横摆力矩和主动前轮转向结合的车辆横向稳定性模糊控制仿真

提出一种基于横摆力矩和主动前轮转向相结合的车辆横向稳定性控制方法,以横摆角速度和侧偏角为控制目标,利用前馈补偿和模糊控制产生横摆力矩和附加的前轮转角,通过控制制动力的分配以及对转向角的修正,使车辆转向行驶时的横摆角速度和侧偏角很好地跟踪参考模型.对转向轮阶跃输入和正弦输入两种工况分别进行了仿真研究,采用横摆力矩和主动前轮转向相结合控制方法,车辆转向时的瞬态及稳态响应优于单独的横摆力矩控制,表明该方法能有效地控制车辆横摆角速度和侧偏角,提高车辆转向时的横向稳定性,同时能有效地减轻驾驶员操纵负担.     

线控转向系统的主动转向控制策略研究

线控转向系统取消了转向盘和转向轮之间的机械连接,可以对前轮进行主动转向控制以增强操纵稳定性和主动安全性.通过使前轮线控转向系统的期望横摆角速度跟踪稳态质心侧偏角为0的四轮转向车辆的横摆角速度,设计线控转向系统的变传动比,主动控制前轮转角.通过时域响应、转向增益、开环总方差等指标对其进行了性能分析.结果表明:采用提出的主动转向控制策略时稳态质心侧偏角大大降低,开环总方差大大降低,从而提高了汽车的操纵稳定性.     

主动前轮独立转向系统分析与研究

为了提高车辆的操稳性,提出了新型主动前轮独立转向系统,介绍了主动前轮独立转向的工作原理和结构形式,建立了系统数学模型;提出了主动前轮独立转向的控制策略,上层控制器采用PI控制,由横摆角速度偏差得出总控制转角,下层控制器负责内外侧转向轮的判断以及计算内外侧转向轮具体的转角;在仿真软件MATLAB/Simulink里进行了控制策略有效性仿真,仿真结果说明对于不足转向车辆,主动前轮独立转向系统能比传统的主动前轮转向系统更有效地提高车辆操纵稳定性。     

基于横摆率跟踪的4WS车辆闭环操纵稳定性

从车辆操纵稳定性多状态量的响应等方面着手,提出了4WS车辆横摆率跟踪多状态最优控制方案,建立了考虑四轮转向车辆动态响应的闭环操纵稳定性仿真模型,比较了采用横摆角速度多状态最优控制方法与前后轮转向比是车速函数的四轮转向控制方法的操纵稳定特性.结果表明对于使用横摆角速度多状态最优控制的4WS车辆,其转向过程中的侧向加速度和横摆角速度等操纵稳定性瞬态特性均明显优于其它4WS控制方法的车辆,同时保持操纵稳定性的稳态特性不变.     

提高车辆安全性的输出反馈自适应控制

研究含有时变参数的车辆动力学模型的输出跟踪控制问题.控制目标是使车辆的横摆角速度和质心侧偏角分别跟踪理想的设定值,通过反推方法设计输出反馈自适应控制器.控制器的输出为主动横摆力矩,通过控制主动横摆力矩来控制车辆的输出响应跟踪理想的输出信号,从而提高车辆的安全性.仿真结果表明,控制器能更好地适应车速和路况的变化,鲁棒性强.

     

基于模糊控制的汽车直接横摆力矩研究

为防止汽车产生测滑,针对汽车直接横摆力矩控制,提出了横摆角速度与质心侧偏角联合控制的模糊控制方法.横摆力矩控制采用分层控制方法,设计了模糊控制器和规则制动力分配方法.模糊控制器根据期望值和车辆状态决策出所需的附加横摆力矩,并通过规则制动力分配方法进行主动差动制动实现.采用Matlab/Simulink与CarSim联合仿真对控制方法进行了仿真验证.结果表明:横摆角速度与质心侧偏角联合控制的横摆力矩模糊控制方法使汽车能够较好地跟踪期望,有效提高汽车极限工况下的行驶稳定性.     

提高车辆安全性的输出反馈自适应控制

研究含有时变参数的车辆动力学模型的输出跟踪控制问题.控制目标是使车辆的横摆角速度和质心侧偏角分别跟踪理想的设定值,通过反推方法设计输出反馈自适应控制器.控制器的输出为主动横摆力矩,通过控制主动横摆力矩来控制车辆的输出响应跟踪理想的输出信号,从而提高车辆的安全性.仿真结果表明,该控制器能更好地适应车速和路况的变化,鲁棒性强.     

一种新型的轮胎力级联估计方法

为了增强车辆主动安全性和底盘的集成控制,根据干扰输入观测器理论,基于简化的车轮动力学模型设计估计器,对每个轮胎纵向力进行估计.此外,基于"自行车"模型,利用车辆动力学,在纵向轮胎力估计值的基础上估计轮胎侧向力.涉及到的车载传感器测量值包括发动机扭矩和转速、轮缸压力、车轮角速度、方向盘转角、侧向加速度和横摆角速度.为验证轮胎力级联估计方法的有效性,应用高保真的车辆动力学软件ve DYNA进行了仿真研究,并与扩展卡尔曼滤波(extended Kalman filter,EKF)方法作对比分析.实验结果表明,轮胎力级联估计方法能够获得车辆轮胎力的估计效果.     

一种基于前馈－反馈复合控制方式的制动稳定性控制方法

设计了一种前馈—反馈复合控制结构，将直接横摆力矩控制和主动前轮转向控制相结合以提高制动稳定性．控制器将前轮转向角视为输入，将外部侧向干扰力和力矩作用视为扰动，通过前馈校正补偿转向角引起的状态变化；同时建立扰动状态观测器，采用反馈控制校正消除外部扰动引起的状态误差．仿真试验证实这种控制方法在提高制动稳定性方面有良好的效果．     

基于终端滑模控制的电动汽车转向稳定性研究

针对电动汽车转向时的稳定性问题,以双轮毂电机电动汽车为研究对象,利用线性二自由度车辆模型得到理想参数,提出了基于横摆角速度的终端滑模横摆力矩控制。同时利用Simulink搭建了整车七自由度的车辆模型,通过低速和高速两种情况来进行算法验证。仿真结果表明,上述算法相对于垂直载荷力矩控制和传统滑模控制而言,能够有效的减少目标参数趋于稳定的时间,抗干扰能力强。力矩分配之后输出力矩作用于轮毂电机,便可以有效的保证车辆运行转向时的安全性和稳定性。     

Motion Control of a 6WD/6WS wheeled platform with in-wheel motors to improve its maneuverability

Multi-axle driving mobile platform that are favored in special environments require high driving performance, steering performance, and stability. Among these, six wheel drive and six wheel steering vehicles hereinafter called 6WD/6WS, gain structural safety by distributing the load and reducing the pitching motion during rapid acceleration and braking. 6WD/6WS mobile platforms are favorable for military use, particularly in off-road operations because of their high maneuverability and mobility on extreme terrains and obstacles. 6WD vehicles that use in-wheel motors can generate independent wheel torque without a need for additional hardware. Conventional vehicles, however, cannot generate an opposite driving force on wheels on both sides. In an independent steering and driving system six-wheel vehicles show better performance than conventional vehicles. This paper discusses the improvement of the cornering performance and maneuverability of 6WD/6WS mobile platform using independent wheel torque and independent steering on each wheel. 6WD/6WS vehicles fundamentally have satisfactory maneuverability under low speed, and sufficient stability at high speed. Consequently, there should be a control strategy for improving their cornering performance using the optimum tire forces that satisfy the driver’s command and minimize energy consumption. From the driver’s commands (i.e., the steering angle and accelerator/brake pedal stroke), the desired yaw moment with virtual steering, desired lateral force, and desired longitudinal force are obtained. These three values are distributed to each wheel as torque and steering angle, based on the optimum tire force distribution method. The optimum tire force distribution method finds the longitudinal/lateral tire forces of each wheel that minimize cost function, which is the sum of the normalized tire forces. This paper describes a 6WS/6WD vehicle with improved cornering performance and the results are validated through TruckSim simulations.

     

Yaw Moment Control Strategy for Four Wheel Side Driven EV

When four wheel side driven EV travals in steering or changes lanes in high speed, the vehicle is easy to side-slip or flick due to the difference of wheel hub motor and a direct effect of vehicle nonlinear factors on vehicle yaw motion, which would affect vehicle handling and stability seriously. To solve this problem, a joint control strategy, combined with the linear programming algorithm and improved sliding mode algorithm, which combines the exponential reaching law and saturation function was proposed. Firstly, the vehicle dynamics model and the reference model according with the structure and driving characteristics of four wheel side driven EV were set up. Then, introduced the basic method of the improved sliding mode variable structure control and complete the sliding mode variable structure controller design basic on vehicle sideslip angle and yaw velocity.The controller accomplish optimal allocation of vehicle braking force through a linear programming algorithm, according to yaw moment produced by the vehicle motion state. Single lane driving simulation results show that the proposed control strategy can not only control vehicle sideslip angle and yaw velocity well, but also accomplish good controlling of the vehicle yaw moment, so as to significantly improve the handling and stability of vehicle.     

Disturbance Observer Based Control for Four Wheel Steering Vehicles With Model Reference

This paper presents a disturbance observer based control strategy for four wheel steering systems in order to improve vehicle handling stability. By combination of feedforward control and feedback control, the front and rear wheel steering angles are controlled simultaneously to follow both the desired sideslip angle and the yaw rate of the reference vehicle model. A nonlinear three degree-of-freedom four wheel steering vehicle model containing lateral, yaw and roll motions is built up, which also takes the dynamic effects of crosswind into consideration. The disturbance observer based control method is provided to cope with ignored nonlinear dynamics and to handle exogenous disturbances. Finally, a simulation experiment is carried out, which shows that the proposed four wheel steering vehicle can guarantee handling stability and present strong robustness against external disturbances.      

Fault‐tolerant path‐following control for in‐wheel‐motor‐driven autonomous ground vehicles with differential steering

Over the past several decades, the automobile industry has denoted significant research efforts to developing in‐wheel‐motor‐driven autonomous ground vehicles (IWM‐AGVs) with active front‐wheel steering. One of the most fundamental issues for IWM‐AGVs is path following, which is important for automated driving to ensure that the vehicle can track a target‐planned path during local navigation. However, the path‐following task may fail if the system experiences a stuck fault in the active front‐wheel steering. In this paper, a fault‐tolerant control (FTC) strategy is presented for the path following of IWM‐AGVs in the presence of a stuck fault in the active front‐wheel steering. For this purpose, differential steering is used to generate differential torque between the left and right wheels in IWM‐AGVs, and an adaptive triple‐step control approach is applied to realize coordinated lateral and longitudinal path‐following maneuvering. The parameter uncertainties for the cornering stiffness and external disturbances are considered to make the vehicles robust to different driving environments. The effectiveness of the proposed scheme is evaluated with a high‐fidelity and full‐car model based on the veDYNA‐Simulink joint platform.     

四轮转向车辆转向解耦的双点跟踪控制

针对四轮转向(4WS)无人车辆路径跟踪中的过约束问题, 本文提出一种前后轮转向解耦的双点跟踪控制策略. 建立4WS车辆单轨运动学模型, 约束前后轮转向角速度, 规划曲率连续的回旋曲线参考位姿序列, 将其解耦为前后轴中心的双点参考轨迹; 以前后轮中心点为控制点, 采用非线性反馈控制的预瞄方法分别获得转向控制率, 双点跟踪误差指数收敛于0. 仿真和实车验证结果表明, 所提出的双点跟踪控制策略横向误差标准差减少0.2 m, 横摆角误差标准差减小3.0?, 具有更大的前后轮转角控制域和较高的跟踪精度     

Coupled nonlinear vehicle control: Flatness-based setting with algebraic estimation techniques

A combined nonlinear longitudinal and lateral vehicle control is investigated. Flatness-based nonlinear control and new algebraic estimation techniques for noise removal and numerical differentiation are the main theoretical tools. An accurate automatic path-tracking via vehicle steering angle and driving/braking wheel torque is thus ensured. It combines the control of the lateral and longitudinal motions in order to track straight or curved trajectories and to perform a combined lane-keeping and steering control during critical driving situations such as obstacle avoidance, stop-and-go control, lane-change maneuvers or any other maneuvers. Promising results have been obtained with noisy experimental data, which were acquired by a laboratory vehicle with high dynamic loads and high lateral accelerations.     

Lane-keeping assistance control algorithm using differential braking to prevent unintended lane departures

This paper describes a hierarchical lane keeping assistance control algorithm for a vehicle. The proposed control strategy consists of a supervisor, an upper-level controller and a lower-level controller. The supervisor determines whether lane departure is intended or not, and whether the proposed algorithm is activated or not. To detect driver′s lane change intention, the steering behavior index has been developed incorporating vehicle speed and road curvature. To validate the detection performance on the lane change intention, full-scale simulator tests on a virtual test track (VTT) are conducted under various driving situations. The upper-level controller is designed to compute the desired yaw rate for the lane departure prevention, and for the guidance with ride comfort. The lower-level controller is designed to compute the desired yaw moment in order to track the desired yaw rate, and to distribute it into each tire′s braking force in order to track the desired yaw moment. The control allocation method is adopted to distribute braking forces under the actuator’s control input limitation. The proposed lane keeping assistance control algorithm is evaluated with human driver model-in-the-loop simulation and experiments on a real vehicle.     

基于流入角实时变化的气动性对操纵稳定性的影响

为研究汽车受侧风影响时风压中心线位置对整车操纵稳定性的影响,在CCM+软件中计算不同风速和不同流入角下的气动力,获得气动力与风速和车速的合速度以及流入角的初始关系曲线.利用MATLAB和Adams/Car联合仿真,搭建空气动力学和车辆动力学的双向耦合模型,以风压中心线与质心的距离为变量进行仿真分析.结果 显示,随着风压中心线由质心前方移动到质心后方:在开环仿真工况中,车辆的侧向位移会减小,但是如果风压中心线位于车辆后方超过一定的距离,车辆会在气动力产生的横摆力矩作用下向另外一侧偏移;闭环仿真工况中,当风压中心线穿过车辆质心时,由于侧向力的存在,方向盘依然需要一个很小的转角以维持直线行驶,风压中心线需要继续后移以保证方向盘稳态时的回正.     

线控转向系统力反馈的研究

线控转向系统取消了转向盘与转向轮的机械连接,所以必须通过电机向驾驶员实时反馈路感,从而使驾驶员感知车辆行驶状态和路面状况.首先建立了包括驾驶员在内的转向盘力反馈模型.提出的路感控制策略包括上层控制策略和下层控制策略.上层控制策略中转向盘回正力矩建模为扭杆弹簧施加的回复力矩,与转向盘转角成线性;下层控制策略对电机电流进行比例积分控制.最后研究了不同驾驶员模型比例系数,积分系数和电流比例积分控制的比例系数,积分系数对转向盘转角跟踪性能的影响.结果表明,遗传算法优化得到的这四个参数,可使得驾驶员较好跟踪转向盘转角,路感电机电流较好跟踪目标电流,实现较好的力反馈.     

四轮独立驱动电动汽车单轮失效稳定性控制

为了解决四轮独立驱动电动汽车驱动系统失效时的转矩分配问题,提出了一种基于规则的驱动力控制分配策略以保证车辆在出现单轮失效情况下的稳定性和动力性。控制器采用双层控制,包括上层控制和下层控制。在上层控制中,根据驾驶员的输入与车辆状态,采用滑模控制理论计算出控制横摆角速度和质心侧偏角的附加横摆力矩。在下层控制中,根据驱动电机失效程度,考虑各约束条件,将计算出的附加横摆力矩合理地分配给各个驱动轮。利用Carsim和MATLAB/Simulink的联合仿真,选择直线、转弯以及Sine wave等工况对提出的转矩分配控制策略进行仿真分析,仿真结果表明所提控制策略能够在提高驱动系统利用率和消除前轮左右输出转矩不同对方向影响的基础上保证车辆的稳定性。