离散线性开关系统切换的模糊方法

在已知离散线性开关系统全局渐近稳定前提下，将线性开关系统切换问题转化为相应T－S模型模糊区域划分问题，通过在线实时调整T－S模型隶属函数参数来确定模糊区域，以二阶离散线性开关系统为例，给出了实现系统全局渐近稳定的模糊切换策略，该方法可扩展到高阶线性开关系统，计算机仿真证实该方法简捷，有效。     

具有m个开关系统的渐近稳定性

研究了一类具有m个开关系统的渐近稳定性,借助于多重Lyapunov函数,给出了该系统全局渐近稳定的充分条件,部分地改进了前人的结果。     

线性开关系统的饱和控制

利用开关系统切换的特点研究了线性开关系统的饱和控制问题,在较弱的条件下,得到了开关系统饱和镇定的结果,即构成开关系统的每个子系统可以是非稳定的,但假定由开关系统构成的某个凸组合系统是可稳的.借助于Lyapunov函数设计饱和控制器,基于凸组合系统的稳定性设计切换规律,引入设计参数满足控制器实现的条件,使开关系统局部渐近稳定.     

一类线性开头系统的渐近稳定性

研究一类线性开关系统的渐近稳定性问题。针对不满足完备性条件的开关系统，利用Lya-punov函数技术，给出了系统渐进稳定的一个充分条件，并举例说明了该方法的实际应用。     

反步法在三相电压型脉冲调宽逆变器控制中的应用

针对三相电压型脉冲调宽(pulse-width-modulation,PWM)逆变器这个时变的、多模态的非线性系统,应用开关函数建立了系统数学模型,引入开关周期平均算子将离散的系统化为连续系统,得到具有参数严格反馈形式的二阶非线性多输入多输出系统数学模型.并对此模型应用反向递推方法,通过逐步选择虚拟控制量和构造李雅普诺夫函数,使每个状态分量具有适当的渐近特性,实现整个系统在大扰动下的全局渐近稳定性,进而得到反馈控制律的一般表达式.将三相电压型PWM逆变器系统参数代入后得到其反馈控制规律.最后通过仿真实验验证了该方法的有效性和正确性.     

基于改进NSGA-Ⅱ算法的开关磁阻电机再生制动优化控制方法

针对采用传统优化算法优化开关磁阻电机再生制动控制参数存在制动能量回馈效率低及制动转矩脉动系数大的问题,提出一种基于渐近约束支配法则的双目标非支配排序遗传算法。首先针对传统双目标非支配排序遗传算法优化开关磁阻电机再生制动控制参数时存在易陷入局部最优解等不足,提出一种渐近约束支配法则,再将基于渐近约束支配法则的双目标非支配排序遗传算法应用于开关磁阻电机再生制动控制参数的优化,并对其效果进行了仿真验证,同时与传统双目标非支配排序遗传算法进行了对比分析,结果表明:基于渐近约束支配法则的双目标非支配排序遗传算法不仅有效解决了易陷入局部最优解的问题,而且显著提高了开关磁阻电机再生制动效率并降低了其转矩脉动系数,取得了满意的优化效果。     

具有线性漂移的随机多模态系统的反馈镇定

研究具有线性漂移的、以Markov链为开关函数的多模态随机系统的反馈镇定,通 过建立多模态随机系统的均方渐近平坦性定理,给出具有线性漂移的多模态随机系统和线性 多模态随机系统的反馈镇定方案,并给出控制器设计中的计算方法,用仿真实例验证了该方 法的效果.     

滞环非线性系统的加权自适应控制

本文通过引入一个非线性补偿环节和一个开关量函数,解决了滞环非线性系统的自适应 控制问题,并分别对滞环宽度已知和未知情况,建立了大范围渐近收敛和稳定的加权自适应控 制算法.这种算法具有渐近最优的控制效果,能用于非最小相位系统.仿真结果表明,该算法 具有良好的动态性能.     

一类开关切换系统的输出反馈镇定

对一类子系统为线性的开关切换系统进行观测器设计，并给出系统动态输出反馈可镇定的充分条件。在所设计的观测器基础上，以系统状态的观测值为依据设计各子控制器和切换方案，使整个闭环系统是指数渐近稳定的。对于切换时间间隔受限制的情况，给出了相应的动态输出反馈可镇定条件和镇定控制方案。实例仿真结果表明，所给出的设计方案是可行的。     

一类具有相似结构的不确定组合大系统的观测器设计

讨论了非线性组合大系统渐近观测器的设计问题。对一类具有相似结构的非线性不确定组合大系统构造出其鲁棒渐近观测器，并举例说明所提出的渐近观测器的设计方法。     

基于语义事务分解的可串行性

数据库应用中长事务的出现严重降低了系统的性能，一些研究者为解决这一问题提出了利用事务的语义信息对事务进行分解的方法，但所得结论仍然存在缺陷．本文从用户定义的后续集出发给出了正确步进串行历史的概念，可以很容易证明正确步进串行历史是用户可接受的正确历史，并以此作为判定一个历史是否正确的基础．重后，证明了当用户给出的后续集满足约束2时，优化前驱图的无环性是判定一个正确历史的充要条件．     

The boundedness of all products of a pair of matrices is undecidable

We show that the boundedness of the set of all products of a given pair Σ of rational matrices is undecidable. Furthermore, we show that the joint (or generalized) spectral radius ρ(Σ) is not computable because testing whether ρ(Σ)1 is an undecidable problem. As a consequence, the robust stability of linear systems under time-varying perturbations is undecidable, and the same is true for the stability of a simple class of hybrid systems. We also discuss some connections with the so-called “finiteness conjecture”. Our results are based on a simple reduction from the emptiness problem for probabilistic finite automata, which is known to be undecidable.     

Velocity field control of a class of electrically-driven manipulators

This article addresses the control of robotic manipulators under the assumption that the desired motion in the operational space is encoded through a velocity field. In other words, a vectorial function assigns a velocity vector to each point in the robot workspace. Thus, the control objective is to design a control input such that the actual operational space velocity of the robot end-effector asymptotically tracks the desired velocity from the velocity field. This control formulation is known in the literature as velocity field control. A new velocity field controller together with a rigorous stability analysis is introduced in this article. The controller is developed for a class of electrically-driven manipulators. In this class of manipulators, the passivity property from the servo-amplifier voltage input to the joint velocity is not satisfied. However, global exponential stability of the state space origin of the closed-loop system is proven. Furthermore, the closed-loop system is proven to be and output strictly passive map from an auxiliary input to a filtered error signal. To confirm the theoretical conclusions, a detailed experimental study in a two degrees-of-freedom direct-drive manipulator is provided. Particularly, experiments consist of comparing the performance of a simple PI controller and a high-gain PI controller with respect to the new control scheme.     

Correctness of Algebraic Extensions of Models of Classification Algorithms

The binary representation of each classification from a subset of a space of admissible classifications is considered. A metric in a unit cube is introduced, and a correct algebra of classification algorithms is constructed. The correctness and completeness of a model of classification algorithms are proved. An example of construction of a complete model for a classification problem is considered.     

Problems of Evolution of Rotations of a Rigid Body under the Action of Perturbing Moments

The rotatory motion of a nearly dynamically spherical rigidbody, which contains a viscoelastic element, is considered. This elementis simulated by a moving mass, connected by a spring and damper to thepoint, situated on one of a principal axis of inertia. The smallparameters caused by the proximity of moments of inertia and thepresence of moving mass are considered to be of the same order. Thespherical coordinates defining the position of the angular velocityvector are introduced. The system of differential equations is obtainedand investigated, the special cases of motion are considered. Theauthors investigate perturbed rotational motions of a rigid body,similar to the regular precession in the Lagrange case, under the actionof the moment that is slowly changing in time and the restoring momentdepending on the angle of nutation. In two problems it is assumed thatthe angular velocity of the body is large and its direction is close tothe axes of dynamic symmetry. In the first problem it is assumed thattwo projections of the vector of the perturbing moment onto principalaxes of inertia of the body are small as compared to the restoringmoment, while the third one is of the same order of the magnitude as themoment in question. In the second problem it is assumed that theperturbing moments are small as compared to the restoring one. Averagedsystems of equations of motion are obtained and investigated in thefirst and the second approximations. Examples are considered.     

基于散乱点的任意拓扑曲面建模及绘制研究

对曲面建模进行了研究,提出了一种基于散乱点的曲面重建方法.给出三维空间的散乱点,采用3个步骤重构出三角化曲面:首先按近似共面程度对点集聚类,把接近共面的点归为同一类,然后根据空间点的邻接关系进行局部调整,最后对点集和点集之间的区域进行三角割分,得到三角化曲面,所得曲面用OpenGL进行绘制.     

Solution of problem of identification of time shift of pseudorandom sequences on the basis of nonlinear probabilistic criteria

A solution of the problem of identification of the time shift of pseudorandom sequences received against a background of interference is proposed. The solution is based on a nonlinear probabilistic criterion—the criterion of minimum a posteriori integral estimation error. An algorithm of nonlinear parametric identification that yields a solution of the problem is synthesized. A numerical example of the identification of the time shift of a concrete sequence that confirms the effectiveness and adequate degree of efficiency of the algorithm proposed in the study is presented.     

Stabilisation of infinitesimally rigid formations of multi-robot networks

This article considers the design of a formation control for multivehicle systems that uses only local information. The control is derived from a potential function based on an undirected infinitesimally rigid graph that specifies the target formation. A potential function is obtained from the graph, from which a gradient control is derived. Under this controller the target formation becomes a manifold of equilibria for the multivehicle system. It is shown that infinitesimal rigidity is a sufficient condition for local asymptotical stability of the equilibrium manifold. A complete study of the stability of the regular polygon formation is presented and results for directed graphs are presented as well. Finally, the controller is validated experimentally.     

Complexity of approximation of 3-edge-coloring of graphs

The problem to find a 4-edge-coloring of a 3-regular graph is solvable in polynomial time but an analogous problem for 3-edge-coloring is NP-hard. To make the gap more precise, we study complexity of approximation algorithms for invariants measuring how far is a 3-regular graph from having a 3-edge-coloring. We show that it is an NP-hard problem to approximate such invariants with an error O(n1−ε), where n denotes the order of the graph and 0<ε<1 is a constant.     

Automatic identification of the interests of web users

In the present article an approach to automatic determination of a user’s sphere of interests is proposed. The approach is based on a method involving clustering of documents which the user is interested in. The process of clustering of documents is reduced to a problem of discrete optimization for which quadratic-and linear-type models are proposed. Identification of interests makes it possible to determine the context of a request without any effort on the user’s part. Different methods are proposed for determining the context of a request. An ant algorithm for solving a quadratic-type discrete optimization problem is also proposed in the present study.