基于解耦控制的同步传动技术的应用研究

对龙门移动式镗铣床同步传动不一致性问题进行研究,用两台直线电机作为龙门柱纵向进给的传动机构,分析了扰动与输出之间存在的耦合,设计出一种解耦控制器,并用龙门框架不平行时所产生的应力变化进行补偿。仿真结果表明,系统性能良好,并能快速实现同步运行。     

PLC在组合机床控制中的应用

本文介绍了PLC对组合机床的控制,分析了其工作原理,详细介绍了其硬件配置和软件设计.     

A parallel algorithm for approximate regularity

Spatial regularity amidst a seemingly chaotic image is often meaningful. Many papers in computational geometry are concerned with detecting some type of regularity via exact solutions to problems in geometric pattern recognition. However, real-world applications often have data that is approximate, and may rely on calculations that are approximate. Thus, it is useful to develop solutions that have an error tolerance.

A solution has recently been presented by Robins et al. [Inform. Process. Lett. 69 (1999) 189–195] to the problem of finding all maximal subsets of an input set in the Euclidean plane that are approximately equally-spaced and approximately collinear. This is a problem that arises in computer vision, military applications, and other areas. The algorithm of Robins et al. is different in several important respects from the optimal algorithm given by Kahng and Robins [Patter Recognition Lett. 12 (1991) 757–764] for the exact version of the problem. The algorithm of Robins et al. seems inherently sequential and runs in O(n^5/2) time, where n is the size of the input set. In this paper, we give parallel solutions to this problem.     

Reducing the overhead of dynamic compilation

The execution model for mobile, dynamically‐linked, object‐oriented programs has evolved from fast interpretation to a mix of interpreted and dynamically compiled execution. The primary motivation for dynamic compilation is that compiled code executes significantly faster than interpreted code. However, dynamic compilation, which is performed while the application is running, introduces execution delay. In this paper we present two dynamic compilation techniques that enable high performance execution while reducing the effect of this compilation overhead. These techniques can be classified as (1) decreasing the amount of compilation performed, and (2) overlapping compilation with execution. We first present and evaluate lazy compilation, an approach used in most dynamic compilation systems in which individual methods are compiled on‐demand upon their first invocation. This is in contrast to eager compilation, in which all methods in a class are compiled when a new class is loaded. In this work, we describe our experience with eager compilation, as well as the implementation and transition to lazy compilation. We empirically detail the effectiveness of this decision. Our experimental results using the SpecJVM Java benchmarks and the Jalapeño JVM show that, compared to eager compilation, lazy compilation results in 57% fewer methods being compiled and reductions in total time of 14 to 26%. Total time in this context is compilation plus execution time. Next, we present profile‐driven, background compilation, a technique that augments lazy compilation by using idle cycles in multiprocessor systems to overlap compilation with application execution. With this approach, compilation occurs on a thread separate from that of application threads so as to reduce intermittent, and possibly substantial, delay in execution. Profile information is used to prioritize methods as candidates for background compilation. Methods are compiled according to this priority scheme so that performance‐critical methods are invoked using optimized code as soon as possible. Our results indicate that background compilation can achieve the performance of off‐line compiled applications and masks almost all compilation overhead. We show significant reductions in total time of 14 to 71% over lazy compilation. Copyright © 2001 John Wiley & Sons, Ltd.     

基于支持向量机与无监督聚类相结合的中文网页分类器

提出了一种将支持向量机与无监督聚类相结合的新分类算法,给出了一种新的网页表示方法并应用于网页分类问题。该算法首先利用无监督聚类分别对训练集中正例和反例聚类,然后挑选一些例子训练SVM并获得SVM分类器,任何网页可以通过比较其与聚类中心的距离决定采用无监督聚类方法或SVM分类器进行分类。该算法充分利用了SVM准确率高与无监督聚类速度快的优点。实验表明它不仅具有较高的训练效率,而且有很高的精确度。     

圆网印花控制系统中的多机通讯实现

根据分布式圆网印花控制系统的具体情况,设计出基于ＲＳ４８５的简化ＢＩＴＢＵＳ总线通讯方案,实现了主机和各从机之间的通讯,满足了系统协调控制的要求。     

压铸机计算机控制系统研究

系统地介绍了28000kN压铸机计算机控制系统的设计。在硬件方面,输入输出板均采用了光隔,抗干扰能力强。在软件设计上,采用定时中断,即实现了高速采样,又可周期性地扫描输入输出端口的状态,循环发出动作指令,这种模拟可编程控制器的程序设计方法,大大提高了整个系统的性能。     

微机控制纤维缠绕三通管机械

本文简单介绍了由计算机控制纤维缠绕三通管的设备工作原理及芯模设计。     

系列变螺距螺杆的设计计算

为了使罐头包装机具有柔性加工的功能并提高设备利用率,根据圆柱形罐的螺杆供送机构的原理,设计开发了可调变螺距螺杆供送机构和对应不同罐径的系列变螺距螺杆。根据对罐的运动规律要求,给出了变螺距螺杆结构参数的设计计算方法以及罐的运动规律的计算分析方法。阐明了罐运动规律与螺杆长度、罐直径、螺距、螺距数之间的关系。研究的变螺距螺杆的设计计算及运动规律分析方法适合常用的罐径系列。     

Identification of large-scale goaf instability in underground mine using particle swarm optimization and support vector machine

An approach which combines particle swarm optimization and support vector machine (PSO–SVM) is proposed to forecast large-scale goaf instability (LSGI). Firstly, influencing factors of goaf safety are analyzed, and following parameters were selected as evaluation indexes in the LSGI: uniaxial compressive strength (UCS) of rock, elastic modulus (E) of rock, rock quality designation (RQD), area ration of pillar (S_p), the ratio of width to height of the pillar (w/h), depth of ore body (H), volume of goaf (V), dip of ore body (α) and area of goaf (S_g). Then LSGI forecasting model by PSO-SVM was established according to the influencing factors. The performance of hybrid model (PSO + SVM = PSO–SVM) has been compared with the grid search method of support vector machine (GSM–SVM) model. The actual data of 40 goafs are applied to research the forecasting ability of the proposed method, and two cases of underground mine are also validated by the proposed model. The results indicated that the heuristic algorithm of PSO can speed up the SVM parameter optimization search, and the predictive ability of the PSO–SVM model with the RBF kernel function is acceptable and robust, which might hold a high potential to become a useful tool in goaf risky prediction research.