井下搜救机器人微行程液压系统设计与研究

井下搜救机器人的控制精度是实现复杂救援任务的关键。针对执行机构的主定位和副定位要求,设计出一种微行程液压控制系统,移除伺服阀元件,增加伺服电机和位移放大液压缸,通过PD控制,其动力台可到达μm级运动精度。基于AMESim建立液压仿真模型,研究不同油液弹性模量、油液黏度、蓄能器体积和蓄能器压力条件下的动力台位移量随时间变化规律,并进行实验验证。研究结果表明,微行程控制的精度和稳定性非常高,通过增大油液弹性模量和油液黏度可有效地提升液压系统响应效率。

基于“误差流”理论的精密线性平台微行程定位精度表征方法

定位精度是衡量精密线性平台运动准确度的关键指标,传统方法无法准确揭示定位误差传递过程,其数学意义与对应分布规律难以准确映射,无法满足微行程尺度的需求。提出一种基于“误差流”理论的概率密度函数传递方法,通过建立微行程尺度下的定位误差数学模型,揭示定位误差传递规律,获取可用于表征定位精度分布规律的行程-定位误差函数,为后续误差预测与补偿提供理论基础与技术支撑。首先,剖析精密线性平台的机械结构,分析误差源,比较宏、微行程尺度下影响定位精度各因素及其权重,获取敏感误差项与相应的分布信息;其次,构建精密线性平台拓扑构型图,揭示定位误差传递规律;第三,基于“误差流”理论,建立“组件加工工艺—加工误差—装配误差—微动特性—微行程定位误差”的数学模型,逐阶段推导微行程尺度下定位精度的函数表达式,建立微行程尺度下定位误差与分布规律的数学映射关系。实验结果表明,影响定位精度各因素权重随行程变化的趋势与基于“误差流”理论的数学模型一致,新方法分布曲线在微行程(0.01~1mm)下与实验结果更接近。

基于AT89C52的多路光栅智能测控仪

根据机床上精密测控的需求,提出了基于光栅位移传感器的微行程测量技术,并设计了一种基于AT89C52单片机和光栅传感器的智能光栅测量系统。阐述了该系统的硬件电路和系统软件处理程序的设计方法;同时对系统的性能以及具体功能实现进行了分析。

基于遗传算法优化的城市标准循环工况构建

针对传统车辆标准循环工况构建中存在的问题,提出了一种基于遗传算法的城市标准循环工况构建方法。以某城市实测行驶工况数据为依据,基于微行程分析理论,对微行程特征参数进行主成分提取及聚类,建立能够反映城市车辆实际运行的行驶工况。利用方差分析确定最佳聚类数,解决了最佳聚类数不易确定的问题。采用遗传算法对代表工况段进行优化修正,以聚类结果中的欧氏距离最小为优化目标,减小其与聚类中心的欧式距离。误差分析表明:提出的工况合成方法所生成的某城市标准循环工况特征参数平均累计误差明显减少,工况精度和一致性得到较大提高。

气缸驱动摆臂式高承载抬起机构

滚道输送线是工业生产中广泛应用的一种装配输送设备,抬起机构是滚道输送线上抬起装配托盘并使之与滚道分离的主要装置。本文提出了一种气缸驱动摆臂摆动实现装配托盘升降的高承载抬起机构,通过对该抬起机构的机械结构和工作原理进行介绍,阐述了该机构的高承载性能和侧置驱动优化空间布局的结构特点;同时,对该抬起机构的承载载荷、运行速度和抬起行程进行了理论分析,给出了一套设计参数。该抬起机构解决了滚道输送线不适应高承载的难题。

On the Asymptotic Behavior of Certain Second Order Differential Equations

Two criteria for asymptotic behavior of certain second order differential equations are obtained. The results extend and improve Feng's theorem.

Application of Modified G'/G-Expansion Method to Traveling Wave Solutions for Whitham-Broer-Kaup-Like Equations

A modified G′/G-expansion method is presented to derive traveling wave solutions for a class of nonlinear partial differential equations called Whitham -Broer- Kaup-Like equations. As a result, the hyperbolic function solutions, trigonometric function solutions, and rational solutions with parameters to the equations are obtained. When the parameters are taken as special values the solitary wave solutions can be obtained.

A Computational Approach to the New Type Solutions of Whitham-Broer-KaupEquation in Shallow Water

Based on computerized symbolic computation,a new method and its algorithm are proposed for searching for exact travelling wave solutions of the nonlinear partial differential equations.Making use of our approach,we investigate the Whitham-Broer-Kaup equation in shallow water and obtain new families of exact solutions,which include soliton-like solutions and periodic solutions.As its special cases,the solutions of classical long wave equations and modified Boussinesq equations can also be found.

Applications of Extended Mapping Deformation Method in Two （3＋1）-Dimensional Nonlinear Models

Based on the extended mapping deformation method and symbolic computation, many exact travelling wave solutions are found for the (3+1)-dimensional JM equation and the (3+1)-dimensional KP equation. The obtained solutions include solitary solution, periodic wave solution, rational travelling wave solution, and Jacobian and Weierstrass function solution, etc.

Modeling and Generating Realistic Background Traffic by Hybrid Approach

One of the key challenges in largescale network simulation is the huge computation demand in fine-grained traffic simulation.Apart from using high-performance computing facilities and parallelism techniques,an alternative is to replace the background traffic by simplified abstract models such as fluid flows.This paper suggests a hybrid modeling approach for background traffic,which combines ON/OFF model with TCP activities.The ON/OFF model is to characterize the application activities,and the ordinary differential equations(ODEs) based on fluid flows is to describe the TCP congestion avoidance functionality.The apparent merits of this approach are(1) to accurately capture the traffic self-similarity at source level,(2) properly reflect the network dynamics,and(3) efficiently decrease the computational complexity.The experimental results show that the approach perfectly makes a proper trade-off between accuracy and complexity in background traffic simulation.

Hot deformation behaviors and processing maps of Mg-Zn-Er alloys based on Gleeble-1500 hot compression simulation

The hot deformation behaviors of as-solution Mg?xZn?yEr alloys (x/y=6, x=3.0, 4.5 and 6.0; y=0.50, 0.75 and 1.00) wereinvestigated on Gleeble?1500 thermal simulator in a temperature range of 200?450 °C at a strain rate of 0.001?1 s?1. The truestress?strain curves showed the dynamic competition between the working hardening and working softening mainly due to thedynamic recrystallization (DRX) occurring during hot compression. The constitutive equations were constructed which couldaccurately predict the peak stress of the alloys. The addition of Zn and/or Er resulted in higher deformation activation energy forMg?3Zn?0.5Er (alloy A). The processing maps were constructed as function of the temperature and the strain rate, providing theoptimum hot working conditions (i.e., at strain of 0.3, Mg?3Zn?0.5Er (alloy A): 380?430 ?C, <0.1 s?1; Mg?4.5Zn?0.75Er (alloy B):380?450 ?C, 0.01?0.1 s?1; Mg?6Zn?1Er (alloy C): 390?440 ?C, 0.01?0.1 s?1). The as-solution treated Mg?4.5Zn?0.75Er (alloy B)demonstrated more optimum hot working window comparing with Mg?3Zn?0.5Er (alloy A) and Mg?6Zn?1Er (alloy C).

New Families of Nontravelling Wave Solutions to Two （3＋1）-Dimensional Equations

In this paper, two (3+1)-dimensional equations are investigated.Auto-Baecklund transformation is obtained, which is used with some ansatze to seek new types ofexact solutions including some arbitrary functions. When these arbitrary functions are taken assome special functions, these solutions possess abundant structures. These solutions containsoliton-like solutions and rational solutions.

Direct Reduction and Exact Solutions for Generalized Variable Coefficients 2D KdV Equation under Some Integrability Conditions

Based on the closed connections among the homogeneous balance （HB） method and Clarkson-KruSkal （CK） method, we study the similarity reductions of the generalized variable coefficients 2D KdV equation. In the meantime it is shown that this leads to a direct reduction in the form of ordinary differential equation under some integrability conditions between the variable coefficients. Two different cases have been discussed, the search for solutions of those ordinary differential equations yielded many exact travelling and solitonic wave solutions in the form of hyperbolic and trigonometric functions under some constraints between the variable coefficients.

Using Symbolic Computation to Exactly Solve the Integrable Broer-Kaup Equations in （2＋1）-Dimensional Spaces

The extended tanh method is further improved by generalizing the Riccati equation and introducing its twenty seven new solutions. As its application, the (2+ 1)-dimensional Broer-Kaup equation is investigated and then its fifty four non-travelling wave solutions have been obtained. The results reported in this paper show that this method is more powerful than those, such as tanh method, extended tanh method, modified extended tanh method and Riccati equation expansion method introduced in previous literatures.

A Comprehensive Comparison of the Analytical and Numerical Prediction of the Thermal History and Solidification Microstructure of Inconel 718 Products Made by Laser Powder-Bed Fusion

The finite-element （FE） model and the Rosenthal equation are used to study the thermal and microstructural phenomena in the laser powder-bed fusion of lnconel 718. A primary aim is to comprehend the advantages and disadvantages of the Rosenthal equation （which provides an analytical alternative to FE analysis）, and to investigate the influence of underlying assumptions on estimated results. Various physical characteristics are compared among the FE model, Rosenthal equation, and experiments. The predicted melt pool shapes compared with reported experimental results from the literature show that both the FE model and the analytical （Rosenthal） equation provide a reasonably accurate estimation. At high heat input, under conditions leading to keyholing, the reported melt width is narrower than predicted by the analytical equation. Moreover, a sensitivity analysis based on choices of the absorptivity is performed, which shows that the Rosenthal approach is more sensitive to absorptivity, compared with the FE approach. The primary reason could be the effect of radiative and convective losses, which are assumed to be negligible in the Rosenthal equation. In addition, both methods predict a columnar solidification microstructure, which agrees well with experimental reports, and the primary dendrite arm spacing （PDAS） predicted with the two approaches is comparable with measurements.

T-transformation Method for Studing the Multi-solitone Solutions of the Korteveg-de Vries Type Equations

In this paper, we propose a new technique of finding the PDE＇s traveling wave solutions based on the T-transformations. Using T-representation method we find a new class ofKorteveg-de Vries solution and propose method for studing the multi-solitone solutions of the Korteveg-de Vries type equations.

A Parallel Algorithm for Adaptive Local Refinement of Tetrahedral Meshes Using Bisection

Local mesh refinement is one of the key steps in the implementations of adaptive finite element methods. This paper presents a parallel algorithm for distributed memory parallel computers for adaptive local refinement of tetrahedral meshes using bisection. This algorithm is used in PHG, Parallel Hierarchical Grid Chttp：//lsec. cc. ac. cn/phg/）, a toolbox under active development for parallel adaptive finite element solutions of partial differential equations. The algorithm proposed is characterized by allowing simukaneous refinement of submeshes to arbitrary levels before synchronization between submeshes and without the need of a central coordinator process for managing new vertices. Using the concept of canonical refinement, a simple proof of the independence of the resulting mesh on the mesh partitioning is given, which is useful in better understanding the behaviour of the biseetioning refinement procedure.

Casoratian Solutions to a Non-isospectral Differential-Difference Kadomtsev-Petviashvilli Equation

In this paper, a non-isospectrai differential-difference Kadomtsev-Petviashvilli equation （n-D△KPE） is presented. Then, the Casoratian solutions of the n-D△KPE are obtained by generalizing Casoratian conditions of the non-isospectrai D△KPE, single-soliton solution is also derived by using Hiorta＇s method.

Anodic behavior and microstructure of Al/Pb-Ag-Co anode during zinc electrowinning

In order to study the anodic behavior and microstmctures of A1/Pb-Ag-Co anode during zinc electrowinning, by means of potentiodynamic investigations, scanning electron microscopy （SEM） and X-ray diffraction （XRD） analyses, the mechanism of the anodic processes playing on the surface of A1/Pb-0.8%Ag and A1/Pb-0.75%Ag-0.03%Co anodes prepared by electro-deposition from methyl sulfonic acid bath for zinc electrowinning from model sulphate electrolytes have been measured. On the basis of the cyclic voltammograms obtained, information about the corrosion rate of the composite in PbO2 region has been concluded. The microstructures were also observed by means of SEM and XRD which showed Pb-0.75%Ag-0.03%Co alloy composite coating has uniform and chaotic orientation tetragonal symmetry crystallites of PbSO4, but Pb-0.8%Ag alloy composite coating has well-organized orientation crystallites of PbSO4 concentrated in the certain zones after 24 h of anodic polarization. It is important that Al/Pb-0.75%Ag-0.03%Co anode oxide film consists of non-conductive dense MnO2 and PbSO4 and a, fl-PbO2 penetrated into which, in fact, are the active centers of the oxygen evolution after 24 h of anodic polarization.

Experimental Tests of the Operating Conditions of a Micro Gas Turbine Device

The aim of this work is to analyze the performance of a commercial micro gas turbine, focusing on the analysis of the fuel consumption and the outlet compressor and turbine temperature at various rpm, and to evaluate and compare the efficiency of the device. A test bench has been assembled with the available equipment in the laboratory of the department of mechanical and aerospace engineering in Roma. By using the software supplied by the manufacturer, the evaluation of the operating performance of the device at different speeds has been performed, obtaining all the values of interest.