关键词： Inverse dynamics control   Robust H-infinity control   Adaptive fuzzy control   Robot manipulator with uncertain dynamics  

摘要： On the basis of inverse dynamics controller as a nominal control portion, two types of novel robust adaptive inverse dynamics control schemes are proposed for the trajectory tracking control of robot manipulator with uncertain dynamics. They are composed of an adaptive fuzzy control algorithm and a nonlinear tracking control model. The adaptive fuzzy control algorithm is employed to approximate the structured uncertainties, and the nonlinear robust control model is designed to eliminate the effects of the unstructured uncertainties and approximation errors. The tuning parameters in the adaptive fuzzy control algorithm are derived through the Lyapunov method. Comparison studies of their control performances with the conventional inverse dynamics controller are carried out, and their validity is demonstrated by numerical simulations of a two-link rotary robot manipulator.

关键词： Poly(butylene terephthalate)   Attapulgite   Crystallization   Differential scanning calorimetry (DSC)   Dynamic mechanical analysis (DMA)  

摘要： Poly(butylene terephthalate) (PBT)/attapulgite (AT) nanocomposites were prepared by in situ polymerization. Morphology of the PBT/AT nanocomposites was observed by scanning electron microscope and polarizing optical microscope. Thermogravimetric analyses were used to examine the thermal stability. The melting behaviors, equilibrium melting temperature, isothermal crystallization behavior of pure PBT and PBT/AT nanocomposites were studied by differential scanning calorimetry. The results show that PBT/AT nanocomposites possess higher thermal stability than pure PBT, and AT nanoparticles play a heterogeneous nucleating agent in PBT crystallization that accelerated the crystallization rate. The PBT/AT nanocomposite with higher AT content could retard the transport of polymer chains to the growing crystals compared with that of PBT/AT nanocomposite in lower AT content. According to dynamic mechanical analysis results, the storage modulus of PBT/AT nanocomposites was markedly improved and the addition of AT nanoparticles promotes the crystallization of PBT, which decreases the amorphous area. Meanwhile, the well-dispersed AT nanoparticles also retard the movement of polymer chain segment and increase the proportion of rigid amorphous region.

关键词： Machinery foundation   design optimization   forced vibration   vibration isolation  

摘要： This paper deals with the problem of optimum design of a foundation for rotating machinery with a view to minimize vibration transmission from a machine source to its supporting structure. The problem of analysis and optimization of the installation systems of machinery has been extensively researched on the assumption of a rigid supporting structure. The design based on a rigid supporting structure model is reasonable for the installation of machinery in many real engineering situations. However, this rigid support based model may not be appropriate for the problem studied herein where the machinery is to be installed on a relatively flexible supporting plate. Thus, a generalized mathematical model of mobility power flow is developed in this paper, with a rotating machine as vibration source, resilient mounts as isolator, and a flexible supporting plate as receiver. The objective of minimizing vibration transmission is realized by optimization of stiffness coefficients of resilient mounts with a constraint on the vibration level of the machine. The design objective is chosen as the minimization of the power flow transmitted to the flexible supporting plate through the resilient mounts at the excitation frequency of the machinery. Both a single excitation frequency and a range of excitation frequencies are considered. A gradient-based mathematical programing method is selected for its advantage of efficiently solving the current type of optimization problem with multiple mounts and multi-degree-of-freedom vibration transmission. The sensitivities of the objective and the constraint functions with respect to the design variables are derived analytically. The design and performance of the optimized machinery foundation is illustrated and discussed using several numerical examples. The optimized mounting system is suitable for the installation case of a rotating machine with a low or medium service speed on a flexible supporting plate structure.

关键词： 空间柔性机械臂   动力学建模   数值求解   仿真验证  

摘要： 针对综合考虑臂杆柔性和关节柔性的空间机械臂刚柔耦合动力学建模,以双连杆机械臂为研究对象,采用假设模态法对柔性臂杆离散化,将柔性关节等效为扭转弹簧,基于Lagrange方程和虚功原理推导模型方程。利用Maple和Matlab软件基于Newmark-β法原理联合求解方程数值解,并用ANSYS和ADAMS软件联合设计仿真模型验证动力学模型的正确性,结果表明:无论在阶跃力矩还是正弦力矩驱动下,动力学模型的输出和ADAMS模型输出的结果一致,很好的证明了动力学仿真程序的正确性。

关键词： polymerase exchange   single molecule   fluorescence microscopy  

摘要： Replication of DNA plays a central role in transmitting hereditary information from cell to cell. To achieve reliable DNA replication, multiple proteins form a stable complex, known as the replisome, enabling them to act together in a highly coordinated fashion. Over the past decade, the roles of the various proteins within the replisome have been determined. Although many of their interactions have been characterized, it remains poorly understood how replication proteins enter and leave the replisome. In this study, we visualize fluorescently labeled bacteriophage T7 DNA polymerases within the replisome while we simultaneously observe the kinetics of the replication process. This combination of observables allows us to monitor both the activity and dynamics of individual polymerases during coordinated leading-and lagging-strand synthesis. Our data suggest that lagging-strand polymerases are exchanged at a frequency similar to that of Okazaki fragment synthesis and that two or more polymerases are present in the replisome during DNA replication. Our studies imply a highly dynamic picture of the replisome with lagging-strand DNA polymerases residing at the fork for the synthesis of only a few Okazaki fragments. Further, new lagging-strand polymerases are readily recruited from a pool of polymerases that are proximally bound to the replisome and continuously replenished from solution.

关键词： 柔性机械手   矢量法   Lagrange方程  

摘要： 首先采用矢量法,尝试对垂直平面内的多自由度柔性机械手系统的动力学模型进行推导。然后以垂直平面三杆柔性机械手为例,简化机械手构件,提取机械手广义坐标变量,应用矢量法推导柔性机械手的动力学方程。最后用maple仿真软件对机械手末端运动情况进行了计算机仿真,验证了矢量法确实能够提高柔性机械手动力学模型精度,并且降低了计算过程中符号运算的复杂程度,是一种比较理想的动力学建模方法。

关键词： 通气机,机械   心力衰竭   血流动力学   正压呼吸  

摘要： 目的观察有创与无创序贯机械通气对老年急性左心衰竭患者血流动力学的影响。方法选择急性左心衰竭患者84例,采用短期有创正压通气(IPPV)后切换为无创正压通气(NIPPV)的撤机方法42例(序贯组),采用IPPV治疗直至撤机42例(对照组)。观察2组治疗前后血流动力学指标:平均动脉压、心率、中心静脉压(CVP)、PaO2、乳酸、LVEF、心输出量、B型钠尿肽(BNP)、系统血管阻力(SVR)、尿量、血管活性药物(多巴胺/多巴酚丁胺)用量的变化,以及机械通气时间、住院时间、并发症的情况。结果序贯组IPPV撤机时、NIPPV撤机时LVEF、心输出量较IPPV前明显增加,BNP、血管活性药物用量较IPPV前明显减少(P<0.05);对照组IPPV撤机时BNP、SVR、血管活性药物用量较序贯组IPPV撤机时明显减少,心输出量明显增加,对照组IPPV撤机时血管活性药物用量较序贯组NIPPV撤机时明显减少(P<0.05);与对照组比较,序贯组总机械通气时间、IPPV时间、住院时间明显缩短,呼吸机相关性肺炎、撤机失败及院内死亡比例明显减少(P<0.05)。结论序贯机械通气能够明显改善老年急性左心衰竭患者血流动力学指标及心功能,减少有创机械通气时间及相关并发症。

关键词： 机械臂   工艺   动力分析  

摘要： 简述了岩石支护及混凝土湿喷机机械臂的基本概论及应用,对人工操作与机械臂湿喷工艺进行了比较,对各关节进行了动力学分析,总结了混凝土湿喷机机械臂的发展历史、研制现状、发展前景以及目前存在的主要问题。

关键词： 双元动力发动机   曲轴   优化分析   ANYSY  

摘要： 针对机械/液压双元动力输出发动机性能问题,本文基于ANSYS对双元动力发动机曲轴进行了优化研究,根据双元动力发动机的动力学模型,在标定工况下分析了双元动力发动机的曲轴负荷,建立了曲轴三维模型,在6种情况下进行了有限元分析,得到优化的载荷工况,建立了曲轴优化模型。优化结果表明,曲轴体积由优化前的2.34×10-3 m3下降为优化后的2.08×10-3 m3,曲轴的总体积减小了11.42%,运转不均匀度由优化前的3.56%降低到3.34%,改善量达到6.18%,优化效果较为明显。该研究为后续的优化设计和分析提供了理论基础,具有广阔的应用前景。

关键词： 机械设备   故障频率   预防措施  

摘要： 设备故障管理是设备状态管理的重要组成部分,是维修管理的基础。随着科学技术的进步,设备的科技含量逐步增加,设备日益高参数化和自动化,设备在企业生产经营活动中的主导地位日益增强。设备各部分、各系统之间的关系更加密切,设备局部异常就会导致整机停运,甚至整个生产作业线或车间停产。所以一旦发生故障,修理费用、停机损失均越来越大,甚至造成严重危害。因此,要分析造成设备发生故障的原因并采取有效的对策,尽量降低设备故障的发生频率。