一个带破圈启发方法的回答集编程系统

回答集编程(answer set programming,ASP)是一种回答集语义下的逻辑编程范例,可应用于非单调推理,叙述式问题求解等领域.本文为ASP提出并实现了一种破圈启发方法与一种基部限制式前向搜索过程,所得到的系统称为LPS.实验结果显示,相对于其他经典的ASP系统,LPS能够有效地解决处于相变难区域中的逻辑程序,通常这些程序被认为是计算困难的.除此以外,通过使用被称为动态变元过滤(dynamic variable filtering,DVF)的技术,LPS可以在计算过程中极大地缩小搜索树的尺寸.     

基于曲率加权累加的动态速度前瞻控制

针对在高速加工、快速检测等高速进给条件下,传统速度控制方法容易导致工件过切、机床抖动等问题,提出了基于离散衔接点曲率加权累加的速度前瞻程序段数动态选择的方法。首先,分析了基于5次样条曲线拟合离散衔接点方法,然后推导了到各衔接点的曲率表达式,最后根据各点曲率加权累加值进行动态速度前瞻程序段控制,并进行了仿真验证。仿真结果表明,动态速度前瞻避免了前瞻路径过短不能完成减速要求和前瞻段数过多占用系统资源,一定程度上解决了速度和精度的冲突问题,提高了系统的性能和加工效率。     

考虑风电接入的协调滚动发电计划

随着大量风电接入电网,风电接入对电力系统发电计划的影响成为一个需要研究的关键问题。文中针对风电接入电网后带来的不确定性,基于最优潮流理论和积留量法的思想,提出了在线有功调度的动态前瞻时间窗口模型,实现了在线有功调度问题在时间维度上的有效解耦。在此基础上,提出了一种能够考虑多时段间各种动态耦合约束条件的动态协调滚动发电计...     

基于多词汇树的对话语音识别搜索策略

在查询类对话语音识别系统中，词汇中的少数几类词往往占有词汇量的很大部分，利用这一重要特点，可以对传统的基于单树结构的搜索算法进行改进。本文在采用基于类的语言模型的条件下，在查询类对话语音识别系统中，对词汇中的若干大类单独建树，从而免除了多数词汇的语言模型look—ahead计算时间和存储空间，并实现了语言分的提前精确运用。针对机票预订口语对话系统的实验表明，该搜索策略与单树方法相比，在同样的计算资源条件下，时间效率有显著提高。     

High-performance CORDIC rotation algorithm based on look-ahead techniques

The Coordinate Rotation Digital Computer (CORDIC) algorithm is a well-known iterative method for the computation of vector rotation. However, the major disadvantage is its relatively slow computational speed. In this article, a high-performance CORDIC rotation algorithm is proposed. Using the look-ahead techniques, the rotation directions can be predicted directly from the input angle. The proposed method can increase performance under maintaining the precision. The experimental results show the efficiency of the proposed methods.     

NURBS曲线实时插补中S型加减速算法的研究

针对在高速高精度加工过程中非均匀B样条曲线(non-uniform rational B-spline,NURBS)的实时插补时,机床加减速容易出现冲击或者振荡现象,提出了S型加减速(S-shape ADC/DEC)前瞻方法。建立了曲线的S型加减速离散采样模型,提出了S型曲线加减速前瞻算法,通过此算法可以根据实际插补轨迹的几何特性,能够自适应地确定加减速点。仿真结果表明该算法可以在保证加工精度的同时有效消除加减速过程中对机床的冲击,提高加工精度。     

小线段高速加工的速度模型研究和实现

针对数控插补中离散化进给速度控制的特点，导出了在直线加减速情况下的小线段长度和轨迹形状误差对进给速度的约束条件；完善了小线段高速加工速度衔接数学模型，形成了能实际应用的工程化方法，该方法以给定的最大预处理段数为条件，根据小线段路径的具体形状和长短、速度变化的平滑性和位置误差精度的要求，求解出离散化的进给速度值。同时提出了在指令进给速度实时变化的情况下进给速度的求解方法。仿真结果表明，此数学模型及离散速度的求解方法能实现进给速度的高速衔接，从而大大提高加工效率。     

一种高速高精的路径动态前瞻规划算法

由于路径规划过程与速度规划过程之间缺乏信息交换,加工过程会出现加工速度与加工质量降低的现象,针对这一问题,提出了种高速、高精的路径动态前瞻规划算法。根据相邻加工路径之间的关系,规划出过渡圆弧半径的初始值;根据当前过渡圆弧与相邻的前一个过渡圆弧之间的关系,调整当前过渡圆弧的半径值;利用前瞻算法,结合具体的速度规划方式,进一步调整过渡圆弧的半径值,以确保加工过程中刀具既可以加速到路径所允许的最大速度,又可以在减速点前进行有效的减速。试验表明,通过将路径规划过程与速度规划过程相结合,算法在系统允许的误差范围内实现了有效的路径规划,并且最大程度地提高了加工速度,在保证加工精度的同时,提高了加工效率。     

A Generalized Acceleration and Deceleration Approach for Continuous Small Line Blocks with Look-ahead

Generally complex 3D contours are divided into a lot of continuous small line blocks by CAD/CAM software. When these small line blocks are used in conventional way,machine tool has to stop at the end of one move before continuing on to the next to meet accuracy requirement,which results in inefficiency.Look-ahead is an intelligent function that aims at adjusting the feed rate automatically to achieve maximum productivity while maintaining accuracy.By now most researchers just utilize the simplest linear acceleration(ACC)and deceleration(DEC)to deal with look-ahead intelligence.A generalized ACC/DEC ap- proach and corresponding optimal look-ahead algorithm based on dynamic back tracking along a doubly linked list are proposed.An improved rounding strategy for reducing interpolation errors is also presented.By using the proposed techniques,arbitrary velocity profiles that offer look-ahead feature and have the desired ACC/DEC characteristics for movement of a lot of continuous line blocks can be generated efficiently.Both simulations and experiments showed the productivity was dramatically increased without sacri- fice of accuracy.     

The Impact of High Speed Machining on Computing and Automation

Machine tool technologies, especially Computer Numerical Control (CNC) High Speed Machining (HSM) have emerged as effective mechanisms for Rapid Tooling and Manufacturing applications. These new technologies are attractive for competitive manufacturing because of their technical advantages, i.e. a significant reduction in lead-time, high product accuracy, and good surface finish. However, HSM not only stimulates advancements in cutting tools and materials, it also demands increasingly sophisticated CAD/CAM software, and powerful CNC controllers that require more support technologies. This paper explores the computational requirement and impact of HSM on CNC controller, wear detection, look ahead programming, simulation, and tool management.