Research on Vehicle Control Technology Using Four-Wheel Independent Steering System

The enhancement of vehicle handling stability and maneuverability through active and independent rear wheels control is presented. Firstly, the configuration of four-wheel independent steering prototype vehide is introduced briefly. Then the concrete overall design of the electronic controllers of four wheel independent steering system （4WIS） is formulated in details. Under the control strategy of zero sideslip angle at mass center, the mathematical model of 4WIS is established to deduce the equations of separated rear wheel steering angles. According to these equations, simulation analysis for 4WIS vehicle performances is finished to show that 4WIS vehicle can improve the maneuverability greatly at low speed and increase the handling stability at high speed. Finally, the road test of 4WIS vehide has performed to verify the correctness of simulation and show that compared with the conventional four wheel steering （4WS） vehicle, the 4WIS vehicle not only improves the kinematical harmony but also decreases steering resistance and lighten abrasion of tires.

Autonomous Tracking Control for Four-Wheel Independent Steering Robot Based on Improved Pure Pursuit

Autonomous tracking control is one of the fundamental challenges in the field of robotic autonomous navigation,especially for future intelligent robots.In this paper,an improved pure pursuit control method is proposed for the path tracking control problem of a four-wheel independent steering robot.Based on the analysis of the four-wheel independent steering model,the kinematic model and the steering geometry model of the robot are established.Then the path tracking control is realized by considering the correlation between the look-ahead distance and the velocity,as well as the lateral error between the robot and the reference path.The experimental results demonstrate that the improved pure pursuit control method has the advantages of small steady-state error,fast response and strong robustness,which can effectively improve the accuracy of path tracking.

MPC-based Torque Distribution for Planar Motion of Four-wheel Independently Driven Electric Vehicles:Considering Motor Models and Iron Losses

The most critical obstacle for four-wheel independently driven electric vehicles(4WID-EVs)is the driving range.Being the actuators of 4WID-EVs,motors account for its major power consumption.In this sense,by properly distributing torques to minimize the power consumption,the driving range of 4WID-EV can be effectively improved.This paper proposes a model predictive control(MPC)-based torque distribution scheme,which minimizes the power consumption of 4WID-EVs while guaranteeing its tracking performance of planar motions.By incorporating the motor model considering iron losses,the optimal torque distribution can be achieved without an additional torque controller.Also,for this reason,the proposed control scheme is computationally efficient,since the power consumption term to be optimized,which is expressed as the product of the motor voltages and currents,is much simpler than that derived from the efficiency map.With reasonable simplification and linearization,the MPC problem is converted to a quadratic programming problem,which can be solved efficiently.The simulation results in MATLAB and CarSim co-simulation environments demonstrate that the proposed scheme effectively reduces power consumption with guaranteed tracking performance.

Research on the Variable Steering Ratio of Four-Wheel-Steering Vehicle

The steering characteristic of a four-wheel-steering vehicle is numerically simulated for in-depth research of the handling stability of four-wheel steering. The research results show that the deteriorating tendency of the steering stability due to the increase of the vehicle speed is improved obviously in the case of four-wheel steering. The approach of variable steering ratio is discussed. The use of the variable steering ratio can not only raise the steering stability of vechicles at high vehicle speed, but also reduce the dicomfort and steering burden of drivers; and hence is helpful for the subjective evaluation of four-wheel steering vehicles.

Analysis of steering performance of differential coupling wheelset

In order to improve the curving performance of the conventional wheelset in sharp curves and resolve the steering ability problem of the independently rotating wheel in large radius curves and tangent lines, a differential cou- pling wheelset （DCW） was developed in this work. The DCW was composed of two independently rotating wheels （IRWs） coupled by a clutch-type limited slip differential. The differential contains a static pre-stress clutch, which could lock both sides of IRWs of the DCW to ensure a good steering performance in curves with large radius and tangent track. In contrast, the clutch could unlock the two IRWs of the DCW in a sharp curve to endue it with the characteristic of an IRW, so that the vehicles can go through the tight curve smoothly. To study the dynamic performance of the DCW, a multi-body dynamic model of single bogie with DCWs was established. The self-centering capability, hunting stability, and self-steering performance on a curved track were analyzed and then compared with those of the conventional wheelset and IRW. Finally, the effect of coupling parameters of the DCW on the dynamic performance was investigated.

Optimal gear shift control strategy for positive independent mechanical split path transmission with automatic shift system

An improvement strategy which controls the shift effort and the power summing planetary gear set of steering clutches and brakes have been proposed based on the dynamic model of synchroniser in order to decrease the wear of synchroniser inserts, make gear shift easy and reduce the shock noise for a positive independent mechanical split path transmission which attached an auto- matic shift system when shifting. A kinetics model for the process of synchroniser engagement is built and analyzed in the paper. Thus for optimizing the gear shift process which is divided into three phases a model reference fuzzy self-adaption system is adopted. Through a 6 000 km road experiment, the control strategy has proved feasible and dependable.

Driver Model-Based Fault-Tolerant Control of Independent Driving Electric Vehicle Suffering Steering Failure

This paper presents a fault-tolerant control(FTC)strategy for a four-wheel independent driving electric vehicle suffering steering failure.The method is based on the functional redundancy of driving and braking actuators to recover the vehicle’s steering ability.A dynamic vehicle model is derived with the function of four-wheel driving.A sliding mode controller with a combined sliding surface is employed as a motion controller,allowing the desired vehicle motion to be tracked by the adaptive drivermodel.An extended Kalman filter-based state estimator is adopted to virtually measure the sideslip anglewhile considering the nonlinear tire force.A new allocation strategy,involving two distribution modes of coordination,is designed.In addition,a weight coefficient adjustment strategy is implemented in optimal mode based on the lateral load transfer,thus improving the steering performance.Simulations are conducted to verify the proposed FTC algorithm.The results demonstrate that steering failure can be effectively covered by the functional redundancy of the driving/braking actuators.

两轴径向独立轮副轨道车辆动力学性能

针对独立车轮导向问题提出后倾角导向方法,使独立轮副轨道车辆获得自导向能力。阐述车辆的自导向原理,利用横向轮轨力和后倾角力臂形成摇头力矩,使独立车轮自动转向。关于中心对称的前后独立轮副分别向相反方向转向,使独立车轮处于径向位置。采用多体动力学方法分析独立轮副轨道车辆的自导向性能。结果表明:在直线轨道上,后倾角对车辆横向位移和摇头角的影响明显。带后倾角车辆出现类蛇行运动现象。具有后倾角的车辆在直线轨道上能够自动复位。在曲线轨道上,左前导向轮具有较大的冲角。后倾角能够使车辆动态对中,最终回到轨道中心线位置。带后倾角的独立轮副轨道车辆在曲线轨道上具有有限的导向能力。

分布式驱动车辆操纵稳定性控制综述

为研究分布式驱动车辆的驱动控制问题,从转向控制、独立驱动控制及2个系统联合控制等3个角度入手,分析了分布式驱动车辆操纵稳定性控制策略的研究进展。首先,基于转向控制技术对影响操纵稳定性的方面进行分类;其次,分析了分层式与集中式控制结构的特点;然后,分析了基于控制结构的操纵稳定性研究;最后,结合分布式驱动车辆操稳性改善的研究现状和技术进展,展望了未来的发展趋势。

床椅一体化机器人设计与实现

针对床椅机器人在室内狭小空间灵活行走的问题,研制一款四轮独立驱动转向的床椅一体化机器人。根据室内狭小空间的转向需求,确定了底盘总体布局方案和主要技术参数。对重要部件进行了理论计算、有限元分析,对驱动轮支架进行了应力及形变分析;在ADAMS软件中建立了床椅机器人的动力学仿真模型,进行了稳定性分析。仿真结果表明,驱动轮支架的强度和刚度均满足设计要求,床椅机器人的各项指标符合国家相关标准的规定。样机试验进一步验证了仿真分析的结果,确认了床椅一体化机器人的稳定性、越障性能和在室内狭小空间的转向性能。

复杂地形六轮独立驱动与转向机器人轨迹跟踪与避障控制

为研究六轮移动机器人在复杂地形的运动控制方法,针对六轮独立驱动与转向机器人复杂地形轨迹跟踪问题,提出一种预测控制和动态补偿的控制方法。基于非完整约束的线性六轮移动机器人运动学模型,以模型预测控制算法为基础,引入比例-积分-微分补偿控制器,抑制动态滞后引起的跟踪误差,设计速度与转向角动态反馈补偿,以应对地形扰动对轨迹跟踪的影响。分析机器人运动过程中障碍物的避碰问题,设计可求解避障轨迹的避障规划器,通过轨迹跟踪系统对局部避障轨迹进行跟踪控制,实现机器人的轨迹跟踪和自动避碰。对轨迹跟踪算法和避障算法进行仿真实验。实验结果表明:在典型工况下,机器人可完成凹形斜坡、凸形斜坡和凹凸地形正弦型轨迹跟踪控制和静态与动态障碍物避碰,验证了新方法的有效性。

An Integrated Control Framework for Torque Vectoring and Active Suspension System

Four-wheel independently driven electric vehicles(FWID-EV)endow a flexible and scalable control framework to improve vehicle performance.This paper integrates the torque vectoring and active suspension system(ASS)to enhance the vehicle’s longitudinal and vertical motion control performance.While the nonlinear characteristic of the tire model leads to a relatively heavier computational burden.To facilitate the controller design and ease the load,a half-vehicle dynamics system is built and simplified to the linear-time-varying(LTV)model.Then a model predictive controller is developed by formulating the objective function by comprehensively considering the safety,energy-saving and comfort requirements.The in-wheel motor efficiency and the power loss of tire slip are treated as optimization indices in this work to reduce energy consumption.Finally,the effectiveness of the proposed controller is verified through the rapid-control-prototype(RCP)test.The results demonstrate the enhancement of the energy-saving as well as comfort on the basis of vehicle stability.

融合模式决策的4WIS车辆路径规划方法

针对四轮独立转向(four-wheel independent steering,4WIS)车辆的路径规划问题,提出了一种融合模式决策的图搜索算法.首先,对4WIS车辆三种运动模式进行建模,并分析其运动模式的运动特性,据此设计多模式节点拓展策略,实现了4WIS车辆多运动模式与路径规划的融合.然后,针对最优节点选取和运动模式决策问题,设计了多目标代价函数,引导4WIS车辆合理切换运动模式,并生成平滑路径.最后,在MATLAB软件上进行仿真实验,在多种场景中测试所提出算法,验证其可行性与有效性.结果表明:提出的算法在路径规划中考虑了三种运动模式的优化组合与模式切换问题,能实现最优运动模式序列和最短路径规划.且该算法求解效率高,所规划路径优异,能充分发挥4WIS车辆的高灵活性与高通过性,有效解决其路径规划问题.

采煤机搬运车独立转向高精控制方法研究

为提高采煤机搬运车转向系统的响应速度和协同性,针对其独立转向特性提出了一种高精度转向控制方法。首先建立了转向系统的数学模型,采用模糊PID控制算法提高系统动态特性,相较于经典PID控制算法,响应时间由1.14 s减小为1.12 s;其次将控制器进行离散化处理,将其应用于实际系统中;最后进行实车实验,通过提高转向控制灵敏度和控制器采样周期,进一步提高了前后车协调转向控制效果。研究内容为其他工程机械独立转向控制的设计提供了参考。

基于CarSim的电动汽车转向灵活性仿真与探究

传统的电动助力转向系统由于是由一套齿轮齿条转向器拉动车轮实现转向的,这就限制了车轮转角使其无法实现真正的阿克曼转向,也限制了车轮的最大转向角度。在CarSim自带模型的基础上,利用Simulink修改其转向子系统,从而建立了一种可实现前轮独立转向的汽车模型。通过双移线仿真试验和方向盘角阶跃响应试验,验证了模型的正确性。通过开环控制和闭环控制试验,证明了模型相对于传统汽车模型有着更好的转向灵活性。研究可为后期的线控转向汽车的灵活性和操稳性研究做出铺垫,对于延长轮胎寿命,提升驾驶感受也具有重要的意义。

四轮独立驱动汽车偏转 差动协同转向路径跟踪

为改善四轮独立驱动汽车在不同车速与路面附着系数下的路径跟踪效果,提出了偏转差动协同转向控制策略。在二自由度动力学模型的基础上,建立多点预瞄与线性二次调节(LQR)结合的前轮偏转转向路径跟踪、滑模控制与四轮转矩优化分配结合的四轮差动转向路径跟踪,采用模糊控制对偏转转向与差动转向路径跟踪的权重进行自适应分配,建立包含路径跟踪层与转角、转矩分配控制层的偏转差动协同控制策略。利用Carsim与Simulink分别建立协同转向路径跟踪与LQR偏转转向路径跟踪联合仿真平台,取车速为54、72 km/h与路面附着系数为0.3、0.8的双移线工况进行仿真得出结论:相较于LQR偏转转向路径跟踪,协同转向路径跟踪在各工况下的横向跟踪精度与稳定性均有所提高。

基于dSPACE的独立轮对主动导向控制策略研究

独立轮对作为低地板列车的关键组成部分,其结构导致其导向性能缺失、磨损和噪声等问题,这些问题成为制约低地板列车发展的主要因素。文章通过已有的独立轮对单轴转向架滚动试验台,结合dSPACE系统搭建了快速控制原型(Rapid Control Prototype,RCP)测试平台,并提出了2种主动导向控制策略,分别开展了独立轮对导向性能验证、Simulink和SIMPACK联合仿真验证,以及主动导向控制策略的半实物仿真台架试验。试验结果表明,独立轮对本身不具备曲线对中能力,当添加主动导向控制后独立轮对能完全无横向偏移。文章所提出的2种主动导向控制策略均能够使采用独立轮对的车辆获得良好的曲线通过性能,在补偿车辆速度和曲线半径的情况下,独立轮对横移量能高效地回复至中心线位置。

四轮毂电机独立驱动车辆转向电子差速控制

对四轮毂电机独立驱动车辆全轮转向电子差速控制策略进行研究.通过对转向运动学进行分析,建立了3自由度转向动力学模型,构建了四轮毂电机独立驱动车辆电子差速控制系统,提出了神经网络PID（NNPID）电子差速转速转矩综合控制策略,计算四轮目标转速,采用4个神经网络PID控制器,协调分配四轮毂电机的转矩,实现电子差速控制的转向.对于不同给定转向角和车速的仿真结果表明,该策略可以提高车辆低速转向的操控性和平稳性.

全轮独立电驱动车辆双重转向控制策略的研究

为全轮独立电驱动车辆提出一种双重转向的控制策略,设计了双重转向的总体控制结构。它是包括三自由度参考车辆模型、横摆力矩确定层和转矩分配层的分层控制体系。在横摆力矩确定层中,设计了基于PID的横摆力矩控制策略;在转矩分配层中,设计了基于纵向驱动力总和不变的转矩分配策略。在此基础上,开发了双重转向控制策略仿真平台,进行了仿真分析和实车试验,试验结果与仿真结果吻合度较高,表明所提出的双重转向控制策略对减小车辆转向半径有明显效果。

四轮独立驱动电动汽车等转矩转弯试验及滑动率分析

针对研制的四轮独立驱动电动试验样车4 WID EV,建立了稳态转向动力学模型。按等转矩模式分配四轮驱动力,进行了不同条件下的转弯试验。采用坐标网格法测绘了样车的行驶轨迹,得到了四轮转弯半径及整车转弯半径的变化情况。转弯试验揭示出驱动轮存在滑动,推导了滑动率的计算公式,并分析了转向轮转角及车速对滑动率的影响规律。结果表明,采用等转矩模式分配四轮驱动力,各轮间存在相互拖拽现象,从而产生功率内循环。