测并优化输出的分配策略。基于车辆动力学计算转矩输出,使用粒子群优化(PSO)算法及路面检测系统修正输出转矩,以某型后驱双轮毂电机样车为基础,设计优化分配算法,通过CarSim搭建整车联合仿真模型验证算法的性能,并以整车控制器为基础对设计的算法进行硬件在环测试。测试结果表明,提出的动态转矩分配策略可以根据实际工况分配驱动轮的转矩,降低驱动轮滑转率,提高整车的驾驶性能。     

分布式驱动电动汽车转矩节能优化分配

为了提高分布式驱动电动汽车的经济性和续航里程,对4个轮毂电机驱动转矩优化分配问题进行研究。通过轮毂电机台架试验得到轮毂电机的驱动效率特性,分析转矩优化分配实现节约整车能耗的可行性;建立侧重提高电机效率的目标函数,使电机转矩处于电机效率Map图中的高效区;建立侧重提高电机响应速度的目标函数,减小转矩分配瞬间电流波动过大带来的能耗;基于模糊理论设计以电机效率为变量的权重函数,实时调节权重来协调2种目标函数,提出一种转矩节能优化分配方法,得到最优的轴间转矩分配系数。在后轴驱动、平均分配、优化分配3种分配方式下进行整车能耗的ECE城市循环工况对比仿真分析。结果表明：提出的节能优化分配方法通过实时优化驱动电机的转矩,避免了电机工作在转矩过大和过小的低效区,提高了整个驱动系统的能量利用率,相比于后轴驱动和平均分配整车能耗效率提高了5.91%和10.54%;实车试验验证了转矩节能优化分配算法的节能效果,优化分配相比另外2种分配方式整车能耗效率分别提高了3.66%和8.58%。     

永磁同步电机的选型及参数校验

根据永磁同步电机在纯电动轿车中的应用特性,结合整车参数及动力性参数需求,对永磁同步电机进行匹配选型。采用MATLAB强大的数学计算功能,结合驱动电机控制器的控制策略,对永磁同步电机能够达到的整车动力性能进行校验,可精确计算出整车的电驱动系统性能,更为精准确定匹配的合理性。     

独立轮驱动电动汽车驱动力分配策略仿真研究

为实现高速状态下驱动转向工况的车辆稳定性,采用层次化控制结构,上层控制器为运动控制器,计算总的纵向力和横摆力矩需求,其中计算横摆力矩采用滑模变结构控制方法;下层控制器为实现所需求的纵向力和横摆力矩,同时提高轮胎力利用率以增加横向操纵稳定裕度,并满足轮胎力极限、电机输出性能等约束条件,采用优化算法计算分配到各个车轮的驱动力。进行高速行驶汽车单移线仿真试验,验证本文提出的控制策略的性能。     

分布式驱动电动汽车复合制动系统转矩分配控制策略仿真

针对分布式驱动电动汽车,提出了一种复合制动系统控制策略。采用分层的制动转矩分配控制结构,上层控制器采用滑模控制策略,对目标纵向力和横摆力矩进行求解,以满足车辆在制动时制动效能和制动稳定性的要求;下层控制器采用加权最小二乘控制,对四轮液压制动转矩和电机制动转矩进行分配,通过增大电机制动力分配的权值达到能量回收的最大化,并采用有效集算法完成目标函数的求解。在此基础上,在Simulink中建立了7自由度整车动力学模型,在对开路面的工况下进行了仿真分析,结果表明:所制定的控制策略能满足要求,在保证车辆制动稳定性的同时,最大限度回收制动能量。     

分布式驱动电动汽车的近似最优转矩矢量控制EI北大核心CSCD

针对分布式驱动车辆系统非线性的特性,提出一种基于最优转矩矢量控制的车辆侧向稳定性控制系统。首先使用魔术公式轮胎模型实时估计轮胎力,搭建轮胎侧偏刚度变化的非线性车辆模型。接着借鉴近似线性二次型规划的最优控制思想,设计基于质心侧向加速度的增益可调的横摆转矩控制方法,并根据驱动电机峰值转矩和轮胎摩擦圆的约束条件进行转矩矢量分配。最后进行Car Sim和Lab VIEW联合仿真和硬件在环实验。结果表明,控制系统能对车辆进行有效的实时控制,在显著改善车辆稳定性的同时不严重影响车辆的纵向性能。     

四轮独立驱动电动汽车驱动力最优控制方法

基于对四轮独立驱动汽车进行的动力学分析,提出通过调节驱动电机的电流来控制各轮纵向力以提高车辆操纵稳定性的策略.建立了驱动系统的动态响应模型,并将其变换为驱动系统控制模型.提出整车控制方案和控制器参考输入的调整方法,并运用最优控制理论设计了驱动系统反馈控制器.最后采用等转矩和等功率驱动力分配策略进行实验,结果表明该方法能取得较好的控制效果.     

混合动力客车自适应巡航控制研究

为减轻驾驶员驾驶负担,综合改善车辆的行驶安全、节能和环保性能,针对所研究的混合动力客车,提出一种自适应巡航控制算法。控制算法采用分层控制结构,由上层控制器和下层控制器组成。上层为多模式切换控制器,它根据本车与前车的行驶状态,得出整车期望加速度;下层为转矩协调控制器,它根据上层控制器得到的期望加速度,对发动机、起动发电集成电机和主电机驱动转矩或制动转矩进行协调控制。开发了基于MICROAUTOBOX的整车控制器,并通过采用模拟雷达信号的转鼓实验台实验和采用真实雷达信号的实际道路实验对所开发的控制系统进行验证。结果表明,所开发的分层控制系统能实现混合动力客车的自适应巡航控制,不仅减轻了驾驶员的驾驶负担和提高了行驶安全性,且在一定程度上实现了节能减排。     

分布式驱动电动汽车的近似最优转矩矢量控制

针对分布式驱动车辆系统非线性的特性,提出一种基于最优转矩矢量控制的车辆侧向稳定性控制系统。首先使用魔术公式轮胎模型实时估计轮胎力,搭建轮胎侧偏刚度变化的非线性车辆模型。接着借鉴近似线性二次型规划的最优控制思想,设计基于质心侧向加速度的增益可调的横摆转矩控制方法,并根据驱动电机峰值转矩和轮胎摩擦圆的约束条件进行转矩矢量分配。最后进行Car Sim和Lab VIEW联合仿真和硬件在环实验。结果表明,控制系统能对车辆进行有效的实时控制,在显著改善车辆稳定性的同时不严重影响车辆的纵向性能。     

基于PSO的新型双电机多模式驱动系统转矩分配策略优化EI北大核心CSCD

本文中对一款装备新型双电机多模式驱动系统的电动汽车进行转矩分配优化。根据双电机多模式驱动系统的特点,建立整车模型,划分不同模式的工作范围,在满足动力性的前提下,面向系统效率,制定基于粒子群优化算法的转矩分配与模式切换策略,并采用离线与在线相结合的方法提高系统的实时响应速度。在Matlab/Simulink建立仿真模型进行仿真并开展硬件在环试验验证,结果表明:系统的平均效率比传统的模式切换策略高3%;能耗比基于遗传算法的转矩分配策略减少11.28%。     

Multi-axle vehicle dynamics stability control algorithm with all independent drive wheel

The stability driving characteristic and the tire wear of 8-axle vehicle with 16-independent driving wheels are discussed in this paper. The lateral stability of 8-axle vehicle can be improved by the direct yaw moment which is generated by the 16 independent driving wheels. The hierarchical controller is designed to determine the required yaw torque and driving force of each wheel. The upper level controller uses feed-forward and feed-backward control theory to obtain the required yaw torque. The fuzzification weight ratio of two control objective is built in the upper level controller to regulate the vehicle yaw and lateral motions. The rule-based yaw moment distribution strategy and the driving force adjustment based on the safety of vehicle are proposed in the lower level controller. The influence of rear steering angle is considered in the distribution of driving force of the wheel. Simulation results of a vehicle double lane change show the stability of 8-axle vehicle under the proposed control algorithm. The wear rate of tire is calculated by the interaction force between the tire and ground. The wear of tire is different from each other for the vehicle with the stability controller or not.     

分布式驱动电动汽车转向工况转矩分配控制研究

针对分布式驱动车辆转向工况在低速下期望提高转向机动性能，高速下期望保证行驶稳定性的需求，充分考虑转向行驶内外侧车轮的转向关系以及车辆动力学，制定了适应车速变化的四轮转矩分配策略，建立了四轮轮毂电机驱动模型以及二自由度参考模型。为了改善分布式驱动转向机动性能，建立自抗扰控制器调整内外侧车轮转矩，形成合理的转速差，减小转向半径，以提高转向机动性；对于高速转向行驶稳定性的需求，通过二次规划方法优化分配各车轮驱动力矩，分析轮胎纵横向附着裕度建立目标函数，并加入附加横摆力矩和路面附着力的限制，进行车轮驱动转矩的在线优化分配，提高车辆转向行驶的稳定性；另外为避免2种控制模式转换时驱动转矩突变，根据车速和稳定性参数制定模糊规则决策2种模式的协调系数，保证2种控制模式的平滑过渡。基于CarSim和MATLAB/Simulink进行联合仿真，并搭建硬件在环平台进行试验，对所提出的方法进行验证。结果表明：在低速转向工况下，提出的分配策略能够调节内外侧车轮产生差速效果，与转矩平均分配的策略相比，转向半径有所减小，提高车辆机动性；高速转向工况下，分配策略能够保证车辆稳定转向，与未考虑稳定性控制的分配策略相比，能更好地跟踪目标轨迹，且横摆角速度控制在参考横摆角速度附近，证明了所提控制策略的有效性。     

电动轮驱动的轿车差速性能试验

电动轮驱动的汽车取消了机械式差速器后,在转向行驶、路面不平及车轮半径不等3种工况下,会出现差速问题。文章进行了实车转向行驶试验和车轮半径不等时的差速试验,验证了对电动轮电机控制按转矩模式控制而转速随动以实现自适应差速的控制策略。电动轮控制器可以实现很好的差速性能,说明采用转矩控制和转速随动的策略是解决汽车电子差速问题的前提和关键。     

基于功能安全的分布式驱动电动汽车前轮失效补偿控制

分布式驱动电动汽车可以实现四轮转矩分配和差动转向,提升整车的动力学控制性能和经济性,但是四轮转矩独立可控的特点也对功能安全提出挑战。当前轮单侧电机出现执行器故障失效情况时,不仅会产生附加横摆力矩降低车辆安全性,差动转向功能的存在还会使车辆严重偏航。基于此,在设计分布式驱动-线控转向一体化底盘的基础上,基于功能安全提出一种分布式驱动电动汽车前轮失效补偿控制策略。首先建立分布式驱动失效动力学模型,分析前轮失效对车辆状态的影响机理,发现单一的驱动转矩截断控制无法满足车辆状态修正需求;其次设计一套备用的线控转向结构,通过变截距滑模控制算法提高切换状态下线控转向系统的转角跟踪性能,并用台架试验验证跟踪的准确性;然后设计自适应失效诊断观测器实时诊断驱动系统的电机故障,在将对应轮进行驱动转矩截断后,通过模型预测控制算法对车轮转矩重新分配实现纵向和侧向的状态跟踪;最后通过仿真和实车试验验证所提失效补偿控制策略的有效性和可用性。研究结果表明：分布式驱动电动汽车前轮单侧电机失效后,备用的线控转向系统能及时矫正前轮转角,所提出的失效补偿控制策略能够快速恢复车辆的稳定性和路径跟踪能力。     

重型商用车汽车轮胎花纹对整车性能的影响

汽车轮胎是汽车的行驶系统的重要组成部分,对汽车保持正常的行驶起着重要的作用.除了承载着全车重量,传递驱动转矩外,车轮还还起着减震和缓冲,转向和制动的作用.轮胎对汽车的驾驶性、通过性、舒适性和安全性都有着直接的影响.文中从各轮胎花纹的性能,轮胎性能对整车性能的影响和分轮位配置花纹的优势,为整车提供更经济,安全,可靠的轮胎花纹的匹配方法.     

Traction/Braking Force Distribution for Optimal Longitudinal Motion During Curve Following

The optimal tire force distribution to maximize acceleration/deceleration of a four-wheel vehicle during cornering is studied. The objective of this research is to investigate the improvement one can expect from the implementation of different vehicle steering and driving mechanisms. We first identify the upper limit imposed by physical laws by assuming all the four wheels can be individually steered and driven. Practical vehicle configurations such as four-wheel-steering (4WS) and four-wheel-drive (4WD) are then considered. The optimization involves equality and inequality constraints and are solved by nonlinear programming techniques.     

Lateral handling improvement with dynamic curvature control for an independent rear wheel drive EV

The integrated longitudinal and lateral dynamic motion control is important for four wheel independent drive (4WID) electric vehicles. Under critical driving conditions, direct yaw moment control (DYC) has been proved as effective for vehicle handling stability and maneuverability by implementing optimized torque distribution of each wheel, especially with independent wheel drive electric vehicles. The intended vehicle path upon driver steering input is heavily depending on the instantaneous vehicle speed, body side slip and yaw rate of a vehicle, which can directly affect the steering effort of driver. In this paper, we propose a dynamic curvature controller (DCC) by applying a the dynamic curvature of the path, derived from vehicle dynamic state variables; yaw rate, side slip angle, and speed of a vehicle. The proposed controller, combined with DYC and wheel longitudinal slip control, is to utilize the dynamic curvature as a target control parameter for a feedback, avoiding estimating the vehicle side-slip angle. The effectiveness of the proposed controller, in view of stability and improved handling, has been validated with numerical simulations and a series of experiments during cornering engaging a disturbance torque driven by two rear independent in-wheel motors of a 4WD micro electric vehicle.     

Integrated Control of Active Rear Wheel Steering and Direct Yaw Moment Control

An integrated control system of active rear wheel steering (4WS) and direct yaw moment control (DYC) is presented in this paper. Because of the tire nonlinearity that is mainly due to the saturation of cornering forces, vehicle handling performance is improved but limited to a certain extent only by steering control. Direct yaw moment control using braking and/or driving forces is effective not only in linear but also nonlinear ranges of tire friction circle. The proposed control system is a model matching controller which makes the vehicle follow the desired dynamic model by the state feedback of both yaw rate and side slip angle. Various computer simulations are carried out and show that vehicle handling performance is much improved by the integrated control system.     

Integrated Control of Active Rear Wheel Steering and Direct Yaw Moment Control

SUMMARY

An integrated control system of active rear wheel steering (4WS) and direct yaw moment control (DYC) is presented in this paper. Because of the tire nonlinearity that is mainly due to the saturation of cornering forces, vehicle handling performance is improved but limited to a certain extent only by steering control. Direct yaw moment control using braking and/or driving forces is effective not only in linear but also nonlinear ranges of tire friction circle. The proposed control system is a model matching controller which makes the vehicle follow the desired dynamic model by the state feedback of both yaw rate and side slip angle. Various computer simulations are carried out and show that vehicle handling performance is much improved by the integrated control system.     

Speed ratio control of a parallel layout double cavity half-toroidal CVT for four-wheel drive

A double cavity half-toroidal CVT has two variators, which gives a hint of a new four-wheel drive without a center differential gear unit by applying each of them to drive front and rear drive shafts independently. Torque re-circulation at cornering or different tire radii between front and rear tire is avoided by compensating the speed ratio of variator. The controller adjusts the attitude angle of power roller of the front variator against the rear by measuring the steering angle at cornering. This paper describes the speed ratio control system of the 4WD-CVT with speed ratio range of 1 : 8.7 and test results of vehicle motion mounted on a 3.2L RV.