Development of a spherical stepper wrist motor

This paper presents the design concept of a new spherical stepper robotic wrist motor capable of three degrees of freedom (DOF) motion in a single joint. The spherical wrist motor has significant potential applications where the demands on wrist torque and workspace are low but high speed manipulation of end-effector orientation is required continuously in all directions. Typical applications are plasma and laser cutting and micro-assembly. The spherical motor is developed on the basis of the principle of variable reluctance stepper motors. This paper highlights the fundamental differences between the operation of a three DOF spherical motor and that of the conventional stepper motor. The establishment of a theoretic basis for design, prototype development and performance prediction is sought. In particular, an analysis of torque prediction is discussed along with the presentation of kinematic and dynamic relationships. A hybrid digital/analog laboratory prototype control circuitry has been developed to demonstrate proof of concept feasibility and to assist in achieving an optimum design.     

PSO-SVM及其在减速机齿轮诊断中的应用

针对支持向量机(SVM)参数一般是人为选取,无法准确取到最佳值的问题,提出了一种基于粒子群算法(PSO)对参数进行优化的支持向量机(PSO-SVM).以减速机齿轮的3类故障类型(正常、磕碰、磨损)数据作为研究资料,组成训练样本集,训练PSO-SVM分类模型,从训练集中抽取部分数据组成测试样本集,对模型进行检验测试.研究表明:PSO-SVM模型分类正确率达到了93.8%,相较未进行参数优化的SVM,算法能更好地找到全局最优解,提高了模型的分类正确率.     

Self-calibration of spherical rectification for a PTZ-stereo system

Since PTZ (pan–tilt–zoom) camera is able to obtain multi-view-angle and multi-resolution information, PTZ-stereo system using two PTZ cameras has much higher capability and flexibility compared with traditional stereo system. In this paper, we propose a self-calibration framework to deal with the calibration of spherical rectification, which can be deemed as a kind of relative pose estimation, for a PTZ-stereo system. The goal of this calibration is to guarantee high performance of stereo rectification, so that stereo matching can be achieved more efficiently and accurately. In this framework, we assume two PTZ cameras are fully calibrated, i.e., the focal length and the local camera orientation can be computed by given pan–tilt–zoom values. This approach, which is based on point matches, aims at finding uniformly distributed point matches in an iterative way. At each iteration, according to the distribution of previously used point matches, the system could automatically guide two cameras to move to collect a new match. Point matching is firstly performed for the lowest zoom setting (widest field of view). Once a candidate match is chosen, each camera is then controlled to zoom in on corresponding point to get a refined match with high spatial resolution. The final match will be added into the estimation to update the calibration parameters. Compared with previous researches, the proposed framework has the following advantages: (1) Neither manual interaction nor calibration object is needed. Calibration samples (point matches) will be added and removed in each stage automatically. (2) The distribution of calibration samples is as uniform as possible so that biased estimation could be avoided to some extent. (3) The accuracy of calibration can be controlled and improved when iteration goes on. These advantages make the proposed framework more practicable in applications. Experimental results illustrate its accuracy.     

Swinging up the spherical pendulum via stabilization of its first integrals

This paper presents a new controller for swinging up the spherical pendulum. The problem of stabilizing the upright equilibrium of the spherical pendulum is typically solved in two steps: First, a controller is used to swing up the pendulum so that it enters some vicinity of the upright equilibrium, and then a locally stabilizing controller is used. The contribution of this paper is the design of a controller that solves the first subproblem for almost all initial conditions. The controller stabilizes the two-dimensional stable manifold of the hyperbolic upright equilibrium. The proposed technique is based on the passivity properties of the spherical pendulum.     

齿轮企业基于面向服务架构的应用集成框架与实现*

针对齿轮企业分布式异构应用系统的信息集成与数据共享问题,结合齿轮企业数字化和信息化的发展方向,深入分析了齿轮企业应用系统的集成运作模式;利用面向服务架构和Web服务技术,构建了齿轮企业应用集成框架,分析了集成框架的通信过程,在.NET环境下实现了应用集成框架的软件架构,并用准双曲面齿轮网络化制造的具体应用实例,来说明和验证了基于Web服务的齿轮应用集成框架的实用性。准双曲面齿轮网络化制造的成功应用,说明该应用集成框架是有效可行的,能够很好地满足齿轮企业信息集成与数据共享的需要。     

一种新的动态关联规则及其挖掘算法

在分析原有定义不足的基础上,提出一种新的动态关联规则,其支持度向量和置信度向量与经典定义相吻合,能更好地反映规则随时间变化的动态信息．进一步提出两种新的动态关联规则挖掘算法：ＩＴＳ和ＥＦＰｇｒｏｗｔｈ．其中：两阶段ＩＴＳ算法具有较好的可理解性;基于扩展ＦＰ树的ＥＦＰｇｒｏｗｔｈ算法适宜于高密度海量数据的挖掘．实验结果表明,该算法具有较好的挖掘性能和可扩展性,适用于动态关联规则的有效挖掘．     

基于齿轮动态激励和弹流润滑的多目标优化

依据齿轮啮合动态激励基本原理和弹性流体动力润滑理论,建立同时追求 齿轮啮合时变刚度激励最小、齿间最小油膜厚度最大（倒数最小）及齿轮传动总体积最小的 约束多目标优化设计数学模型。对现有的用于两目标优化设计的粒子群优化方法加以改进, 给出了约束3 目标优化设计方法。利用Matlab 编制优化程序,并对范例进行分析计算。优 化过程及结果表明,采用较多的齿数,在小于1 的范围内采用较大的正变位系数,适度采用 较大的压力角可以增大轮齿啮合综合刚度谱图中基频谐波的幅值,有效地提高齿轮传动系统 抵抗内部激励振动的能力及性价比。     

一种属性重要性定义方法及其在约简中的应用*

针对基于Pawlak和基于条件熵的属性重要性约简算法存在的局限性,提出了一种基于分辩矩阵的属性重要性约简算法。首先详细分析了这两类属性约简算法产生局限性的原因;然后据根属性在分辩矩阵中区分对象时所起的作用的情况,给出了一种基于分辩矩阵的属性重要性定义方法,并且通过该方法计算分辩矩阵中属性的重要性;最后按照属性重要性大小的顺序来依次添加属性到核集中,直至获取决策表的一个最小约简。实例分析表明,该算法能够有效找到最小约简,与其它法相比,当决策表中条件属性较多时,该算法能够大幅减少计算工作量。     

An efficient spherical mapping algorithm and its application on spherical harmonics

The sphere is a natural and seamless parametric domain for closed genus-0 surfaces. We introduce an efficient hierarchical optimization approach for the computation of spherical parametrization for closed genus-0 surfaces by minimizing a nonlinear energy balancing angle and area distortions. The mapping results are bijective and lowly distorted. Our algorithm converges efficiently and is suitable to manipulate large-scale geometric models. We demonstrate and analyze the effectiveness of our mapping in spherical harmonics decomposition.     

新型故障监测传感器在机载云台电动舵机中的应用

设计并实现了一种基于光生伏打隔离器PVI—1050NS的新型故障监测传感器,该传感器能实时监测电动舵机驱动电路中的过流、过压、过温等故障信号。通过对该故障信号的处理,可以判断驱动电路的故障位置,迅速进行定位并进行故障处理,保障了电动舵机运行的可靠性与安全性。实验结果表明:该故障监测传感器具有较高的灵敏度,大大提高了系统的可靠性。     

Symbolic integration of a product of two spherical Bessel functions with an additional exponential and polynomial factor

We present a Mathematica package that performs the symbolic calculation of integrals of the form

(1)     

一种图像距离定义及其在置乱效果评价中的应用

针对传统欧氏距离不能真实刻画图像间差异程度的不足,考虑到图像中任意位置灰度信息与其周围邻域灰度存在紧密关系,提出一种考虑邻域灰度信息的图像距离新定义,并用其构造一种描述图像置乱效果好坏的评价函数。实验结果表明,该评价方法能够较好地刻画图像的置乱程度,反映了加密次数与置乱程度之间的关系,与人的视觉基本相符。而且对于不同的图像,该评价方法能在一定程度上反映所用的置乱变换在各置乱阶段的效果。     

一种新的DDOS攻击及其防护措施研究

分布式拒绝服务(DDoS)攻击是非常有效的网络攻击,而且很难进行防护。一种称为分布式反射拒绝服务(DRDoS)的新的DDoS攻击使攻击者不需要控制代理端,只通过向大量服务器发送服务请求,利用通信协议规则使得服务器返回的数据被“反射”到攻击目标(可能是主机、服务器,也可能是路由器)而使其瘫痪。文章通过实例、示意图等方法详细分析了DDoS和DRDoS攻击的原理,从技术上和策略上提出了可行的防护技术手段。     

A kind of structure model for double porosity medium systems and its application

This paper studies problems of modeling and simulation for infinite dimensional systems. In the early 1960s, Barenblatt and the others proposed well-known permeable models through double porous media. It is an essential hypothesis for their theory that every point belongs to both the fracture system and the pore system in a domain. However, in real gas or oil reservoirs, distribution of fractures and pores is so heterogeneous that the ideal “duality” does not exist anywhere and the double porosity structure disappears locally, i.e. double porosity structure or single porosity structure may occur alternatively. Based upon the facts, we derive an ad hoc function expressed by integration, set up a block structure model as well as its approximate semi-discrete form for the variable structure system, and prove uniqueness and existence of the solutions. Applying this model to the identification problem for the fracture–pore domain we get a feasible method to determine the position of fracture system and pore system and take a practical example to verify the usefulness of the structure model for a gas reservoir.     

An improved dynamic modeling of a multibody system with spherical joints

A dynamic modeling of multibody systems having spherical joints is reported in this work. In general, three intersecting orthogonal revolute joints are substituted for a spherical joint with vanishing lengths of intermediate links between the revolute joints. This procedure increases sizes of associated matrices in the equations of motion, thus increasing computational burden of an algorithm used for dynamic simulation and control. In the proposed methodology, Euler parameters, which are typically used for representation of a rigid-body orientation in three-dimensional Cartesian space, are employed to represent the orientation of a spherical joint that connects a link to its previous one providing three-degree-of-freedom motion capability. For the dynamic modeling, the concept of the Decoupled Natural Orthogonal Complement (DeNOC) matrices is utilized. It is shown in this work that the representation of spherical joints motion using Euler parameters avoids the unnecessary introduction of the intermediate links, thereby no increase in the sizes of the associated matrices with the dynamic equations of motion. To confirm the efficiency of the proposed representation, it is illustrated with the dynamic modeling of a spatial four-bar Revolute-Spherical–Spherical-Revolute (RSSR) mechanism, where the CPU time of the dynamic modeling based on proposed methodology is compared with that based on the revolute joints substitution. Finally, it is explained how a complex suspension and steering linkage can be modeled using the proposed concept of Euler parameters to represent a spherical joint.     

新阈值二进小波去噪算法在齿轮信号中的应用

在齿轮的激光检测过程中,由于各种噪声源的影响,原始信号会出现特征信息弱化的现象,影响了齿轮检测的准确性。为解决该问题,在分析传统软、硬阈值函数不足的基础上,提出了一种新阈值函数和二进小波变换相结合的去噪方法。在该方法中构建了一个可以调节的新阈值函数,该阈值随二进小波分解系数的变化以指数形式动态调整,克服了传统硬阈值函数不连续和传统软阈值函数存在偏差的问题。经仿真实验验证,该方法的信噪比和适用性具有明显的改善。     

Auto-parametric semi-trivial and post-critical response of a spherical pendulum damper

The pendulum vibration damper modelled as a two degree of freedom strongly non-linear auto-parametric system is investigated. A kinematic external excitation in the suspension point is applied. The excitation is considered to be horizontal and harmonically variable in time. A semi-trivial solution and its stability are analyzed. Special attention is paid to the resonance domain. In certain domains of pendulum and excitation parameters the semi-trivial solution does not exist in this domain and various post-critical three-dimensional regimes occur. Some of them are non-stationary despite the harmonic excitation. Three different types of the resonance domain are investigated. Their main properties depend significantly on dynamic parameters of the pendulum and of the external excitation amplitude. An analytical and numerical study brings forth several recommendations for designers of these devices. Their aim is to avoid any post-critical response regimes endangering the pendulum functionality.     

一种固体水分传感器的研究及应用

为检测固体含水量而研制的一种固体水分传感器,该传感器采用热导原理,利用固体物料湿度的不同对传感器散热造成的不同来测定湿度。这种新型水分传感器在自身发热的情况下,利用物料含水量不同时,升温、降温时间的不同来检测物料含水量。试验证明:该固体水分传感器精度达到5%。作为一种低成本的固体水分传感器,可以达到较高的精度,有较大的应用空间。     

A new kind of fuzzy regression modeling and its combination with fuzzy inference

In this paper, a new kind of fuzzy regression model suggested by the author in papers [1] and [2] will be restated more clearly. Then a consistency between the new fuzzy regression modeling and fuzzy inference modeling will be presented, showing its added advantage for application problems. Based on the consistency, a method for combining fuzzy regression and fuzzy inference will be introduced in this paper. This will serve as the starting point for applying the two kinds of information resources, quantitative and qualitative information resources, simultaneously in practical prediction problems. This work was supported by a Research Enhancement Grant, WTAMU, 2003.     

Efficient 3D shape matching and retrieval using a concrete radialized spherical projection representation

We present a 3D shape retrieval methodology based on the theory of spherical harmonics. Using properties of spherical harmonics, scaling and axial flipping invariance is achieved. Rotation normalization is performed by employing the continuous principal component analysis along with a novel approach which applies PCA on the face normals of the model. The 3D model is decomposed into a set of spherical functions which represents not only the intersections of the corresponding surface with rays emanating from the origin but also points in the direction of each ray which are closer to the origin than the furthest intersection point. The superior performance of the proposed methodology is demonstrated through a comparison against state-of-the-art approaches on standard databases.