机器人适从运动的混合控制

本文研究了理想情形下一类机器人适从运动的混合控制。对于一个机械臂手端与刚性环境发生光滑接触的类型,本文给出了一种约束描述,并进行分析。在此基础上,通过将控制变量分成两个分属于相互垂直的子空间的控制:力控制和运动控制,将机械臂动力学方程分裂成两个。一个用于力控制,另一个用于运动控制。从而对混合控制的思想有了更好的理解,使力控制和运动控制的设计能单独分别进行,为寻找混合控制提供了简便途径。     

浅谈降低国内航空复合材料结构成本的途径

从20世纪60年代末至今,先进树脂基复合材料(以下简称复合材料)以其轻质、高强、抗疲劳等优异性能及耐腐蚀、可设计、易于整体成型等特点,在航空领域得到极大的推崇.     

虚拟人力资源及其模式研究

虚拟人力资源是随着虚拟组织出现和知识经济的兴起而产生的新的人力资源的管理方式。近年来,随着信息技术的进一步升级,虚拟人力资源也出现了新的变化和演进。本文讨论了虚拟人力资源的定义,虚拟人力资源产生的理论背景,并较为完整地梳理了包括众包在内的虚拟人力资源的各种模式。     

复合材料机翼油箱盖板的制造和质量控制

介绍了采用开模膨胀橡胶法制造带加强筋的复合材料机翼整体油箱油箱盖板的一次共固化的工艺方法.针对初期制造的油箱盖板存在的比较严重的质量问题,包括翘曲、筋条尺寸超差、大面积分层及空隙密集等,提出了相应的设计修改、工艺改进和质量控制措施,最终制造出合格的制件.通过了功能试验和飞行考核.     

流动注射分光光度法测定废水中挥发酚

基于４－氨基安替比林显色原理，采用流动注射技术，建立了炼油废水中挥发酚的快速测定方法，分析速率为４０个试要／ｈ，线性范围为０．７５～２３．０μｇ／ｍｌ苯酚标准溶液连续测定１０次，相对标准偏差为２．８％，对炼油废水样，测定结果与标准方法无显著性差异，获得满意的结果。     

On the association of quiet-time Pi2 pulsations with IMF variations

The association of quiet-time Pi2 pulsations with the variations of the interplanetary magnetic field (IMF) has been examined by using three reported events, occurring during extremely quiet intervals, of which the first was on 10 March 1997, the second 27 December 1997, and the third 11 May 1999. For the first event, the onset time of ground Pi2s maps to the IMF structure bearing a variation cycle of north-to-south and north again as seen by Wind in the upstream region and Geotail in the magnetosheath. Likewise, the second and the third events have respectively, four and three recurrent turnings propagating to the Earth sensed by multiple satellites. The comparison of geomagnetic perturbations, auroral brightenings, and energetic particle data in the magnetotail with the IMF observations shows successive substorm-like activations accompanied by ground Pi2 onsets. For a clear variation cycle, the first Pi2 burst appears 36 ± 8 min after southward turning of the IMF and the second one follows14 ± 4 min after a northward turning. Moreover, ground Pi2 onsets recur under low IMF clock angle conditions. These observational results can be interpreted with the prevailing models of externally triggered substorm. But the solar wind coupling to the magnetosphere under quiet conditions proceeds in a less efficient way than under substorm time conditions. Consequently, we suggest that recurrent quiet-time Pi2s can be associated with IMF variations and their cause can be the same as those for substorm times.     

Adaptive neural network control of nonlinear systems with unknown dynamics

In this study, an adaptive neural network control approach is proposed to achieve accurate and robust control of nonlinear systems with unknown dynamics, wherein the neural network is innovatively used to learn the inverse problem of system dynamics with guaranteed convergence. This study focuses on the following three contributions. First, the considered system is transformed into a multi-integrator system using an input–output linearization technique, and an extended state observation technique is used to identify the transformed states. Second, an iterative control learning algorithm is proposed to achieve the neural network training, and stability analysis is given to prove that the network’s predictions converge to ideal control inputs with guaranteed convergence. Third, an adaptive neural network controller is developed by combining the trained network and a proportional-integral controller, and the long-standing challenge of model-based methods for control determination of unknown dynamics is resolved. Simulation results of a virtual control mission and an aerospace altitude tracking mission are provided to substantiate the effectiveness of the proposed techniques and illustrate the adaptability and robustness of the proposed controller.     

Prediction of nonlinear pilot-induced oscillation using an intelligent human pilot model

This paper proposes a method to predict nonlinear Pilot-Induced Oscillation (PIO) using an intelligent human pilot model. This method is based on a scalogram-based PIO metric, which uses wavelet transforms to analyze the nonlinear characteristics of a time-varying system. The intelligent human pilot model includes three modules: perception module, decision and adaptive module, and execution module. Intelligent and adaptive features, including a neural network receptor, fuzzy decision and adaptation, are also introduced into the human pilot model to describe the behavior of the human pilot accommodating the nonlinear events. Furthermore, an algorithm is proposed to describe the procedure of the PIO prediction method with nonlinear evaluation cases. The prediction results obtained by numerical simulation are compared with the assessments of flight test data to validate the utility of the method. The flight test data were generated in the evaluation of the Smart-Cue/Smart-Gain, which is capable of reducing the PIO tendencies considerably. The results show that the method can be applied to predict the nonlinear PIO events by human pilot model simulation.     

基于ANCF的松弛绳索动力学建模与仿真

传统绝对节点坐标方法(ANCF)绳索模型是基于梁单元建立的,其不能反映纤维绳索的不可抗压和松弛特性。考虑纤维绳索初始松弛余量,给出了绳索非线性轴向应力-应变关系。绳索在松弛状态下轴向力接近于零,在张紧状态下表现出线弹性特性。在此基础上,采用绝对节点坐标方法推导了松弛绳索动力学模型。通过静力学和动力学仿真,将传统绳索模型和松弛绳索模型进行对比,结果表明:在重力及不同集中载荷作用下,松弛绳索相比于传统绳索都具有更大的变形;分析移除集中载荷后绳索的动力学响应可知,传统绳索在振动过程中始终处于张紧状态,且绳索上各点振动同步,而松弛绳索会在张紧和松弛状态之间不断转换,绳索上各点的振动存在相位差,能够更好地反映绳索在松弛状态下的动力学特性。     

中介机构参与预算绩效评价问题研究——基于财政部门的问卷调查

推进中介机构参与预算绩效评价是我国预算绩效管理的重点内容,基于财政部门的问卷调查表明：该项工作尚处于起步阶段,需要财政部门、中介行业组织和中介机构等方面协同配合,通过完善评价规范,合理设计委托代理与付费机制,加强中介机构能力培育与资格管理,落实结果应用等促进中介机构参与预算绩效评价.