自由漂浮空间机器人的运动学分析及仿真

自由漂浮空间机器人与地面机器人最大的区别是其末端执行器的运动不仅仅和各个关节的运动有关,而且与各个连杆、基座的质量分布及其运动轨迹紧密相关.因此,自由漂浮空间机器人的运动学与其动力学是密不可分的.运用螺旋理论、动量守恒定律对这样的机器人系统进行分析,得到了包含系统质量在内的运动雅可比矩阵,并给出了系统运动的图形仿真结果.     

柔性冗余度机器人动力学规划

考虑机器人的结构柔性,研究了利用冗余度机器人的"自运动"同时进行振动抑制和机器人关节力矩优化的方法.研究表明,在进行柔性冗余度机器人的动力学优化时,应从振动和关节力矩两方面考虑.若单考虑振动抑制,机器人的关节力矩将可能无穷增大,使算法失效;若单考虑关节力矩优化,机器人臂末端的振动将有可能发散.这里给出的算法同时考虑了这两方面.不同于冗余度机器人传统的优化方法--机器人雅克比矩阵的零空间优化法,这里从最优控制论的方法着手,研究了考虑结构变形的冗余度机器人利用其自身的"自运动"进行振动抑制和关节力矩优化.仿真结果,证明了这种优化方法是完全可行的.     

被动冗余度空间机器人动力学控制

研究了被动冗余度空间站机器人的动力学控制问题，包括非完整系统的运动规划，渐进稳定的动力学控制规律；在动力学控制中，利用被动冗余度机器人“非完整自运动”的运动学优化方法完成机器人的动力学控制，构造的动力学闭环控制律保证机器人运动过程中末端跟踪期望的运动轨迹，通过三连杆空间站机器人模型进行了仿真，结果证明了得到的结论。     

基于可操作度的单冗余度机器人容错性指标

当冗余度机器人关节出现故障时,必将影响其灵活性.即使正常操作时具有较高的灵活性,如果关节出现故障也可能导致雅可比矩阵奇异,致使机器人不能沿任意方向运动.针对单冗余度机器人出现一个关节故障的情形,用可操作度分析此类机器人的容错性,并提出新的运动学和动力学容错性评价指标,所给指标计算量小、易于在线实时运算,最后给出优化算例,证实了所给评价指标的有效性.     

冗余度机器人力控制的运动学稳定性分析

把非冗余度机器人位置／力混合控制方案引入到冗余度机器人，用线性化的动力学模型对其运动学稳定性进行分析，提出一种改进的基于运动学稳定的冗余度机器人混合控制策略。仿真研究结果证明了所提出方法的有效性。     

基于螺旋理论模块化机器人运动学分析与仿真

基于螺旋理论对模块化机器人的速度级和位移增量级运动学关系进行了分析,开发了模块化冗余度机器人的逆运动学控制算法.针对模块化机器人可能具有任意自由度和任意构型、可以经常快速安装和拆卸、易于可重构且由系列化、标准化部件组合的特性,开发了具有自动建模功能的模块化机器人仿真系统.该仿真系统由模块构造器、机器人建造器、图形示教和运动规划仿真器等分系统组成.通过一个7-DOF模块化串联机器人抓放工件的演示实例验证了所提算法和仿真系统的实用性.     

空间四面体翻滚机器人运动学分析及仿真实验

对四面体及多面体机器人的研究现状进行了分析.介绍了空间四面体翻滚机器人的结构,由6根伸缩臂和4个顶部节点平台组成,通过伸缩臂的运动可以使四面体的重心失稳,实现翻滚运动.结合四面体翻滚机器人的运动形式,给出了翻滚的临界条件,根据不同的运动阶段对四面体翻滚机器人进行了运动学分析.利用Adams虚拟样机技术对四面体翻滚机器人进行了运动学仿真,并进行了样机的实验,验证了方法的正确性.该分析结果可进一步用于空间四面体翻滚机器人的动力学分析和优化设计.     

轮式移动机器人运动学逆问题及机体稳定性

移动式机器人可以认为是操作机器人和步行机的组合,它具有更灵活和更大的工作空间.因此移动式机器人适合用于远程操作,无论是在太空还是地面,最通用的移动式机器人是轮式移动式机器人.轮子导致了非完整约束.在本文中,这种非完整约束以及有关的运动几何学得到了分析,在此基础上建立了轮式移动机器人运动学逆问题的两种求解公式.其次,提出了一种控制自运动的方法以解决活动平台的稳定性问题.这种方法通过仿真验证了其正确性.     

平面并联机器人的轨迹控制与在线监控

提出了三自由度平面并联机器人的运动学控制方法,通过逆向运动学求解实现对机器人的轨迹规划;提出完成并联机器人在线监控的2个步骤:首先利用解析法实现并联机器人的正向运动学分析,再综合运用二分法和插值法进行正解的在线计算.还研究和完成了基于PC的模块化机器人控制系统设计,该设计主要包括使用C+ +语言完成并联机器人运动学控制算法编程和设计基于PMD(Performance Motion Devices)的模块控制器.该控制系统在三自由度模块化平面并联机器人上进行了演示,并将在MATLAB下实现的数值法与C+ +语言编写的解析法进行了比较,其结果验证了运动学算法和运动控制器的性能.      

双冗余度机器人的避碰运动规划方法研究

对双冗余度机器人的避碰运动规划进行了研究分析,发展和改进了一种基于距离函数的冗余度机器人避碰方法,提高了该方法的通用性和可靠性.      

Learning in an immersive digital theater

The Houston Museum of Natural Science, in collaboration with Rice University has an outreach program taking portable digital theaters to schools and community sites for over five years and has conducted research on student learning in this immersive environment. By using an external independent evaluator, the effectiveness of NASA-funded Education and Public Outreach (EPO) projects can be assessed. This paper documents interactive techniques and learning strategies in full-dome digital theaters. The presentation is divided into Evaluation Strategies and Results and Interactivity Strategies and Results. All learners from grades 3–12 showed statistically significant short-term increase in knowledge of basic Earth science concepts after a single 22-min show. Improvements were more significant on items that were taught using more than one modality of instruction: hearing, seeing, discussion, and immersion. Thus immersive theater can be an effective as well as engaging teaching method for Earth and Space science concepts, particularly those that are intrinsically three-dimensional and thus most effectively taught in an immersive environment. The portable system allows taking the educational experience to rural and tribal sites where the underserved students could not afford the time or expense to travel to museums.     

Scaling analysis and model estimation of solar corona index

A monthly average solar green coronal index time series for the period from January 1939 to December 2008 collected from NOAA (The National Oceanic and Atmospheric Administration) has been analysed in this paper in perspective of scaling analysis and modelling. Smoothed and de-noising have been done using suitable mother wavelet as a pre-requisite. The Finite Variance Scaling Method (FVSM), Higuchi method, rescaled range (R/S) and a generalized method have been applied to calculate the scaling exponents and fractal dimensions of the time series. Autocorrelation function (ACF) is used to find autoregressive (AR) process and Partial autocorrelation function (PACF) has been used to get the order of AR model. Finally a best fit model has been proposed using Yule-Walker Method with supporting results of goodness of fit and wavelet spectrum. The results reveal an anti-persistent, Short Range Dependent (SRD), self-similar property with signatures of non-causality, non-stationarity and nonlinearity in the data series. The model shows the best fit to the data under observation.     

Stochastic particle acceleration by the forced interaction of relativistic current sheets

We address the problem of interacting relativistic current sheets in self-consistent kinetic plasma simulations within the framework of the Particle-In-Cell model. The interaction is enforced in head-on collisions of up to 10 current sheets at relativistic bulk speeds. The simulations are motivated by the general problem of Poynting flux dissipation in ‘striped wind’ configurations presumably governing the relativistic outflows pervasive in pulsar winds and gamma-ray bursts. We identify the generation of non-thermal particles and formation of a stable power-law shape in the particle energy distributions f(γ) dγ ∝ γ^−s dγ. In 1D, a spectral index s ∼ 2 is observed and attributed to a stochastic Fermi-type acceleration mechanism. In 2D, the generic index of s ∼ 3–4 is retained as in previous simulations of individual current sheets. Whereas in 2D the high energy cut-off is constrained by the limited dissipation of magnetic energy, in 1D the process converts the bulk motion of current sheets towards directed particle momentum of an exclusive class of non-thermal particles.     

Development of a gas chromatography compatible Sample Processing System (SPS) for the in-situ analysis of refractory organic matter in martian soil: preliminary results

In the frame of the 2009 Mars Science Laboratory (MSL) mission a new sample preparation system (SPS) compatible with gas chromatography–mass spectrometry (GC–MS) has been developed for the in situ analysis of complex organic molecules in the Martian soil. The goal is to detect, if they exist, some of the key compounds that play an important role in life on Earth including carboxylic acids, amino acids and nucleobases.     

基于LuGre模型的电液加载系统摩擦补偿

为了提高电液加载系统控制精度,针对摩擦问题提出了基于LuGre摩擦模型的前馈补偿方法.建立了用于摩擦仿真分析和补偿器设计的电液加载系统数学模型;通过实验获取并分析了相关的摩擦数据;基于实验数据进行LuGre模型参数辨识,把LuGre模型和辨识结果引入电液加载系统数学模型,并进行仿真结果与实际摩擦数据的对照,证明了LuGre摩擦模型的准确性.设计前馈补偿器,进行了实验对比,实验结果表明前馈补偿器可将摩擦产生的控制误差有效地降至未补偿时的30%左右.      

CoRoT and Kepler results: Solar-like oscillators

The space-borne observatories CoRoT (Convection Rotation and planetary Transits) and Kepler have provided photometric time series data of unprecedented precision for large numbers of stars. These data have revolutionized the fields of transiting exoplanets and asteroseismology. In this review some important asteroseismic results obtained using data from the CoRoT and Kepler space missions concerning stars that show solar-like oscillations are discussed. These results comprise, among others, measurements of the location of the base of the convection zone and helium second-ionization zone in main-sequence stars, the presence (or not) of core-helium burning in red-giant stars, as well as differential rotation in these stars.     

Return to Europa: Overview of the Jupiter Europa orbiter mission

Missions to explore Europa have been imagined ever since the Voyager mission first suggested that Europa was geologically very young. Subsequently, the Galileo spacecraft supplied fascinating new insights into this satellite of Jupiter. Now, an international team is proposing a return to the Jupiter system and Europa with the Europa Jupiter System Mission (EJSM). Currently, NASA and ESA are designing two orbiters that would explore the Jovian system and then each would settle into orbit around one of Jupiter’s icy satellites, Europa and Ganymede. In addition, the Japanese Aerospace eXploration Agency (JAXA) is considering a Jupiter magnetospheric orbiter and the Russian Space Agency is investigating a Europa lander.     

Radioactivity of the Moon and planets

In this report the main results of the study of radioactivity of the solar sistem bodies are considered. The radioactivity of the Moon and planets was measured by means of vehicles in situ. The radioactivity of the lunar samples, brought to the Earth was studied with laboratory equipment.     

基于最小值原理的冗余度机器人动力学控制

为了解冗余度机器人全局法优化中数值求解的困难,本文讨论了动力学方程的建立,无约束和有约束最优控制问题之间的内在联系,重点分析了求解最优控制问题的数值方法,文中提出了双向异步积分迭代的求解正则方程组的直接迭代法,较好解决了状态方程和协态方程稳定相逆给求解两点这值问题带来的困难。     

基于GPS载波相位的微卫星姿态算法研究

GPS姿态系统是利用GPS载波相位测量来确定载体的航向和姿态角。本文对微卫星的GPS姿态系统进行了研究。重点解决短基线的GPS状态算法，讨论了姿态价格函数的了小化方法。测试结果表明，所提的算法对小于1m的基线是有效的。