984 resultados para Interplanetary trajectory


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本文提出了机器人末端过空间三点作空间圆弧运动的一种有效轨迹规划方法,并成功地应用于我们开发的电子装配机器人中.理论分析与实验分析的结果一致

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本文探讨了稳定逆动力学与基于观测的状态误差反馈镇定器集成实现柔性机械臂末端轨迹跟踪的控制策略.基于观测器可以充分利用由稳定逆动力学生成的理想状态轨迹信息,实现全状态误差的反馈镇定以消除末端轨迹跟踪的扰动误差。

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研究了不确定性环境下移动机器人躲避运动轨迹未知的移动障碍物的一种新方法.通过实时最小均方误差估计算法预测每个障碍物的位置及运动轨迹,并利用模式识别中最小均方误差分类器的修正模型计算出机器人的局部避障路径,再运用船舶导航中使用的操纵盘技术来确定每个导航周期中移动机器人的速.度仿真结果表明了该方法的可行性

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提出了求解某武器系统导弹弹道轨迹的两种方法:计算机仿真和系统辨识方法.详细介绍了导弹系统的计算机仿真模型,并利用控制理论和数值分析的方法对仿真模型求解;根据系统辨识理论,将整个系统看作“黑箱”,建立与输入、输出数据等价的模型,引入折息因子对模型进行辨识.最后分别给出了计算机仿真试验曲线和系统辨识试验曲线,证明了两种求解方法的有效性。

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为工业机器人机械手提出了一种稳定跟踪控制法.这种控制方法由前馈控制器、反馈控制器组成.前馈控制根据期望轨线用计算力矩法得到;反馈控制由线性PID控制项和非线性PD控制项组成,这种控制方法能使跟踪误差逐渐趋近于零.最后,给出了PUMA560机器人的计算机仿真实验验证此控制方法的有效性

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针对双机械臂搬运单一物体的协调操作系统,提出了一类有效的最优关节轨迹规划方法。该法在机械臂的关节空间内采用分段归一化的无因次量,将其运动轨迹与运动时间解耦,运用非线性规划法优化无因次量运动轨迹。将所规划的无因次轨迹方程作为机械臂产生实际运动轨迹的发生器,由双臂的运动学约束条件和爪端所允许的不协调误差及各手臂的取道点,即可快速生成所期望的系统运动轨迹。为保证双臂能充分协调运动,提出了调整因子的概念。

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本文针对多连杆柔性机械臂的运动轨迹控制问题,讨论了动力学建模、控制系统结构设计以及鲁棒自适应控制算法,运用假设模态方法得到了柔性机械臂动力学近似方程,通过对柔性机械臂动力学特性分析,建立了等价动力学模型,依此提出了一种鲁棒自适应控制算法,并给出了仿真研究结果。

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为了使机器人跟踪给定的期望轨线,提出了一种新的基于机器人运动重复性的学习控制法.在这种方法中机器人通过重复试验得到期望运动,这种控制法的优点:一是对于在期望运动附近非线性机器人动力学的近似表达式的线性时变机械系统产生期望运动的输入力矩可不由估计机器人动力学的物理参数形成;二是可以适当的选择位置、速度和加速度反馈增益矩阵,从而加快误差收敛速度;三是加入了加速度反馈,减少了速度反馈,减少了重复试验的次数.这是因为在每次试验的初始时刻不存在位置和速度误差,但存在加速度误差.另外,这种控制法的有效性通过PUMA562机器人的前三个关节的计算机仿真结果得到验证。

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研究了移动机器人反馈控制问题.这里所考虑的机器人是一个两轮驱动的具有非完整性的移动机器人小车.考虑了笛卡儿空间中轨线跟踪问题的扩展.且表明只要参考小车保持运动,在虚设的参考小车位形周围的小车位形的稳定成为可能.提出了最优控制律并给出了仿真结果。

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本文提出了基于机械臂关节驱动力矩约束方程规划其关节最优运动轨迹的一种有效方法.该方法运用矩阵范数理论简化机械臂的动力学约束方程;在机械臂的关节空间内采用归一化的无因次量运用非线性规划法优化其运动轨迹.将所规划的无因次量轨迹方程作为机械臂产生实际运动轨迹的发生器,通过给定机械臂各运动段的起始和终止关节坐标,由系统的动力学约束方程计算出整个运动段所允许的最短运行时间,即生成所期望的运动轨迹.本文的轨迹规划方法计算效率高,可用于在线轨迹规划,文中通过算例证实了该方法的实用性.

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本文提出了步行机器人运动控制算法。该方法以相对运动学原理为基础,把机体的运动规划问题转化为腿的足端轨迹规划问题,从而使步行机器人运动控制问题得到大大简化.并应用该方法对全方位三角步态算法及稳定性进行分析求解.

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Seismic While Drilling (SWD) is a new wellbore seismic technique. It uses the vibrations produced by a drill-bit while drilling as a downhole seismic energy source. The continuous signals generated by the drill bit are recorded by a pilot sensor attached to the top of the drill-string. Seismic wave receivers positioned in the earth near its surface receive the seismic waves both directly and reflection from the geologic formations. The pilot signal is cross-correlated with the receiver signals to compute travel-times of the arrivals (direct arrival and reflected arrival) and attenuate incoherent noise. No downhole intrusmentation is required to obtain the data and the data recording does not interfere with the drilling process. These characteristics offer a method by which borehole seismic data can be acquired, processed, and interpreted while drilling. As a Measure-While-Drill technique. SWD provides real-time seismic data for use at the well site . This can aid the engineer or driller by indicating the position of the drill-bit and providing a look at reflecting horizons yet to be encountered by the drill-bit. Furthermore, the ease with which surface receivers can be deployed makes multi-offset VSP economically feasible. First, this paper is theoretically studying drill-bit wavefield, interaction mode between drill-bit and formation below drill-bit , the new technique of modern signal process was applied to seismic data, the seismic body wave radiation pattern of a working roller-cone drill-bit can be characterized by theoretical modeling. Then , a systematical analysis about the drill-bit wave was done, time-distance equation of seismic wave traveling was established, the process of seismic while drilling was simulated using the computer software adaptive modeling of SWD was done . In order to spread this technique, I have made trial SWD modeling during drilling. the paper sketches out the procedure for trial SWD modeling during drilling , the involved instruments and their functions, and the trial effect. Subsurface condition ahead of the drill-bit can be predicted drillstring velocity was obtained by polit sensor autocorrelation. Reference decovolution, the drillstring multiples in the polit signal are removed by reference deconvolution, the crosscorrelation process enhance the signal-to-noise power ratio, lithologies. Final, SWD provides real-time seismic data for use at the well site well trajectory control exploratory well find out and preserve reservoirs. intervel velocity was computed by the traveltime The results of the interval velocity determination reflects the pore-pressure present in the subsurface units ahead of the drill-bit. the presences of fractures in subsurface formation was detected by shear wave. et al.

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On the basis of analyzing the principle and realization of geo-steering drilling system, the key technologies and methods in it are systematically studied in this paper. In order to recognize lithology, distinguish stratum and track reservoirs, the techniques of MWD and data process about natural gamma, resistivity, inductive density and porosity are researched. The methods for pre-processing and standardizing MWD data and for converting geological data in directional and horizontal drilling are discussed, consequently the methods of data conversion between MD and TVD and those of formation description and adjacent well contrast are proposed. Researching the method of identifying sub-layer yields the techniques of single well explanation, multi-well evaluation and oil reservoir description. Using the extremum and variance clustering analysis realizes logging phase analysis and stratum subdivision and explanation, which provides a theoretical method and lays a technical basis for tracing oil reservoirs and achieving geo-steering drilling. Researching the technique for exploring the reservoir top with a holdup section provides a planning method of wellpath control scheme to trace oil and gas reservoir dynamically, which solves the problem of how to control well trajectory on condition that the layer’s TVD is uncertain. The control scheme and planning method of well path for meeting the demands of target hitting, soft landing and continuous steering respectively provide the technological guarantee to land safely and drill successfully for horizontal, extended-reach and multi-target wells. The integrative design and control technologies are researched based on geology, reservoir and drilling considering reservoir disclosing ratio as a primary index, and the methods for planning and control optimum wellpath under multi-target restriction, thus which lets the target wellpath lie the favorite position in oil reservoir during the process of geo-steering drilling. The BHA (bottomhole assembly) mechanical model is discussed using the finite element method, and the BHA design methods are given on the basis of mechanical analyses according to the shape of well trajectory and the characteristics of BHA’s structure and deformation. The methods for predicting the deflection rate of bent housing motors and designing their assemblies are proposed based on the principle of minimum potential energy, which can clearly show the relation between the BHA’s structure parameters and deflection rate, especially the key factors’ effect to the deflection rate. Moreover, the interaction model between bit and formation is discussed through the process of equivalent formation and equivalent bit considering the formation anisotropy and bit anisotropy on the basis of analyzing the influence factors of well trajectory. Accordingly, the inherence relationship among well trajectory, formation, bit and drilling direction is revealed, which lays the theory basis and technique for predicting and controlling well trajectory.

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Glaciers in west China are the sources of the major great rivers in Asia, and the solid water resources are crucial to China and South Asia. Black carbon (BC) results in very complex climate effects not only in the atmosphere, but accelerates the melting after its deposit on the surface of snow/ice. As the main distributed area of glaciers in China, the Tibetan Plateau (TP) and Xinjiang region are abutted by South Asia, Central Asia, and Russia, and east China, and the atmospheric environment would be influenced by the BC emitted from these regions. Whereas, the BC’s temporal and spatial distributions for concentration in the mid and top troposphere in west China, its transport, and its radiative forcing after deposited on the snow/ice surface are not well understood at the present. In the field, we collected samples from surface snow, snow pits, ice core, and aerosol in the glaciers, analyzed BC content mainly by the thermo-oxidized method in the laboratory, and discussed temporal and spatial distributions for BC concentrations in glaciers, the transport, and its impacts on the environment. Several conclusions were derived as follows: 1_Spatial distribution and the impact on albedos for BC concentrations in snow/ice: the BC concentrations in the surface snow for the investigated glaciers could be placed in areas, the Tianshan Mountains > the central TP > the Pamirs > the Qilian Mountians > the Himalayas. This distribution could be attributed to the elevation of the glaciers, the topography of the TP, and more regional emissions. Probably significant impacts on the albedos of the glacier surface could be caused by BC deposits, and the estimated reduced albedos on the glaciers are 9.8% (the Zhadang glacier), 8.7% (the Miao’ergou Riverhead No.3 glacier), and 6.8% (the Kuitun River Haxilegen No.48 glacier), and 6.2% (the Dongkemadi glacier), and 5.3% (the La’nong glacier), and 4.2% (the Muztagata glacier), etc. 2_The temporal variance of BC concentrations in ice of the East Rongbuk Glacier (ERG) and its climatic implications: major cations and anions (e.g., SO42- and Ca2+) concentrations in aerosols during summer monsoon seasons showed their close relationships with the sources of air masses, in which the variance of SO42- concentrations suggested the atmospheric environment over the ERG was significantly influenced by the aerosols from South Asia. BC record based on an ice core suggested its deposit was dominantly transported by monsoons in summers and by westerlies in other seasons, and the BC from South Asia in summers dominated the varying trend of its concentrations in the ice core and caused higher concentrations in summers than those in other seasons. In the past 50 yrs, BC concentrations showed fluctuations, whereas showed an increasing tread in the most recent decade, and exceeded 50 μg kg-1 in the summer of 2001; correspondingly, the radiative forcing caused by BC showed an increasing trend since 1990s, and exceeded 4.5 W m-2 in the summer of 2001. 3_Cabonaceous aerosols in the Nam Co region: organic carbon (OC) concentration accounted for ~95% and BC for ~5% in the total carbonaceous aerosol concentration, which was significantly influenced by summer precipitations. OC was dominantly derived from fossil fuel burning and BC from both fossil fuel and biomass burning. Trajectory analysis and aerosol optical depth suggested the atmospheric environment in the Nam Co region was most probably influenced by the emissions from South Asia. The potential source regions of air pollutants in the Nam Co regions in summers might be Bangladesh and east India, and in winters might be the Indo-gangetic basin. The scavenging ratio of atmospheric BC by rainfalls was less than those at other sites. West China is a less-developed region for industry, where BC concentrations in the atmosphere and snow/ice could be significantly influenced by the emissions from the abutted regions with rising industries (South Asia, Central Asia, and Russia). For example, snow/ice BC concentrations in the glaciers of the Parmirs, the Tianshan Mountains, and the Qilian Mountains in the northeast margin of the TP might be more influenced by the emissions from Centrial Asia (transported by the westerlies), those in the glaciers of the Himalayas might be more influenced by the emissions from South Asia (transported by the monsoons and the westerlies), and atmospheric carbonaceous aerosols might also be more influenced by the emissions from South Asia (transported by the monsoons and the westerlies). The BC concentrations in some glaciers might cause significant impacts on the albedos for the glaciers, and therefore enhanced the radiative forcings, for example, the ERG. The research on the relationships among atmospheric and snow/ice BC and its radiative forcing, variance of snow cover, mass balance of glaciers, and climate forcing would be needed in future.

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Rockfall is a geological evolution process involving detachment of blocks or boulders from a slope face, then their free falls, bouncing, rolling or sliding, and finally deposition near the toe of the slope. Many facts indicate that the rockfall can cause hazards to peoples, and it can be regarded as a geological hazard. A rockfall event may only involve a boulder or rock, and also several ones. When there are peoples, buildings, or other man-made establishments within the scope of rockfall trajectory, losses will be possibly induced in tenns of human lives or damages to these facilities. Researches into mechanism, kinematics, dynamics, hazard assessment, risk analysis, and mitigation measures of rockfalls are extremely necessary and important. Occurrence of rockfall is controlled by a lot of conditions, mainly including topographical, geomorphic, geological ones and triggering factors. The rockfall especially in mountainous areas, has different origins, and occurs to be frequent, unexpected, uncertain, in groups, periodic and sectional. The characterization and classification of the rockfalls not only increase knowledge about rockfall mechanism, but also can instruct mitigation of the hazards. In addition, stability of potential rockfalls have various sensitivity to different triggering factors and changes of geometrical conditions. Through theoretical analyses, laboratory experiments and field tests, the author presents some back-analysis methods for friction coefficients of sliding and rolling, and restitution coefficients. The used input data can be obtained economically and accurately in the field. Through deep studies on hazard assessment methods and analysis of factors influencing rockfall hazard, this paper presents a new assessment methodology consisting of preliminary assessment and detailed one. From the application in a 430 km long stretch of the Highway, which is located between Paksho and Nyingtri in Tibet, the methodology can be applicable for the rockfall hazard assessment in complex and difficult terrains. In addition, risk analyses along the stretch are conducted by computing the probability of encountering rockfalls and life losses resulting from rockfall impacts. Rockfall hazards may be mitigated by avoiding hazardous areas, clearness of dangerous rocks, reinforcement, obstructing the rockfalls, leading the rockfalls, warning and monitoring for rockfalls, etc. Seen from present remedial level of rockfall hazards, different mitigation measures, economical and effective buffering units, monitoring tecliniques and consciousness of environmental protection for rockfall mitigations should be further developed.