轧机液压伺服位置系统的无模型自适应控制

针对轧机液压伺服位置系统存在参变量多、强耦合等非线性因素,难以建立系统精确数学模型的问题,将无模型自适应控制算法应用于轧机液压伺服位置系统中;该算法仅使用被控系统的在线或离线输入/输出(I/O)数据便可完成控制器的设计,无需任何系统数学模型信息,以解决传统控制算法对数学模型的依赖性问题。MATLAB仿真结果表明,无模型自适应控制算法具有更快的收敛速度和更小的稳态误差,并且对扰动的鲁棒性更好。     

模糊控制用于高精度 CNC 系统多轴轨迹联动研究

分析了数控机床伺服进给系统的动特性对多坐标联动轮廓加工误差的影响规律，提出了模糊推理耦合轮廓误差补偿方法的原理，并给出了相应的控制算法及实现措施。该方法依据系统的轮廓误差，通过自适应模糊控制手段向各联动轴提供附加补偿作用，进而提高ＣＮＣ系统的轮廓加工精度。通过在四轴数控机床上实验，证明该补偿方法的可行性。     

软件伺服系统位置控制分析

针对交流永磁同步电机伺服系统在高速进给时位置跟随误差较大这个问题，分析了一种新型位置前馈方案，给出了位置控制器的模型和软件伺服实现方法．实验证明，该方案具有高精度控制的特点，可在保证系统稳定性的基础上，明显提高位置控制精度．     

伺服驱动系统无模型自适应控制

高速高精的应用场合要求伺服驱动系统需要具备很好的动态响应性能和很强的鲁棒性来应对外界的干扰.但系统参数时变特性、不确定性以及非建模动态等因素导致伺服驱动系统的精确模型无法辨识得到.提出一种基于虚拟参考反馈校正的伺服驱动系统无模型自适应控制方法.该方法实时采集过程输入和输出数据,以当前系统运行状态的最新数据序列更新PI控制器参数,达到自适应控制的目的,保证系统的跟随性能.并且该方法结合稳定性约束条件以确保整定出来的伺服参数位于系统的稳定域内.仿真和实验结果表明,相比传统PI控制,提出的无模型自适应控制方法具有更好的动态响应性能、稳定性和鲁棒性.     

多通道电液伺服系统的变结构自适应控制

针对多通道电液位置伺服系统存在的参数时变，通道间的耦合作用和外干扰等特点，提出了一种模型跟随变结构自适应控制方法，该系统具有较高的伺服跟踪精度和较强的鲁棒性，无需在线辨识。     

前馈控制方法在非轴对称表面加工中的应用

解决非轴对称曲面的车削加工控制中压陶瓷伺服刀架的滞后问题,消除加工中的滞后误差,在分析压电陶瓷刀具迟滞缺点的基础上建立了3种消除迟滞误差的前馈控制数据模型,即：升压模型,峰值降压模型及任意点降压模型,用这些数字模型进行补偿加工实验,最大位移误差为0．05um,补偿前后的加工精度对比表明,采用前馈控制补偿的加工方法能够大大降低加工中的迟滞误差,提高非轴对称曲面的加工精度。     

一种新型三自由度液压伺服关节的动力学模型

建立了一种新型三自由度液压伺服关节的动力学空间模型,提出了一种自适应控制补偿方法,该方法能够消除死区造成的位置跟踪误差．利用Madab对该动力学模型进行了仿真试验研究,仿真试验结果表明,死区对位置跟踪误差有直接影响,该关节的动力学系统是稳定的,采用自适应控制补偿方法,可以使位置跟踪精度误差小于0．1％,且系统输出无超调．同时,系统对负载变化不敏感,具有较强的鲁棒性．     

考虑气动伺服阀流体力的压力控制系统设计

提出了考虑气动伺服阀流体力的精密压力控制系统设计的新方法.建立了喷嘴挡板式伺服阀内流体力的计算模型和差压控制系统的线性模型.基于该模型,利用数值计算法设计了压力控制系统的PID控制器和干扰观测器.考虑伺服阀后的流体力能够进行压力控制系统的最优设计,并提高了参考输入的追踪性和系统的抗干扰性方面的控制效果.仿真与实验结果验证了该模型的正确性.     

基于核回归区间模型的电液位置伺服系统故障检测

针对电液位置伺服系统在运行过程中存在非线性、干扰性、复杂性以及参数不确定性等问题,提出了基于核回归区间模型的电液位置伺服系统故障检测方法。该方法利用反映系统诸多不确定性的无故障可测输入-输出数据,建立能控制核回归模型精度、又能平衡该模型结构复杂性的区间模型,用于判断电液位置伺服系统的实际输出是否越过系统健康运行时的区间输出,进而实现故障检测。该方法由于考虑了基于区间的动态阈值对故障进行检测,消除了传统的固定阈值易引起故障误报现象,所以具有一定的自适应性能力。实验论证了所提出的故障检测方法,可用于电液位置伺服系统故障的实时检测。     

模型参考控制在两级驱动伺服系统中的应用

基于计算机硬盘的两级驱动伺服系统，采用模型参考控制改善VCM伺服环的输出，并将其回馈给MA伺服环作为输入，利用MA高频宽、响应快等优点，调节VCM输出及位置误差信号，获得较为理想的复合输出结果。实验仿真结果验证了本文控制算法的有效性。     

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.     

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with