【作者】 赵志萍；

【导师】 刘暾；

【作者基本信息】 哈尔滨工业大学 ， 飞行器设计， 2010， 博士

【摘要】 “嫦娥工程”一期的顺利完成标志着中国航天正式进入了深空探测的新时代。在接下来的二期不载人探月工程中,月球车扮演着极其重要的角色。月球车相关技术的研究领域十分广阔,本文针对性的进行了以下几方面的研究。提出了一种新构型的月球车行走系统。月球车行走系统的设计能否满足月球探测的要求是保证探月任务圆满完成的基础。月球表面地形非常复杂,整个月面覆盖着厚度不等的松散的月壤层,遍布大小不等的砂石、沟壑等障碍物,因此月球车的行走系统要具有很好的越障和过沟能力,同时在车轮发生打滑时仍然具有足够的牵引能力来驱动月球车行走。针对以上要求提出并设计了一种新型六轮月球车行走系统。该行走系统采用六轮独立驱动,车轮在车体两侧呈不对称分布,相当于有六个车轮轴,增加了车体的越障和过沟能力。在摇臂和车体底盘的连接处增加了电机驱动机构,可以抬起车轮以协助越障,并且可以重新分配载荷,使得在个别车轮发生打滑时仍能为车体提供适当的牵引力,还可将车轮折叠便于安装在整流罩中。针对新构型的月球车进行了动力学分析、仿真与实验研究。首先建立了月球车整体系统结构图,然后运用牛顿-欧拉方法建立了整车的质心运动方程、绕质心转动方程、摇臂力矩平衡方程、车轮驱动方程,并且添加了几何约束和速度约束,使得方程组封闭可解。由于该月球车的车轮在车体两侧不对称分布,且所建立的方程组为微分代数方程,使得方程组求解的难度增加,最终采用有限差分法进行解算。根据土壤力学原理对实验用土壤进行了参数测定实验,得到粗略的土壤力学参数。然后对月球车在平地(硬地和松软土壤)、斜坡、越障、越沟等典型行走性能进行了计算机仿真,得出了一些对实际操作有参考价值的数据。在7×9米室内试验场地进行了行走实验。实验表明新构型月球车能够攀越高度达到0.2m(大于车轮半径0.125m)的障碍物,并且能够越过0.3m宽的沟壑(大于车轮直径),证明该月球车具有较好的行走性能。提出并设计了一种高精度的月球车单轮气浮实验装置。为了更好的在地面研究月球车在六分之一重力下的工作状况,同时更好的研究车轮与土壤相互作用地面力学,以及各车轮单独及考虑到其它轮间相互影响时的工作特点,利用月球车单轮实验装置进行地面研究是一种常用的方法。针对目前的月球车单轮实验装置采用机械导轨带来的摩擦会对实验测量数据产生较大影响的问题,提出并设计了月球车单轮气浮实验装置。该实验装置在水平和竖直方向均采用了气体润滑技术,充分利用气体支承摩擦小,运动平稳的优点,从而抵消滑轨所带来的不可测摩擦力,对精确完成实验数据的测量起到很大作用。同时还设计了伺服系统水平追踪系统,使承托板移动时电缆和气管的变化、不规则干扰等与主工作系统隔离,保证系统工作精度。利用该实验台可以进行单个车轮驱动动力学和控制性能研究、可以研究各车轮间相互制动和推进作用、车轮与土壤相互作用,以及针对新构型行走系统的改善月球车车轮牵引力能力的研究。提出了一种基于立体视觉的特征光源辅助月球车定位系统并进行了实验研究。该定位系统由月球飞行器的下降级上的两台相距不远的摄像机和一台激光测距仪组成,结合月球车上的特征光源辅助装置,可以确定月球车上特定点(例如质心)在惯性基准系中的位置信息,同时还可以得到月球车的姿态信息。针对该系统应用CMU的James Bruce的连通域分析方法提出了一种月球车实时位姿算法并进行了仿真研究,仿真结果表明该算法在计算速度和精度能满足要求且算法对于噪声有一定的鲁棒性。最后在7×9平方米的实验场地进行了实验研究,实验结果表明该定位系统可实现足够的精度,适用于小范围的月球车导航。更多还原

【Abstract】 The success of the first stage of Chang’e Project indicates that the Chinese as-tronautics has entered a new era of deep space exploration. In the second stage ofunmanned lunar exploration, lunar rover will play a very important role. The re-search areas of lunar rover are very extensive, however only a few aspects of newkine of lunar rover are illustrated in this dissertation.The mobile system is the key part of lunar rover,which determines the efficacyof lunar exploration. The surface of the moon is such complicated that the wholeterrain is covered by loose soil, different sizes of rocks and sands, and obstacleslike gullies. Therefore, it is necessary for the lunar rover to be capable of crossingover obstacles and the gullies. Especially when the slipping of one or more wheelsoccurs, the lunar rover could still move with enough traction. In view of the aboverequirements, a new kind of mobile system of a six-wheeled lunar rover is designed.The Six wheels, set asymmetrically at both sides of rover body, could be driven in-dependently. They are equivalent to six wheel axles, increasing the ability of cross-ing over obstacles. And there are also motors in the joints of rocker arms, which canassist in crossing by raising wheels and redistribute the loading weight. Moreover,when one or more wheels slip, the rover can still get proper traction from thesemotors and also the wheels are easily folded up to be fixed in cowling.Considering the new kine of lunar rover, Newton-Euler method is adopted todeduce the equations of centroid movement of overall rover, rotary movementaround mass center, rotary motion of suspension levers for suspension points anddrive equations for wheels. Meanwhile, the geometry and velocity constraints aregiven. As the layout of wheel arrangement are asymmetric and the the dynamicequations are differential-algebraic equations, the difficulty of solving equations isincreased. So the finite difference method is employed to solve equations in thisdissertation. The parameters of soil for experiment are measured using the terra-mechanics principle. The performances of rover motions on flat and slope terrain,climbing obstacle and passing ditch are analyzed by simulation, and through simu-lation, certain useful results are acquired for drive. According to the dynamicsimulation results, several verifying experiments of lunar rover movements are car- ried out in 7×9 m2 test bed. The lunar rover has the ability to climb obstacle of 0.2m which is higher than wheel radius and pass ditch of 0.3m which is wider than wheel diameter. The experimental results verify dynamic model and the simulation results.The monocycle air-float experimental equipment for lunar rover is designed, which could be used to research the working condition of lunar rover in six to one gravity on earth and study wheel-soil interaction terramechanics and the wheel working features. The equipment employs gas lubrication technique in horizon and vertical and the gas bearing has the advantages of less friction and smooth move-ment. Due to these advantages, the immeasurable friction of sliding track can be bucked and get accurate experiment results. The servo system for level tracking system is designed to isolate the variable, irregularity disturbance of electric cables and air pipes caused by pallet moving and guarantee the precision of system. By using the experimental equipment, the following researches can be carried out: sin-gle wheel drive dynamics and control performance, each wheel brake and promote mutually, wheel-soil interaction terramechanics experiments and changing tractive ability of motion system for the new kind of lunar rover.An attitude and position estimation system for lunar rover based on colored dot targets is proposed. This system consists of two cameras assembled at the descend stage of lunar vehicle and a laser ranger finder. Utilizing the dot targets on lunar rover, the attitude and position of the rover can be determined. Considering the connection region analysing method porposed by James Bruce, an attitude and po-sition estimation algorithm is proposed.The computer simulation indicates the cal-culation speed and presision of the algorithm can meet the requirements, also the altorichm has certain robustness for noise. The experiment in 7×9 m2 test bed shows the efficiency of this attitude and position estimation method. The precision of this method is enough for most applications.更多还原