4WS整车虚拟样机建模与动力学仿真

为了改善汽车在高速行驶转弯时的操纵稳定性,运用动力学仿真软件ADAMS,在其专业汽车模块ADAMS/CAR下研究了4WS汽车建模及其瞬态和稳态操纵动力学特性。以质心侧偏角和横摆角速度响应为评价指标,在角阶跃输入下高速转弯时,对前后轮转角成比例关系的4WS汽车和FWS汽车分别做了动力学仿真研究。对比分析了两者的质心侧偏角和横摆角速度响应特性,从分析结果得出,后轮主动参与转向,总体上有助于改善汽车在高速行驶转弯时的动力学响应特性,但是不同的因素也会对操纵稳定性产生不利的影响。     

重型车辆流量控制式ECHPS系统建模与仿真

关于车辆转向液压系统优化控制问题,针对重型商用车辆传统的具有固定助力特性的HPS系统存在的高速时转向操纵安全性差的问题,提出一种旁通流量控制式电控液压助力转向(ECHPS)系统,建立了ECHPS的机械和液压子系统模型及整车二自由度动力学模型。分析了转向系统可变助力特性的设计要求,建立了ECHPS助力特性MATLAB/Simulink仿真模型,通过仿真计算得到了ECHPS在不同车速下的转向助力特性曲线。仿真结果表明,所设计的ECHPS可变助力特性同时满足了低速时的转向轻便性要求和高速时的良好转向"路感"和操纵稳定性,并得到旁通流量与车速的关系曲线为设计ECHPS旁通流量阀开度的控制策略提供了基本依据。     

遗传算法优化线控转向系统角传动比的研究

线控转向系统取消了转向盘与转向轮的机械连接,可以根据车况灵活改变角传动比以提高汽车的操纵稳定性.首先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、二自由度整车模型.然后研究了包括轨道误差总方差、方向误差指标、驾驶员转向负担三项指标的开环总方差.最后利用遗传算法,以开环总方差为适应度函数,对不同车速下的传动比进行优化.结果表明,各车速下的传动比使得开环总方差较小,提高了车道跟踪性能、方向稳定性能.降低了驾驶员的转向负荷,从而提高汽车的操纵稳定性.     

匀变速工况下汽车的转向特性仿真研究

为了研究转向工况下的汽车操纵稳定性问题,由于受到外界环境干扰和转弯离心力的影响,为保证行驶的稳定性,需准确获得变速转向工况下的动力特性,建立汽车转向工况下匀变速运动的线性二自由度动力学模型,并从整车控制的角度出发,以横摆角速度作为判据,用仿真分析模型。为提高汽车的响应特性,进行了匀变速工况下汽车的转向仿真研究。仿真结果表明,在匀加速转向时,汽车的横摆角速度响应是逐渐增加;在匀减速转向时,汽车的横摆角速度响应逐渐减小,可为汽车在转向工况下的操纵控制提供有益的参考。     

电动汽车线控转向系统性能分析与参数优化

研究电动汽车操纵稳定性优化问题,电动汽车采用线控转向系统,可靠性差,成本高.为提高操纵稳定性和主动安全性,提出对设计的线控转向系统的实体结构进行适当简化,建立了电动汽车线控转向系统的动力学模型.然后,研究了电机及减速器等的结构参数对系统频率响应特性和时域响应特性的影响,进行了电动汽车线控转向系统性能分析.最后,对系统的稳定性条件,采用非线性带约束优化算法进行了电动汽车线控转向系统的参数优化仿真.结果表明,经过参数优化后,电动汽车的操纵稳定性大大提高,可用于指导转向系统的参数设计与匹配.     

考虑高速公路横向坡道转向行驶操纵稳定性的汽车轴距和轮距分析

为分析汽车轴距和轮距设计对操纵稳定性的影响,建立高速公路横向坡道转向行驶的汽车转向动力学模型,并在MATLAB/Simulink软件中建立相应的仿真模型.采用某型汽车设计轴距和轮距进行仿真,得到以不同速度在不同横向坡度道路上转向行驶时的横摆角速度、侧向加速度和质心侧偏角.根据该型汽车的转向特性和侧翻阈值评价其在高速公路...     

汽车线控转向系统的建模与仿真研究

研究汽车转向稳定性控制问题。针对线控转向系统的可变转向特性对汽车操纵影响稳定性,为保证行驶安全性,通过分析线控转向系统的工作原理和结构特点,建立线控转向系统各组成部分的数学模型,结合驾驶员模型和整车模型,对线控转向系统的可变角传递特性和力传递特性进行仿真。仿真结果表明:SBW系统能够获得与传统转向系统同样清晰的路感,并且SBW系统能够保持稳定的转向灵敏度,从而改善了汽车的稳定性,为保证行驶的安全提供了依据。     

电液耦合转向系统建模与控制方法研究

电液耦合转向(EHCS)系统是同时具备电动助力和液压助力的新型转向系统,是提高商用车转向性能的一种方案.目前该系统工程化缺乏理论研究,为满足转向系统转向路感、转向轻便性、操纵稳定性及主动回正等性能要求,提出基于助力特性曲线设计,结合模糊PID控制的双层控制策略.完成控制器设计以后,在分析系统各部分数学模型基础上,构建了Simulink/Trucksim联合仿真模型并对结果进行仿真.结果 表明:模糊PID控制下不同车速的电机实际电流跟踪性能满足要求,设计的助力特性使EHCS相较于传统转向系统具有更好的转向性能,验证了控制策略的有效性.     

四轮转向汽车最优转向控制研究

为了充分发挥四轮转向技术在改善汽车操纵稳定性方面的优势,对汽车转向的理想状态进行分析,构建理想转向模型。依据具有二次型性能指标的最优控制理论,以汽车转向理想模型作为跟踪目标,采用基于状态反馈和前轮前馈的控制策略,对四轮转向汽车后轮转向控制规律进行研究。利用Matlab工具,对所提出的后轮转向最优控制方法进行仿真。仿真结果表明：所设计的后轮转角最优控制器改善汽车转向的瞬态与稳态响应特性,其瞬态响应的超调量减少,稳定时间缩短;侧向滑移的稳态值有所降低,从而提高汽车转向的操纵稳定性。     

四轮线控转向系统的转向控制策略研究

为了控制汽车的质心侧偏角,同时保持汽车的转向增益不变,研究了四轮线控转向系统的后轮转向控制策略和前轮转向控制策略.首先建立了四轮转向整车二自由度模型,然后基于稳态质心侧偏角为零得到两种后轮转向控制策略:与前轮转角成比例型和横摆角速度反馈型,前者不改变系统极点,后者改变系统极点.基于转向增益不随车速改变得到二者的前轮转向控制策略.仿真表明,提出的前轮转向控制策略可以保持固定转向增益,降低驾驶员负担;后轮转向控制策略可以实现零质心侧偏角稳态值,控制车辆姿态,改善操纵稳定性.     

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.      

Directional control–response compatibility of joystick steered shuttle cars

Shuttle cars are an unusual class of vehicle operated in underground coal mines, sometimes in close proximity to pedestrians and steering errors may have very serious consequences. A directional control–response incompatibility has previously been described in shuttle cars which are controlled using a steering wheel oriented perpendicular to the direction of travel. Some other shuttle car operators are seated perpendicular to the direction of travel and steer the car via a seat mounted joystick. A virtual simulation was utilised to determine whether the steering arrangement in these vehicles maintains directional control–response compatibility. Twenty-four participants were randomly assigned to either a condition corresponding to this design (consistent direction), or a condition in which the directional steering response was reversed while driving in-bye (visual field compatible). Significantly less accurate steering performance was exhibited by the consistent direction group during the in-bye trials only. Shuttle cars which provide the joystick steering mechanism described here require operators to accommodate alternating compatible and incompatible directional control–response relationships with each change of car direction.

Practitioner Summary: A virtual simulation of an underground coal shuttle car demonstrates that the design incorporates a directional control–response incompatibility when driving the vehicle in one direction. This design increases the probability of operator error, with potential adverse safety and productivity consequences.     

整车建模和转向性能分析

转向性能研究中一般会更多地关注方向盘力矩的变化。所以,转向系统对分析精度起决定性影响,必须建立详尽的模型来描述其内部特性,如惯性、刚度、摩擦、阻尼和助力曲线,这些因素对方向盘力矩变化有非常显著的影响,以致影响转向性能。本文阐述了在AMESim软件中建立液压助力转向系统和整车模型的过程。首先提出了一种新的计算转向阀过流面积的方法,以获得真实的转向助力特性,然后建立了包含这个比较详尽的转向系统的整车动力学模型,用于转向性能研究,最后选用了几种实车道路试验结果来验证此模型的准确性。     

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.     

汽车驾驶模拟器转向盘回正系统设计

在汽车驾驶模拟器的研发中,对于转向盘回正系统的模拟,可以增强驾驶员操作时的触感,使交通安全实验数据更加可靠.从转向盘回正力矩数学模型研究出发,采用直流力矩电机作为模拟系统中回正力矩的生成部件,设计了整个转向盘回正模拟系统的组成,提出了相应的控制策略.     

基于神经网络的室外移动机器人前轮转向模型

针对室外移动机器人的行驶特点,将车体模型划分为前轮转向模型、速度模型和位姿 模型三个部分.提出用模糊集合与神经网络相结合来建立车体前轮转向模型的方法.首先将对 前轮转向特性影响较大的行车速度模糊化,然后利用神经网络建立各模糊速度下的前轮转向模 型,最后由逆模糊化过程求得模型的实际输出.实验结果表明,该方法能较准确地反映车体的前 轮转向特性并具有鲁棒性强和易于实现的特点.     

基于电动轮的多轴全轮转向汽车驱动控制研究

本文就一种基于电动轮控制的多轴车的全轮转向系统的优点进行了概述。所介绍的这种多轴车的特点是：采用电动轮驱动、电动助力转向系统和全轮转向系统。电动轮驱动有效地提高了多轴车的经济性和环保性;电动助力转向系统则有效地改善了驾驶空间的布置,为汽车的轻量化、电子化和经济性研究提供了有利条件;全轮转向系统的双相位转向有效地改善了多轴车的转向问题,提高了汽车转向的通过性和平顺性。     

双舵机模糊控制在智能车控制中的应用

在智能车系统的设计中,转向控制直接影响着智能车的性能,若采用普通的PID控制算法,前车轮在不断的偏转过程中连续性并不是很理想。提出了模糊控制算法,并且在硬件上采用双舵机分别实时地控制每一个前轮的转角,有效地解决了系统的快速性与稳态误差之间的矛盾。大量的实验结果表明,该方法可以明显地提高智能车系统的性能。     

Vehicle Dynamics Modeling and Electronic Stability Program/ Active Front Steering Sliding Mode Integrated Control

Chassis integrated control can significantly improve vehicle handling stability and comfort. Because of the complexity of the problem, it has attracted significant research attention. We built a vehicle nonlinear dynamic model with multi‐degree freedom, including body movement, wheel movement, and electronically controlled hydraulic power steering system. We compared the magic formula tire model, Dugoff tire model, brush tire model, and LuGre dynamic friction tire model and steady model. The precision of the model was verified by a comparison between simulation results and the real vehicle test results. Then, based on the vehicle dynamics model, an AFS (active front steering) controller was designed based on sliding mode variable structure control, and an AFS and ESP (electronic stability program) integrated coordination controller was proposed. Finally, based on the nonlinear tire model and multi‐DOF (degree of freedom) vehicle model, sinusoidal and step steering angle input simulation analysis was proposed on different road friction coefficients. The results show that the vehicle has better response characteristics with coordinated control strategy when compared with AFS and ESP only control. The evidence suggests that the proposed integrated control system in this paper can improve vehicle stability and safety.     

Control strategy of a novel electric power steering system integrated with active front steering function

A novel electric power steering system(EPS) integrated with active front steering(AFS) is developed.It has functions of both AFS system and EPS system with two actuator units:the AFS actuator unit and the EPS actuator unit.The AFS actuator unit controls the displacement transfer behavior of the steering system,and improves the handling stability under adverse road conditions by varying the steering ratio directly related to the speed and road conditions.The EPS actuator unit controls the force transfer beha...