Robust tracking control design for uncertain robotic systems with persistent bounded disturbances

In this study, a robust nonlinear L_∞‐gain tracking control design for uncertain robotic systems is proposed under persistent bounded disturbances. The design objective is that the peak of the tracking error in time domain must be as small as possible under persistent bounded disturbances. Since the nonlinear L_∞ ‐gain optimal tracking control cannot be solved directly, the nonlinear L_∞ ‐gain optimal tracking problem is transformed into a nonlinear L_∞ ‐gain tracking problem by given a prescribed disturbance attenuation level for the L_∞ ‐gain tracking performance. To guarantee that the L_∞ ‐gain tracking performance can be achieved for the uncertain robotic systems, a sliding‐mode scheme is introduced to eliminate the effect of the parameter uncertainties. By virtue of the skew‐symmetric property of the robotic systems, sufficient conditions are developed for solving the robust L_∞ ‐gain tracking control problems in terms of an algebraic equation instead of a differential equation. The proposed method is simple and the algebraic equation can be solved analytically. Therefore, the proposed robust L_∞ ‐gain tracking control scheme is suitable for practical control design of uncertain robotic systems. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Flow patterns in gas-assisted injection molding process in a channel

The flow field of a long bubble steadily expelling a viscous fluid confined by two closely located parallel plates is examined. In order to investigate the influence of bubble size on the flow field, a theoretical bubble profile is used to replace the complicated procedure for computing simultaneously the interface between the gas surface and fluid flows. The present study showed the two typical flow patterns and also a third flow pattern of the stagnation point moving in the region of the bubble tip front during transformation of the two typical flow patterns. The vorticity patterns are also drawn for various bubble profiles and are examined for their effect on the flow. The velocity field is also presented from two different viewpoints and the phenomena is examined. The stagnation point located on the center line between the bubble tip to the upstream is only found in the small range of in a channel, where λ is ratio of the bubble width to the distance between two parallel plates.     

Dynamics of Flexible Multibody Systems Using Virtual Work and Linear Graph Theory

By combining linear graph theory with the principle of virtualwork, a dynamic formulation is obtained that extends graph-theoreticmodelling methods to the analysis of flexible multibody systems. Thesystem is represented by a linear graph, in which nodes representreference frames on rigid and flexible bodies, and edges representcomponents that connect these frames. By selecting a spanning tree forthe graph, the analyst can choose the set of coordinates appearing inthe final system of equations. This set can include absolute, joint, orelastic coordinates, or some combination thereof. If desired, allnon-working constraint forces and torques can be automaticallyeliminated from the dynamic equations by exploiting the properties ofvirtual work. The formulation has been implemented in a computerprogram, DynaFlex, that generates the equations of motion in symbolicform. Three examples are presented to demonstrate the application of theformulation, and to validate the symbolic computer implementation.     

建设项目设计阶段投资控制系统的建立与分析

针对建设设计阶段独立使用价值工程、优化设计和限额设计等方法进行投资控制的局限性,借鉴系统论、控制论、信息论等思想和方法,建立了设计阶段投资控制系统。系统主要由探测元件、控制元件和执行元件组成,探测元件进行设计阶段的信息收集;控制元件通过审核将各项投资控制活动与投资控制目标进行对比,提出应对策略;执行元件完成应对策略。通过投资控制系统的执行,实现对设计阶段各项活动的全面系统控制,从管理层面上解决设计阶段投资控制活动割裂问题,进而改善设计阶段整体投资控制效果。     

基于消除地方高校成长上限基模的实证研究——以江西M学校为例

本文基于系统动力学反馈基模分析方法,在分析江西地方高校发展的成长上限基模和对策基模的基础上进行实证研究,引入相关数据,构建消除成长上限基模的顶点赋权模型,并提出综合对策思考。     

液滴在热液相介质中上升汽化时的传热与传质

本文分析了液滴在不互溶的液相介质中上升汽化时的传热和传质,导出了数模,进行了数值求解,获知在泡滴与液相接触的汽液边界处温度下降和浓度升高,存在着溶液的过冷(或过饱和)边界层。实验结果与数模计算结果表明,该模型能够较好地预測液滴汽化的整体特性。     

Investigation of the size effect on optical properties of polycrystalline Ge deposition by pulse laser deposition

The size effect of optical properties of the polycrystalline Ge/Si films prepared by pulse laser deposition (PLD) is investigated by photoluminescence (PL) and photocurrent (PC) spectra. The size of Ge nanocrystals is precisely controlled by the pulsed deposition time and then observed by the atomic force microscopy (AFM). The average size of Ge nanocrystals is about 2, 5 and 25 nm for 1, 2 and 3 min deposited sample, respectively. The size effect on optical properties of Ge nanocrystals has been analyzed by photoluminescence (PL) and photocurrent (PC) spectra. The PL peaks shift from 0.799 eV for 1 min to 0.762 eV for 3 mins; at the same time, the photocurrent peaks of the films sharply changes from 0.781 eV to 0.749 eV, the shifts of PL and PC are contributed to the quantum size effect of Ge nanocrystals.     

超细片状铝粉和铝银浆的制备

超细鳞片状铝粉和铝银浆由于其特殊的二维平面结构，具有良好的遮盖力、显著的屏蔽效应、光学反射能力；超细鳞片状铝粉和铝银浆颜料的制备方法很多，本文采用机械化学法制备超细鳞片状铝粉和铝银浆。     

A TDOA location algorithm based on data fusion

A new positioning method in mobile networks is presented. Based on the data fusion technology, it processes multi-layer information fusion for the location estimates achieved by the Chan algorithm, which increases mobile positioning accuracy effectively by only using measured difference of arriving (TDOA) signals. The method is simple and practical, especially when the location estimates are corrupted by the non-line-of-sight (NLOS) error. It not only has high positioning accuracy, but also reduces the location failure probability. Results from computer simulation show that the proposed method is effective in various environments. __________ Translated from Journal of Dalian University of Technology, 2005, 45(1): 138–141 (in Chinese)     

谈应变能力在体操教学中的应用

提高体操的教学质量,关键在教师的素质,而教师在体操教学中的应变能力是体育教师的必备素质之一.分析了影响教师应变能力的各种因素及在完成体操教学任务中的重要性及人作用.