一种新的改善机器人动态精度的方法

从机器人关节反馈控制系统模型出发,本文提出了一种利用补偿指令轨迹来改善机器人动态精度的方法,并指出了这一方法实施的全过程.利用这一方法对机器人实施控制,不仅可以从根本上克服由于重力负载和杆件离心效应等因素的干扰给控制系统带来的动态精度问题,而且还可消除由于反馈控制系统本身的固有特性所决定的系统的动态跟踪误差.通过在 PUMA560上的数值研究,证明了本文理论方法的正确性.     

An object design framework for structural engineering

Object-oriented principles have introduced several useful concepts for developing complex software systems. As a result, several methodologies have been suggested for the overall design of software systems based on these concepts. Methodologies and frameworks for designing objects that are to be part of the software systems are currently lacking. This paper proposes anobject design framework andmethodology, which utilizes the object-oriented concepts, for planning, organizing and designing structural engineering design objects. Design objects in an integrated structural engineering system are complex and often related to each other in various different ways. The paper also identifies several important relationships among structural engineering design objects. These relationships serve as communication channels through wich design objects send messages to and receive responses from each other. Several examples, drawn from reinforced concrete structures, will be presented to demonstrate the object design methodology and to illustrate how the framework is effective in reducing the complexity of design objects in an integrated structural engineering system.     

Efficient Parallel Algorithms for Some Graph Theory Problems

In this paper,a sequential algorithm computing the aww vertex pair distance matrix D and the path matrix Pis given.On a PRAM EREW model with p,1≤p≤n^2,processors,a parallel version of the sequential algorithm is shown.This method can also be used to get a parallel algorithm to compute transitive closure array A^* of an undirected graph.The time complexity of the parallel algorithm is O(n^3/p).If D,P and A^* are known,it is shown that the problems to find all connected components,to compute the diameter of an undirected graph,to determine the center of a directed graph and to search for a directed cycle with the minimum(maximum)length in a directed graph can all be solved in O(n^2/p logp)time.     

A Lower Bound for Nearly Minimal Adaptive and Hot Potato Algorithms

Recently, Chinn et al. [10] presented lower bounds for store-and-forward permutation routing algorithms on the n \times n mesh with bounded buffer size and where a packet must take a shortest (or minimal ) path to its destination. We extend their analysis to algorithms that are nearly minimal. We also apply this technique to the domain of hot potato algorithms, where there is no storage of packets and the shortest path to a destination is not assumed (and is in general impossible). We show that ``natural' variants and ``improvements' of several algorithms in the literature perform poorly in the worst case. As a result, we identify algorithmic features that are undesirable for worst-case hot potato permutation routing. Recent works in hot potato routing have tried to define simple and greedy classes of algorithms. We show that when an algorithm is too simple and too greedy, its performance in routing permutations is poor in the worst case. Specifically, the technique of [10] is also applicable to algorithms that do not necessarily send packets in minimal or even nearly minimal paths: it may be enough that they naively attempt to do so when possible. In particular, our results show that a certain class of greedy algorithms that was suggested recently by Ben-Dor et al. [6] contains algorithms that have poor performance in routing worst-case permutations. Received August 24, 1995; revised May 27, 1997.     

Shortest paths of bounded curvature in the plane

Given two oriented points in the plane, we determine and compute the shortest paths of bounded curvature joining them. This problem has been solved recently by Dubins in the no-cusp case, and by Reeds and Shepp otherwise. We propose a new solution based on the minimum principle of Pontryagin. Our approach simplifies the proofs and makes clear the global or local nature of the results.     

Obtaining sample path derivatives by source code instrumentation

This paper describes a process for determining the value of the gradient of the real outputs of a program with respect to its real parameters. CalledGradient Instrumentation, it is a mechanical process of insertion into the program's source code. The resulting program yields the gradient without the re-execution of the program. The sample path derivatives of many discrete event dynamical system simulations can be found using Gradient Instrumentation, by treating them as deterministic programs. The technique can also be applied to continuous simulations. The subject of a patent, Gradient Instrumentation yields derivatives of any order.     

寻找公共树的一种计算机算法

用公共树转换的方法求出两个具有相同边集和相同秩的图的所有公共树,同时求出相应的公共树的符号,并给出了实现算法的程序框图。     

精确计算n维Mesh网络和n维Torus网络的平均最短路径长度

ｎ维ｍｅｓｈ网张和ｎ维ｔｏｒｕｓ网络是分布存储多机系统中最常用的拓扑结构。网络的平均最短路径长度是网张性能的重要指标。     

通用后置处理中生成固定循环加工指令

介绍了在通用后置处理系统中输出各种固定循环加工指令的实现方法。通过对当今主流数控机床编程手册进行研究，设计数控机床特性文件，该文件与刀位轨迹文件，刀具信息相结合就可以输出各类数控机床的循环加工代码。采用相同的实现方法。也可以实现其它数迭机床控制指令的输出。该系统已经在FUNAC，FIDIA，SIEMENS等数控机床进行成功的试验。     

依靠弯道控导河势流路

在天然河道中，河势演变虽具有一定的随机性，但仍有一定的规律可循，在一个河段内，一般可归纳出2－3条基本流路，为控制河势变化，需要选择出一条基本流路进行河道整治，当连续发生枯水期或洪水期时，部分河段的河势可能出现大的变化，为防止不利河势向下游传播，可修建较长的龙头弯道工程，利用龙头弯道工程分段调整，控导河势，保持河势稳定。