基于地面机器系统的表层月壤沉陷行为研究

It is important to develop planetary rover for planetary exploration. Preventing rover from sinkage is crucial especially especially to unpiloted planetary rover under lower gravity environment. Quick judgment of sinkage possibility of rover wheel on soft lunar soil is a feasible method according to the in situ information such as images of physiognomy and wheel imprint which could be sent to the earth control center. Researching the sinkage behavior of wheel on the lunar surface soil and establishing the rover wheel sinkage model of lunar soil are urgent needed key technologies for estimating rover lunar mobility, deciding rover wheel motion, choosing rover travel path to avoid trap. It could also provide technical index of preparation lunar soil simulant with similar mechanical properties as in situ lunar soil for troubleshooting rehearsed test by means of rebuilding in situ lunar soil mechanical situation in the laboratory at earth. The proposed project will focus on the sinkage behavior of lunar soil in surface layer based on the previous studies in this scope using lunar terrain-machine system theory. Some test apparatus will be developed, and a series of lunar soil simulant with different specific gravity will be manufactured to find ways for simulating lower gravity environment. Then slip-sinkage experiments of single wheel and model rover will be conducted using soil bin equipment to find the sinkage rule of lunar soil. The images of rover wheel imprint will be analyzed to obtain the characteristic parameters of sinkage of lunar soil. The model to describe sinkage relationship between lunar soil and rover wheel will be established for researching the sinkage behavior under various conditions, and finally the predication method of sinkage behavior of lunar soil in surface layer would be put forward. The results will provide the technical method and basic data for lunar exploring and other planetary exploration therefore will have important significance for planetary rover.

星球表面巡视探测是深空探测发展的必然选择，对于低重力环境下无人驾驶的巡视探测器，防止因沉陷导致探测器失效至关重要。根据就位地貌信息和轮辙形态，快速判断探测器是否将要发生沉陷是可行的方法，建立月壤/车轮沉陷模型，是评估探测器的月面通过性、决定探测器车轮动作、选择探测器避障行驶路径急需的关键技术。研究表层月壤沉陷行为还可以为在地面再现探测器就位情况，进行排障模拟演习试验提供具有力学相似性的模拟月面整备技术指标。 在前期相关研究基础上，本项目采用地面机器系统理论方法，重点研究月球表层月壤的沉陷行为。设计低重力模拟试验装置，制备不同比重的模拟月壤，实现低重力环境模拟；开展土槽滑转沉陷试验和模型车试验，研究沉陷规律；分析轮辙图像信息，提取轮辙的沉陷特征参数；建立月壤/车轮沉陷模型，研究不同条件下的沉陷行为，提出表层月壤沉陷行为预测方法，为我国探月工程和深空探测提供技术方法和基础数据，具有重要的意义。

研究星球探测器与星球土壤的相互作用规律，对探月工程以及其他深空探测的在轨探测器作业能力评估和控制方案决策具有理论意义和技术需求。..采用地面机器系统理论方法，设计了多种可倾斜式低重力模拟试验装置，分离出倾斜状态下重力垂直倾斜方向的侧向力对轴向力的影响，得到土槽条件下剔除侧向力噪声后的正向力分布规律，实现了重力环境近似模拟；研制了高精度轻载土槽测试系统，开展滑转条件下轮壤相互作用试验研究，基于传统沉陷模型和轮壤接触应力分布线性化公式，结合土槽试验结果，建立了适合滑转条件的沉陷模型，能准确预测轻载荷条件下车轮沉陷；研制出土槽试验轮辙图像数字信息系统，采集实时车轮沉陷数值，并提取轮辙表观沉陷值及轮辙空间几何的特征参数，通过研究试验因数对车轮沉陷的影响规律，以及车轮实际沉陷和表观沉陷的对应关系，为通过轮辙表观沉陷预测车轮实际沉陷提供依据。通过轮壤作用关系的线性化推导和简化，建立了简洁的挂钩牵引力模型用于星球车在轨沉陷预估，利用土槽试验进行模型修正，建立了用于星球车在轨沉陷预估的模型，提出了表层月壤沉陷行为预测方法，既可以为星球车在沉陷前进行预警评估，也可为发生沉陷后的地面模拟脱困试验提供沉陷状态数据。提出适用于模型筛网轮的压力沉陷模型，基于土壤参数和轮土接触等效面积，预测筛网轮在压力作用下的沉陷行为，为进一步评估月球或者火星巡视探测器的通过性，预防车轮过度下陷提供了理论技术方法。.研究结果表明，月壤的力学特性受重力环境、整备方法等可以引起其颗粒堆积状态改变的因素影响，松散态和细颗粒不利于巡视器的通过性。挂钩牵引力模型的拟合值与土槽实测值的误差小于9%；沉陷模型利用月球车位姿、质心等参数并结合月球车的车辙信息，计算出轮上载荷和滑转率，能够较好地反映筛网轮沉陷行为，置信度均为0.99，相关系数均在0.9以上，其计算快速准确，可用于月球车在轨评估车轮前方月壤的力学特性和通过性能评估。