双前桥转向车辆操纵稳定性分析

建立了双前桥转向车辆的线性二自由度车辆模型,进行了理论分析和数学公式推导。以某8X4载货车为例,基于最小转弯直径范围确定转向瞬心位置区间,讨论了转向瞬心位置对车辆稳态响应和瞬态响应的影响。     

线控转向稳态增益与动态反馈校正控制算法

以29自由度汽车动力学模型为基础,提出了保证线控汽车转向增益不变的稳态控制策略,使线控汽车转向特性不随车速和转向盘转角变化;提出了基于状态反馈的动态校正稳定性控制算法。仿真和驾驶模拟器实验表明,基于转向增益不变的稳态控制策略保证了汽车转向特性不变,减轻了驾驶员的负担,适合于更多的驾驶人群;基于状态反馈的动态校正稳定性控制算法有效提高了汽车的稳定性。     

Stationar- und Ubergangsverhalten von Sattel- und Lasttugen bei der Kreisfahrt: Lineare Berechnungen

ABSTRACT

Steady and Transient Turning of Tractor-Semitrailer and Truck-Trailer Combinations: A Linear Analysis

A simplified analysis is made of the yaw stability and control of the two types of the commercial vehicle combinations (tractor-semitrailer, truck-trailer) at a constant forward velocity during steady and transient turning. The combined vehicle is treated as a linear dynamic system (Fig. 2). The steer angle at the front wheels of the tractor (or truck) and the steady-state responses if the road verhicle train (yaw rate, articulation angles and sideslip angle) are calculated (Equations 18 to 25). Exploratory calculations are performed to determine the influence of the cornering stiffness of the tires for the two types of the vehicle combinations upon the steady-state responses (Figs. 7 to 10). For a linear simplified model of articulated vehicle the steady-state turning behaviour is stable also under conditions of rather high driving speed (70 km/h). A simplified analysis of the transient turning behaviour of the two types of road trains has shown the tractor-semitrailer to preserve stability even under driving speeds exceeding 70 km/h (Fig. 13), whereas the truck-trailer combinations appear to become oscillatory unstable if the driving speed rises above the 60 km/h margin (Fig. 14).     

Stationar- und Ubergangsverhalten von Sattel- und Lasttugen bei der Kreisfahrt: Lineare Berechnungen

Steady and Transient Turning of Tractor-Semitrailer and Truck-Trailer Combinations: A Linear Analysis

A simplified analysis is made of the yaw stability and control of the two types of the commercial vehicle combinations (tractor-semitrailer, truck-trailer) at a constant forward velocity during steady and transient turning. The combined vehicle is treated as a linear dynamic system (Fig. 2). The steer angle at the front wheels of the tractor (or truck) and the steady-state responses if the road verhicle train (yaw rate, articulation angles and sideslip angle) are calculated (Equations 18 to 25). Exploratory calculations are performed to determine the influence of the cornering stiffness of the tires for the two types of the vehicle combinations upon the steady-state responses (Figs. 7 to 10). For a linear simplified model of articulated vehicle the steady-state turning behaviour is stable also under conditions of rather high driving speed (70 km/h). A simplified analysis of the transient turning behaviour of the two types of road trains has shown the tractor-semitrailer to preserve stability even under driving speeds exceeding 70 km/h (Fig. 13), whereas the truck-trailer combinations appear to become oscillatory unstable if the driving speed rises above the 60 km/h margin (Fig. 14).     

On Lateral Dynamics of Vehicles Based on Nonlinear Characteristics of Tires

The problems of vehicle lateral dynamics based on nonlinear characteristics of tires are discussed in this paper. A new nonlinear perturbation model on the cornering behavior of the tire is constructed. The nonlinear influences of tires on the steady-state steering behavior, dynamic response and handling stability of vehicle are discussed, applying the approximate analytical methods for nonlinear vibration. An analytical criterion of stability is obtained. Some numerical examples are given.     

On Lateral Dynamics of Vehicles Based on Nonlinear Characteristics of Tires

The problems of vehicle lateral dynamics based on nonlinear characteristics of tires are discussed in this paper. A new nonlinear perturbation model on the cornering behavior of the tire is constructed. The nonlinear influences of tires on the steady-state steering behavior, dynamic response and handling stability of vehicle are discussed, applying the approximate analytical methods for nonlinear vibration. An analytical criterion of stability is obtained. Some numerical examples are given.     

Development of a generalised equivalent estimation approach for multi-axle vehicle handling dynamics

This paper devotes analytical effort in developing the 2M equivalent approach to analyse both the effect of vehicle body roll and n-axle handling on vehicle dynamics. The 1M equivalent vehicle 2DOF equation including an equivalent roll effect was derived from the conventional two-axle 3DOF vehicle model. And the 1M equivalent dynamics concepts were calculated to evaluate the steady-state steering, frequency characteristics, and root locus of the two-axle vehicle with only the effect of body roll. This 1M equivalent approach is extended to a three-axle 3DOF model to derive similar 1M equivalent mathematical identities including an equivalent roll effect. The 1M equivalent wheelbases and stability factor with the effect of the third axle or body roll, and 2M equivalent wheelbase and stability factor including both the effect of body roll and the third-axle handling were derived to evaluate the steady-state steering, frequency characteristics, and root locus of the three-axle vehicle. By using the recursive method, the generalised 1M equivalent wheelbase and stability factor with the effect of n-axle handling and 2M equivalent generalised wheelbase and stability factor including both the effect of body roll and n-axle handling were derived to evaluate the steady-state steering, frequency characteristics, and root locus of the n-axle vehicle. The 2M equivalent approach and developed generalised mathematical handling concepts were validated to be useful and could serve as an important tool for estimating both the effect of vehicle body roll and n-axle handling on multi-axle vehicle dynamics.     

电动客车稳态转向特性仿真研究

利用虚拟样机分析软件ADAMS建立了整车多体动力学模型,并进行了仿真分析。研究了由电池布置带来的前后轴载荷变化(整车质心位置变化)和横向稳定杆对转向性能的影响。结果显示,整车在空载和满载时均为不足转向;后轴载荷比例增加对稳态转向不利;加装横向稳定杆可以大大改善车厢侧倾,对稳态转向有一定改善。     

Dynamics analysis of an omni-directional vehicle

In a modern society, traffic congestion is a major problem in every metropolis. To solve the problem of traffic congestion an innovative omni-directional vehicle is proposed. This research has mainly focussed on developing the comprehensive vehicle dynamics model for an omni-directional road vehicle. Then the stability of the vehicle in the yaw plane was analysed under different scenarios based on the response of the side slip angle. Finally an active steering PID controller was suggested and which, according to the results of the simulation, improved the yaw plane stability.     

半挂汽车列车弯道行驶横向稳定性分析

为了进一步研究半挂汽车列车弯道行驶横向稳定性,运用动力学理论以及虚拟样机仿真软件ADAMS,建立了具有21自由度的半挂汽车列车虚拟样机,通过将稳态转向试验和转向盘角阶跃输入试验所得仿真结果与实车试验所得曲线相比较进行仿真模型的校验,分析了半挂汽车列车在弯道行驶极限工况下有关参数与时间的变化关系曲线,并分析极限工况所产生的原因。     

Critical review of handling diagram and understeer gradient for vehicles with locked differential

The steady-state cornering behaviour of rear-wheel drive vehicles fitted with locked differential is critically analysed by means of simple, albeit carefully formulated, vehicle models, which allow for a rigorous theoretical analysis. Results obtained for some classical manoeuvres, with either constant forward speed, steer angle or turning radius, clearly show that, in the case of locked differential, the vehicle cornering behaviour is strongly affected by the manoeuvre. As an important consequence, the handling diagram is not unique and the understeer gradient is no longer dependent only upon the lateral acceleration, as in vehicles equipped with an open differential. Accordingly, this study shows that some typical tools and concepts of vehicle dynamics are indeed inadequate in the case of locked differential.     

基于MPC的分布式驱动越野车辆原地转向控制研究

针对轮毂电机分布式驱动越野车辆在狭小空间快速机动的需求,设计了一种分层结构的原地转向控制策略。基于动力学原理分析了各轮载荷、附着条件对原地转向横摆速度的影响机理,并搭建原地转向运动学模型,上层采用模型预测控制算法设计原地转向理想轨迹以及期望的横摆角速度,开发基于PI滑模控制的横摆运动跟踪算法,通过补偿转向横摆力矩以提高方向角控制的鲁棒性和稳定性,下层以最优轮胎利用率为目标,设计二次规划算法优化分配各轮附加横摆力矩。dSPACE硬件在环测试结果表明,所提出的控制算法可在保证稳定性的前提下实现原地转向,大幅提高了车辆的转向机动性,在方向盘动态输入仿真中,车辆最大转弯半径为0.157 m,转向中心的最大偏移量为3.610 m;同时,驾驶员能对转向过程进行闭环控制,实现了原地转向过程中横摆速度的实时调节。     

五轴转向重型汽车转向性能的研究

以多体系统动力学理论为基础,利用ADAMS建立了五轴转向重型汽车的整车虚拟样机模型,对该模型进行了仿真分析.由分析结果可知,转向轮转角越大,轮胎磨损越严重.为提高重型汽车的灵活性,延长轮胎的使用寿命,对该模型进行了优化.通过仿真分析可知,优化后的转向性能明显提高.同时分析比较了五轴转向重型汽车与前两轴转向重型汽车的转向性能,结果表明,五轴转向重型汽车转弯半径小,轮胎磨损小.     

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.     

Lane-keeping benefits of practical rear axle steer

The classic two-degree-of-freedom yaw-plane or ‘bicycle’ vehicle model is augmented with two additional states to describe lane-keeping behaviour and further augmented with an additional control input to steer the rear axle. A simple driver model is hypothesised where the driver closes a loop on a projected lateral lane position. The driver can select the preview distance to compensate driver/vehicle dynamics, consistent with the ‘cross-over’ model found in the literature. A rear axle steer control law is found to be a function of the front axle steering input and vehicle speed that exhibits stability similar to a positive-real system, while at the same time improving the ability of the driver/vehicle system to track a complex curved lane and improving steady-state manoeuvrability. The theoretically derived control law bears similarity to practical embodiments allowing a deeper understanding of the functional value of steering a rear axle.     

转向盘转角阶跃输入下半挂汽车列车操纵稳定性仿真分析

基于包括任意载荷分布的非线性轮胎模型在内的半挂汽车列车整车模型,应用汽车列车动力学仿真软件Arc Sim,分析了半挂汽车列车在转向盘转角阶跃输入时的转向特性。通过在不同车速、不同结构参数等条件下的仿真计算,揭示了半挂汽车列车的转向特性与车速、结构参数之间的内在联系,给出了半挂汽车列车转向特性在这些条件下的表现特征,为半挂汽车列车操纵稳定性分析提供了参考和借鉴。     

Sensitivity of Driver-Vehicle Performance to Vehicle Characteristics Revealed in Open-loop Tests

The advantages of being able to objectively specify desirable vehicle handling characteristics, which can be determined without recourse to closed-loop tests on a prototype vehicle, are widely recognised. This paper reviews the studies that have attempted to find a relationship between closed-loop task performance, and driver subjective opinion, and various steady-state and transient characteristics revealed in open-loop tests of the vehicle. It is found that the level of definition of these relationships is not sufficient to justify mandatory regulations for vehicle design. However, the basic requirements for steering control sensitivity, and the rapidity and stability of the fixed-control dynamic response of vehicles in normal manoeuvres, are beginning to emerge. Data are particularly lacking for the closed-loop effects of vehicle sideslipping characteristics, free-control responses and vehicle behaviour in limit manoeuvres.     

Effect of handling characteristics on minimum time cornering with torque vectoring

In this paper, the effect of both passive and actively-modified vehicle handling characteristics on minimum time manoeuvring for vehicles with 4-wheel torque vectoring (TV) capability is studied. First, a baseline optimal TV strategy is sought, independent of any causal control law. An optimal control problem (OCP) is initially formulated considering 4 independent wheel torque inputs, together with the steering angle rate, as the control variables. Using this formulation, the performance benefit using TV against an electric drive train with a fixed torque distribution, is demonstrated. The sensitivity of TV-controlled manoeuvre time to the passive understeer gradient of the vehicle is then studied. A second formulation of the OCP is introduced where a closed-loop TV controller is incorporated into the system dynamics of the OCP. This formulation allows the effect of actively modifying a vehicle's handling characteristic via TV on its minimum time cornering performance of the vehicle to be assessed. In particular, the effect of the target understeer gradient as the key tuning parameter of the literature-standard steady-state linear single-track model yaw rate reference is analysed.     

车辆动力学稳定性控制的仿真研究

对车辆动力学稳定性控制的控制原理，控制策略，控制逻辑和算法进行了理论分析。在此基础上，对车辆动力学稳定性控制进行了仿真分析，结果表明，车辆动力学稳定性控制能够改善车辆在高速下或在滑路上转向时的操纵性和稳定性。     

Vehicle lift-off modelling and a new rollover detection criterion

The modelling and development of a general criterion for the prediction of rollover threshold is the main purpose of this work. Vehicle dynamics models after the wheels lift-off and when the vehicle moves on the two wheels are derived and the governing equations are used to develop the rollover threshold. These models include the properties of the suspension and steering systems. In order to study the stability of motion, the steady-state solutions of the equations of motion are carried out. Based on the stability analyses, a new relation is obtained for the rollover threshold in terms of measurable response parameters. The presented criterion predicts the best time for the prevention of the vehicle rollover by applying a correcting moment. It is shown that the introduced threshold of vehicle rollover is a proper state of vehicle motion that is best for stabilising the vehicle with a low energy requirement.