提升四足机器人行走稳定性的对角步态规划方法

针对四足机器人在采用对角步态行走中容易失稳的问题,提出了通过改变对角步态中支撑足的初始位姿来改善并提升运动稳定性的方法.结合零力矩原理,找到四足机器人支撑足最佳初始膝关节转角θ₁和髋部前向关节转角θ₂,从而确定四足机器人支撑足的最佳初始位姿.仿真表明:四足机器人运动采用不同初始位姿时,运动过程中的稳定性不同.当取最佳初始位姿时,四足机器人的机身偏转量最小,稳定性最好.由此证明,通过调整支撑足的初始状态可以有效提高四足机器人在采用对角步态行走过程中的稳定性.      

基于虚拟模型的四足机器人控制策略

为提高四足机器人在对角小跑(Trot)步态下的行走稳定性,并减小控制策略的复杂程度,提出了一种基于虚拟模型的四足机器人控制策略;将四足机器人控制策略分为支撑相及机身运动控制、摆动腿相运动控制及足端轨迹规划三部分;在Trot步态下行走时支撑相中存在的前后对角支撑足,在分析四足机器人支撑足受力情况后,并添加相关的约束条件,实现了四足机器人足端力及力矩可控;并通过在四足机器人机身的质心位置添加相应的虚拟弹簧阻尼组件,实现了四足机器人姿态和高度控制;通过在摆动腿足端实际位置与环境之间添加虚拟的弹簧阻尼组件并结合足端轨迹规划实现了四足机器人柔顺行走以及足端轨迹跟踪精确性;通过Matlab和CoppeliaSim建立联合对比仿真验证了控制策略的有效性和优越性。     

四足机器人坡面质心调整方法

为了实现稳定的坡面运动,设计了小腿采用液压缸的四足机器人.基于对角小跑步态,提出一种通过改变机器人前腿小腿腿长和保持后腿小腿腿长不变来实现坡面质心调整的方法.以机器人质心在斜面的投影点落在支撑对角线交点处为判据,对该质心调整方法进行了稳定性分析,得到姿态调整的确定值.对零冲击复合摆线足端轨迹规划方法进行了改进,以减少四足机器人坡面上的足地接触冲击.利用Adams和Matlab对四足机器人坡面trot步态运动进行了联合仿真.仿真结果表明所提出的质心调整方法和足端轨迹规划方法能够实现机器人在20°坡面上的稳定行走.      

脊柱型四足机器人运动学建模及对角小跑步态规划

针对四足机器人在常规对角小跑步态中绕对角支撑线的翻转力矩会导致机器人失衡问题,在运动学建模和失衡原因分析的基础上提出了2种新颖的对角小跑步态规划方法:叠加腿部侧摆运动的对角小跑步态和叠加脊柱偏航摆动的对角小跑步态.前者引入腿的侧摆关节的运动调节支撑腿足端轨迹,后者增加脊柱偏航关节的运动调节机器人的重心并保持足端轨迹不变,这2种方法均使机器人重心在整个对角小跑步态周期位于对角支撑线上.仿真结果显示,相比于常规对角小跑步态和足端轨迹后移的对角小跑步态,提出的对角小跑步态规划方法显著提高了机器人运动的稳定性.此外,提出的规划方法在存在模型误差时具有鲁棒性.     

基于速度矢量的6足机器人三角间歇步态规划与分析

为提高大惯量6足机器人行走的稳定性与连续性,提出了基于速度矢量的三角间歇步态.该步态以三角间歇步态为基础,统一映射平动与转动速度矢量为绕旋转中心转动,达到6足机器人全方向行走且速度平滑切换的目的.首先,由旋转中心理论计算中心坐标,在足端工作空间约束下计算最大旋转速度;其次,对摆动相采用足端0冲击摆线轨迹规划,支撑相采用增量式轨迹规划以便于编程计算连续运动指令实现变速度矢量运动;最后,在虚拟样机和物理模型上进行不同步态的对比实验.结果表明采用基于速度矢量的三角间歇步态晃动幅度与方差最小,提出的方法可保证大惯量6足机器人连续稳定的全方位运动.      

基于复合摆线轨迹的四足机器人稳定性分析

为了缩短四足机器人的研发周期,进一步提高其运动稳定性,基于复合摆线轨迹对不同步态周期下四足机器人的稳定性进行了研究.给出了四足机器人结构设计,并建立运动学模型进行运动学分析.采用复合摆线法进行轨迹规划,然后进一步结合运动学模型得到各关节驱动函数,并将其导入到ADAMS模型中设置相关约束进行动力学仿真.将机体翻转角作为主...     

四足机器人斜坡对角小跑运动控制研究

能否在斜坡上稳定行走是判断四足机器人运动性能的一个重要标准.针对四足机器人采用对角小跑步态在斜坡地形上的运动,建立机器人结构简化模型并进行运动学分析,完成了该步态下的足端轨迹规划,并提出一种基于模糊控制的姿态调整方法,通过调节机器人支撑相关节角来减小机身运动过程中的横滚角波动,从而提升机器人斜坡行走的稳定性.Adams...     

液压四足机器人关键步态参数优化

针对四足液压仿生机器人walk步态中足端轨迹规划问题,提出了通过优化步高和步长这两个关键步态参数来提高机器人行走稳定性的方法。通过聚合交叉的方法进行实验设计,用速度和步长及仿真得到的评价函数值进行三维曲面拟合,用速度截取所拟合的曲面得到不同速度下的最优步长。较优的步高确定采用二分法。步高和步长的优化效果用评价函数和Adams仿真进行验证,其中评价函数的构造充分考虑了表征机器人机身姿态平稳性的多组参数;四足机器人行走的仿真实验表明使用所述方法优化后的步态参数进行足端轨迹规划,得到的机器人静步态具有优异的运动性能表现。      

四足机器人坡面运动时的姿态调整技术

提出了一种四足机器人对脚小跑步态下的坡面运动姿态调整策略.采用复合摆线对机器人足端轨迹进行规划,以减小足端在换相点处与地面间的瞬时冲击;以机器人质心在斜面上的落点到支撑线的距离为判据进行四足机器人坡面运动稳定性分析,得到其姿态调整的确定值.在Adams中建立了四足机器人的虚拟样机模型并进行了仿真试验,试验结果证实所提出的姿态调整策略对提高四足机器人坡面运动稳定性有效.      

负载型四足步行平台静步态行走虚拟模型控制

为实现负载型四足步行平台静步态柔顺行走,减小控制方法的复杂程度,提出了一种基于机体虚拟模型的步行平台静步态行走控制方法。将平台静步态行走控制分为支撑阶段足端力的求解、摆动腿的运动控制及机体运动控制三部分。对于静步态行走支撑阶段中存在的三足及四足支撑阶段,分别在平台整体受力分析基础上,通过添加相应的约束条件,实现了其各方向的力可控。通过在摆动腿足端实际位置与理想位置之间添加虚拟的弹簧阻尼元件实现了足端轨迹跟踪准确性及足端着地时的柔顺性。通过在机体实际位置及期望位置之间添加相应的虚拟弹簧阻尼元件,结合平台机体轨迹规划实现其静步态行走。并通过机动平台平地及爬越台阶静步态行走仿真验证了控制算法的有效性。     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

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-