姿态受控漂浮基空间机器人系统协调运动的反演滑模控制

讨论了载体位置无控、姿态受控情况下,具有外部扰动的漂浮基空间机器人载体姿态与机械臂各关节协调运动的反演滑模控制问题.结合系统动量守恒关系及拉格朗日方法,建立了漂浮基空间机器人完全能控形式的系统动力学方程.以此为基础,基于反演设计方法,设计出空间机器人载体姿态与机械臂各关节协调运动的滑模控制方案.数值仿真结果验证了该控制方案的有效性.     

漂浮基空间机器人姿态与末端爪手协调运动的反演滑模控制

讨论了载体位置无控、姿态受控情况下,具有外部扰动的漂浮基空间机器人系统的控制问题.结合系统动量守恒关系及拉格朗日方法,建立了漂浮基空间机器人的运动Jacobi关系及系统动力学方程.以此为基础,借助于反演设计方法,设计出空间机器人载体姿态与机械臂末端爪手协调运动的滑模控制方案.此方案可有效地减少控制系统的在线计算时间,更能满足空间机器人这一时变系统控制的实时、在线要求.数值仿真结果证实了该控制方案的有效性.     

双臂空间机器人系统动力学与关节运动的非线性反馈控制

利用拉格朗日方程建立了漂浮基双臂空间机器人系统的动力学方程,给出了载体位置、姿态均不受控制情况下,双臂空间机器人关节运动的非线性反馈控制规律.结果表明,在系统动力学模型及参数较精确确定情况下,本文提出的控制方案能够有效地控制双臂空间机器人系统完成关节空间的指定运动,而不需对其载体的位置、姿态进行主动控制.仿真计算结果证实了方法的有效性.     

双臂空间机器人惯性空间轨迹的非线性反馈跟踪控制

讨论了载体姿态及位置均不受控制的自由漂浮双臂空问机器人系统的轨迹控制问题.首先,根据双臂空间机器人系统的动量、动量矩守恒关系及系统的Jacobian矩阵,得出机械臂末端抓手加速度与关节角速度、角加速度的关系.然后,根据Roberson-Wittenburg方法推导出系统动力学方程.以此为基础,设计了自由漂浮双臂空间机器人系统机械臂末端抓手惯性空间轨迹的非线性反馈跟踪控制方案.仿真结果证明了上述控制方法的有效性.     

基于时延估计和鲁棒H_∞控制的工业机器人跟踪控制

针对六自由度工业机器人系统,结合时延估计控制和鲁棒H∞控制的优点,提出了一种鲁棒H∞时延估计跟踪控制算法.该算法不需要机器人的复杂动力学模型,避免了机器人逆动力学的在线实时计算;采用时延估计在线获得机器人系统的未知动力学和外界干扰,并对控制过程加以补偿;通过引入L2增益控制,可实现对时延估计误差的L2干扰抑制,从而进一步提高了系统的鲁棒性.同时,利用Lyapunov函数和Riccati不等式保证了闭环系统的渐近稳定性和H∞鲁棒性能.该算法计算简单,结构固定,鲁棒性强,易于实现.文中还通过二自由度机器人的仿真实验证明了该算法是有效的.     

基于神经网络的空间柔性机械臂PID快速学习控制

针对自由漂浮柔性空间机器人的轨迹跟踪问题,提出一种径向基函数（RBF）神经网络控制策略.首先建立漂浮基柔性空间机器人的非线性动力学方程,考虑到RBF神经网络良好的逼近能力,柔性臂的非线性逆动力学模型通过RBF网络来逼近,采用PID控制器与神经网络控制器来共同保证系统稳定性,其误差代价函数由PID控制器提供,采用固定中心参数,而扩展宽度采用启发式关系确定,网络权值采用改进的最优准则算法进行调整来实现快速学习能力.仿真结果表明了这种RBF神经控制器能够达到较快的误差收敛速度.     

自由漂浮双臂空间机器人关节空间轨迹跟踪的变结构滑模控制

利用多刚体系统动力学的方法对载体位置、姿态均不受控制的浮动基双臂空间机器人系统的运动学、动力学作了分析,并结合系统的动量守恒及动量矩守恒关系建立了系统的动力学方程.以此为基础,对双臂空间机器人关节追踪关节空间期望轨迹的控制问题作了研究.考虑到双臂空间机器人系统的结构复杂性及某些参数的变动性,根据具有较强鲁棒性的变结构滑模控制理论,设计了轨迹跟踪控制的变结构滑模控制方案.此控制方案的优点在于:在操作过程中不需要对双臂空间机器人载体的位置、姿态进行主动控制,因此将大大减少位置、姿态控制装置的燃料消耗.通过对该机器人系统的仿真计算,证实了文中提出的变结构滑模控制方案的有效性.     

时延下遥微操作机器人系统滑模变结构控制研究

针对遥微操作机器人系统在实际远程手术应用中存在时延而易导致系统不稳定且难以控制的问题,通过系统动力学建模和时延下系统理想性能的定义,设计了一种保持系统稳定和良好操作性能的新型控制方案.在该方案中主机械手采用基于期望特性的阻抗控制而从机械手采用基于指数趋近律的滑模变结构控制策略.仿真实验结果表明了该方案的有效性和鲁棒性,系统能在时延下较好地实现位置比例跟踪和力比例跟踪.     

分块建模关节机器人的PI鲁棒滑模控制

为实现机器人关节位置镇定和轨迹跟踪控制,控制律的设计须针对确定的机器人动力学模型,由于机器人结构参数、作业环境的外界干扰及结构振动等不确定性因素的存在,会造成机器人动力学模型不确定.为此,设计3个RBF神经网络分别对不确定机器人模型中的3个不确定项进行分块建模,得到机器人估计模型,神经网络的权值采用自适应算法.针对机器人估计模型设计PI鲁棒滑模控制律.将所设计的控制器用于三关节机器人的三个关节的力矩控制,研究结果表明:三关节均约在1 s时达到期望位置和跟踪期望轨迹,镇定误差和跟踪误差也快速、稳定地趋于零.通过定义基于积分型的Lyapunov函数,利用Lyapunov稳定性理论证明了控制系统是全局渐近稳定的.     

不确定轮式机器人动力学鲁棒路径跟踪控制

使用预知期望几何路径函数描述跟踪误差,将路径跟踪问题转化为输出调节问题,基于机器人的动力学模型运用输入输出线性化方法得到运动学-动力学混合控制律,再使用反步法得到动力学控制律;基于类Lyapunov方法设计不确定参数自适应律,保证在未知定常参数情况下跟踪误差仍能够渐近收敛.最后给出了渐近稳定性的证明,数字仿真证实了该控制方案的有效性.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that