基于模糊自适应PID的无人驾驶车辆路径跟踪控制

在无人驾驶车辆路径跟踪控制过程中,针对控制对象发生变化时传统PID控制器难以对其控制参数进行实时调整的问题,提出一种以预瞄理论为基础的模糊自适应PID控制方法.以前轮转角作为控制系统的输入,设计基于横向偏差和航向偏差的模糊自适应PID路径跟踪控制器.分析量化因子和比例因子的选取原则,利用模糊理论对PID参数进行自适应调整;基于Carsim与Simulink对所提算法进行联合仿真实验.仿真结果表明:模糊自适应PID较传统PID改善了控制器的动态性能且具有较好的自适应能力.     

车辆轨迹的预瞄与模糊分数阶比例-积分-微分控制

为提高无人车辆轨迹控制的精度,提出了一种基于预瞄误差建模和优化模糊分数阶PID控制的车辆路径跟踪方法。根据车辆动力学特性,引入预瞄横向误差模型,以预瞄横向误差为输入,车辆前轮转角为输出,调整转角角度减小偏差实现轨迹跟踪,设计模糊分数阶PID跟踪控制器。该控制器在PID的基础上结合分数阶理论,同时利用粒子群算法优化的模糊控制器对参数进行在线调整。在CarSim/Simulink联合仿真平台进行仿真研究。研究结果表明,本文所设计的控制器可行有效,为轨迹控制的研究提供了参考。     

智能车辆局部路径规划与跟踪控制算法研究

针对无人驾驶汽车局部路径规划与跟踪控制，提出一种基于改进A^*算法的局部路径动态规划算法及一种基于改进LQR算法控制理论结合模糊控制与PID控制的路径跟踪控制算法。主要包括：搭建无人车辆在Frenet坐标系下利用栅格法构建预行驶区域模型；优化改进节点扩展方向，提出针对无人驾驶的五邻域扩展节点方式；A^*算法一次规划出代价值最小的目标节点，二次A^*算法规划出实时动态最优路径。另外，搭建以路径曲率变化率和横向误差变化率为状态变量的横向路径模糊跟踪控制模型，搭建以纵向误差和纵向误差变化率为状态变量的模糊PID控制模型解决参数难调问题。通过Carsim、Simulink与Perscan联合仿真平台验证设计的路径规划与跟踪控制算法有效性。     

基于转向响应特性的智能车辆轨迹跟踪双闭环控制

智能车辆轨迹跟踪的准确性与鲁棒性是车辆运动控制性能的重要表征,基于路径预瞄信息的跟踪控制研究使车辆性能显著提升. 然而,车辆转向系统响应不足给车辆实时准确的基于预瞄信息跟踪参考轨迹带来挑战. 针对此问题,实时引入转向系统状态建立双闭环轨迹跟踪控制结构,保证智能车辆轨迹跟踪控制算法对转向系统响应不足的鲁棒性. 具体结构外环基于预瞄信息使用模型预测控制求解最优转向角,内环基于转向状态误差使用PID方法设计反馈控制律以补偿转向响应不足. 双闭环结构耦合控制输入保证了车辆鲁棒最优跟踪控制. 最后通过Carsim与Simulink联合仿真,验证了该双闭环控制结构的有效性.      

基于LQR的智能驾驶汽车横纵向控制研究

为了提高智能驾驶汽车跟踪控制器的稳定性和跟踪精度,提出了一种基于线性二次型调节器(LQR)控制算法和驾驶员预瞄模型的横向跟踪控制策略,结合纵向比例-积分-微分(PID)控制算法实现横纵向控制。首先建立带有前馈的LQR控制器,采用梯度下降优化算法优化LQR控制器权重参数,并在此基础上引入驾驶员预瞄模型,设计了基于经验的预瞄距离自适应控制器;其次建立双PID纵向控制器进行速度控制。最后通过Carsim和Matlab/Simulink联合仿真以及实车测试验证,结果表明：仿真工况下最大横向偏差小于0.035 m,最大航向偏差小于0.09 rad,实车测试工况下也能够良好遵循规划轨迹的整体趋势,速度跟踪效果良好且前轮转角与横摆角速度变化平稳。因此,该控制器能够保证较高精度且平稳的轨迹跟踪,在高速状态下更为明显。     

模糊自整定PID航向控制算法优化及其性能评判

针对PID航向控制算法初始值选择的合理性对控制器性能所起的重要作用,文章通过建立PID航向控制算法的Kp、Ki和Kd初始值计算模型,实现对模糊自整定PID航向控制算法的优化;基于智能化SIHC仿真研究平台,全面测试了优化的航向控制算法性能,并利用改进的航向跟踪及保持性能评判算法定量评判了航向控制算法的性能。测试结果表明,优化后的模糊自整定PID航向控制算法具备自动根据环境条件和船舶操纵特性确定PID初始值的能力,算法的实用性及适应性得到提升。     

基于滚动预瞄模型的纯跟踪算法

针对无人驾驶车辆采用纯跟踪算法对不同曲率路径跟踪时,出现道路适应能力弱和跟踪精度差的问题,提出一种基于代价的滚动预瞄模型(rolling preview model, RPM),以提高纯跟踪算法跟踪精度与鲁棒性。首先,根据车辆运动学与阿克曼转向几何,提出预瞄轨迹的确定方法以及预瞄轨迹与待跟踪路径间的几何约束;其次,设计道路弯曲度加权项并构建目标函数对预瞄轨迹进行优化,以获得预瞄距离的最优值;最后,在ROS/Gazebo仿真环境下设置不同初始状态与不同曲率的工况进行对比仿真实验,并在空旷环境中对8字形路径进行实车跟踪实验。实验结果表明,所提出的滚动预瞄模型能够根据预瞄轨迹与待跟踪路径的几何关系有效调节预瞄距离,相较于麻省理工(Massachusetts Institute of Technology, MIT)算法和Stanley算法,滚动预瞄模型在特殊初始状态、大曲率道路下有利于跟踪精度的提高。     

无人驾驶高速4WID-4WIS车辆路径跟踪单点预瞄控制

针对无人驾驶高速四轮独立驱动独立转向(4WID-4WIS)车辆的驱动冗余、强非线性和不确定特性,提出一种基于控制分配和自抗扰控制法的路径跟踪单点预瞄控制方法。首先建立车辆单点预瞄路径跟踪系统的动力学模型。然后构建以控制分配器为核心的控制系统,使用自抗扰控制方法设计单点预瞄解耦控制器;提出目标生成器的类惯性环节算法,讨论其合理性;给出4WID-4WIS车辆路径跟踪控制分配问题的求解方法。最后进行仿真,结果表明所提方法能够实现快速、高精度的双移线圆弧路径跟踪控制。     

基于驾驶员行为的神经网络无人驾驶控制

针对铰接式自卸车的转向特性,提出了一种基于驾驶员行为的神经网络无人驾驶控制方法.建立了以激光雷达、角度传感器为主要环境信息的采集系统,通过分析铰接式车辆转向特征建立铰接式自卸车运动学模型和动力学模型,利用ADAMS动力学软件建立车辆动力学模型并进行车辆稳态测试.建立基于最优预瞄控制的人工神经网络控制算法的驾驶员模型,通过ADAMS-Matlab/Simulink联合仿真验证模型.最后搭建真实巷道环境进行直线路段回正实验和曲线路径跟踪实验,结果显示,该控制模型在变曲率路段中,横向位置偏差小于可通过路径宽度的10%,航向角偏差优化90%,表明该神经网络驾驶员控制模型收敛速度快,稳态特性好,具有良好的无人驾驶能力.     

基于动力学和预瞄理论的超车路径跟踪控制

为提高辅助超车安全性,对超车换道的规划路径进行预瞄跟踪控制研究。基于汽车侧向动力学模型和预瞄理论,推导出转向角到预瞄误差的传递关系,得到路径跟踪控制器。在Simulink中建立跟踪控制器,在Carsim中建立车辆模型和规划路径,定义二者的传递参数,分别对五次多项式超车路径和Carsim自带双移线路径进行路径跟踪控制的仿真。仿真结果表明,在高速120 km/h限速内超车时,除极小半径弯道和大角度转向外,实际行驶路径对规划路径的跟踪误差不超过0.2 m,平均跟踪误差均小于0.09 m,并且平均预瞄距离大约在10 m时跟踪效果较好,证明了控制器对超车路径跟踪的有效性。     

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-