Dynamic characteristics of hydraulic power steering system with accumulator in load-haul-dump vehicle

Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and discussed with SIMULINK software and hydraulic control theory. The results show that the dynamic characteristics of hydraulic power steering system are improved obviously by using bladder accumulator, the hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle generates vibration at the initial stage under the normal steering condition of pulse input, and its static response time is 0.25 s shorter than that without bladder accumulator. Under the normal steering working condition, the capacity of steering accumulator for absorbing pulse is directly proportional to the cross section area of connecting pipeline, and inversely proportional to the length of connecting pipeline. At the same time, the precharge pressure of nitrogen in steering accumulator should be 60%80% of the rated minimum working pressure of hydraulic power steering system. Under the abnormal steering working condition, the steering cylinder piston may obtain higher motion velocity, and the dynamic response velocity of hydraulic power steering system can be increased by reducing the pressure drop of hydraulic pipelines between the accumulator and steering cylinder and by increasing the rated pressure of hydraulic power steering system, but the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle have nothing to do with the precharge pressure of nitrogen in steering accumulator.

Simulation of Steering Performance for Electric Drive Tracked Vehicle

According to the analysis of the fundamental steering theories of the electric drive tracked vehicle, a new effective electric drive tracked vehicle model is built in this paper. And the simulation of the steering performance of the vehicle is made. The results show that the electric transmission has great advantage on the steering performance aspect; the small radius steering and even the pivot steering is realizable, and the agility and the rapidness is wonderful. The regenerative energy can be fully utilized by controlling.

Modeling and Kinematics Simulation of Hydro-mechanical Split Path Steering Device of Tracked Vehicle Based on CATIA

Based on the working principle of hydro-mechanical split path of tracked vehicle, a operating gear was developed which was controlled by steering wheel and match with transmission case. Then CATIA software was used to build the three-dimensional model and carry out dynamic simulation of the mechanism. The result indicates that the design of the mechanism fulfills the request.

Dynamic Modeling and Analysis of 9-DOF Omnidirectional Legged Vehicle

The omnidirectional legged vehicle with steering-rails has a specific mechanism feature, and it can be controlled flexibly and accurately in omnidirectional motion. Currently there lacks further research in this area. In this paper, the mechanical characteristics of independent walking control and steering control and its kinematics principle are introduced, and a vehicle has a composite motion mode of parallel link mechanism and steering mechanism is presented. The motion direction control of the proposed vehicle is only dependant on its steering rails, so its motion is simple and effective to control. When the relative motion between the walking and steering is controlled cooperatively, the vehicle can walk perfectly. By controlling the steering rails, the vehicle can walk along arbitrary trajectory on the ground. To achieve a good result of motion control, an equivalent manipulator model needs to be built. In terms of the mechanism feature and the kinematic principle, the simplified manipulator model consists of a rail in stance phase, a rail in swing phase, and an equivalent leg. Considering the ground surface slope during walking, a parameter of inclination angle is added. Based on such a RPP manipulator model, the equations of motion are derived by means of Lagrangian dynamic approach. To verify the dynamic equations, the motion of the manipulator model is simulated based on linear and nonlinear motion planning. With the same model and motion parameters, the dynamic equations can be solved by Matlab and the calculation data can be gained. Compared with the simulation data, the result confirms the manipulator dynamic equations are correct. As a result of such special characteristics of the legged mechanism with steering rails, it has a potential broad application prospects. The derivation of dynamics equation could benefit the motion control of the mechanism.

Design of a Preview Controller for Articulated Heavy Vehicles

The paper presents a preview controller design for ATS （active trailer steering） systems to improve high-speed stability of AHVs （articulated heavy vehicles）. An AHV consists of a towing unit, namely tractor or truck, and one or more towed units which called trailers. Individual units are connected to one another at articulated joints by mechanical couplings. Due to the multi-unit configurations, AHVs exhibit unique unstable motion modes, including jack-knifing, trailer swing and rollover. These unstable motion modes are the leading cause of highway accidents. To prevent these unstable motion modes, the preview controller, namely the LPDP （lateral position deviation preview） controller, is proposed. For a truck/full-trailer combination, the LPDP controller is designed to control the steering of the front and rear axle wheels of the trailing unit. The calculation of the corrective steering angle of the trailer front axle wheels is based on the preview information of the lateral position deviation of the trajectory of the axle center from that of the truck front axle center. Similarly, the steering angle of the trailer rear axle wheels is calculated by using the lateral position deviation of the trajectory of the axle center from that of the truck front axle. To perform closed-loop dynamic simulations and evaluate the vehicle performance measure, a driver model is introduced and it ＇derives＇ the AHV model based on well-defined testing specifications. The proposed preview control scheme in the continuous time domain is developed by using the LQR （linear quadratic regular） technique. The closed-loop simulation results indicate that the performance of the AHV with the LPDP controller is improved by decreasing rearward amplification ratio from the baseline value of 1.28 to 0.98 and reducing transient off-tracking by 95.03%. The proposed LPDP control algorithm provides an alternative method for the design optimization of AHVs with ATS systems.

基于Simulation X的多轴转向系统功能安全仿真分析

基于ISO 26262《道路车辆功能安全》的标准要求,对特种车的多轴电液转向系统进行分析,以提高系统的安全性和可靠性。运用Simulation X软件建立详细的多轴特种车仿真模型,通过模拟故障模式注入进行仿真试验。对仿真结果和数据进行分析,评估得到故障的严重性、暴露度和可控性,从而确定相应的汽车安全完整性等级。基于故障注入仿真的汽车功能安全分析方法,在系统早期设计阶段可以作为评估架构安全性的重要手段。

自动紧急转向工况下驾驶员离位响应的一体化仿真研究

为了探究自动紧急转向过程中驾驶员的动态响应,采用主动安全技术和被动安全防护策略相结合的方式,进行特定自动紧急转向场景下驾驶员离位响应的一体化仿真研究.基于模型预测控制算法建立自动紧急转向控制模型,使用PreScan、CarSim和Simulink等软件进行联合仿真,获取车辆在转向过程中的动态响应;结合主动人体模型和驾驶员侧约束系统模型,分析车辆及驾驶员的运动特征以及主动卷收器安全带对驾驶员离位的改善效果.结果表明,在72 km/h的行驶速度下,车辆和驾驶员在纵向换道距离分别为40 m、50 m和60 m的左侧自动紧急转向过程中运动响应分为右倾和左倾两个阶段;右倾阶段车辆横向加速度、侧倾角以及主动人体模型的最大离位量明显高于左倾阶段;随着纵向换道距离的增加,驾驶员头部的最大横向离位量由89.56 mm降低到70.22 mm和53.05 mm;主动卷收器安全带的应用有效改善了驾驶员的离位程度,驾驶员头部最大横向离位量分别降低18.90%、49.56%和67.62%,胸部最大横向离位量分别降低12.70%、41.63%和53.69%,提高了驾驶员在自动紧急转向阶段的安全性.

数字轨道胶轮列车全轴转向控制策略仿真

[目的]DRT(数字轨道胶轮列车)(以下简称“数轨列车”)具有多车厢、多转向轴的复杂走行结构,与传统胶轮列车具有较大差异,故需结合转向系统架构设计与响应参数,设计一种全轴转向控制策略,以实现数轨列车的平稳、安全、高效运行。[方法]分别对单节、双节、多节车辆建立数轨列车模型;通过建模成功将复杂的三编组车辆模型简化为四自由度刚体运动模型,将数轨列车的转向系统控制问题转化为对四个控制点的运动学控制问题,并提出了一种数轨列车全轴转向控制策略。[结果及结论]MATLAB软件仿真结果表明:提出的全轴转向控制策略方法,能够将数轨列车的运动轨迹偏差控制在10 cm内。

履带车动力学模型离心力影响边界探究与模型验证

针对考虑离心力时履带车动力学模型在控制算法应用中计算量过高的问题,理论计算了离心力对模型计算精确度的影响范围,并对动力学模型进行了仿真验证。论文首先理论分析了三种履带车动力学模型,以转向极偏移量为衡量离心力影响程度的指标,基于某履带车结构参数进行了理论计算,确定了可以忽略离心力影响的运动学范围。为验证该范围下滑移滑转模型的有效性,利用CoppeliaSim和Simulink进行了仿真对比,结果表明,在该运动学约束下,滑移滑转模型与履带车适配性较好,对减小履带车模型计算量有重要意义。

分布式驱动电动汽车四轮转向与横摆力矩集成控制研究

针对四轮独立驱动与独立转向的分布式驱动电动汽车稳定性控制问题,提出了一种四轮转向与横摆力矩集成控制策略。采用分层控制结构,基于模糊理论设计上层控制器,根据期望横摆角速度、期望质心侧偏角与实际值的偏差,计算附加后轮转角和附加横摆力矩;下层控制器包括四轮转角控制器和四轮力矩分配器,附加后轮转角控制器根据转向盘转角和车速分别采用比例前馈加模糊反馈或阿克曼转向进行附加后轮转角控制,四轮力矩分配器根据附加横摆力矩需求采用二次规划算法对四轮力矩进行优化分配。选取典型实验工况,通过联合仿真实验对后轮转向与横摆力矩集成控制策略进行验证。结果表明:集成控制策略能有效提高分布式驱动电动汽车稳定性。

基于模拟退火算法优化增益的车辆传动比算法设计

针对线控转向(SBW)系统车辆进行研究,基于定横摆角速度增益法设计变传动比算法,并依照系统结构与设计目的对算法改进修正。采用模拟退火算法,以郭孔辉院士提出的操纵稳定性综合评价指标函数作为优化算法目标函数,对经验选取的定增益值进行优化,得到全局最优定增益值。以全局最优增益值作为最终传动比算法设计依据。对所设计传动比算法进行仿真分析,结果表明,采用优化后增益值传动比算法的SBW车辆具有更好的转向性能,并有效减轻驾驶员的操作负担。

四轮转向车辆后轮转角控制方法研究

为提高四轮转向车辆在低速时的机动性,建立了包括侧向运动、横摆运动的整车2自由度四轮转向车辆动力学模型,总结归纳了四轮转向车辆后轮转角控制方法,搭建了CarSim和Matlab/Simulink联合仿真平台,使CarSim中建立的整车模型的实际转向状态接近预设的2自由度理想转向状态,通过设置包括前轮角阶跃输入在内的3种工况进行了不同控制方法的仿真对比分析。结果表明:文中所提到的几种控制策略均能改善四轮转向车辆在低速时的机动性,使车辆具有更高的机动运动能力,为找到一种四轮转向车辆后轮转角最优控制策略奠定了基础。

基于自抗扰控制的分布式铰接车辆转向控制

铰接车辆通过前后车体间的相对转动实现转向行驶,这种特殊的转向形式导致其转向稳定性差,转向运动控制精度要求高。针对此问题,以某四轮分布式驱动井下支架搬运铰接车为原型,构建包括车身模型、轮胎模型和单阀控双非对称缸液压转向系统在内的分布式铰接车辆11自由度非线性动力学模型,并设计基于自抗扰控制器的液压转向控制系统,用以提升铰接车辆的转向稳定性。为验证此方法的有效性,建立MATLAB/Simulink仿真模型,进行初始车速为2.5 m/s的转向分析,并在同种工况下,加入外界干扰力矩,以PID控制器为对照组,对比分析两种液压转向系统控制器的抗扰动性能。仿真结果表明:基于ADRC控制的液压转向系统的转向角度误差在0.017 rad以内,且转向角度跟踪速度快,相对于PID控制器具有更好的抗扰动性能,有效提高了铰接车辆的转向稳定性。

GWO-PID控制算法的汽车线控转向系统研究

为了提高汽车转向系统工作性能,对其线控转向系统进行了研究。首先,在对线控转向系统结构与原理分析基础上,建立其动力学模型;基于MATLAB/Simulink软件,建立其仿真模型。在此基础上,研究线控转向系统PID控制算法,对前轮转角进行控制。为进一步提高系统稳定性,采用灰狼算法对PID参数进行优化。最后,采用双移线实验工况进行仿真实验;结果表明所研究的转向系统具有良好的转向性能、GWO-PID控制算法较之PID控制算法可使汽车转向相关关键指标参数更快达到稳态值,提高了汽车转向稳定性和行车安全性。

跨坐式单轨车辆的横向平稳性研究

为减小转向架相对轨道梁的摇头角,在车辆通过曲线时,跨坐式单轨车辆的辅助导向装置的输出力矩与二系悬挂摇头力矩相互抵消,直接影响车辆运行的横向平稳性。通过动力学仿真,分析车辆运行速度,以及辅助导向装置油气弹簧预压力对转向架和车体的横向振动加速度功率谱密度影响,确定不同预压力下油气弹簧对横向平稳性的影响。仿真结果表明:横向平稳性处于优秀等级,受车速影响较大,受油气弹簧预压力的不利影响较小;随着油气弹簧预压力增加,横向振动功率谱密度的谱值均略有增加,但影响较小。

基于七自由度车辆模型仿真平台的轮胎操纵稳定性仿真分析

利用基于MATLAB SIMULINK的七自由度车辆模型仿真平台,以轮胎PAC2002模型为输入,进行车辆操纵稳定性仿真,并与实车测试结果对比。结果证明客观性能指标仿真结果与实车测试主观评价结果的一致性较好,基于七自由度车辆模型仿真平台可以较好地预测轮胎的转向性能,也可以在一定程度上预测操纵稳定性。

转向盘角阶跃输入横摆角速度响应时间影响因素分析

汽车转向盘角阶跃输入下的横摆角速度响应时间的优劣关系到汽车的操纵稳定性,也是汽车研发过程中需要关注的试验数据。本文通过应用CARSIM软件建立整车模型,改变不同的影响因素的值,分析仿真结果,从而对改进汽车汽车转向盘角阶跃输入下的横摆角速度响应时间提供参考,对优化汽车操纵稳定性具有重要意义。

四轮驱动电动汽车差动助力转向系统联合仿真与试验

基于AMESim软件建立了四轮独立驱动电动汽车动力学仿真模型,并应用Matlab/Simulink建立了差动助力转向控制系统模型,在此基础上研究了旨在降低转向盘手力和辅助转向轮回正的左右前轮转矩分配控制策略,并采用后轮差动实现车辆横摆校正。联合仿真结果表明,该差动助力转向控制策略在满足转向轻便性、路感回馈及辅助回正基本要求的同时,还可以补偿前轮差动驱动对车辆稳定性的影响,提高了差动助力转向技术的实际应用能力。通过差动助力转向控制系统的快速原型实车双移线道路试验进一步验证了该系统的转向助力可行性和路感保持能力。

履带车辆转向动力学仿真

本文采用机械系统动力学分析与建模通用方法 ,通过总体参考系、动参考系、连体参考系来描述车辆与地面运动和相互作用关系 ,并综合考虑了包括离心力等因素对履带车辆转向的影响 ,对其在水平硬地面转向过程进行了动力学分析和动态仿真计算。对履带车辆低速转向的仿真与试验结果进行了对比分析 ,说明所建模型与实际履带车辆的转向动态过程基本一致 ;高速情况下分别对有无离心力影响两种情况进行了仿真 ,结果的对比分析说明了离心力对履带车辆高速转向的影响。

电动助力转向系统的建模与仿真技术

概述了电动助力转向系统(EPS)的结构和工作原理,并介绍了电动助力转向系统助力特性的设计方法。在分析了电动助力转向系统各组成部分数学模型的基础上,构建了基于Simulink的电动助力转向系统仿真模型。采用了PID和直流斩波控制策略对电动机目标电流进行闭环跟踪控制。仿真结果表明:所设计的助力特性较好地协调了转向轻便性和路感之间的矛盾,同时,电动机实际电流较好地跟踪了目标电流,从而验证了控制策略的有效性。