A Comparative Study of Four Wheel Steering Models Using the Inverse Solution

An inverse solution study of various four wheel steering models is carried out for the purpose of comparison of steering/braking input needed to track a lane change maneuver. Optimal control is used to solve the non-linear inverse problem. Comparisons are made when the vehicle is coasting, when the time required to track the trajectory is minimized with appropriate utilization of brake/traction forces, and in a front wheel lock situation. A rear steering model which produces neutral steering characteristics displayed the best steering behavior with respect to ease of steering.     

汽车转向梯形故障检测机理研究

通过对汽车转向梯形机构进行合理简化,建立了相应的数学模型,推导出了汽车前轮转向前张角与转向梯形底角之间的变化规律:当汽车外侧车轮转到某一定值时,内侧车轮转角受同侧梯形底角的影响,并且内轮转角变化与同侧梯形底角变化成反比。经试验验证了此结论的正确性,由此使得利用现有的检测设备即可实现对汽车转向梯形工作状态的在线检测。     

Some Inverse Solutions to an Automobile Path-Tracking Problem with Input Control of Steering and Brakes

An approximate inverse solution for a laterally telescoped automobile is obtained where the two inputs, namely the steering angle and the brake/tractive forces, are determined so as to perform a specified lane change maneuver. The optimal control approach is shown to be useful in obtaining some of the many feasible inverse solutions where the same tracking task is performed with different steering inputs by applying different brake/tractive forces. A comparison is made between the tractive forces required for front and rear drive automobiles when the vehicle is to be accelerated to the same final speed during the same lane-change maneuver.     

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.     

Additional 4WS and Driver Interaction

This investigation is based on a complex 4-wheel vehicle model of a passenger car that includes steering system and drive train. The tyre properties are described for all possible combined longitudinal and lateral slip values and for arbitrary friction conditions. The active part is an additional steering system of all 4 wheels, additionally to the driver's steering wheel angle input. Three control levels are used for the driver model that thereby can follow a given trajectory or avoid an obstacle.

The feedback control of the additional 4 wheel steering is based on an observer which can also have adaptive characteristics. Moreover a virtual vehicle model in a feedforward scheme can provide desired steering characteristics.

To get information for critical situations a cornering manoeuvre with sudden u-split conditions is simulated. Further a similar manoeuvre is used to evaluate the reentry in a high friction area from low friction conditions. And finally the performance of the controller is shown in a severe lane change manoeuvre.     

基于整车多自由度的电动助力转向系统建模与仿真

在电动助力转向系统（EPS）的数学模型和整车八自由度模型基础上,建立了基于Matlab／Simulink的电动助力转向系统仿真模型。基于扭矩输入对电动助力转向系统应用PID进行助力控制。仿真结果表明,所设计的电动助力转向系统在改善转向轻便型和路感的同时,具有很好的抗干扰性能,能提高汽车行驶的操纵稳定性和安全性。     

Nonlinear PI front and rear steering control in four wheel steering vehicles

Vehicle steering dynamics show resonances, which depend on the longitudinal speed, unstable equilibrium points and limited stability regions depending on the constant steering wheel angle, longitudinal speed and car parameters.

The main contribution of this paper is to show that a combined decentralized proportional active front steering control and proportional-integral active rear steering control from the yaw rate tracking error can assign the eigenvalues of the linearised single track steering dynamics, without lateral speed measurements, using a standard single track car model with nonlinear tire characteristics and a non-linear first-order reference model for the yaw rate dynamics driven by the driver steering wheel input. By choosing a suitable nonlinear reference model it is shown that the responses to driver step inputs tend to zero (or reduced) lateral speed for any value of longitudinal speed: in this case the resulting controlled vehicle static gain from driver input to yaw rate differs from the uncontrolled one at higher speed. The closed loop system shows the advantages of both active front and rear steering control: higher controllability, enlarged bandwidth for the yaw rate dynamics, suppressed resonances, new stable cornering manoeuvres, enlarged stability regions, reduced lateral speed and improved manoeuvrability; in addition comfort is improved since the phase lag between lateral acceleration and yaw rate is reduced.

For the designed control law a robustness analysis is presented with respect to system failures, driver step inputs and critical car parameters such as mass, moment of inertia and front and rear cornering stiffness coefficients. Several simulations are carried out on a higher order experimentally validated nonlinear dynamical model to confirm the analysis and to explore the robustness with respect to unmodelled dynamics.     

线控转向系统转向盘力回馈控制模型的研究

根据轮胎和传统转向系的力学特性提出了利用车轮转角和车速计算得到转向盘回馈力的思路,并以此建立了线控转向系统转向盘回馈力控制模型,仿真和试验表明该模型能够满足路感要求。     

Pro/E机构运动仿真模块在双前轴转向传动机构匹配设计中的应用

介绍了应用Pro/E机构运动仿真模块进行运动仿真的工作流程.通过应用Pro/E机构运动仿真模块对双前轴转向传动机构进行匹配设计的实例,论述了商用车双前轴转向传动机构的设计理论要求、初步的传动机构实体建模方法以及转角特性分析方法、理论模型与实体模型的转角特性数据处理与分析,以及实体模型的优化设计方法,并简要介绍了转向传动机构与悬架系统的运动十涉分析方法.     

Active Steering Systems Based on Model Reference Adaptive Nonlinear Control

This paper presents a model reference adaptive nonlinear control strategy for active steering of a two wheel steering car which is realized by steer-by-wire technology. The ideal fixed property of a steering system, which is provided by a reference model, is attained by D * control. The proposed method can treat the nonlinear relationships between the slip angles and the lateral forces on tires, and the uncertainties on the friction of the road surface, whose compensations are very important under critical situations. Some results of realtime simulation with a steering equipment show the effectiveness of the proposed method.     

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。     

Active Steering Systems Based on Model Reference Adaptive Nonlinear Control

This paper presents a model reference adaptive nonlinear control strategy for active steering of a two wheel steering car which is realized by steer-by-wire technology. The ideal fixed property of a steering system, which is provided by a reference model, is attained by D * control. The proposed method can treat the nonlinear relationships between the slip angles and the lateral forces on tires, and the uncertainties on the friction of the road surface, whose compensations are very important under critical situations. Some results of realtime simulation with a steering equipment show the effectiveness of the proposed method.     

On the feasibility of the optical steering wheel sensor: Modeling and control

This paper discusses the development of a system model for the wireless steering wheel angle sensor and steering wheel system for the evaluation of the steer by wire system in a vehicle dynamic system. The steering wheel sensor is a wireless, contact-less sensor utilizing an optical medium for angle detection. The optical medium is operated based on a photodiode and photo-detector head. A reflecting disc or code-wheel, working similar to a compact disc, is used to reflect the light from the photodiode back to the photo-detector. The beam is reflected based on the content in the reflective disc to measure the relative angle through a micro-controller. The proposed wireless steering sensor and steer by wire system is modeled using the Matlab/Simulink and their performance is investigated to evaluate the steering response, vehicle dynamics, and steering feel of the system. Finally, the feasibility of the proposed system is discussed based on the developed model and simulation results.     

Interaction of vehicle and steering system regarding on-centre handling

For the on-centre handling behaviour of vehicles the steering system is absolutely important. To investigate the interaction of the vehicle and steering system a validated, especially tailored simulation model was developed. Some meaningful vehicle and steering system parameters are altered to show the influence on steering wheel torque, steering feel and understeer. The results underline the importance of an accurate steering system model. Identified measures to improve the centre feel and steering response were a stiffer torsion bar, a higher cornering stiffness or a lower overall steering ratio. The steering response, however, suffers when the centre feel is improved by a higher trail. The steering rack friction reduces mainly the steering response while the steering column friction decreases the centre feel whereas a stiffer torsion bar lessens the understeer tendency.     

基于驾驶员在环的EPS试验台开发

汽车转向系统性能与汽车的操纵稳定性和舒适性有关,对汽车的行驶安全起着至关重要的作用。随着动力转向系统的发展,电动助力转向系统的优势逐渐突出。这里运用七自由度汽车模型,拟设计出一种基于驾驶员在环的转向测试试验台,将驾驶员操纵的油门踏板和转向信号实时采集,通过信号运算和汽车动力学模型实时仿真,实现转向力矩的模拟和车辆状态信息的输出,并可以快速进行EPS系统的开发验证。     

Interaction of vehicle and steering system regarding on-centre handling

For the on-centre handling behaviour of vehicles the steering system is absolutely important. To investigate the interaction of the vehicle and steering system a validated, especially tailored simulation model was developed. Some meaningful vehicle and steering system parameters are altered to show the influence on steering wheel torque, steering feel and understeer. The results underline the importance of an accurate steering system model. Identified measures to improve the centre feel and steering response were a stiffer torsion bar, a higher cornering stiffness or a lower overall steering ratio. The steering response, however, suffers when the centre feel is improved by a higher trail. The steering rack friction reduces mainly the steering response while the steering column friction decreases the centre feel whereas a stiffer torsion bar lessens the understeer tendency.     

影响车辆转向瞬态响应特性的因素研究

利用ADAMS/CAR二次开发模块,建立了国产某小客车的整车多体系统动力学仿真模型。分析了车辆转向盘角阶跃输入和脉冲输入时的瞬态响应特性,并对相关的影响因素进行了预测分析,通过调整后轮侧倾刚度等参数,优化转向瞬态特性响应结果,经过样车的试验验证了优化结果。     

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。     

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。     

汽车转向非线性平衡点求解新方法及其应用

针对汽车转向非线性稳定性平衡点确定问题,提出了求解汽车转向非线性平衡点的一种新方法。建立了汽车转向非线性2自由度模型,采用简化魔术公式轮胎模型描述非线性轮胎侧向力。给出了转向非线性平衡点的表示,对粒子群算法进行了简要分析,提出了求解转向平衡点的粒子群算法。设计了前轮转角、路面附着系数和车速分别变化的3种行驶条件,对3种行驶条件下的转向非线性平衡点进行了求解。结果表明,粒子群算法可以准确求得汽车转向非线性平衡点,适应值小于设置的10-4的精度。