机床结构模块化设计中CAD模型与有限元模型的数据交换

提出了基于结构有限元静、动态特性分析的模块化设计的框架；针对设计系统CAD模型与有限元数据相互传送难点，根据不同情况，给出模型转换的实现方法：直接转换法、标准零件库方法和中心数据库方法，重点讨论了利用中心数据库进行数据传送的方法。     

CAS wavelet method for solving the fractional integro-differential equation with a weakly singular kernel

In this paper, a computational method for numerical solution of a class of integro-differential equations with a weakly singular kernel of fractional order which is based on Cos and Sin (CAS) wavelets and block pulse functions is introduced. Approximation of the arbitrary order weakly singular integral is also obtained. The fractional integro-differential equations with weakly singular kernel are transformed into a system of algebraic equations by using the operational matrix of fractional integration of CAS wavelets. The error analysis of CAS wavelets is given. Finally, the results of some numerical examples support the validity and applicability of the approach.     

A revisit to stochastic near-optimal controls: The critical case

This paper revisits the stochastic near-optimal control problem considered in Zhou (1998), where the stochastic system is given by a controlled stochastic differential equation with the control variable taking values in a general control space and entering both the drift and diffusion coefficients. A necessary condition of near-optimality is derived using Ekeland’s variational principle, spike variation techniques, and some delicate estimates for the state and the adjoint processes. We improve the error bound of order from “almost” ${\epsilon }^{\frac{1}{3}}$ in Zhou (1998) to “exactly” ${\epsilon }^{\frac{1}{3}}$.     

Conformational Modeling of Continuum Structures in Robotics and Structural Biology: A Review

Hyper-redundant (or snakelike) manipulators have many more degrees of freedom than required to position and orient an object in space. They have been employed in a variety of applications ranging from search-and-rescue to minimally invasive surgical procedures, and recently they even have been proposed as solutions to problems in maintaining civil infrastructure and the repair of satellites. The kinematic and dynamic properties of snakelike robots are captured naturally using a continuum backbone curve equipped with a naturally evolving set of reference frames, stiffness properties, and mass density. When the snakelike robot has a continuum architecture, the backbone curve corresponds with the physical device itself. Interestingly, these same modeling ideas can be used to describe conformational shapes of DNA molecules and filamentous protein structures in solution and in cells. This paper reviews several classes of snakelike robots: (1) hyper-redundant manipulators guided by backbone curves; (2) flexible steerable needles; and (3) concentric tube continuum robots. It is then shown how the same mathematical modeling methods used in these robotics contexts can be used to model molecules such as DNA. All of these problems are treated in the context of a common mathematical framework based on the differential geometry of curves, continuum mechanics, and variational calculus. Both coordinate-dependent Euler–Lagrange formulations and coordinate-free Euler–Poincaré approaches are reviewed.     

基于二重积分滑动面的Buck变换器滑模研究

利用状态空间平均方法建立了Buck变换器的数学模型,该模型考虑了电容和电感的串联等效电阻,仿真结果与电路模型的仿真结果基本一致,其准确性较高;基于该数学模型,分别设计了PID控制和PWM滑模控制,滑模控制基于二重积分滑动面,并利用了电流信息。仿真结果表明,在负载突变情况下,基于二重积分滑动面的PWM滑模电流控制具有更好的动态响应特性和稳态误差调节特性。     

软组合概率神经网络分类器人脸识别方法

概率神经网络分类器具有学习速度快、易于实现的特点,而且其输出是后验概率, 使得分类器的软组合变得容易。利用概率神经网络的这些特点,提出了软组合概率神经网络分类器人脸识别方法,该方法包括3步:(1)对人脸图像做不完全小波包分解;(2)用包含低频成分的小波子空间图像训练概率神经网络分类器;(3)用模糊积分组合训练好的分类器。将该方法与3种基于矩阵子空间的人脸识别方法在JAFFE、YALE、ORL和FERET 4个人脸数据库上进行了实验比较,结果表明,提出的方法在识别精度和CPU时间两方面均优于其他3种方法。     

栅元有效共振积分的CUDA算法设计与实现

核反应堆中需要实时精确地计算堆芯和增殖材料的有效共振积分或群截面来实现反应堆的安全控制。整个计算过程因为涉及大量的积分运算和庞大的核素截面数据,采用常规的计算方法,计算时耗相当大。基于统一计算设备架构(CUDA)平台,利用图形处理器(GPU)的计算能力,对整个计算过程进行并行化分解,多线程同时运算,大幅度提升计算速度,降低时耗。实验结果表明,在GPU上并行计算所得结果与原始数据没有明显差异,且加速效果显著。     

Two general integral inequalities and their applications to stability analysis for systems with time‐varying delay

Integral inequalities have been widely used in stability analysis for systems with time‐varying delay because they directly produce bounds for integral terms with respect to quadratic functions. This paper presents two general integral inequalities from which almost all of the existing integral inequalities can be obtained, such as Jensen inequality, the Wirtinger‐based inequality, the Bessel–Legendre inequality, the Wirtinger‐based double integral inequality, and the auxiliary function‐based integral inequalities. Based on orthogonal polynomials defined in different inner spaces, various concrete single/multiple integral inequalities are obtained. They can produce more accurate bounds with more orthogonal polynomials considered. To show the effectiveness of the new inequalities, their applications to stability analysis for systems with time‐varying delay are demonstrated with two numerical examples. Copyright © 2016 John Wiley & Sons, Ltd.     

Design and implementation of a block‐backstepping based tracking control for nonholonomic wheeled mobile robot

This paper presents formulation of a novel block‐backstepping based control algorithm to overcome the challenges posed by the tracking and the stabilization problem for a differential drive wheeled mobile robot (WMR). At first, a two‐dimensional output vector for the WMR has been defined in such a manner that it would decouple the two control inputs and, thereby, allow the designer to formulate the control laws for the two inputs one at a time. Actually, the decoupling has been carried out in a way to convert the system into block‐strict feedback form. Thereafter, block‐backstepping control algorithm has been utilized to derive the expressions of the control inputs for the WMR system. The proposed block‐backstepping technique has further been enriched by incorporating an integral action for enhancing the steady state performance of the overall system. Global asymptotic stability of the overall system has been analyzed using Lyapunov stability criteria. Finally, the proposed control algorithm has been implemented on a laboratory scale differential drive WMR to verify the effectiveness of the proposed control law in real‐time environment. Indeed, the proposed design approach is novel in the sense that it has judiciously exploited the nonholonomic constraint of the WMR to result in a reduced order block‐backstepping controller for the WMR, and thereby, it has eventually yielded a compact expression of the control law that is amenable to real‐time implementation. Copyright © 2015 John Wiley & Sons, Ltd.     

Evolutionary variational inequality with long-term memory and applications to economic networks

The aim of this paper is to present the relation between an evolutionary variational inequality with long-term memory and Lagrange multipliers. More precisely, we study the oligopolistic market equilibrium problem in which the profit function depends also on previous events of the market by means of a long-term memory which takes into account the previous states of the equilibrium. Moreover, thanks to the variational formulation, we are able to show existence and regularity results for equilibrium solutions. Then, we apply the infinite dimensional duality theory through which we obtain the existence of Lagrange multipliers which are great utility in order to understand the behaviour of the market. Finally, an example is provided, which allows to analyse the influence of the long-term memory on the equilibrium solution.