基于DSP的电液比例方向阀频率特性测控系统设计

针对电液比例方向阀频率特性测试问题,提出了一种基于数字信号处理器(DSP)的电液比例方向阀频率特性测控方案。阐述了测试系统整体结构与工作原理。设计了DSP的硬件系统与软件系统,建立了电液比例方向阀频率特性测试实验系统。在建立的实验台上测试了某电液比例方向阀的频率特性。实验结果表明:研制的基于DSP的电液比例方向阀频率特性测控系统工作可靠,自动化程度高,明显提高了频率特性测试效率。     

先导式大流量电液比例方向阀建模与仿真研究

先导式大流量电液比例方向阀控制精度高、响应速度快,能精确实现流量的方向控制和比例控制,这对于电液比例系统的高精度控制及其整体性能提高具有重要的意义。针对某型号的先导式大流量电液比例方向阀建立其静、动态特性和先导阀与主阀匹配研究的仿真模型,进行理论计算和仿真研究。仿真结果表明该阀的静、动态特性较好,先导阀与主阀匹配良好,为阀优化设计奠定了基础。     

液压支架试验台远程多缸同步控制系统设计

为解决30 000kN液压支架试验台活动平台及垂直外加载平台远程四缸同步控制技术难题,设计了基于PXI平台和LabVIEW RT的液压支架试验台远程多缸同步控制系统。采用高频电液比例方向阀作为调高油缸液压系统的执行元件,高精度位移传感器作为实时闭环系统的反馈元件,通过在嵌入式实时控制器中运行模糊PID控制算法,实时调整比例方向阀开口度,从而实现调高油缸的同步。实际应用表明,在液压支架试验台活动平台调高过程中,该系统的四缸最大同步误差为0.91 mm,四缸最小同步误差为0.63mm。     

基于虚拟仪器的电液比例方向阀静动态特性综合CAT系统

首次采用压力传感器构成压差反馈闭环控制,解决了电液比例方向阀稳态流量特性测试时阀压降恒定问题,使其在测试过程中阀压降波动控制在国标规定的5%以内.采用虚拟仪器技术实现了对电液比例方向阀的静动态综合特性测试,主要包括静态特性的稳态流量特性、压力增益特性、负载流量特性、流量压降特性和动态特性的频率特性、阶跃响应特性,并给出了某电液比例方向阀各种特性的实测结果.     

液压混合动力履带车辆联合制动模糊控制

针对液压混合动力履带车辆联合制动系统,为了实现制动过程平稳性,提出了基于制动力分配原则的模糊控制策略.首先在MATLAB中建立了能量再生制动系统和机械制动系统以及车辆动力学仿真模型,然后设计了以制动力分配系数为控制变量的联合制动模糊控制器,给出了模糊控制规则,建立了控制系统仿真模型,并在不同制动强度条件下对车辆制动过程进行仿真.仿真结果表明,联合制动模糊控制系统能够有效回收制动能量,同时与PID控制相比明显改善和提高了履带车辆制动过程稳定性.     

大型导弹起竖过程最优时间轨迹规划研究

关于导弹起竖优化控制问题,对导弹起竖过程的最优时间轨迹规划问题进行研究,提高导弹起竖过程的快速性和平稳性.由于多级液压缸换级碰撞带来的液压冲击引起系统振动,提出采用分级规划的策略.在对每一级进行轨迹规划时,为保证起竖过程的平稳性,在综合考虑装备实际中的液压系统压力、流量及导弹横向过载约束的基础上,根据五次多项式和非对称组合正弦函数的两种最优时间轨迹规划方法,建立了相应的最优时间轨迹规划模型进行求解.对含二级液压缸的大型导弹起竖过程最优时间轨迹规划仿真算例验证了改进的分级规划策略和最优时间轨迹规划方法的有效性.     

机器人化悬臂式掘进机液压行走驱动系统建模

为了解决机器人化悬臂式掘进机行走控制问题,在对该掘进机液压行走驱动系统的工作原理分析的基础上,建立了该系统的数学模型。该数学模型悬臂式掘进机行走驱动系统中电液比例方向阀的电压与阀芯位移关系式和流量方程、液压马达的流量与扭矩方程、比例方向阀的阀芯位移与液压马达角速度关系方程以及方向阀的输入电压与液压马达角速度的传递函数。仿真实验结果表明,所建立数学模型与实际基本吻合,为机器人化悬臂式掘进机性能分析和控制系统设计提供了实用的数学模型。     

机器人液压挖掘机运动系统的建模与控制

首先利用机器人运动学将铲斗的理想运动轨迹和各工作装置的目标转角序列联系起来,然后利用拉格朗日方程建立各工作装置的运动学模型,最后推导出LUDV液压驱动系统的电液模型,从而得到了挖掘机器人运动系统的完整模型．针对系统动力学的高非线性、参数的不确定性、外界干扰及比例方向阀的死区及非线性增益等特点,提出一种建立在自适应鲁棒控制基础上的非连续映射方法来处理运动系统并利用鲁棒反馈来消除近似误差．最后利用动臂控制试验来验证控制方法的正确性．     

基于反推的电液比例系统共振频率控制

针对电液比例系统的非线性以及不确定性因素对破碎频率控制的影响,设计反推的频率控制方法.建立电液比例阀控液压马达的破碎机构的非线性模型,特别是考虑了比例阀的动态频率和阻尼特性,将系统的各不确定性参数对破碎频率的影响等效为液压马达轴上的负载波动;设计基于反推的控制律,构建各步骤的误差信号、虚拟控制信号和目标函数间的关系,在不确定性有界的前提下保证了液压马达输出转速渐近跟踪的稳定性.给出频率控制系统的模型参数,并在基于Matlab6.5的环境下进行了仿真研究以及车载试验,结果表明,对于具有不确定性因素的电液比例频率控制系统,反推控制策略具有较好的控制性能,能够满足共振式破碎机的工程应用要求.     

大功率液压系统能量损耗的仿真研究

该文建立了大功率液压机的阀控电液伺服系统仿真模型,分析了电磁比例方向阀通过节流控制流量而位移或速度控制时产生的能量损耗,从而导致系统的液压油温度的升高,影响液压系统的稳定工作。通过计算机仿真,分析了直接驱动大功率液压机的能量损耗与控制方式之间的矛盾。在同样控制精度下,采用迭代学习PID控制器比PID控制器时的能量损耗低一个数量级。最后,给出了采用迭代学习PID控制器时,液压机滑块位移与系统压力的仿真曲线以及实际应用的采样曲线。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.