A new cost effective 3D measurement audit and model comparison system for verification tasks

A new unified system application for the production audit in an aerospace industry is presented in this paper which comprises two key application tools such as (a) 3D PAMT (production audit measurement tool) and (b) 3D PACT (production audit compare tool). In spite of the facts that above functionalities are modular wise independent, commonly they are related in terms of assisting the production audit task. 3D PAMT facilitates the verification of manufactured parts to be within a pre-defined threshold range using a calibrated stereo camera with the safety test engineer interaction in order to select the matching disparity points. The distance between datum points with or without reference to a planar reference surface model can be obtained. We describe the system flow, plus validate the technique via a number of experimental datasets. 3D PACT allows the identification of discrepancies between a computed 3D point cloud model and the corresponding digital mock-up point cloud model. Usually, the computer aided geometry model is built before an actual installation. This knowledge about the components of an installation assembly is available as semantic information in an extendable markup language (XML) format of the CATIA model. We have provided an use case study of a sample assembly with components such as cube, pyramid, rectangular prism and triangular prism. The proposed cost-effective and robust framework for 3D measurement audit and model comparison is based on the input available from a digital camera and the semantic metadata knowledge available from geometry models which can be used for verification tasks.     

结构数字化样机在舰载雷达上的探索

随着数字化、网络化和三维技术的发展,雷达的结构设计从传统的CAD／CAE向全三维数字化协同设计和仿真的方向发展。本文对舰栽雷达结构数字化样机的建设进行了探索。通过协同研发平台实现了雷达研制过程中过程、工具、数据、知识的一体化管理,提高了雷达结构设计效率和质量。     

Further Reducing the Redundancy of a Notation Over a Minimally Redundant Digit Set

Redundant notations are used implicitly or explicitly in many digital designs. They have been studied in details and a general framework is known to reduce the redundancy of a notation down to the minimally redundant digit set. We present here an operator to further reduce the redundancy of such a representation. It does not reduce the number of allowed digits since removing one digit to a minimally redundant digit set is a conversion to a non redundant digit set and this is an expensive operation. Our operator introduces some correlation between the digits to reduce the number of possible redundant notations for any represented number. This reduction is visible in small useful operators like the elimination of leading zeros. We also present a key application with a CMOS Booth recoded multiplier. Our multiplier is able to accept both a redundant or a non redundant input with very little modifications and almost no penalty in time or space compared to state-of-the-art non redundant multipliers.     

ARMA implementation of diffraction operators with inverse-rootsingularities

The integral of a time-domain diffraction operator which has an integrable inverse-root singularity and an infinite tail is numerically differentiated to get a truncated digital form of the operator. This truncated difference operator effectively simulates the singularity but is computationally inefficient and produces a convolutional truncation ghost. The authors therefore use a least-squares method to model an equivalent autoregressive moving-average (ARMA) filter on the difference operator. The recursive convolution of the ARMA filter with a wavelet has no truncation ghost and an error below 1% of the peak diffraction amplitude. Design and application of the ARMA filter reduces computer (CPU) time by 42% over that repaired with direct convolution. A combination of filter design at a coarse spatial sampling, angular interpolation of filter coefficients to a finer sampling, and recursive application reduces CPU time by 83% over direct convolution or 80% over Fourier convolution, which also has truncation error     

Approximate realization of digital fractional forward operator using digital IIR filter

In this paper, a simple and an efficient approach for approximating the digital fractional forward operator z ^m (0?<?m?<?1) using digital infinite impulse response (IIR) filter is proposed. In this method, the coefficients of the closed form digital IIR filter derived for the approximation of the fractional forward operator, in a given frequency band, are based on approximation of fractional order systems. First, analog rational function approximation, in a given frequency band, of the fractional power zero (FPZ) is given. Then, the forward difference generating function is used to obtain a closed form IIR digital filter equivalent of the continuous FPZ, which approximates the digital fractional forward operator. Finally, illustrative examples have been presented to illustrate the effectiveness of the proposed design technique of the fractional forward operator z ^m approximation and its use in performing a fractional m-step prediction.     

数字图像处理技术在边缘特征提取中的应用

边缘检测是计算机视觉和图象处理中基础而又重要的课题。分析几种应用于数字图像处理中的边缘检测算子,根据它们在实践中的应用结果进行研究,通过matlab仿真结果对各种边缘检测算法的优劣进行了比较、选择,论述了获得清晰、完整的边缘轮廓的方法及步骤。     

Modeling, identification, and real-time control of bucket hydraulic system for a wheel type loader earth moving equipment

>The earth moving equipment industry is quickly gearing up to achieve great gains in efficiency, performance, safety, and operator comfort by the rapid deployment of recent digital control technology in its products. There are two major types of earth moving equipment operating in large numbers: excavators and wheel type loaders. Excavators have received much attention by the industry recently. The wheel type loader product studied in this paper is another example of a high volume versatile machine at the opposite end of the configuration spectrum. A state of the art electro-hydraulic open centered non-pressure compensated valve control system is studied to evaluate the potential gains by implementing digital velocity servo control. The control objectives are to (1) meet operator perceived response requirements, (2) meet operator perceived smoothness requirements, (3) create a sub-system that could accept commands from an autonomous high level planning controller.

Closed loop digital velocity control is successfully implemented in the racking motion of a wheel loader using a standard proportional-integral (PI) and a dynamic valve transform algorithm. The dynamic valve transform is a function of hydraulic flow rate which is a function of engine speed and rod end cylinder pressure. Robustness of performance was verified through extensive system modeling, validation, and hardware tests on a large Caterpillar wheel loader model 990. © 1998 Published by Elsevier Science Ltd. All rights reserved.     

基于CCS的数字图像边缘检测的设计

数字图像边缘检测的设计大多是基于Matlab软件设计的,这与工程化还有一定的距离。针对这一不足,给出了数字图像边缘检测Sobel算子以及程序设计流程,并在CCS v3.1的软件仿真环境下进行仿真实验。通过3个实例的分析,验证了基于CCS的数字图像边缘检测设计的可行性。结果表明,使用Sobel算子实现了图像边缘检测,这为图像处理提供了一种硬件实现的方法。     

Nonlocal discrete regularization on weighted graphs: a framework for image and manifold processing

We introduce a nonlocal discrete regularization framework on weighted graphs of the arbitrary topologies for image and manifold processing. The approach considers the problem as a variational one, which consists of minimizing a weighted sum of two energy terms: a regularization one that uses a discrete weighted p-Dirichlet energy and an approximation one. This is the discrete analogue of recent continuous Euclidean nonlocal regularization functionals. The proposed formulation leads to a family of simple and fast nonlinear processing methods based on the weighted p-Laplace operator, parameterized by the degree p of regularity, the graph structure and the graph weight function. These discrete processing methods provide a graph-based version of recently proposed semi-local or nonlocal processing methods used in image and mesh processing, such as the bilateral filter, the TV digital filter or the nonlocal means filter. It works with equal ease on regular 2-D and 3-D images, manifolds or any data. We illustrate the abilities of the approach by applying it to various types of images, meshes, manifolds, and data represented as graphs.     

Discrete Simulation of a Class of Distributed Systems Using Functional Analytic Methods

This paper investigates the discrete simulation of the solution of initial-boundary-value problems that typically arise in technical areas. Since many of them lead to unbounded and non-self-adjoint differential operators, we have to use a rather general theory as a mathematical basis. For the class of sectorial operators with a compact resolvent operator, the solution of initial-boundary-value problem can be represented by means of a certain holomorphic semigroup. It is shown that the solution can be expanded with respect to the canonical system of the considered operator. Such an expansion corresponds to a multi-dimensional functional transformation in the frequency domain. This fact leads to simple structures for the realization of the resulting system. Computationally efficient numerical algorithms can be derived by proper methods well-known from the theory of digital signal processing. Published online: April 2006     

Development of a Unified Design, Test, and Research Platform for Wind Energy Systems Based on Hardware-in-the-Loop Real-Time Simulation

Traditionally, offline modeling and simulation has been the tool of choice for improving wind energy system control strategies and their utility system integration. This paper exploits how a newly established real-time hardware-in-the-loop (HIL) test facility, which is designed for testing all-electric ship propulsion systems, can be utilized for wind energy research. The test site uses two 2.5-MW/220-rpm dynamometers and a 5-MW variable voltage and frequency converter to emulate a realistic dynamic environment, both mechanically and electrically. The facility is controlled by a digital real-time electric power system simulator that is capable of simulating electrical networks and control systems of substantial complexity, typically with a 50-$muhboxs$time step. Substantial input/output allows the feedback of measured quantities into the simulation. A 15-kW mock-up motor–generator set is used to demonstrate some critical aspects of the concept including the implementation of a proposed neural-network-based sensorless maximum wind energy capture control. From the dynamic test results presented, it is concluded that the proposed system shows great potential for the development of a unified wind energy design, test, and research platform.     

数字电视的条件接收系统原理与应用

数字电视指将传统的模拟信号转化为数字进行处理、传输和接收的系统。数字电视的条件接收系统运用各种数字技术通过对节目的加扰处理，使只有授权用户才能收看被加扰节目，从而保障运营商的利益，保证数字电视发展。 本文主要闻述当前前数字电视使用的条件接收系统的基本原理，以及实际中应用两种条件接收方式的设计和实现，并比较两种方式的优势和不足。最后介绍当前国内数字电视发展的现状。     

基于CCS的图像边缘检测和提取设计

Matlab对数字图像的处理在工程化方面存在一定的不足。针对这一不足,利用硬件仿真平台CCS,采用数字图像灰度梯度最大值法、Sobel算子边缘检测算法对数字图像进行检测,实现了数字图像的边缘提取。实验表明,Sobel算子边缘检测算法对数字图像进行边缘检测和提取的效果比较理想,且为图像处理提供了一种硬件实现方法。     

IP数字电视节目的远程传输实践及技术分析

基于MSTP和IP城域网络两种主流的运营网络,介绍IP数字电视节目传输的几种常用方法,并就各自特点和容易产生故障的原因作了具体分析,力求为IP数字电视节目的远程传输提供一套比较完整的解决方案。     

基于改进的Tustin算子的分数阶数字积分器设计

根据传统的Tustin积分算子的积分原理,改变Tustin积分算子的采样间隔,提高积分精度,以此得到了改进的新算子,然后通过Lagrange FIR分数阶延迟滤波器把新积分算子中的分数阶项转换为整数阶,最后采用连续分数展开(CFE)的方法实现了分数阶数字积分器设计.实验证明,设计的分数阶数字积分器在幅频特性上面明显优于传统方法设计的分数阶数字积分器.     

Teleoperation of a robot manipulator using a vision-based human-robot interface

Remote teleoperation of a robot manipulator by a human operator is often necessary in unstructured dynamic environments when human presence at the robot site is undesirable. Mechanical and other contacting interfaces used in teleoperation require unnatural human motions for object manipulation tasks or they may hinder human motion. Previous vision-based approaches have used only a few degrees of freedom for hand motion and have required hand motions that are unnatural for object manipulation tasks. This paper presents a noncontacting vision-based method of robot teleoperation that allows a human operator to communicate simultaneous six-degree-of-freedom motion tasks to a robot manipulator by having the operator perform the three-dimensional human hand-arm motion that would naturally be used to complete an object manipulation task. A vision-based human-robot interface is used for communication of human motion to the robot and for feedback of the robot motion and environment to the human operator. Teleoperation under operator position control was performed with high accuracy in object placement on a target. Semi-autonomous traded and shared control using robot-vision guidance aided in achieving a more accurate positioning and orientation of the end-effector for object gripping tasks.     

分数阶数字FIR微分器的快速WSLD设计算法

一阶逼近格林瓦尔-莱特尼科夫(G-L)加权系数的计算具有准确快速的递推公式,而高阶逼近鲁比希加权系数的求解则复杂度高,计算消耗时间长。本文通过傅里叶变换证明了鲁比希算子的逼近阶,并基于移位鲁比希算子提出一类四阶逼近的加权移位鲁比希差分(WSLD)算子。从数字信号处理角度分析WSLD算子滤波特性,设计基于WSLD算子的分数阶数字FIR微分滤波器并进行数值仿真验证。对比Al-Alaoui、鲁比希2种典型分数阶算子,结果表明,利用WSLD算子求解分数阶数字FIR滤波器滤波系数的算法简单、高效,且相对其他算子能有效减小吉布斯效应影响。     

多模态门电路自动合成算法的研究

提出了一种全新的多模态门电路自动合成的方法,利用"图"这种数据结构来表示电路,并专门设计出一系列修改电路结构和参数的操作算子,最终成功地实现了多模态门电路的自动合成.实验表明该方法能够有效地自动合成各种多模态门电路.     

基于地面广播的手机电视

手机电视业务可以利用蜂窝移动网络和地面/卫星数字广播来实现,其相关技术有4种:基于移动网实现技术、基于地面数字广播网实现技术、基于卫星实现技术和基于应用层实现技术。DVB-H和T-DMB是2种典型的地面数字广播电视标准,前者是DVB组织为通过地面数字广播网络向手持终端提供多媒体业务所制订的传输标准,后者是韩国推出的基于欧洲厂商开发的尤里卡147数字音频广播(Eureka-147DAB)的地面数字多媒体广播标准。目前开展手机电视业务面临着标准、频率资源、管制和终端等方面的问题,其运营模式存在移动运营商单独运营、广电单独运营和两者合作运营模式3种。手机电视是广电和通信产业融合的重要尝试,主管部门的协调和技术标准的制订将直接影响未来三网融合的进程。     

Design of digital FIR variable fractional order integrator and differentiator

This paper presents an easy and simple method to design variable fractional order digital FIR integrators and differentiators based on fractional order systems. First, closed-form digital IIR fractional order integrators and differentiators have been obtained from the analog rational functions approximations, in a given frequency band, of the fractional order integrator s ^?m and differentiator s ^m (0?<?m?<?1) through the Tustin generating function. Then, closed-form digital FIR fractional order integrators and differentiators by truncation of the digital IIR ones have been derived. Next, polynomial interpolation has been used to design digital FIR variable fractional order integrators and differentiators that can be implemented by the Farrow structure. The main feature of variable fractional order operator is that its order can be changed without re-designing a new fractional order operator. Some examples have been presented through the paper to illustrate the performance and the effectiveness of the proposed design method. The results obtained have been discussed and have been compared to one of the most recent works in the literature using the same design parameters.