月球车沙地行驶动力学建模与仿真

提出建立刚性车轮在松软路面行驶的动力学模型的新方法.该方法对车轮进行离散化处理,基于沉陷理论、剪切理论和被动土压理论预测轮壤接触表面的相互作用力,从而可以对车轮表面的应力分布以及电动机转矩进行分析.进一步地将子模型整合到主副摇臂月球车悬架系统中,建立在松软干砂表面行驶的动力学模型.通过仿真,对移动系统中各个车轮表面的应力分布以及驱动电动机转矩进行分析.为验证模型的正确性,开发了信号处理模块和主副摇臂移动系统试验平台,开展主副摇臂月球车移动系统在干沙表面的移动性能试验研究,对仿真和试验中的车轮功耗以及滑移率进行比较.结果表明主副摇臂移动系统动力学模型具有较好的可信性,该建模方法可以用于高效率的多轮多轴月球车的动力学分析.     

8轮扭杆摇臂式月球车车轮与月面间动载荷分析

对车轮与月面间的动载荷进行分析是为了改善月球车行驶平顺性和操纵稳定性.针对8轮扭杆摇臂式月球车结构特点,即每2个与同一摇臂连接的车轮所传递的月面不平度输入相互耦合,对月面不平度的激励进行了等效处理,得到了等效月面不平度函数,以此为基础建立了7自由度月球车振动模型及其振动微分方程.通过对振动微分方程进行傅立叶变换及运用Runge-Kutta数值分析方法进行求解,利用Matlab软件编程计算,确定了8轮扭杆摇臂式月球车悬挂系统的刚度与阻尼合理取值范围.     

汽车ABS系统的PID控制策略及仿真分析

运用汽车动力学理论,建立了PID控制器模型、制动时整车动力学模型、车轮模型。提出了以滑移率为控制目标的ABS系统的控制仿真分析,将PID控制器应用于单个ABS系统控制研究,以车轮滑移率为控制目标,通过轮速与车速传感器采集汽车速度、车轮转速,计算出汽车各轮胎实际滑移率,与期望滑移率进行比较后,将二者的偏差作为PID控制器的输入量,反复调节控制器的控制参数,使其实际滑移率始终处于最佳滑移率附近,通过PID控制最终使汽车在最佳滑移率所对应的地面制动力下进行制动。     

六轮车辆滑移转向动力学建模和运动特性分析

轮式滑移转向车辆由于其机动灵活和结构简单可靠而具有广泛的应用价值。针对一种六轮车辆,车轮触地点的速度分析、轮轴转动副摩擦分析和车辆力平衡关系,建立了稳态滑移转向时的动力学模型,分析了车辆主要结构参数和左右侧车轮转速的不同对滑移转向的瞬心位置、转向角速度和车轮所需力矩的影响规律。研究结果可为六轮车辆的合理设计和实现滑移转向时的轮速控制与驱动提供理论依据。     

月球车坡路行驶地面力学模型与运动性能分析

坡路是崎岖月面环境的典型路况,在分析月球车轮地相互作用模型基础上,建立月球车坡路行驶地面力学模型.同时考虑到前面车轮对月壤扰动变形的影响,在表征不同车轮的沉陷量时,引入沉陷率系数.建立月球车三维可视化仿真平台,并通过对比仿真试验结果与实车试验数据,验证仿真的正确性.通过月球车坡路行驶运动过程仿真分析,给出月球车坡路行驶运动控制策略:当坡度角大于26.6°时,应进行避障,而当月球车具有足够的车轮牵引力时,应控制车轮速度,使月球车在最佳滑转率下行驶.     

月球车差动平衡机构的建模及仿真

车体平衡机构是摇臂悬架式月球车移动系统的重要组成部分,起到调节摇臂悬架运动和受力,减小主车体因地形变化所受的扰动作用.基于轮系式月球车车体差动平衡机构的结构设计,综合考虑了轮齿啮合刚度、摇臂轴扭转变形及齿轮传动回差的影响,建立了虚拟样机模型,在ADAMS软件环境下进行了动态仿真分析,得出该机构的动态特性,为该机构的改进及其在月球车上的实际应用提供了参考依据.     

月球探测车的运动学建模

给出了六轮摇臂-转向架式月球探测车的运动学建模方法。该模型共有6个自由度，包括沿x、y、z方向的移动和绕x、y、z方向的转动。为了获得月球探测车的位置和姿态，正运动学方程由车轮的雅可比(Jacobian)矩阵推导，并对矩阵方程进行了求解；逆运动学方程为已知探测车本体的运动速度，确定单个车轮的驱动速度，以达到期望的探测车位姿。该运动学模型为月球探测车的运行、运动控制系统的设计及自主导航提供了理论基础。     

混合驱动五杆月球车动力学分析

根据月球车腿式移动机构的优点,针对混合驱动五杆月球车用拉格朗日法推出混合驱动五杆月球车的动力模型,得出各杆线速度和驱动力的表达式。通过设置具体参数对混合驱动五杆月球车模型进行分析,得出了混合驱动月球车的五杆机构运动仿真图、主动关节等效惯量,耦合惯量和驱动力矩的变化规律。结果表明,对于给定的运动规律,机构的位形对系统的主动关节等效惯量、耦合惯量和驱动力矩的影响较大。     

月球车车轮与土壤相互作用的力学特性分析

月球车车轮的结构特征及其与土壤相互作用的力学特性对月球车的运动性能有着重要的影响,了解车轮的以上特性对整车的设计有着重要作用。基于地面力学中土壤的承压、剪切模型,建立了刚性车轮在塑性土壤上运动的力学方程,并通过实例计算分析了车轮的运动状态及结构参数变化对其力学参量的影响,为月球车车轮的性能测试和设计改进提供了参考数据。     

巧处理造型机无缓冲故障

造型机的压实头一般采用摇臂式,摇臂的转入、转出采用气—液联合传动。运动过程要求摇臂转动速度要快,快到终点时,缓冲要好,其中转动速度由气缸行程控制,缓冲的好坏程度是由缓冲缸油量控制。转动缓冲的好坏程度将直接影响造型机     

Virtual simulation system with path-following control for lunar rovers moving on rough terrain

Virtual simulation technology is of great importance for the teleoperation of lunar rovers during the exploration phase,as well as the design of locomotion systems,performance evaluation,and control strategy verification during the R&D phase.The currently used simulation methods for lunar rovers have several disadvantages such as poor fidelity for wheel-soil interaction mechanics,difficulty in simulating rough terrains,and high complexity making it difficult to realize mobility control in simulation systems.This paper presents an approach for the construction of a virtual simulation system that integrates the features of 3D modeling,wheel-soil interaction mechanics,dynamics analysis,mobility control,and visualization for lunar rovers.Wheel-soil interaction experiments are carried out to test the forces and moments acted on a lunar rover’s wheel by the soil with a vertical load of 80 N and slip ratios of 0,0.03,0.05,0.1,0.2,0.3,0.4,and 0.6.The experimental results are referenced in order to set the parameters’ values for the PAC2002 tire model of the ADAMS/Tire module.In addition,the rough lunar terrain is simulated with 3DS Max software after analyzing its characteristics,and a data-transfer program is developed with Matlab to simulate the 3D reappearance of a lunar environment in ADAMS.The 3D model of a lunar rover is developed by using Pro/E software and is then imported into ADAMS.Finally,a virtual simulation system for lunar rovers is developed.A path-following control strategy based on slip compensation for a six-wheeled lunar rover prototype is researched.The controller is implemented by using Matlab/Simulink to carry out joint simulations with ADAMS.The designed virtual lunar rover could follow the planned path on a rough terrain.This paper can also provide a reference scheme for virtual simulation and performance analysis of rovers moving on rough lunar terrains.     

月球车月面支撑通过性研究及车轮优化设计

车轮是月球车唯一与月面接触,并通过与月壤作用产生动力推动月球车在月面行走的部件,对月球车车轮的月面支撑通过性研究是保障月球车移动性能的关键环节.从提高附着力、控制沉陷量和减小滚动阻力三方面着手,分析了各因素的影响作用,据此提出了车轮优化方案,有限元仿真分析显示,该车轮方案具有较好的支撑通过性能.     

基于应力分布的月球车轮地相互作用地面力学模型

轮地相互作用地面力学在月球车的设计、性能评价、控制和仿真等方面具有重要作用,是目前基于动力学进行月球车相关研究的瓶颈。基于此,利用针对月球车开发的车轮—土壤相互作用测试系统进行试验,结合试验数据对传统车辆轮地相互作用正应力和切应力分布模型进行修正,并分析月球车轮刺高度对应力分布的影响,从而提出随滑转率变化改变沉陷指数的经验公式,以反映土壤侧向流动等引起的滑转沉陷。对应力分布公式积分得到集中力/力矩计算模型,并结合试验数据进行验证。在载荷为80 N,滑转率从0.05增加到0.6时,模型对于车轮垂直载荷、挂钩牵引力和驱动力矩的计算值与试验数据相比,相对误差不超过10%。模型能够反映滑转沉陷和轮刺效应,可以有效地用于月球车轮地相互作用力学的计算。     

Landing control method of a lightweight four-legged landing and walking robot

The prober with an immovable lander and a movable rover is commonly used to explore the Moon’s surface. The rover can complete the detection on relatively flat terrain of the lunar surface well, but its detection efficiency on deep craters and mountains is relatively low due to the difficulties of reaching such places. A lightweight four-legged landing and walking robot called “FLLWR” is designed in this study. It can take off and land repeatedly between any two sites wherever on deep craters, mountains or other challenging landforms that are difficult to reach by direct ground movement. The robot integrates the functions of a lander and a rover, including folding, deploying, repetitive landing, and walking. A landing control method via compliance control is proposed to solve the critical problem of impact energy dissipation to realize buffer landing. Repetitive landing experiments on a five-degree-of-freedom lunar gravity testing platform are performed. Under the landing conditions with a vertical velocity of 2.1 m/s and a loading weight of 140 kg, the torque safety margin is 10.3% and 16.7%, and the height safety margin is 36.4% and 50.1% for the cases with or without an additional horizontal disturbance velocity of 0.4 m/s, respectively. The study provides a novel insight into the next-generation lunar exploration equipment.     

Nanofriction Mechanisms Derived from the Dependence of Friction on Load and Sliding Velocity from Air to UHV on Hydrophilic Silicon

This paper examines friction as a function of the sliding velocity and applied normal load from air to UHV in a scanning force microscope (SFM) experiment in which a sharp silicon tip slides against a flat Si(100) sample. Under ambient conditions, both surfaces are covered by a native oxide, which is hydrophilic. During pump-down in the vacuum chamber housing the SFM, the behavior of friction as a function of the applied normal load and the sliding velocity undergoes a change. By analyzing these changes it is possible to identify three distinct friction regimes with corresponding contact properties: (a) friction dominated by the additional normal forces induced by capillarity due to the presence of thick water films, (b) higher drag force from ordering effects present in thin water layers and (c) low friction due to direct solid–solid contact for the sample with the counterbody. Depending on environmental conditions and the applied normal load, all three mechanisms may be present at one time. Their individual contributions can be identified by investigating the dependence of friction on the applied normal load as well as on the sliding velocity in different pressure regimes, thus providing information about nanoscale friction mechanisms.     

新型月球车的特点与性能分析

随着国内外掀起的新一轮的探月高潮，新型的月球车越来越受到人们的关注。本文针对月球探测的特点和要求，提出了一种两轮并列式月球车，并对此月球车的特点和性能进行分析；同时，结合两轮并列式月球车的结构和性能，提出了以两轮并列式月球车为子系统的群控策略以降低月球探测的风险，提高月球探测的效率。     

TRACTIVE PERFORMANCE ANALYSIS ON RADIALLY DEPLOYABLE WHEEL CONFIGURATION OF LUNAR ROVER VEHICLE BY DISCRETE ELEMENT METHOD

With the consideration of volume constraint of launch vehicle and trafficability of rover vehicle on lunar regolith terrain, a new design of radially deployable wheel is presented. For the purpose of achieving the meso-mechanics and dynamical behavior of lunar soil particles as well as macro-parameters of tractive performance for radially deployable wheel, the interaction between two types of wheel configurations and lunar soil particles is analyzed by means of discrete element method. The network of contact forces, the displacement vector chart, and the deformation of lunar soil beneath wheels are plotted. The equations of soil thrust, motion resistance, drawbar pull and driven torque are derived in granular scale based on the coordinates transformation and algebraic summation. The calculated results show that there is sufficient traction for both 6-split and 12-split radially deployable wheels with 304 mm outspread diameter to negotiate lunar regolith terrain specified here; the value of drawbar pull enhances with the increase of split number of radially deployable wheel, however, the required driven torque increases simultaneously, therefore, the tractive efficiency decreases.     

载人月球车车轮设计及基于弹性车轮轮壤相互作用的力学模型研究

针对目前月球车车轮难以适应载人运输的需求,设计一种具有轮毂轮辋滑槽机构的金属丝编织筛网式的载人月球车车轮,用来保证车轮的更换便易性及减振抗冲击性。对筛网轮在月壤上行驶的过程建模,验证模型的准确性后,与同等尺寸的传统刚性轮进行对比,表明所设计的车轮结构轻便,比有轮棘刚性轮具备更好的减振抗冲击性;同时其依靠自身的弹性变形增大与地面的接触面积从而比无轮棘刚性轮具有更大的牵引力。对一般弹性车轮的轮壤相互作用应力分布模型进行改进,引入斜率因子以反映车轮的变形,在1 000 N与1 500 N的载荷下及滑转率为0.2时,把改进模型计算得到的挂钩牵引力与仿真输出值进行对比,相对误差不超过15%。引入牵引系数对所设计车轮在不同载荷下的行驶通过性评估,根据可决系数拟合出牵引系数-载荷曲线,建立拟合方程,近而对提高车轮的行驶通过性进行最佳载荷评估。     

虚拟现实环境下月球车运动仿真系统设计研究

虚拟现实技术的出现为月球漫游车的设计、优化等提供了新的有效手段.研究了在虚拟现实环境下基于物理的月球车运动仿真系统,设计并构建了系统的功能模块和体系结构.研究了相关几何模型的真实感建模、月球车运动仿真、实时碰撞检测、多通道立体渲染等支撑技术,据此设计开发了一种月球车运动仿真的原型系统,该原型系统可实现月球车在真实感凹凸月面上的运动仿真,支持鼠标、键盘与虚拟月球车进行交互,具有良好的真实感和沉浸感.