光电跟踪伺服系统二次跟踪控制

为提高光电跟踪伺服系统的跟踪精度,对输入信号未知条件下系统跟踪问题进行了研究。在单位负反馈系统基础上提出二次跟踪控制方法,并对系统频域特性进行了研究。结合光电跟踪伺服系统的特点,在跟踪探测器输出延迟条件下进行了控制律设计。仿真结果表明二次跟踪控制大幅提高了伺服系统对机动目标的稳态跟踪精度,比PI控制提高39倍,比PI+速度滞后补偿控制提高9倍,测试结果表明在40 m s延迟作用下,目标做50°/s,30°/s2等效正弦运动时稳态跟踪精度达到1′。     

结合深度强化学习与变形五次多项式的搬运机器人关节轨迹规划

针对在生产节拍固定的情况下搬运机器人各关节的运动轨迹及时间分配问题,构建基于深度强化学习与变形五次多项式相结合的搬运机器人关节轨迹时间分配模型;设计以节拍要求、速度约束和加速度约束为目标的奖励函数,搭建神经网络,利用MATLAB/Simulink软件,得到满足生产节拍和运动学约束的时间序列,并利用单臂四自由度搬运机器人仿真实验,验证所构建模型的可行性和有效性。结果表明：单臂四自由度搬运机器人各关节的运行时间均为5.89 s,其中平移关节1、 3的最大速度分别为2 597.84、 1 697.97 mm/s,最大加速度分别为19 532.11、 31 302.61 mm/s²;旋转关节2、 4的速度大小相等且方向相反,最大角速度均为137.53 (°)/s,最大角加速度均为1 180.51 (°)/s²,均未超过运动学约束;所构建的模型可以解决在指定生产节拍下搬运机器人关节轨迹时间分配问题,实现搬运机器人搬运过程中各关节的运动均衡,改善搬运机器人运行的稳定性和有效性。     

均值耦合多电机滑模速度同步控制

针对传统阿胶制粒机多电机速度同步控制精度低和控制系统响应速度慢的问题,提出了一种无速度传感器的多电机均值耦合非奇异全局快速Terminal滑模速度同步控制方法。首先,设计转速自适应磁链观测器,避免了加热筒体温度较高导致电机速度传感器检测精度不足的问题;然后,利用均值耦合策略对多电机转速进行耦合控制,实现系统误差全局补偿,保证多电机速度误差同步收敛;其次,通过设计具有非线性函数的非奇异全局快速Terminal滑模面,实现电机速度误差在有限时间内全局快速收敛,并消除了Terminal滑模的奇异问题,提高了单电机速度跟踪精度,降低了多电机间速度同步误差;最后,利用Lyapunov函数证明了观测器和控制器的稳定性及收敛性。仿真与实验结果表明：速度观测器能够在0.4 s内实现速度跟踪,当系统存在负载扰动时,调节时间小于0.05 s,具有良好的跟踪性能和稳态精度;与均值耦合滑模多电机速度同步控制相比,本文控制方法能够在0.15 s内实现对期望转速的跟踪,各电机同步误差调节时间减少了1.2 s,响应速度快,能够有效抑制负载扰动,具有更好的动态调节能力、稳态精度和鲁棒性,可满足阿胶制粒工艺的要求。     

基于反双曲正切函数的变步长LMS算法

针对定步长的LMS算法无法同时满足低稳态误差和快收敛速度这个需求,本文提出了一种基于反双曲正切函数的变步长LMS算法. 该算法基于反双曲正切函数构建步长与误差信号之间的非线性函数关系式,以此来替代LMS算法中的定步长,实现了对步长因子的动态调整. 文中详细讨论了新的变步长函数中参数α,β和γ对于算法性能的影响,并和其他几种较新的变步长算法进行了性能比较. 仿真结果表明,所提算法很好地兼顾了收敛速度、稳态误差和跟踪性能,在系统辨识、正弦信号去噪和自适应线性预测方面表现出了优异的性能.      

等速肌力训练在膝关节损伤后功能恢复影响的研究

采用Cybex-600型等速运动测试仪对11例膝关节损伤患者的患侧膝屈伸肌进行等速运动训练,研究膝关节在运动损伤后通过等速训练对膝关节功能恢复及关节周围肌肉力量的影响.选用在不同测试速度(60(°)/s、120(°)/s和180(°)/s)时的屈伸肌峰力矩、单次最大做功量和平均功率等指标对训练结果进行评定,研究结果表明:在运动损伤后的恢复期通过等速运动训练后,对上述指标均可产生良好的影响,与对照组相比,具有统计学意义;经过膝关节等速训练,可加速膝关节损伤后的康复过程,对增加膝关节周围肌肉力量、保持膝关节的稳定性、防治退行性骨关节病变的发生均具有重要的意义.     

基于非仿射模型的高超声速飞行器预设性能控制器

针对高超声速飞行器非仿射模型提出预设性能控制方法,设计了一种新型预设性能函数来保证控制器的动态性能和稳态性能,通过构造误差转化函数将最初的受限系统转化为等效的不受限系统来简化控制器设计.将高超声速飞行器纵向动力学模型分解为速度和高度子系统并分别设计控制律.对于高度子系统,使用高阶跟踪微分器对误差进行估计,引入模糊函数对未知项进行逼近,避免了反演控制中的反复求导;对于速度子系统,直接根据预设性能函数设计比例积分控制器.所设计的控制律在参数不确定和干扰的情况下保证了期望的动态性能和稳态精度,同时降低了计算量.最后,通过仿真实验验证了控制器的有效性.      

惯性加速度辅助卫星接收机跟踪环路算法

针对卫星接收机在强干扰高动态环境难以定位导航的问题,提出了基于惯性加速度辅助卫星跟踪环路算法,通过惯性加速度估算环路多普勒频移变化率,压缩了环路需承载的动态性,从而减少环路等效噪声带宽,降低了跟踪环路带内干扰,提高卫星接收机抗干扰能力.对所提算法的普适性、动态性、抗干扰性以及惯导估算误差影响等方面进行了仿真评估,仿真结果验证了算法的正确性,同时证明所提算法相比传统算法动态性大大提升,抗干扰能力提升5~8,d B,可以容忍较大惯导辅助信息误差,为算法工程化奠定了基础.     

基于PFC-(PID-H_∞)300MN模锻水压机动梁速度跟踪控制

提出基于PFC-(PID-H∞)的双闭环串级速度跟踪控制策略,内环为基于PID-H∞串级控制的凸轮转角控制环,外环为基于预测函数控制器的动梁速度控制环。将内控制环及后续水路系统看作PFC的广义被控对象,将广义被控对象简化为一阶加纯滞后对象,作为PFC的预测模型,设计水压机动梁速度跟踪控制系统,从模型失配、外加干扰2个方面对控制系统进行仿真。仿真和试验结果表明:该控制系统稳态精度、动态品质、跟踪性能和鲁棒性好,在不同载荷下,动梁速度控制精度为0.26～1.35mm/s。     

冲击谱激励下齿轮系统的动力学性能

依据德国BV043/85标准确定船用齿轮系统冲击谱,并转换为等效的双半正弦加速度冲击载荷。借助I-DEAS软件,利用杆单元、弹簧单元及四面体单元,建立包括齿轮、传动轴、轴承和箱体等组成的整个齿轮系统动力有限元分析模型,计算了齿轮系统的振动模态以及双半正弦加速度冲击载荷下的振动速度、振动加速度及动态应力。最后结合强度判定准则,分析了齿轮系统的抗冲击性能。     

基于跟踪回路误差限制的惯导辅助载波跟踪回路模式研究

惯导(INS)对接收机载波跟踪回路的辅助,能够减弱或抵消载体动态影响,降低回路带宽,减少回路跟踪误差,也是实施超紧耦合技术的主要特点。具体分析了FLL和PLL的各组成误差,推导了稳态载波相位误差、载波多普勒频移误差与INS速度误差之间的关系,基于跟踪回路误差的限制和稳定回路的门限,具体给出了在相位辅助和频率辅助两种不同模式下对INS速度误差的限制条件。分析表明,考虑INS辅助精度的影响,采用INS对载波跟踪的频率辅助更具可行性,最后仿真验证了频率辅助的有效性。     

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