6×6无人地面车辆差速转向分析与优化

差速转向越来越多的被应用于无人地面车辆,介绍了差速转向相比于传统转向轮转向的一些优势,并对差速转向进行了简单的运动学分析.差速转向消耗的功率大,提出通过调整悬架装置改善转向效率,并对车辆悬架调整前后的模型进行静力学分析.     

独立悬架车辆转向轮侧滑及检测设备适应性分析

从侧向力的角度分析了转向桥为独立悬架的车辆转向轮侧滑的产生机理,对目前常用的两种独立悬架车辆转向轮侧滑试验台的适应性进行了研究分析,提出了改造建议。     

轿车随动悬架侧倾转向特性的初步研究

为进一步改善高速行驶汽车的直线稳定性及转向特性，人们对悬架的转向效应给予了更多的关注，各具有转向功能的悬架系统在轿车上变得更加完善，随动式悬架就是其中之一，本文对具有随动转向功能的悬架系统－雪铁龙ZX系列轿车随动悬架转向原理及转向特性作了分析，并着重研究了随动悬架的侧倾转向效应对汽车操纵性能的影响，得出了初步结论。     

基于统一模型的转向-悬架系统最优综合控制方法

通过对车辆底盘系统中的转向和悬架系统建立统一的数学模型,利用M atlab/S imu link仿真,结合最优控制理论,分别对被动悬架兼前轮转向系统与主动悬架兼四轮转向综合控制系统进行了对比研究。理论分析与仿真试验表明,综合控制系统下车辆的操纵稳定性和平顺性都得到了很大的提高。     

分段式转向梯形断开点的优化设计

文章建立了某轮式车辆的前独立悬架和转向系统的参数化模型,阐述了分段式梯形断开点设计需要遵循的两点原则,分析了断开点三个方向坐标对阿克曼转向特性以及车轮跳动过程中前束角变化的影响,以实际外轮转角与理论外轮转角差值最小以及前束角变化最小为优化目标,对断开点位置进行了优化分析。研究结果表明,断开点坐标的优化可以改善车辆转向特性,同时提高转向系统与悬架系统的运动协调性,为轮式车辆转向梯形的设计提出了较为合理的优化方案。     

车辆半主动悬架与助力转向集成控制的仿真研究

为协调车辆操纵稳定性和行驶平顺性,基于底盘系统动力学原理,建立了半主动悬架和电动助力转向的综合模型,对半主动悬架和电动助力转向系统进行集成控制.运用二次反馈法和PID策略分别对悬架的可调阻尼和转向系统的助力进行控制.仿真结果表明,在集成控制情况下,车辆的操纵稳定性和平顺性均优于悬架或转向单独控制的效果.     

大功率履带推土机的差速转向技术

应用运动学分析的方法,对大功率履带推土机差速转向机构的工作原理及使用特点进行了讨论与分析.由此得出转向液压马达的旋转方向决定了推土机转向的方向,转向液压马达的旋转速度决定了推土机转向半径的大小,同时说明了差速转向机构具备转向轻便、转弯半径小、不需维护与调整的优点.结果表明差速转向技术比传统的转向离合器-制动器式转向技术具有更大的优越性.     

独立悬架车辆转向轮侧滑检测调整方法分析

通过对独立悬架车辆向轮侧滑检测与调整方法分析，解释了独立悬架车辆的经侧滑一次检测合格率低；车辆前轮定位值符合说明书规定值，前轮侧一却较大；以及某些车辆轮侧滑量符合要求，却仍出现前前轮方向飘，轮胎异常磨损等现象。     

四轮独立驱动轮毂式电动汽车转向控制策略研究

对四轮独立驱动轮毂式电动汽车转向控制策略进行研究,建立了整车控制系统,提出了基于滑模变结构算法的转速转矩协调控制策略;基于Ackermann-Jeantand转向模型计算车辆转向所需的四轮差速,通过滑模控制器和转矩分配模块计算车辆稳定所需的四轮转矩,在车辆差速行驶的同时协调分配四轮的转矩。仿真结果表明,该控制方法简单有效,能提高电动汽车转向的稳定性和操纵性。     

悬架转向特性的汽车操纵稳定性分析

为进一步改善汽车直线行驶稳定性及转向行驶特性，近年来，人们对悬架系统的导向功能给予了更多的关注，具有转向功能的悬架系统相继得到发展。钢板弹簧县架系统“轴转向”效应的应用；前后轮转向主动控制的四轮转向（４ＷＳ）系统；以及使悬架系统具有合适的变形转向功能，其中，多链节（多连杆）悬架结构和雪铁龙ＺＸ系列轿车的随动悬架便是代表。本文对这些结构各异的悬架系统的转向特性进行了对比分析，着重分析了雪铁龙ＺＸ系列     

汽车操纵稳定性与前轮摆振的非线性仿真分析

以某轿车为例,建立3自由度整车系统动力学模型,利用常微分方程稳定性理论和数值仿真计算,详细研究整车的稳态转向特性和系统失稳后的前轮摆振特性。阐明汽车的操纵稳定性与前轮摆振特性同属汽车整车稳定性问题,前者是负刚度系统,后者是负阻尼系统。在一定的参数组合下,具有不同转向特性的汽车都或多或少地存在摆振现象,这与实际情况相符,建议适当增加转向系阻尼和刚度以减小甚至消除摆振的发生。     

Multi-Body Dynamics in Full-Vehicle Handling Analysis under Transient Manoeuvre

This paper presents a 94 degrees of freedom non-linear multi-body dynamics model of a vehicle comprising front and rear suspensions, steering system, road wheels, tyres and vehicle inertia. The model incorporates all sources of compliance: stiffness and damping, all with non-linear characteristics. The model is used for the purpose of vehicle handling analysis. A simulation run, pertaining to a double lane change is undertaken in-line with the ISO 3888 standard.     

Links between subjective assessments and objective metrics for steering

The characteristics of steering perception are decisive factors for overall driver preference and for vehicle safety. Car manufacturers are continuously required to tune the characteristics of the vehicle and have a strong need to be more effective in the design and evaluation of cars. Using only objective metrics (OM) can result in unwanted steering feel and using only subjective assessments (SA) is time-consuming, costly and non-repetitive. Before a tool can be built to predict the steering feel in front-end development and to improve design knowledge from the full vehicle level to the component level, links between subjective assessments and objective metrics must be found and analysed. The data collected for the study presented in this paper include subjective ratings from expert drivers and objective measurements made with steering robots, involving twelve expert drivers and over twenty vehicles across four different vehicle classes. Linear regression and neural network analysis (NN) have been used to explore reliable subjective-objective links. The tools and methods used in this research showed promising results. Most of the links found concern response and torque feedback. The preferred ranges of some crucial objective metrics leading to more desirable steering feel have been defined and presented. The results indicate that it would be possible for car manufacturers to develop new vehicles more effectively with a steering feel in line with the design criteria by using the tools and methods investigated in this paper.     

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.     

Achieving anti-roll bar effect through air management in commercial vehicle pneumatic suspensions

ABSTRACT

This paper introduces the concept of managing air in commercial vehicle suspensions for reducing body roll. A conventional pneumatic suspension is re-designed to include higher-flow air hoses and dual levelling valves for improving the dynamic response of the suspension to the body roll, which commonly happens at relatively low frequencies. The improved air management allows air to get from the air tank to the airsprings quicker, and also changes the side-to-side suspension air pressure such that the suspension forces can more readily level the vehicle body, much in the same manner as an anti-roll bar (ARB). The results of a multi-domain simulation study in AMESim and TruckSim indicate that the proposed suspension configuration is capable of providing balanced airflow to the truck’s drive-axle suspensions, resulting in balanced suspension forces in response to single lane change and steady-state cornering steering maneuvers. The simulation results further indicate that a truck equipped with the reconfigured suspension experiences a uniform dynamic load sharing, smoother body motion (less roll angle), and improved handling and stability during steering maneuvers commonly occurring in commercial trucks during their intended use.     

变路面车辆稳定性控制策略研究

建立了某四轮汽车9自由度车辆模型和轮胎动力模型,并提出了一种基于侧向力利用系数的差动制动、主动转向切换控制策略。模拟了汽车以车速24.5m/s行驶时的一个紧急避让情况,研究了无控制模式、差动制动控制模式、联合控制模式下的车辆横摆角速度、质心侧偏角、质心侧向位移的变化。结果表明,所提出的差动制动联合主动转向技术的控制策略可以满足变路面下车辆稳定性控制要求。     

Modelling and control of a new differential steering concept

This paper presents a new steer-by-wire concept using an all-wheel drive vehicle layout with in-wheel motors while completely omitting the application of any dedicated steering device. Steering is based on the so-called differential steering principle which generates the necessary steering moment about the kingpins by a traction force difference between left and right sides of the vehicle. In order to investigate the behaviour of the vehicle and to design the underlying control algorithms, a planar vehicle model is presented, where the vehicle is described as constrained non-holonomic system requiring a special treatment. A state feedback linear controller for controlling of the lateral dynamics of the vehicle at higher speeds and a simple PI angle controller for low-speed manoeuvring are developed. The resulting behaviour of the system is investigated by various simulation experiments demonstrating a comparable steering performance of the new steering concept as that of conventional passenger cars.     

Trends in vehicle motion control for automated driving on public roads

ABSTRACT

In this paper, we describe how vehicle systems and the vehicle motion control are affected by automated driving on public roads. We describe the redundancy needed for a road vehicle to meet certain safety goals. The concept of system safety as well as system solutions to fault tolerant actuation of steering and braking and the associated fault tolerant power supply is described. Notably restriction of the operational domain in case of reduced capability of the driving automation system is discussed. Further we consider path tracking, state estimation of vehicle motion control required for automated driving as well as an example of a minimum risk manoeuver and redundant steering by means of differential braking. The steering by differential braking could offer heterogeneous or dissimilar redundancy that complements the redundancy of described fault tolerant steering systems for driving automation equipped vehicles. Finally, the important topic of verification of driving automation systems is addressed.     

Overturning Stability of Three Wheeled Motorized Vehicles

Three wheeled motorized vehicles are a major mode of public transport in many countries. These vehicles are prone to overturning even during normal turning and obstacle avoidance maneuvers. This paper presents a parametric analysis of a mathematical model of the vehicle and evolves guidelines for improving the overturning stability in terms of vehicle geometry and suspension properties.

Differential equations governing the dynamic behavior of the vehicle are derived on the basis of a six degree of freedom model. The vehicle response to variations in steering, engine power and braking inputs is then numerically simulated. The effects of vehicle geometry and elasto-damping suspension coefficients on the vehicle stability are presented. The results indicate an optimum position of the center of gravity where the vehicle is most stable. While stiffer suspensions favour stability, there exists an optimum value of suspension damping for which the minimum wheel load is a maximum.