【作者】 陈世荣；

【导师】 杨杰；

【作者基本信息】 中国科学技术大学 ， 精密仪器及机械， 2009， 博士

【摘要】 由于月球与地球物理环境(温度、温差、重力、大气密度等等)的巨大差异,由于月面与地面状态的差异,我国二期工程将要研制发射的月球探测器一月球车,为了完成科学探测目标,它在月球上首先是保证能生存,第二是保证能按指令行走。因此,月球车在月球不同区域巡游和完成探测任务时面临的首要问题之一是月球车在月面的通过性问题。曾经登上月球的前苏联和美国的月球车都曾因月球车的通过性能不足导致车轮下陷无法前进而影响探测计划.月球车的通过性能主要包括月球车的车轮月壤支撑通过性问题、不平月面的几何通过性问题和越障能力。本文从月球车车轮-月壤力学着手研究车轮对月壤的支撑通过性,研究车轮在月壤表面的驱动能力及车轮尺寸参数的选择依据,接着研究月球车在月球不平地形的几何通过性问题和安全通过月球不平地形的车轮驱动力优化设计,最后研究月球车对岩石障碍的越障能力,具体内容如下1、摇杆-转向架式月球车结构。目前对月球车移动机构的研究主要集中在底盘式悬挂移动机构、关节式移动机构、主动变形式移动机构和摇杆-转向架移动机构,其中摇杆-转向架移动机构综合性能最好,其结构形式简单、复杂地形适应能力、车轮支撑力波动范围小和越障能力强。接触角对于摇杆-转向架式月球车来说是个很重要的参数,其影响着摇杆-转向架移动机构各车轮的受力分布。本文基于速度投影定理,给出了计算摇杆-转向架式月球车各车轮接触角的计算式,接触角的计算是第四章中优化车轮驱动力的基础。2、车轮在松软月面的驱动能力与在平整地面的驱动力有很大不同,车轮在松软的月面将会产生下陷和滑动。基于Bekker轮-地力学理论的车轮驱动力计算公式复杂,不适合直接计算,为实现车轮驱动力预测,为车轮驱动力优化提供计算基础,本文采用基于最小二乘法的数据拟合方法对车轮驱动力进行数值拟合计算,为实时的车轮驱动力预测提供可行的方法,从而实现对车轮驱动力的优化。月球车的通过性能与车轮在月壤上的下陷深度、车轮驱动力以及车轮的驱动效率这三方面因素密切相关。综合考虑三方面的因素,本文经过数值拟合计算提出了车轮尺寸选择依据并获得合理的车轮尺寸参数区域。3、车轮驱动力实验。本文设计了车轮驱动力实验系统,尽可能模拟月海状态,做了不同牵引力条件和不同轮面状态下的通过性试验,取得了一组实验数据。车轮驱动力实验中测量的参数包括车轮在沙面前进时的车轮驱动电机速度、车轮前进速度和下陷深度,这些参数通过数值拟合计算可以得出车轮驱动力大小,通过分析并对比数值拟合计算结果,给出了最佳车轮的参数范围。虽然通过增大车轮滑动率可以产生更大的驱动力,但大的滑动率降低了驱动效率,提高车轮的驱动效率对能源有限的月球车很重要的。为了增强车轮驱动力,减小滑动率,在车轮表面均匀地增加轮刺,车轮在前进时会获得由轮刺挤压沙壤而产生的额外驱动力,使车轮驱动力得到增强。轮刺增大驱动力、减小滑动的同时也带来了车轮在垂直沙面方向上周期性的位移波动,这是对月球车前进稳定性不利的一个影响因素,车轮前进速度也山于轮刺的作用产生了周期性的波动。车轮在垂直地面上的周期波动和前进速度的波动对于月球车来说是一个周期性的激励,其频率应与月球车系统的固有频率避开,防止月球车前进时产尘较大的振动。由带有轮刺的车轮产生的波动周期是车轮电机转速、车轮尺寸、轮刺密度和滑动率的函数,本文通过分析给出了车轮波动频率计算公式,为避免产生月球车系统共振提供设计依据。4、月球车的不平月面几何通过性。摇杆-转向架式月球车每个车轮都具有独立的驱动系统,在不平月面时各轮接触角各不相同,单独考虑每个车轮的月面通过性是不全面的。如果车轮驱动力输出不协调控制,在松软月面前进时很容易因为某一个车轮受力过大而导致下陷过深失去驱动能力,使整个月球车无法前进,所以车轮驱动力的协同控制是月球车在不平月面几何通过性的重要保证。本文基于序列二次规划算法优化摇杆-转向架式月球车车轮系统驱动力输出,建立保证月球车在月壤平稳安全通过的力学约束方程,以车轮驱动功率和驱动力变化最小为目标函数优化车轮驱动力输出,使月球车平稳前进的同时车轮驱动电机功率消耗最小,这对能源有限的月球车来说是很有意义的。通过建立摇杆-转向架式月球车动力学方程,模拟月球车通过不平月面时车轮驱动力优化输出,通过MATLAB软件编写仿真程序并输出优化仿真结果。5、越障能力。摇杆-转向架式月球车必须具有很强的地形适应能力和越障能力。首先研究了摇杆-转向架移动机构尺寸对月球车越障能力的影响,综合通过性能、占有空间,得到了摇杆-转向架移动机构的合理设计参数,并通过ADAMS进行了仿真验证。月球车车体内部科学仪器不同的布置方式会产生不同的重心位置,月球车车体重心布置直接影响着摇杆-转向架月球车的越障能力,不合适的重心位置会使月球车失去越障能力。基于准静力学研究重心位置对于摇杆-转向架式月球车越障能力的影响,并获得满足越过台阶障碍要求的重心位置可行域,为车体内科学仪器的布置提供依据。更多还原

【Abstract】 There is much big difference between moon and earth,such as temperature,rang of temperature varying,gravity and vacuum.The lunar rover will be lunched in second stage of moon exploration of china.Surviving on the moon is first thing for lunar rover.The second thing is to cruise on the moon.So one of the most important questions is lunar terrain trafficability for lunar rover.The lunar rovers of former Soviet Union and America ever sank deeply in lunar soil and exploration plan were changed because lunar terrain trafficability of lunar rover was poor.Yrafficability of lunar rover includes trafficability of wheel supporting, geometric trafficability on tough lunar terrain and capability of climbing obstacle. This paper researches on driving force of wheel on lunar soil,the criterion of selecting wheel dimension,geometric trafficability on tough lunar terrain,the driving force optimization of wheel for moving safely on the moon,capability of climbing obstacle. The details are following:1.Analysis on the characteristic of lunar rover of rocker and bogie.Now researchers who make researches on mobile system of lunar rover mostly focus on chassis suspension mechanism,joint mobile mechanism,shape shifting mobile mechanism and rocker and bogie mechanism.All of these,the rocker and bogie mechanism is best. It has simple structure,the ability to adapt tough terrain,narrow range of wheel supporting force varying and good capability of climbing obstacle.Contact angle is an important parameter for lunar rover of rocker.and bogie.It affects the wheel force distributing of lunar rover.The formula of calculating contact angle was gained based on velocity projection theorem in this paper.It will be used in optimization of force driving of wheel.2.Driving force of wheel on soft lunar soil is much different with wheel on the ground of the earth.Wheel sinks and slides easily on lunar soil.The driving force formula of wheel based on Bekker formula is much complex,for forecasting driving force,curve fitting based on least squares method was introduced to simplify formula driving force.The driving force can be calculated through measuring wheel sinkage and slide.The diameter and width of wheel decide the trafficability of lunar rover on tough lunar terrain.The criterion of selecting dimension of wheel was developed with a view of wheel sinkage,driving force and driving efficiency. 3.Experiments of wheel driving force.The experiment system of driving force was established for testing driving force characteristics of wheel moving on soft soil which force characteristics is similar to lunar soil.The parameters which were measured in driving force experiment include velocity of driving motor,velocity of wheel and wheel sinkage.These parameters can be calculated to derivate driving force of wheel. The difference between actual driving force of wheel and driving force of calculation was compared and the range of wheel dimension was recommended.Increasing slide can decrease efficiency of wheel driving though driving force can be increased through increasing slide.In experiments,grousers were added to wheel surface to increase driving force of wheel.Grousers can increase driving force of wheel.Yet grousers also introduce vertical wave of wheel.It is disadvantageous to stability of lunar rover.The frequency of wheel wave is a function of velocity of wheel motor, dimension of wheel,density of grousers and wheel slide.The formula of frequency of wheel wave was derivated in this paper.It is a criterion of avoiding sympathetic vibration of lunar rover.4.Geometric trafficability on tough lunar terrain.Every wheel of lunar rover of rocker and bogie has an own driving system.The contact angles of wheels on tough lunar terrain are different.So considering trafficability of every single wheel isn’t circumspect.If driving force of wheels are not concerted,it will happen that some wheel sinks and can’t produce driving force since wheel sinks too deeply.So cooperative controlling of driving force of wheel is a key of trafficability on tough lunar terrain.Based on SQP algorithm,driving force of wheel was optimized. Optimization is based on restriction of moving safely and smoothly.The aim of optimization is to minimize power consume of motors and varying range of driving force.It is important for lunar rover which power is limited.Dynamic equation of Lagrange was established.It was simulated that lunar rover moves on tough terrain moon.And optimization results of wheel driving force were derivated through Matlab software.5.Analysis on capability of climbing obstacle.The lunar rover of rocker and bogie must has good capability of climbing obstacle and adaptive for tough lunar terrain. The dimension of rocker and bogie mechanism was determined according to lunar terrain and design of climbing obstacle.The body of lunar rover has different position of gravity when arrangement of instrumentation in body is different.The position of gravity affects capability of climbing obstacle;improper position of gravity center depresses climbing obstacle capability.The feasible range of gravity center was found out through quasi-static analysis.更多还原