Effects of Wind on Steady-state Scan Characteristics and Hit Probability of Terminal-sensitive Projectile

The wind effects on steady-state scan characteristics and hit probability of terminal-sensitive projectile were discussed in this paper. Considering wind as the constitutions of the average wind and the impulsive wind, a simplified wind field model was established for the ballistic calculation of the steady-state scan phase; under the windy condition, the effects of the range wind and the beam wind on the steady-state scan characteristics of the terminal-sensitive projectile were analyzed in detail and its hit probabilities for a certain armored target were calculated. The calculated results show that, when the wind speed exceeds a certain value, the hit probabilities of terminal-sensitive projectile drop rapidly; the wind effects must be considered in the application of the terminal-sensitive projectiles. This paper provides some theoretical references for the fire wind speed correction and the global structure optimization of the terminal-sensitive projectile.

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.

Study on Characteristic of Electric Power Assist Steering System

A pinion-type electric power steering (EPS) equipped on a sedan is reached in this paper. A three-freedom dynamic model of this system is created. The variables affecting assist character is analyzed. The formulas of simpled steering resistance force and the relationship between assist gain and vehicle speed are presented for the first time. Assist character is found based on the parameters of a sedan at last. This assist character is fit for the control rule of the EPS system through analyzing this character. The assist character figure offers reference for system design and control. Furthermore, this research method has generality for assist character of different kinds of vehicles.

Analysis on steering characteristics of crawler pipeline robot

In order to improve the elbow passing performance and different diameter adaptability of pipeline robot,a supported crawler pipeline robot is designed,which adopts screw nut mechanism and hinge four-bar mechanism to adapt to the complex environment such as variable diameter pipeline and elbow.The steering characteristics passing through the elbow are studied,the kinematic of pipeline robot bending steering is established,the geometric constraint(GC)and steering constraint(SC)in the elbow are analyzed,and the steering experiment is conducted.The results show that the robot can pass through the elbow by the SC model.The SC model can reduce the motor current and energy consumption when the robot passes through the elbow.

FLEXIBLE 2-DOF STEERING MODEL OF MULTI-AXLE HEAVY-DUTY VEHICLE

A flexible two degrees of freedom (2-DOF) steering model of multi-axlevehicle (MAV) is presented with considering the effect of frame flexibility based on the classic2-DOF model. A method to calculate the frame flexibility is derived by using three moments equation.The steering stability of MAV is analyzed. The steering performance of MAV is also researched infrequency domain. Simulation results show that the dynamic effects of flexible model are more severethan rigid model and the flexible effect of frame will weaken the steering stability of MAV.Different disposals of steering axles lead to different steering characteristics of MAV. Thein-phase steering mode improves the steering characteristics and stability at high speed. Theanti-phase steering mode increases the steering mobility at low vehicle speed.

Intelligent Vehicle Human-Simulated Steering Characteristics Access and Control Strategy

As the traditional control algorithm is over-dependent on accurate vehicle model in intelligent vehicle steering control, a human-simulated intelligent control method is proposed based on experienced driver steering characteristics. Intelligent vehicle unmanned steering system dynamics model and the driver model are set up.Through experienced drivers' trial run experiment, the analysis is mainly conducted on the double lanes condition.After the transformation of coordinates on global positioning system(GPS) derivative, the path information of local coordinates is accessed. The ideal driver steering path is obtained through fuzzy C-means clustering algorithm. The human-simulated intelligent controller is designed. Characteristic model is established according to the ideal and practical steering angle deviation and the deviation rate. Besides, the corresponding control rules and control modality set are designed. The joint simulation under CarSim joint/Simulink environment shows that the humanoid steering controller designed in this paper has better tracking performance than the model predictive control.

Driver-automation shared steering control considering driver neuromuscular delay characteristics based on stackelberg game

To promote the intelligent vehicle safety and reduce the driver steering workload,stackelberg game theory is adopted to design the shared steering control strategy that takes the driver neuromuscular delay characteristics into account.First,a shared steering control framework with adjustable driving weight is proposed,and a coupling interaction model considering the driver neuromuscular delay characteristics is constructed by using the stackelberg game theory.Moreover,the driver-automation optimal control strategy is deduced theoretically when the game equilibrium is reached.Finally,simulation and virtual driving tests are carried out to verify the superiority of the proposed method.The results illustrate that the raised method can enhance the vehicle safety with low driving weight intervention,and it can achieve better auxiliary effect with less control cost.In addition,the driver-in-the-loop test results show that the proposed strategy can achieve better performance in assisting drivers with low driving skills.

电动助力转向系统Carsim-Simulink联合仿真控制研究

电动助力转向系统作为电动汽车的主流配置,其性能好坏对整车转向操纵稳定性能有重要影响。以某款自主品牌电动汽车EPS系统为研究对象,进行动力学分析并依次建立Simulink子系统模型。根据实车参数,设计直线型助力特性曲线并输入前述模型,最终建立Carsim/Simulink联合仿真运动学模型并开展国标操纵稳定性仿真试验。结果表明:在方向盘转向角脉冲和角阶跃试验中,较无EPS助力控制车型,有EPS助力控制车型具有良好的车辆瞬态响应度和操纵稳定性;在转向轻便性试验中,验证本款车型助力特性合理,车辆具有较好的助力效果。

基于传递矩阵法的指向式旋转导向工具主轴振动特性

指向式旋转导向工具应用于井眼轨迹控制时,其主轴的动力学特性将直接影响到井眼轨迹控制效果及作业安全,而在钻进工况下,工具钻压传递机构在主轴上的位置对主轴的动力学特性起着重要的作用。因此,为了分析钻压传递机构的位置对主轴动力学特性的影响,利用多体系统传递矩阵法建立了指向式旋转导向工具外壳-轴承-主轴系统的动力学模型。通过推导主轴上任意节点的几何和力学方程,该研究能够评估钻压传递机构的位置对主轴动态性能的影响规律。结合实例运算分析了钻压传递机构的安装位置对主轴固有频率和振型的影响,探讨了工具造斜时,钻压传递机构安装位置对主轴动态位移的影响。结果表明,随着钻压传递机构安装位置距离钻头越远,主轴固有频率和动态位移均增大,因此在满足工作要求下,推荐钻压传递机构安装位置尽可能靠近钻头端。为验证基于传递矩阵法建立的主轴动力学模型的正确性以及钻压传递装置安装位置对主轴动态位移影响规律,在指向式旋转导向工具试验台架上进行了钻进工况下主轴测点偏移量测试试验,结果表明,试验测得的数据与理论计算的数据基本吻合,误差最大仅为6.47%。

考虑履带机器人转向特性的全局路径规划

针对传统A星路径规划算法忽略车辆转向过程,导致规划路径行程时间较长的问题,提出了考虑履带车转向特性的改进A星算法。首先,扩大A星算法的搜索邻域,提高转向角的灵活度。其次,分析考虑履带车的转向特性,将转向时间加入到代价函数中,建立以时间最短为目标的代价函数,缩短履带车的行程时间。最后,构建删除冗余节点和新增优化节点的规则,改善路径的平滑性使规划的路径进一步优化。通过Matlab仿真和实车实验进行研究,研究结果表明:改进算法在路径长度、转向次数和行驶时间方面都有了减少,规划的路径要优于传统A星算法和对比文献算法。改进A星算法能有效提高所规划路径的质量,提升履带机器人的自主巡航能力和智能化水平。

乘用车双电机冗余电动助力转向系统研究

为了提高电动助力转向系统的安全性以及可靠性,基于乘用车提出一种双电机冗余电动助力转向技术,采用转向执行双助力电机,可以从硬件上实现冗余,避免任意单电机发生故障时导致转向系统的失效,不仅可以满足转向系统对于轻便型、助力跟随性的要求,还可以减轻单个助力电机的负载提高电机的使用寿命。针对提出的问题,介绍了对双电机阻力转向系统整体结构及工作原理,并对其关键零部件进行分析论述。搭建双电机冗余系统仿真模型,双电机电流分配采用“一主一辅”的控制方式,并进行方向盘多种工况仿真验证。针对助力转向出现抖动问题,结合“扫频试验”,设计输出转矩超前滞后补偿方式进行相位校正补偿。通过实车试验验证了该算法的准确性和有效性。实验结果表明双冗余电动助力转向系统极大提高了转向力矩的稳定性,抑制其扰动性,有较好的助力效果,极大提高系统的可靠性和安全性。

推靠式旋转导向系统钻具组合力学性能分析

针对基于动力学特性的旋转导向钻具安全性能研究较少。为此,综合考虑钻具结构、钻井参数、钻柱与井壁接触等参数,基于Lagrange方程建立了全井钻柱系统动力学模型,采用有限单元法对模型离散,并采用Newmark-β求解,根据旋转导向钻具结构和钻具属性,研究了扶正器安装位置、柔性节尺寸、钻压影响因素下的旋转导向钻具组合动力学特性和安全性能。研究结果显示:安装扶正器能显著降低旋转导向钻具组合的横向振动;柔性节的长度对旋转导向钻具组合的安全性能影响很大,合理的长度能显著降低横向振动,反之则会起到相反的效果;增加钻压会增加底部钻具组合的横向位移,工程上不建议在使用旋转导向工具时采用高钻压提高钻井速度。研究结论可为旋转导向工具研究和应用提供理论支撑。

应用AMESim双转向器全液压转向系统特性分析

为全液压转向系统设置双转向器可以解决大排量需求的问题,但此种布置会影响系统的动态响应特性,因此分析系统的可行性。根据某自卸车全液压转向系统的结构特点,对单转向器系统的关键参数进行分析和设计,获取各参数的数值;根据车辆转向参数的需求,对转向系统的压力损失和温升进行校核,以验证系统可否满足需求;根据前述分析,采用AMESim搭建分析模型,通过转角输入验证模型准确性,并验证负载、输入变化对系统特性的影响;基于转向系统试验台,通过输出特性分析,对前述设计和分析模型进行验证。结果可知:双转向器系统压力损失满足要求,最高温升控制在56.8℃,控制在系统要求的范围内;影响双转向器系统输出特性和油液流量的因素主要是方向盘转速和系统负载,其他因素基本无影响,仅对系统的响应时间产生影响;试验测试平台获取的角速度阶跃输入下的,转向器输出口压力、流量放大器输出口流量与仿真分析结果误差控制在5%以内,表明分析模型和结果的可靠性,为此类分析设计提供参考。

基于曲线拟合的液压动力转向器转阀棱边坡口设计方法研究

转阀棱边坡口结构对液压动力转向器的助力特性影响非常大,但对于棱边坡口结构的设计方法研究较少。根据转阀的结构和工作原理,建立液压动力转向器的转阀阀口过流面积数学模型和AMESim仿真模型,通过与试验结果进行对比,验证了模型的可靠性;依据新型产品的助力特性设计目标,提出一种基于曲线拟合的棱边坡口设计方法,依据助力特性的设计目标,利用MATLAB软件求解了棱边坡口曲线解析式中的参数。仿真结果表明:所设计的棱边坡口结构能够满足设计要求,验证了设计方法的有效性,为液压动力转向器优化设计提供了参考。

电动助力转向系统NVH特性数据采集与性能评价

针对汽车电动助力转向系统NVH特性数据存在多点位异步采样误差较大,且选取性能评价依据单一的问题,设计一种二十四通道NVH特性数据同步采集与多角度特性分析系统;采用多个数据采集模块联结、同步动态随机存储器读写、高速串行计算机扩展总线融合的方式,实现二十四通道NVH特性数据的同步精确采集与快速传输;从机械性能与声振特性方面对电动助力转向系统NVH特性进行多角度分析与评价。结果表明,与传统测试方法相比,所提方法可实现多点位同步高精度采样与多角度信号时频域分析,每个通道数据采集速率可达200 kHz/s,时频域分析依据更丰富、更全面。

不同车型组合的车头时距特性研究

为研究信号交叉口交通流的运行特征,提高交叉口的通行能力,缓解交通拥堵,对车头时距的影响因素和分布特征进行分析。首先,根据车辆尺寸分为4种车型组合;然后,基于VISSIM仿真获取各类型车辆的车头时距数据,探讨不同车型组合、车辆转向和车道位置对车头时距的影响;最后,采用对数正态分布和韦布尔分布检验不同组合的车头时距数据的拟合效果,并检验模型的拟合优度。结果表明:根据不同车型组合,车头时距由大到小为大型车-大型车、大型车-小型车、小型车-大型车和小型车-小型车;根据不同车型组合下的转向,车头时距由大到小为左转、右转和直行;根据不同车型组合下的车道位置,车头时距由大到小为外侧车道、中间车道和内侧车道。

Investigations on control algorithm of steady-state cornering and control strategy for dynamical correction in a steer-by-wire system

To improve the handling performance of a steer-by-wire (SBW) vehicle, a series of control logics are proposed. Firstly, an algorithm for enhancing the maneuvering in steady-state cornering is presented. On this basis, two categories of control strategies are used to dynamically correct and compensate the transient state steering responses and vehicle behaviors. Simulator tests including subjective evaluations and virtual field tests are both conducted to make comprehensive investigations on the series of control logics. The subjective evaluations demonstrate that the SBW vehicle with a specifically selected value of steering sensitivity tends to be more desirable for driving than a conventional one in which a fixed steering ratio exists. The virtual field tests indicate that the control strategies for dynamical correction and compensation could effectively improve the handling per-formances of an SBW vehicle by reducing the work load of drivers, enhancing the track-holding performance, and improving steering response properties.

基于骨架模型的重卡转向轮运动学特性研究

为解决传统转向轮运动学分析方法复杂及更改周期长的问题,提出了基于骨架模型的分析方法。以某重卡为研究对象,通过CATIA软件以参数化的方式创建系统骨架、零件骨架,并保持系统骨架与零件骨架之间的映射关系。在零件骨架模型之间添加相关运动副,建立DMU模型;对转向轮进行运动学分析,得到相关参数随车轮跳动的变化关系、左右转向轮转角的对应关系。该方法无需建立三维零件模型,通过调整参数的方式即可修改骨架模型和运动学特性。

长轴距车辆四轮转向控制算法设计

车辆长轴距设计在不增加车身长度的前提下可有效增大站立面积,增加单车载客量,在城市化发展的今天其设计已成为一种技术趋势,但对车辆的低速通过性和高速稳定性提出了新的挑战。对此,文章以长轴距商用车为研究对象,基于车辆动力学和汽车悬架设计理论,首先设计了长轴距车辆关键参数,搭建了整车18自由度动力学仿真模型;接着根据整车设计参数,以质心侧偏角度趋向于零为控制目标,设计了四轮转向控制算法;最后,研究了整车在不同转弯半径的稳态圆周工况和不同速度下的转角脉冲工况下,前轮转向控制和四轮转向控制对车辆动力学性能的影响。仿真结果表明,四轮转向设计在低速转弯半径为R15稳态圆周转弯工况下,通过空间从4.6 m降低到3.9 m,能有效地提升车辆前后轴的循迹能力,提升车辆行驶的通过性和安全性;在极速100 km/h脉冲工况下,侧向加速度峰值从4 m/s2降低到1.5 m/s2,横摆角速度峰值从11°/s降低到3°/s,因此,在高速转角脉冲工况下能够有效降低车辆侧偏角、侧向加速度和横摆角速度等动力学指标量,提升车辆的高速行驶的安全性、稳定性和舒适性。

SBW系统中驾驶员转向特性控制研究

针对多样化的驾驶员特性参数对线控转向影响研究。首先在分析驾驶员特性参数对转向控制影响的基础上,构建单点预瞄模型;其次,采用驾驶模拟器平台在典型工况下采集驾驶员转向特性数据,提取数据特征值;然后,设计RBF自适应神经网络控制器,以适应不同驾驶员特性的前轮转角控制;最后对所设计的控制器针对不同车速、不同驾驶员特性进行仿真试验。试验结果表明:基于RBF自适应神经网络控制器可以实现车辆在不同车速下的稳定转向,车速响应效率提升约(7.9~17.1)%,对于不同驾驶员特性具有良好的自适应效果,可提高驾驶员转向舒适性与安全性。