浅谈汽车的转向系统（二）

三、电液助力转向系统 与前两种转向系统不同．电液助力转向系统的转向助力特性在工作时可以改变．它主要有两种类型电控液压助力转向系统和电动液压助力转向系统．目前汽车上应用最多的是电动液压助力转向系统．     

汽车电动助力转向的控制策略

汽车电动助力转向作为一种新型的动力转向方式,在行车安全、节约能源、保护环境等方面具有传统液压助力转向无可比拟的优势,它取代液压助力转向已是大势所趋。文中就国内外电动助力转向的控制策略进行了研究,并就各自的特点进行了分析说明。     

电动助力转向（EPS）技术研究

电动助力转向系统是一种新型的汽车转向系统,具有以往任何助力转向系统所不具备的助力效果和车速感应能力,其核心部件电控单元能根据车速和方向盘操控力矩的不同决定是否助力以及助力的大小.电动助力转向技术已目趋成熟,它有取代液压动力转向的趋势,是一项紧扣当今汽车发展主题,符合未来汽车发展趋势的高新技术.本文在介绍国内外汽车电动助力转向的发展现状,详细分析了电动助力转向的工作原理,从分析电动助力转向系统的关键技术入手,围绕电动助力转向系统的结构分析和控制策略两大关键技术展开研究分析,为汽车电动助力的发展奠定基础.     

BMW电动机械式助力转向系统原理与典型故障分析

<正>一、液压式和电动机械式助力转向系统的区别液压式和电动机械式助力转向系统的主要区别在于产生助力力矩的方式不同。液压转向系统的特点在于通过内燃机的皮带传动机构或电气方式驱动助力泵。助力泵在液压系统内形成用于产生转向助力的压力或体积流量。电动机械式助力转向系统(EPS)直接通过一个电机产生转向助力,电机将其力矩施加到转向柱或转向器上。因此该系统通常还需要附     

电子控制电动助力转向系统的研究与发展

本文简要介绍了汽车转向系统的发展历程，重点讨论一种新型的转向系统一电子控制电动助力转向系统(EPS)，并同传统的转向系统进行了对比，分析了电动助力转向系统的特性，阐述了电动助力转向系统的基本结构、工作原理和评价指标，指出了电动助力转向系统今后的发展方向和趋势。     

电控汽车转向系统的维修特点

1.转向助力系统的维修按照动力源的不同,电控汽车的转向助力系统划分为液压助力、真空助力和电动助力等3种类型。现代轿车转向系统的发展趋势是采用电动助力。     

汽车电动助力转向技术分析

文中介绍了电动助力转向的发展现状、结构特点和工作原理,分析了电动助力转向的助力特性以及控制策略,并且展望了电动助力转向的发展趋势。     

单片机控制的汽车电动助力转向系统

电动助力转向是一种新型汽车动力转向技术。提出了一种微处理器采用P87C591单片机控制的汽车电动助力转向方案，系统采用闭环电流控制，利用PWM技术调节电机端电压达到控制电机电流(力矩)的目的。实验表明，该系统具有良好的电动助力转向特性。     

汽车电动助力转向系统助力性能的仿真研究

助力性能是评价汽车电动助力转向系统性能的重要指标，助力性能直接关系到汽车转向操作的安全性。以电动助力转向系统的跟踪性能和稳定性为控制系统设计目标，将经典控制理论的PID控制与虚拟样机技术相结合应用于电动助力转向控制系统的设计，创建了电动助力转向系统机电一体化仿真模型。计算机仿真结果证实．所设计的PID控制算法使电动助力转向系统具有良好的跟踪性能和稳定性，仿真结果为电动助力转向控制系统的设计提供了依据。     

电动助力转向系统助力特性研究

概述了电动助力转向系统(EPS)的结构和工作原理,并介绍了电动助力转向系统助力特性的设计方法。在分析了电动助力转向系统各组成部分数学模型的基础上,构建了基于Simulink与carsim的电动助力转向系统仿真模型,仿真结果表明:所设计的助力特性较好地协调了转向轻便性和路感之间的矛盾。     

基于神经网络的电动转向系统助力特性研究

基于综合目标函数的误差反向传播学习算法，设计了用于该离散化转向助力特性的BP神经网络结构，进行了离线训练，并在电动转向综合试验台上实现了在线控制。实现了全车速范围的非线性转向助力，克服了转向助力盲区。     

智能汽车自动紧急转向避撞的跟踪控制方法对比研究

为了提高智能汽车的主动安全性,提出3种不同的自动紧急转向避撞跟踪控制方法。首先建立汽车避撞简化模型,对制动、转向及两者相结合的3种不同避撞方式进行对比分析。其次,为深入研究汽车避撞过程中的实际响应,建立包含转向、制动及悬架3个子系统耦合特性的底盘18自由度统一动力学模型,并进行相关试验验证。随后构建智能汽车自动紧急转向避撞控制框架,对五次多项式参考路径和七次多项式参考路径的横摆角速度和横摆角加速度进行对比分析。接着以线性2自由度转向动力学模型为参考对象,对最优控制四轮转向、最优控制前轮转向、前馈与反馈控制相结合的前轮转向3种不同的跟踪控制系统分别进行设计。最后,以汽车底盘18自由度统一动力学模型为研究对象,对上述3种避撞控制系统进行仿真试验对比分析。研究结果表明：与制动避撞相比而言,转向避撞所需的纵向距离有较大降低,随着车速的增加和路面附着系数的越低,效果越明显;七次多项式参考路径比五次多项式参考路径的避撞过渡过程更为平缓,当实际车速与控制器所用车速不一致时,前者避撞性能表现更优;最优四轮转向控制系统在高、低2种不同附着路面都具有较好的避撞效果,最优前轮转向控制系统次之,而前馈与反馈相结合的前轮转向控制系统在低附着路面上则表现出严重的失稳。     

A theoretical model of speed-dependent steering torque for rolling tyres

ABSTRACT

It is well known that the tyre steering torque is highly dependent on the tyre rolling speed. In limited cases, i.e. parking manoeuvre, the steering torque approaches the maximum. With the increasing tyre speed, the steering torque decreased rapidly. Accurate modelling of the speed-dependent behaviour for the tyre steering torque is a key factor to calibrate the electric power steering (EPS) system and tune the handling performance of vehicles. However, no satisfactory theoretical model can be found in the existing literature to explain this phenomenon. This paper proposes a new theoretical framework to model this important tyre behaviour, which includes three key factors: (1) tyre three-dimensional transient rolling kinematics with turn-slip; (2) dynamical force and moment generation; and (3) the mixed Lagrange–Euler method for contact deformation solving. A nonlinear finite-element code has been developed to implement the proposed approach. It can be found that the main mechanism for the speed-dependent steering torque is due to turn-slip-related kinematics. This paper provides a theory to explain the complex mechanism of the tyre steering torque generation, which helps to understand the speed-dependent tyre steering torque, tyre road feeling and EPS calibration.     

一种减轻装有EPS汽车转向扭矩的控制策略

本文提出了一种新的电动助力转向系统的控制策略,以减小车辆静止时改变方向所需的转向力。以前尝试通过减少不良的转向振动来减少转向扭矩失败的原因是因为高辅助增益往往会产生震荡或增加噪声敏感性。为了消除此种振动,开发出一种基于控制齿轮角速度的控制策略,它是在简化的转向模型的基础上开发出来的。这个实验获得了很好的齿轮角速度的估计值,这样就有可能消除方向盘所有旋转速度下的振动。实验证明在方向盘大转速变换下,转向扭矩显著降低,无振动传输给司机。所提出的控制策略使用一个辅助来获得超过原来的三倍以上的增益。此外,所提出的控制策略不需要补充传感器。     

基于MATLAB/SIMULINK的车轮外倾角对车辆高速转向稳定性的影响研究

基于Matlab/Simulink建立了考虑汽车车身侧倾转向的3自由度仿真模型,研究了车轮外倾角对汽车高速转向稳定性的影响。结果表明前轮正外倾角、后轮负外倾角有利于提高转向稳定性,特别是在大转角的危险工况可以避免发生侧滑和侧翻。     

EPS电动机模型的建立及实现

EPS（电动助力转向系统）应用于众多车型，代表未来动力转向的发展方向。文章通过对EPS的分析，初步设定了用于该EPS的激他式直流电动机方案。通过建立电动机的数学模型，在MATLAB中实现了该模型，并通过仿真分析，进一步验证了该选择方案的正确性。指出所选择建立的电动机模型，对电动助力转向系统仿真分析中电动机模型的建立选择具有一定的借鉴作用。     

Theory and experimental research on six-track steering vehicles

The structural characteristics and steering behaviour of a six-track vehicle are described in this paper. Kinematic analysis for skid steering of a six-track vehicle under steady-state conditions on firm ground is conducted, with the relationship between thrust force and speed instantaneous centre of the track–terrain interface taken into consideration. A mechanical model for steady steering of a six-track vehicle is also presented based on the kinematic analysis. In this model, the steering inaccuracy and efficiency are defined to evaluate steering performance. The steering performance of a six-track vehicle is numerically simulated to analyse the effect of the structural parameters and deflection angles on tracks. A virtual prototype model is established based on the multi-body dynamics software RecurDyn for steering simulation and the findings coincide well with theoretical results. The theory and the virtual prototype simulations presented are verified by a power test of a bucket-wheel excavator. The method for analysing the steering performance of a six-track vehicle proposed in this paper provides a basis for designing a six-track vehicle.     

基于变权重系数的分布式驱动无人车轨迹跟踪

为了提高分布式无人车轨迹跟踪的精度，提出了基于自主与差动协调转向控制的轨迹跟踪方法。首先，在车辆三自由度模型基础上，基于模型预测控制（MPC）实时计算前轮转角以控制车辆进行自主转向轨迹跟踪。在此过程中，为了提高自主转向下车辆的轨迹跟踪精度与行驶的稳定性，考虑多种因素，利用经验公式及神经网络控制对MPC的预瞄步数和预瞄步长进行多参数调整，实现预瞄时间的自适应控制。其次，在恒转矩需求的情况下，以轨迹偏差为PID控制器的输入及左右轮毂电机转矩为输出进行差动转向控制，实现了差动转向下的轨迹跟踪控制。然后，通过设置权重系数的方法将自主与差动转向相结合。考虑到车辆横纵向动力学因素，采用模糊控制及经验公式对权重系数进行了调整，从而在提高车辆转向灵活性与轨迹跟踪效果的同时保证车辆行驶的稳定性。CarSim与Simulink联合仿真以及实车试验结果表明：与自主转向轨迹跟踪相比，采用变权重系数的协调控制可以在不同的工况下提高车辆的转向灵活性与轨迹跟踪的精度，轨迹跟踪偏差的均方根值改善率达到了11%。所提出的协调转向控制方法可为分布式驱动车辆转向灵活性的提高及轨迹跟踪精度的改善提供一种新的思路。     

Steering disturbance rejection using a physics-based neuromusculoskeletal driver model

The aim of this work is to develop a comprehensive yet practical driver model to be used in studying driver–vehicle interactions. Drivers interact with their vehicle and the road through the steering wheel. This interaction forms a closed-loop coupled human–machine system, which influences the driver's steering feel and control performance. A hierarchical approach is proposed here to capture the complexity of the driver's neuromuscular dynamics and the central nervous system in the coordination of the driver's upper extremity activities, especially in the presence of external disturbance. The proposed motor control framework has three layers: the first (or the path planning) plans a desired vehicle trajectory and the required steering angles to perform the desired trajectory; the second (or the musculoskeletal controller) actuates the musculoskeletal arm to rotate the steering wheel accordingly; and the final layer ensures the precision control and disturbance rejection of the motor control units. The physics-based driver model presented here can also provide insights into vehicle control in relaxed and tensed driving conditions, which are simulated by adjusting the driver model parameters such as cognition delay and muscle co-contraction dynamics.     

Vehicle steering returnability with maximum steering wheel angle at low speeds

In this paper, an analytical model with suitable vehicle parameters, together with a multi-body model is proposed to predict steering returnability in low-speed cornering with what is expected to be adequate precision as the steering wheel moves from lock to lock. This model shows how the steering response can be interpreted in terms of vertical force, lateral force with aligning moment, and longitudinal force. The simulation results show that vertical steering rack forces increase in the restoring direction according to steering rack displacement for both the inner and outer wheels. As lateral forces due to side-slip angle are directed toward the medial plane of the vehicle in both wheels, the outer wheel pushes the steering wheel in the returning direction while the inner wheel does not. In order to improve steering returnability, it is possible to increase the total steering rack force in both road wheels through adjustments to the kingpin axis and steering angle. This approach is useful for setting up a proper suspension geometry during conceptual chassis design.