Stabilization of underwater vehicle dynamics with symmetry-breaking potentials

We show how to stabilize, in stages, arbitrary steady translations of an underwater vehicle with feedback that derives from a potential and deliberately breaks symmetry in the dynamics. First, rotational symmetry is broken to ensure stability in the momentum parameters. Then, translational symmetry is broken to prevent drift. Stability of the closed-loop system is proved using the energy-Casimir method. A resulting property of the control law is robustness to model parameter uncertainty.     

Symmetry Definitions for Constraint Satisfaction Problems

We review the many different definitions of symmetry for constraint satisfaction problems (CSPs) that have appeared in the literature, and show that a symmetry can be defined in two fundamentally different ways: as an operation preserving the solutions of a CSP instance, or else as an operation preserving the constraints. We refer to these as solution symmetries and constraint symmetries. We define a constraint symmetry more precisely as an automorphism of a hypergraph associated with a CSP instance, the microstructure complement. We show that the solution symmetries of a CSP instance can also be obtained as the automorphisms of a related hypergraph, the k-ary nogood hypergraph and give examples to show that some instances have many more solution symmetries than constraint symmetries. Finally, we discuss the practical implications of these different notions of symmetry.     

Symmetry building Monte Carlo-based crystal structure prediction

Methods are presented that allow for the automatic increase and preservation of symmetry during global optimization of crystal structures. This systematic building of symmetry allows for its incorporation into structure prediction simulations even when the space group information is not known a priori. It is shown that simulations that build and maintain symmetry converge much more rapidly to ground state crystal structures than when symmetry is ignored, allowing for the treatment of unit cells much larger than would otherwise be possible, especially when beginning from the P1 space group.     

Symmetry Breaking Constraints for Value Symmetries in Constraint Satisfaction

Constraint satisfaction problems (CSPs) sometimes contain both variable symmetries and value symmetries, causing adverse effects on CSP solvers based on tree search. As a remedy, symmetry breaking constraints are commonly used. While variable symmetry breaking constraints can be expressed easily and propagated efficiently using lexicographic ordering, value symmetry breaking constraints are often difficult to formulate. In this paper, we propose two methods of using symmetry breaking constraints to tackle value symmetries. First, we show theoretically when value symmetries in one CSP correspond to variable symmetries in another CSP of the same problem. We also show when variable symmetry breaking constraints in the two CSPs, combined using channeling constraints, are consistent. Such results allow us to tackle value symmetries efficiently using additional CSP variables and channeling constraints. Second, we introduce value precedence, a notion which can be used to break a common class of value symmetries, namely symmetries of indistinguishable values. While value precedence can be expressed using inefficient if-then constraints in existing CSP solvers, we propose efficient propagation algorithms for implementing global value precedence constraints. We also characterize several theoretical properties of the value precedence constraints. Extensive experiments are conducted to verify the feasibility and efficiency of the two proposals.     

具有屈膝行为的双足被动行走模型

参考人类下坡行走运动特点,提出一种具有屈膝行为的双足被动行走模型.采用5质点4杆被动行走模型,设计支撑腿在行走过程中弯曲,通过对支撑腿膝关节弯曲时刻的调整,求解得到模型在不同斜面上的稳定周期行走步态.仿真结果表明,模型实现了在坡度范围小于0.39 rad的斜面上稳定行走步态.与传统步态相比,稳定行走的坡度范围显著提高,在较大坡度上也具有很好的稳定性.     

Evolutionary learning of a fuzzy controller for wall-following behavior in mobile robotics

The design of fuzzy controllers for the implementation of behaviors in mobile robotics is a complex and highly time-consuming task. The use of machine learning techniques such as evolutionary algorithms or artificial neural networks for the learning of these controllers allows to automate the design process. In this paper, the automated design of a fuzzy controller using genetic algorithms for the implementation of the wall-following behavior in a mobile robot is described. The algorithm is based on the iterative rule learning approach, and is characterized by three main points. First, learning has no restrictions neither in the number of membership functions, nor in their values. In the second place, the training set is composed of a set of examples uniformly distributed along the universe of discourse of the variables. This warrantees that the quality of the learned behavior does not depend on the environment, and also that the robot will be capable to face different situations. Finally, the trade off between the number of rules and the quality/accuracy of the controller can be adjusted selecting the value of a parameter. Once the knowledge base has been learned, a process for its reduction and tuning is applied, increasing the cooperation between rules and reducing its number.     

平面控制系统的线性对称性

本文讨论了二维非线性系统在线性群作用下的对称性,及GL(2,R)的所有连通子群.换言之,本文研究了控制系统的一切可能的线性对称性.文中给出各种情况下的充分必要条件,并且对各类线性对称系统的构造给出完整的描述,从而显示了大量对称控制系统的存在性.     

科技美学中对称、对偶在日常教学中的应用

对称、对偶都是美学中的基本要素.作为一名教育工作者在教学活动中适当运用美学元素作为教学手段,不断改进教学方法,而且能够从中收益,获得美的享受,是一件十分快乐的事情.本文从应用的角度阐述美学原理在具体教学实践中的巧用,结合多年的教学体会,在电工基础、物理学、信号与系统等课程领域,运用对称、对偶等美学元素,使教学活动更加生动、形象.既活跃了课堂气氛,又加深了学生的理解和记忆,取得了良好的教学效果.     

生物交哺行为启发的群体机器人搜集行为研究

为了提高群体机器人系统的整体性能,受生物系统中普遍存在的交哺现象的启发,在原来多机器人系统的基本行为的基础上,提出了一种引入交哺行为的多机器人协作机制。机器人依靠有限的感知能力和局部交互功能,以自组织方式执行目标搜集任务。机器人的内部状态变量反映其执行任务的情况以及对环境和其他机器人的评价。比较机器人的内部状态变量,可以判断是否需要交哺和交哺的方向性。主要目的是减少机器人之间的冲突,降低系统能量消耗的同时,提高机器人搜集目标的效率。最后通过计算机仿真实验以及与其他多机器人协作方法比较,分析该方法对提高系统性能的有效性。     

基于车体对称及颜色聚类的车牌自动定位方法*

对车牌区域的准确定位是实现自动车牌识别的一个关键问题。提出了一种综合考虑车体对称特性以及采用颜色聚类的高效车牌定位算法。该算法首先对待分析图像所属的场景进行识别,自动将图像分类为白天场景类或夜晚场景类;然后针对不同场景图像使用不同的车牌定位方案进行处理。对夜间场景中的车牌采用二次定位法,而对白天场景中的车牌采用结合车体对称轴定位并考虑车牌区域文本特征的方法。实验结果显示,该方法对图像场景分类以及车牌定位的总体准确率都达到了95.7%。     

基于局部对称性的特征点加工策略及应用

在基于词袋模型的图像检索框架中,图像包含的SIFT特征点往往数量比较大,特征不够强。因此图像检索系统的效率和性能往往受影响。基于SIFT特征点的性质和视觉显著性原理,提出了SIFT特征点的局部对称性度量方法,并且在图像检索框架中嵌入了基于对称性的SIFT特征点过滤方法和加权策略,以提升SIFT特征点的利用效率。在牛津大学建筑物图像集上的实验结果表明,提出的基于对称性的SIFT特征点选择策略能有效地提高图像检索的性能。     

LOGUE: an architecture for task and behavior object transmission among multiple autonomous robots

This paper proposes a new communication and control architecture which improves the capability and the flexibility of multiple autonomous robot systems in performing a complicated task and coping with unpredictable situations. This system treats robot’s information as a Behavior Element Object (BEO) and a Task Object (TO) in terms of Object Oriented paradigm. Both BEO and TO can be serialized, so they can be communicated among the robots and behavior server system in the network. The action manager module, device module, and some checking mechanisms are also designed for executing new TO or BEO sent from other robots or a server system. A simulation and basic experiments are presented for a situation of robots’ relief for an emergency purpose.     

对称式八步直线生成算法

分析了直线生成模式与直线斜率之间的关系,提出了一种八步增量算法.该算法一次能画四个像素,结合直线的对称性,在一次循环中可以画八个像素.该算法只用到了整数加法运算、减法运算和左移位运算,大大降低了硬件实现的复杂度,同时有效地提高了速度,易于硬件实现.     

Symmetry reductions for model checking of concurrent dynamic software

Symmetry reduction techniques exploit symmetries that occur during the execution of a system in order to minimize its state space for efficient verification of temporal logic properties. This paper presents a framework for concisely defining and evaluating symmetry reductions currently used in software model checking, involving heap objects and processes. An on-the-fly state space exploration algorithm combining both techniques will also be presented. Second, the relation between symmetry and partial-order reductions is investigated, showing how ones strengths can be used to compensate for the others weaknesses. The symmetry reductions presented here were implemented in the dSPIN model-checking tool. We also performed a number of experiments that show significant progress in reducing the cost of finite-state software verification.     

激光间接驱动对称性分析的GPU并行求解

在激光间接驱动惯性约束聚变(ICF)辐射对称性分析中,当靶表面网格离散细密时,面元辐射能流计算耗时长,严重制约实验设计仿真及优化的快速开展,针对上述问题提出了基于GPU的并行计算方法,在CUDA架构下,通过网格单元视角因子计算过程到GPU各运算线程的映射,结合雅可比迭代法求解系数矩阵对角占优方程组快速收敛的特点,实现了对ICF分析模型靶表面辐射能流的高效计算.以三维仿真软件IRAD3D为平台,神光-Ⅱ激光装置和神光-Ⅲ原型装置的两个实验靶模型为案例,实验结果表明,改进方法能够充分利用GPU的硬件特性,对称性分析和参数优化的加速比在1000左右,大大提高了实验设计的效率.     

Symmetry,beauty and chaos in Chebyshev's paradise

Chebyshev polynomials and Halley maps are used as a reservoir for the generation of several visually striking and intricate classes of symmetrical and chaotic patterns. Relatively simple numerical recipes are included to encourage reader involvement.     

Emergence of multiagent spatial coordination strategies through artificial coevolution

This paper describes research investigating the evolution of coordination strategies in robot soccer teams. Each player (viewed as an agent) is provided with a common set of skills and is assigned to perform over a delimited area inside a soccer field. The idea is to optimize the whole team behavior by means of a spatial coadaptation process in which new players are selected in such a way to comply with the already existing ones. The main results show that, through coevolution, we progressively create teams whose members act on complementary areas of the playing field, being capable of prevailing over a standard opponent team with a fixed formation.     

基于声辐射模态的作动器对称位置的研究

在汽车噪声优化控制领域中,作动器位置布置会影响噪声控制效果。以简支板为例,根据声辐射模态的解耦主动控制的控制方法已经取得了良好的降噪效果,但作动器的不同对称位置布置对降噪产生的效果以及所需电压值是不同的。提出将分别对前四阶声辐射模态建立电压模型,对前八阶声辐射模态建立声功率模型,通过在MATLAB上进行仿真,结果确定能使所需电压最小,控制效果最好的理想降噪对称位置。