线控转向系统动力学模型的研究

准确简单的线控转向系统动力学模型是研究线控转向的各种控制策略和参数匹配的基础.建立了线控转向系统的人-车-路闭环动力学模型,包括道路模型、驾驶员模型、控制器模型、转向盘总成模型、整车模型(包括车身模型、轮胎模型)及前轮转向总成模型等.基于以上模型,研究了驾驶员模型参数:驾驶员的补偿转向增益和认知时间延迟引起的死区时间变化对实际侧向偏移到目标侧向偏移的传递函数频率响应的影响.结果表明,选择不同的参数对线控转向系统的操纵稳定性影响较大,应合理选择相关参数.     

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.     

电动物料搬运车动力转向技术的发展现状

叙述了各种动力转向系统的结构、特点、分类及应用;介绍了动力转向领域相关现状的研究工作,重点介绍了电动液压助力转向系统和电动助力转向系统的性能特点、国内外的发展及研究现状,探讨动力转向技术的发展趋势.     

Fault-tolerant automobile steering based on diversity of steer-by-wire, braking and acceleration

Steer-by-wire (SBW) systems, which have no mechanical linkage between the steering wheel and front wheels, are expected to improve vehicle safety through better steering capability. SBW system failures, however, can cause hazardous driving situations. This paper introduces fault-tolerant architecture based on diversified steering mechanisms consisting of SBW backed up with steering by braking and acceleration during SBW failures. These backup steering functions are chosen according to driver's intention of deceleration and acceleration. A loss of SBW function during front-obstacle avoidance on a straight highway is investigated by driving simulator experiments. The results show that the driver can maneuver the vehicle by the steering wheel during the SBW failures. Both cost and volume increase by excessive redundancy within SBW is avoided by the diversified design, thus facilitating SBW application on new-generation vehicles.     

线控转向系统瞬时故障容错控制

针对车辆线控转向系统(steer by wire,SBW),提出了一种基于系统模型的瞬时故障层次化容错控制方法,用于提高线控转向控制的可靠性。首先分析了SBW系统结构特点和工作原理,然后给出了SBW系统的系统模型,提出了瞬时故障容锚控制框架,详细设计了SBW系统节点级和系统级的瞬时故障容错控制机制,最后利用AADL(Architecture Analysis and Design Language)-Ocarina搭建了SBW仿真系统,对提出的容错方法进行仿真验证。仿真结果表明,本文提出的层次化容错控制方法能够有效地检测SBW系统瞬时故障,实现容错控制,提高系统运行可靠性。     

Geared PM coreless motor modelling for driver’s force feedback in steer-by-wire systems

Gearboxes allow for changes in the motor’s torque and speed ranges, thus allowing the motor to function at its best operation ranges. As a consequence, smaller and low cost motors can be used in comparison with direct drive motors. Nevertheless, gearboxes introduce nonlinearities to the system such as friction, backlash and flexibility. When geared motors are employed, a controller using a torque sensor or a torque observer is normally required to compensate for the drawbacks associated with the gearbox and the servo-amplifier. The design of such a controller requires the comprehensive knowledge of the system’s dynamics. In this paper, a general approach to model accurately amplifier–motor–gearbox assemblies has been developed. This approach that takes into account backlash, flexibility, friction for stiction and sliding, identification procedures, is applicable to a wide range of amplifier–motor–gearbox assemblies. It is explained by applying it to a particular case: an amplifier–motor–gearbox assembly for a driver’s force feedback system. In the design of driver’s force feedback systems for steer-by-wire systems or for high fidelity Human in the Loop (HiL) driving simulators, either direct drive motors or geared motors are used, independently of the motor type. The assembly considered here is composed of a two stage planetary gearbox, a coreless PMDC motor and a linear four quadrant servo-amplifier. It is installed in an X-by-wire (XBW) vehicle prototype, Both the amplifier and the mechanical components were built in the model. The four quadrant operating modes of the amplifier were taken into account. Friction within both the motor and the gearbox are modelled using a modification of the LuGre friction model that allows friction to be considered as load-dependent. Backlash and flexibility in the gearbox are considered together using a fifth order polynomial for each rotational direction. The identification procedures necessary to calculate the parameters of the model are presented. Because all the parameters of the model have a direct physical significance, these identification procedures are easy to realize. Comparisons between simulations realized with Simulink and the experimental data for three typical driving situations show that the model is highly accurate at representing real system dynamics.     

基于线控转向系统操作稳定性的研究

针对汽车线控转向系统的操作稳定性问题,研究了固定转向灵敏度型与γ和β联合控制策略,之后设计了基于dSPACE的线控转向硬件在环仿真实验台架对算法进行实验验证.按照国家标准中转向瞬态响应实验中的要求,验证了汽车在此控制策略下的操纵稳定性能     

线控转向系统全状态反馈控制策略的研究

为了根据车况和驾驶员喜好实现最优的操纵特性(不足转向、过度转向和中性转向),需要主动控制前轮转角.线控转向系统利用车辆全状态(横摆角速度和质心侧偏角)反馈控制策略优化驾驶员的转向输入,主动控制前轮转角来优化车辆的转向特性,高速时具有适当的不足转向特性,低速时具有适当的过度转向特性,从而在反应快速和安全性之间很好的权衡.其中通过状态观测器估计侧偏角.结果表明,在紧急操纵时可以代替驾驶员协调使车辆保持稳定,正常操纵时补偿物理参数或操纵条件的变化而保持操纵特性的一致.