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.     

多轮分布式电驱动车辆双重转向分层控制系统设计

为了提高多轮分布式电驱动车辆在复杂机动环境下的转向能力,设计了一种基于直接横摆力矩控制的双重转向系统。该控制系统采用分层结构,上层为横摆力矩决策层,下层为驱动力分配层。在控制系统上层,基于无迹卡尔曼滤波和递归最小二乘结合算法进行路面辨识;根据车辆状态信息和路面条件自适应调节滑移转向比,由车辆动力学模型和滑移转向比确定双重转向参考模型;针对滑模面附近非连续特性造成的控制信号抖动现象,将滑模控制算法进行改进,设计了滑模条件积分控制器,使车辆实际横摆角速度追踪双重转向参考模型计算出期望横摆角速度。系统下层在保证车辆总驱动力的前提下,基于控制分配规则将上层广义目标控制力需求分配至各执行器。最后,利用硬件在环实时仿真平台进行控制策略验证。结果表明,分层控制系统较好地实现了路面识别功能和车辆双重转向功能,针对不同路面工况对车辆进行了有效地行驶控制,减小了车辆在狭小弯曲地区的转弯半径,抑制了车辆状态参数及电机转矩的颤振和抖动,改善了车辆小半径行驶的转向机动性和高速行驶稳定性。     

分布式驱动电动汽车操纵稳定性控制仿真

本文研究通过直接横摆力矩控制来提高分布式驱动电动汽车稳定性问题。针对充分发挥四轮独立驱动电动汽车各电机独立可控的特点来提高车辆稳定性的问题,提出了基于滑模变结构控制原理的车辆稳定性分层控制策略。其中,以横摆角速度和质心侧偏角为控制变量,设计了上层附加横摆力矩层。考虑地面附着条件和电机外特性约束,设计了下层动态转矩分配层。通过Simulink与Carsim联合仿真表明,所设计控制策略提高了车辆的稳态行驶能力,增强了车辆的横向稳定性,控制策略行之有效。     

轮毂电机驱动汽车区域极点配置横向稳定性控制

分布式驱动结构给车辆动力学控制带来机遇和挑战,如何可靠地实现其横向稳定性控制是关键技术。考虑车辆参数的不确定性,提出了基于区域极点配置的轮毂电机驱动汽车横向稳定性控制策略,分析了保性能权重矩阵参数对控制性能的影响;为了能最大限度地利用路面附着能力,利用轮毂电机驱动力和制动力共同产生横摆力矩,并结合驱动模型切换提出了规则化转矩分配控制策略;通过数值仿真和硬件在环仿真开展了控制系统的性能分析。结果表明,所提出的基于区域极点配置的上层控制策略不仅能改善汽车的操纵稳定性,而且对轮胎侧偏刚度等参数不确定性具有较强的鲁棒性;同时,下层规则化转矩分配控制策略能确保在低附着路面可靠实现转矩分配。     

4WID/4WIS电动车建模和特殊工况仿真

介绍了四轮独立驱动/四轮独立转向(4WID/4WIS)电动车的特点,基于Matlab/Simulink搭建了各子系统及整车的动力学仿真模型,设置了该类型电动车特有的驾驶模式选择功能。模型允许对4个车轮输入不同的驱动转矩和转角;考虑了驱动电机、转向电机的动态响应特性。针对4WID/4WIS电动车特有的蟹行、斜行和原地转向工况进行了仿真。结果表明,模型能够较好地反映4WID/4WIS电动车的动力学响应特性。     

基于行驶场景模型的线控辅助转向系统仿真

线控转向系统取消了转向盘和转向轮的机械连接,由控制算法折算转向电机驱动转矩并通过电控实现传动比的改变。针对实际转向过程中存在的转向过度或转向不足等问题,本文中在动态输出反馈控制框架下,根据车辆运动学和动力学理论,结合车辆2自由度模型提出了基于行驶场景模型的角传动比动态协调控制机制,建立了线控辅助转向系统的转角控制算法。最终通过转向过程中的速度、加速度、横摆角速度和轨迹的仿真,并与其它转向控制算法和机械转向进行对比,验证了系统对转向过程主动调控和施加补偿或修正控制的有效性与实时性。     

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。     

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。     

转矩式限滑差速器对后轮驱动汽车操纵稳定性影响的研究

采用7自由度车辆动力学模型,对装用JA1020LSD型转矩式限滑差速器的后轮驱动汽车进行了操纵稳定性研究。通过仿真分析和道路试验研究表明:装用限滑差速器后增加了后轮驱动车辆的不足转向趋势,即改善了操纵稳定性,但转向力矩略有增加。     

全轮独立电驱动车辆双重转向控制策略的研究

为全轮独立电驱动车辆提出一种双重转向的控制策略,设计了双重转向的总体控制结构.它是包括三自由度参考车辆模型、横摆力矩确定层和转矩分配层的分层控制体系.在横摆力矩确定层中,设计了基于PID的横摆力矩控制策略;在转矩分配层中,设计了基于纵向驱动力总和不变的转矩分配策略.在此基础上,开发了双重转向控制策略仿真平台,进行了仿真分析和实车试验,试验结果与仿真结果吻合度较高,表明所提出的双重转向控制策略对减小车辆转向半径有明显效果.     

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。     

Dynamics characteristics analysis and control of FWID EV

Compared with internal combustion engine (ICE) vehicles, four-wheel-independently-drive electric vehicles (FWID EV) have significant advantages, such as more controlled degree of freedom (DOF), higher energy efficiency and faster torque response of an electric motor. The influence of these advantages and other characteristics on vehicle dynamics control need to be evaluated in detail. This paper firstly analyzed the dynamics characteristics of FWID EV, including the feasible region of vehicle global force, the improvement of powertrain energy efficiency and the time-delays of electric motor torque in the direct yaw moment feedback control system. In this way, the influence of electric motor output power limit, road friction coefficient and the wheel torque response on the stability control, as well as the impact of motor idle loss on the torque distribution method were illustrated clearly. Then a vehicle dynamics control method based on the vehicle stability state was proposed. In normal driving condition, the powertrain energy efficiency can be improved by torque distribution between front and rear wheels. In extreme driving condition, the electric motors combined with the electro-hydraulic braking system were employed as actuators for direct yaw moment control. Simulation results show that dynamics control which take full advantages of the more controlled freedom and the motor torque response characteristics improve the vehicle stability better than the control based on the hydraulic braking system of conventional vehicle. Furthermore, some road tests in a real vehicle were conducted to evaluate the performance of proposed control method.     

独立轮电驱动车辆主动操纵稳定控制研究

提出了采用变增益参考模型的滑模跟踪控制策略,以横摆角速度和侧滑速度为控制对象,独立控制左右轮驱动力产生直接横摆力矩,提高了车辆在极限工况下的操纵稳定性,并改善了车辆固有的转向特性。改进的滑模控制算法减小了系统抖振并具有较强的鲁棒性。     

电子差速系统轮胎附着特性模拟仿真研究

电子差速系统相对于传统的机械式差速器可以实现转矩的精准分配,根据轮胎的纵向运动特性以及侧向运动特性,结合轮胎滑移率让内外侧车轮在过弯时拥有足够的附着力,减小整车的横摆角速度,提高过弯稳定性。采用后轮双电机的驱动方案,驱动电机采用直接转矩控制的方法,由整车控制器将指定的计算转矩信号发送给电机控制器完成动力分配,所需转矩根据驾驶员的加速踏板及方向盘转角,运用阿克曼转向模型计算得到。     

Vehicle stability control system for enhancing steerabilty,lateral stability,and roll stability

The Vehicle stability control system is an active safety system designed to prevent accidents from occurring and to stabilize dynamic maneuvers of a vehicle by generating an artificial yaw moment using differential brakes. In this paper, in order to enhance vehicle steerability, lateral stability, and roll stability, each reference yaw rate is designed and combined into a target yaw rate depending on the driving situation. A yaw rate controller is designed to track the target yaw rate based on sliding mode control theory. To generate the total yaw moment required from the proposed yaw rate controller, each brake pressure is properly distributed with effective control wheel decision. Estimators are developed to identify the roll angle and body sideslip angle of a vehicle based on the simplified roll dynamics model and parameter adaptation approach. The performance of the proposed vehicle stability control system and estimation algorithms is verified with simulation results and experimental results.     

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.     

一种汽车ESP仿真模型的研究

基于Pacejka的"魔术公式"轮胎模型,建立了包括汽车纵向与横向移动、横摆、侧倾和4个车轮的转动的8自由度动力学模型.设计了由汽车仿真模型和驱动系统、四通道制动系统、制动踏板、转向盘与油门踏板等实物以及控制器(ESP)等部分组成的半实物仿真平台.以侧向加速度与横摆角速度为仿真控制变量对模型进行仿真测试.仿真与实车测试数据相当接近,为ESP的研究提供了有效的模型.     

An investigation on motor-driven power steering-based crosswind disturbance compensation for the reduction of driver steering effort

This paper describes a lateral disturbance compensation algorithm for an application to a motor-driven power steering (MDPS)-based driver assistant system. The lateral disturbance including wind force and lateral load transfer by bank angle reduces the driver's steering refinement and at the same time increases the possibility of an accident. A lateral disturbance compensation algorithm is designed to determine the motor overlay torque of an MDPS system for reducing the manoeuvreing effort of a human driver under lateral disturbance. Motor overlay torque for the compensation of driver's steering torque induced by the lateral disturbance consists of human torque feedback and feedforward torque. Vehicle–driver system dynamics have been investigated using a combined dynamic model which consists of a vehicle dynamic model, driver steering dynamic model and lateral disturbance model. The human torque feedback input has been designed via the investigation of the vehicle–driver system dynamics. Feedforward input torque is calculated to compensate additional tyre self-aligning torque from an estimated lateral disturbance. The proposed compensation algorithm has been implemented on a developed driver model which represents the driver's manoeuvreing characteristics under the lateral disturbance. The developed driver model has been validated with test data via a driving simulator in a crosswind condition. Human-in-the-loop simulations with a full-scale driving simulator on a virtual test track have been conducted to investigate the real-time performance of the proposed lateral disturbance compensation algorithm. It has been shown from simulation studies and human-in-the-loop simulation results that the driver's manoeuvreing effort and a lateral deviation of the vehicle under the lateral disturbance can be significantly reduced via the lateral disturbance compensation algorithm.     

A novel fuzzy logic correctional algorithm for traction control systems on uneven low-friction road conditions

The traction control system (TCS) might prevent excessive skid of the driving wheels so as to enhance the driving performance and direction stability of the vehicle. But if driven on an uneven low-friction road, the vehicle body often vibrates severely due to the drastic fluctuations of driving wheels, and then the vehicle comfort might be reduced greatly. The vibrations could be hardly removed with traditional drive-slip control logic of the TCS. In this paper, a novel fuzzy logic controller has been brought forward, in which the vibration signals of the driving wheels are adopted as new controlled variables, and then the engine torque and the active brake pressure might be coordinately re-adjusted besides the basic logic of a traditional TCS. In the proposed controller, an adjustable engine torque and pressure compensation loop are adopted to constrain the drastic vehicle vibration. Thus, the wheel driving slips and the vibration degrees might be adjusted synchronously and effectively. The simulation results and the real vehicle tests validated that the proposed algorithm is effective and adaptable for a complicated uneven low-friction road.