数控机床直线伺服系统反推滑模控制的研究

针对高速高精数控机床直线伺服系统,考虑参数变化、外部负载扰动和摩擦力等不确定因素对系统伺服性能的影响,设计自适应反推滑模控制器 (ABSMC).由系统位置、速度误差建立滑模面,利用反推理论推导出反推滑模控制律.实际应用中不确定确界未知,通过设计自适应律修正不确定确界观测值.经分析验证,并与反推滑模控制相比,自适应反推滑模算法在保证系统全局一致渐进稳定情况下,能很好抑制不确定因素对系统性能的影响,对参考指令位置跟踪鲁棒性强,同时抖振得到明显削弱.     

电液伺服系统的自适应一般模型控制

针对电液伺服系统跟踪控制问题,提出一种基于等价输入的自适应一般模型控制方案。在电液伺服系统存在建模误差、时变参数和不可测扰动的情况下,控制器能够有效地跟踪系统被控参数;且控制器参数整定方便,物理意义明确。通过仿真表明,该控制方法对非线性的电液伺服系统实现自适应控制是正确有效的。     

基于连续滑模控制的电液伺服系统轨迹追踪控制

为改善电液伺服系统的轨迹追踪精度,设计一种连续滑模控制器,用于对电液伺服系统进行轨迹追踪控制。在电液伺服系统的建模过程中,以控制阀阀芯位移为依据,得到了电磁线圈上的电压及电流方程。在液压流体的作用下,建立气缸内液压流体的流量方程。根据系统的轨迹误差,构造滑动面模型。在开环传递函数状态空间模型的基础上,建立控制律的连续方程,进而得出连续滑模控制器,以克服电液伺服系统的不确定性和扰动性,控制其对标定轨迹进行精确追踪。与干扰观测器对标定轨迹的追踪结果相比,该方法在追踪弧形及方波标定轨迹时,追踪精度分别提高了31.23%和39.98%。该方法能有效改善电液伺服系统的轨迹追踪精度。     

基于自适应反演的电液伺服系统设计

研究了电液位置伺服系统的自适应反演控制策略.针对电液位置系统的非线性数学模型,采用反演设计算法并设计GCMAC神经网络逼近系统不确定性,从前向后逐步递推得到了系统的控制Lyapunov函数.基于Lyapunov稳定性理论,给出了鲁棒自适应控制律和GCMAC神经网络权值调整算法,确保系统稳定且输出跟踪误差渐近收敛于零.仿真结果证明了该控制策略的有效性.     

不确定性电液位置伺服系统的自适应滑模控制

本文针对 确定性的电液位置伺服系统的跟踪控制问题，提出了一种自适应滑模控制设计方法，所提出的自适应滑模控制器对系统的不确定性具有较强理棒性，并且跟踪性能良好。     

基于Haar小波的双直线电机自适应滑模控制北大核心

针对双直线电机伺服系统的同步控制精度易受耦合干扰、负载扰动和模型不确定性等因素影响,提出了一种基于Haar小波逼近的自适应滑模同步控制方法。采用滑模位置控制器克服扰动对伺服系统的影响,提高抗干扰性能;为削弱滑模控制引起的系统抖振,采用Haar小波基函数逼近系统动态模型中的时变非线性函数,进一步提高系统鲁棒性;同时采用自适应算法在线整定逼近函数的权值,并基于Lyapunov稳定理论证明了控制系统的渐进收敛性。实验结果表明,基于Haar小波的自适应滑模控制与滑模控制相比,不仅提高了系统的跟踪精度和同步精度,还增强了系统的鲁棒性。     

泵控缸电液位置伺服系统的自适应模糊滑模控制

针对泵控缸电液位置伺服系统的跟踪控制问题,设计了自适应模糊滑模变结构控制器.为了使等效控制器的设计不依赖于对象的精确数学模型,利用自适应模糊系统代替等效控制器,并且为了消除外界干扰、抑制抖振,利用模糊系统动态调节控制增益.仿真结果表明,该方法能保证系统具有较优的动态响应和稳态控制精度,并且对外界干扰及结构参数不确定性具有很强的鲁棒性.     

仿人智能与滑模控制相融合的液压无模型控制

针对电液伺服位置系统是一个多变量、强耦合、非线性控制系统,考虑到现有基于模型的控制方法对系统动力学模型的依赖性,以及未建模动态对系统控制性能的影响,设计了一种仿人智能控制与滑模控制相融合的液压系统无模型控制。为了提高系统的响应速度和稳态精度,将仿人智能控制的偏差与偏差变化率的乘积融入到滑模控制,设计一种全新的滑模函数,与无模型控制器结合,提出改进的无模型控制器。在相同条件下,通过无模型自适应控制、无模型自适应滑模控制与所提出的仿人智能控制与滑模控制相融合无模型控制进行仿真比较,结果表明,所设计的控制器收敛快,稳态误差小,且提高对扰动和模型变化的适应性。     

基于改进自适应高阶滑模的液压缸位移跟踪控制

电液伺服系统具有高度非线性、模型参数不确定等特点，给液压缸位移跟踪控制造成了困难。高阶滑模是一种变结构非线性控制方法，它可以实现系统的鲁棒控制，同时抑制系统的抖动，非常适用于电液伺服系统的控制。但高阶滑模也存在控制器的参数难以设置、系统响应速度慢的问题。对此，提出在自适应高阶滑模的基础上加入比例反馈的复合控制策略。针对高阶滑模的控制参数难以设置的问题，提出基于时滞控制理论的参数自适应调整算法，既保证了系统稳定又降低了控制信号的抖动幅值。在自适高阶滑模的基础上加入比例控制以提高系统的响应速度。建立了电液伺服系统的仿真模型，仿真结果表明：自适应高阶滑模使控制信号的振幅进一步减小，有效抑制了液压缸的抖动；加入比例控制之后，系统的响应速度大幅提升，位移跟踪误差也显著减小。     

动压缸电液伺服压力系统自适应反步双滑模控制

给出了轨道路基测试装置液压原理图、动压缸电液伺服压力系统数学模型和AMESim模型。将动压缸电液伺服压力系统拆分为动压缸位移子系统和动压缸输出压力子系统两部分,在此基础上,设计了一种自适应反步滑模控制方法:采用双滑模结构,分别构造动压缸位移子系统滑模自适应控制和动压缸输出压力子系统反步滑模自适应控制,给出了不确定参数的自适应律,并对该方法的稳定性进行了证明。最后将该方法作用于动压缸电液伺服压力系统AMESim模型上,仿真结果表明:该方法不仅可以有效地估计系统中参数,实现对目标期望变量精确地跟踪,具有比积分滑模自适应控制(ISAC)更好的控制性能和跟踪性能;而且可以有效地减小参数不确定性对跟踪性能的影响,具有较好的鲁棒性能。     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.