Optimization of automated high-speed modular placement machinesusing knowledge-based systems

This paper introduces an optimizer for a new family of modular, multistation, walking beam, high-speed chip mounters. The objective is to optimize the machines in a manner that would streamline the use of nozzles and part feeder mechanisms and at the same time increase throughput. The optimization of these machines is a large NP-complete problem, and therefore, a heuristic search method is needed to solve the problem in reasonable time. Four knowledge-based systems are introduced to solve this problem. These systems were designed to emulate human experts, who have optimized these types of machines manually. Benchmarks were performed for 18 industrial test cases. The results show that overall, the knowledge-based systems outperformed software supplied by the vendor of the machine in both feeder slot savings and throughput. This performance represents a key improvement, and a prototype system has been implemented in our industrial partner's factory     

Multiobjective placement of electronic components using evolutionary algorithms

The optimal placement of electronic components on a printed circuit board is a well-studied optimization task. However, despite the involvement of multiple conflicting objectives, researchers have mainly used a single objective of minimizing the overall wire length or minimizing the overall heat generation or minimizing the overall time delay in its functioning. In this paper, the problem is treated as a two-objective optimization problem of minimizing the overall wire length and minimizing the failure-rate of the board arising due to uneven local heat accumulation. The proposed strategy uses a novel representation procedure and a multiobjective evolutionary algorithm capable of finding multiple Pareto-optimal solutions simultaneously. Moreover, the flexibility and efficacy of the proposed strategy have been demonstrated by simultaneously optimizing the placement of components and the layout of the board. The convergence and the extent of spread obtained in the solutions reliably by repetitive applications of the proposed procedure should encourage further application of the approach to more complex placement design problems.     

Collision resolution algorithms in multistation packet-radionetworks

The performance of a multistation packet-radio network in which the nodes of the network employ some collision resolution algorithm (CRA) for accessing a shared radio channel is analyzed. The two CRAs considered here are the binary-tree CRA (BTCRA) and the clipped binary-tree CRA (CBTCRA). The exact analysis of a multistation network with these access schemes is intractable. Therefore, the authors present an approximate method that captures the interactions among the nodes of different stations. The mean idea is to view the interference among the nodes of different stations as independent random noises and compute the probabilities of these noises, taking into account the interactions between the nodes. Numerical results of the approximate analysis are presented and compared with the results of simulations     

SMT优化系统的设计与实现

文章针对基于SMT系统优化的旅行商问题进行了分析和研究,对SMT系统优化进行了系统分析设计,介绍了如何减少X—Y工作台运动,提出两种针对环球HSP贴片机最优路径的优化算法,并基于一种方法编程实现了基本方案。最后在HSP贴片系统上使用本解决方案,大幅度提高了生产效率,证明了本解奥方案的优越性和高效性,同时也为用其它算法解决SMT系统优化问题提供了一种可参考的思路。     

SMT优化系统的设计与实现

基于SMT系统优化的旅行商问题（TSP）进行了分析和研究,对SMT系统优化进行了系统分析设计,介绍了如何减少X-Y工作台运动,提出两种针对环球HSP贴片机最优路径的优化算法,并基于一种方法编程实现了基本方案。最后在HSP贴片系统上使用本解决方案,大幅度提高了生产效率,证明了本解决方案的优越性和高效性,同时也为用其它算法...     

SMT优化系统的设计与实现

表面组装技术是当今电子工业的支柱技术。这些年来随着市场竞争的日益加剧、产品投放市场的时间日益缩短、生产周期越来越短和新技术不断引入,如何提高SMT系统的生产效率就变得越来越重要,因此基于SMT系统优化的旅行商问题(TSP)就被提出来了。针对基于SMT系统优化的旅行商问题进行了分析和研究,对SMT系统优化进行了系统分析设计,介绍了如何减少X-Y工作台运动,提出两种针对环球HSP贴片机最优路径的优化算法,并基于一种方法编程实现了基本方案。最后在HSP贴片系统上使用本解决方案,大幅度提高了生产效率,证明了本解决方案的优越性和高效性,同时也为用其它算法解决SMT系统优化问题提供了一种可参考的思路。     

贴片机X/Y轴快速高精度定位的实现

负载惯量和外界干扰是影响贴片机X,Y轴快速高精度定位的两个关键因素。本文针对负载惯量和外界干扰对控制性能的影响,提出了基于RBF神经网络的自适应滑模控制算法。利用RBF神经网络的万能逼近特性实现对外加干扰和被控对象模型信息的逼近,运用自适应控制算法计算前馈补偿量以补偿负载惯量和摩擦力对运动性能的影响,采用滑模控制算法以抑制其他不确定干扰对运动控制的影响。通过仿真分析可以得出,所采用的控制算法能够有效地补偿负载惯量和外界干扰对定位性能的影响,从而实现贴片机X,Y轴的快速高精度定位。     

Implementing scheduling algorithms in high-speed networks

The fluid generalized processor sharing (GPS) algorithm has desirable properties for integrated services networks and many packet fair queueing (PFQ) algorithms have been proposed to approximate GPS. However, there have been few high-speed implementations of PFQ algorithms that can support a large number of sessions with diverse rate requirements and at the same time maintain all the important properties of GPS. The implementation cost of a PFQ algorithm is determined by: (1) computation of the system virtual time function; (2) maintenance of the relative ordering of the packets via their timestamps (scheduling); and (3) regulation of packets based on eligibility time, in some algorithms. While most of the recently proposed PFQ algorithms reduce the complexity of computing the system virtual time function, the complexity of scheduling and traffic regulation is still a function of the number of active sessions. In addition, while reducing the algorithmic or asymptotic complexity has been the focus of most analysis, it is also important to reduce the complexity of basic operations in order for the algorithm to run at high speed. We develop techniques to reduce both types of complexities for networks of both fixed and variable size packets. Regulation and scheduling are implemented in an integrated architecture that can be viewed as logically performing sorting in two dimensions simultaneously. By using a novel grouping architecture, we are able to perform this with an algorithmic complexity independent of the number of sessions in the system at the cost of a small controllable amount of relative error. To reduce the cost of basic operations, we propose a hardware-implementation framework and several novel techniques that reduce the on-chip memory size, off-chip memory bandwidth, and off-chip access latency. The proposed implementation techniques have been incorporated into commercial ATM switch and IP router products     

Quantifying SMT decoupling capacitor placement in dc power-busdesign for multilayer PCBs

Noise on a dc power-bus that results from device switching, as well as other potential mechanisms, is a primary source of many signal integrity (SI) and electromagnetic interference (EMI) problems. Surface mount technology (SMT) decoupling capacitors are commonly used to mitigate this power-bus noise. A critical design issue associated with this common practice in high-speed digital designs is placement of the capacitors with respect to the integrated circuits (ICs). Local decoupling, namely, placing SMT capacitors in proximity to ICs, is investigated in this study. Multilayer PCB designs that employ entire layers or area fills for power and ground in a parallel plate structure are considered. The results demonstrate that local decoupling can provide high-frequency benefits for certain PCB geometries through mutual inductive coupling between closely spaced vias. The associated magnetic flux linkage is between the power and ground layers. Numerical modeling using an integral equation formulation with circuit extraction is used to quantify the local decoupling phenomenon. Local decoupling can effectively reduce high-frequency power-bus noise, though placing capacitors adjacent to ICs may limit routing flexibility, and tradeoffs need to be made based on design requirements. Design curves are generated as a function of power-bus layer thickness and SMT capacitor/IC spacing using the modeling approach to quantify the power-bus noise reduction for decoupling capacitors located adjacent to devices. Measurement data is provided to corroborate the modeling approach     

Optimal LC-VCO design through evolutionary algorithms

The need for implementing low cost, fully integrated RF wireless transceivers has motivated the widespread use CMOS technology. However, in the particular case for voltage-controlled oscillators (VCO) where ever more stringent specifications in terms of phase-noise must be attained, the design of the on-chip LC tank is a challenging task, where fully advantage of the actual technologies characteristics must be pushed to nearly its limits. To overcome phase-noise limitations arising from the low quality factor of integrated inductors, optimization design methodologies are usually used. In this paper a model-based optimization approach is proposed. In this work the characterization of the oscillator behaviour is guaranteed by a set of analytical models describing each circuit element performance. A set of working examples for UMC130 technology, aiming the minimization of both VCO phase noise and power consumption, is addressed. The results presented, illustrate the potential of a GA optimization procedure design methodology yielding accurate and timely efficient oscillator designs. The validity of the results is checked against HSPICE/RF simulations.     

Cognitive radio spectrum allocation using evolutionary algorithms

Cognitive radio has been regarded as a promising technology to improve spectrum utilization significantly. In this letter, spectrum allocation model is presented firstly, and then spectrum allocation methods based on genetic algorithm (GA), quantum genetic algorithm (QGA), and particle swarm optimization (PSO), are proposed. To decrease the search space we propose a mapping process between the channel assignment matrix and the chromosome of GA, QGA, and the position of the particle of PSO, respectively, based on the characteristics of the channel availability matrix and the interference constraints. Results show that our proposed methods greatly outperform the commonly used color sensitive graph coloring algorithm.     

表面贴装胶粘剂涂覆工艺的选择与优化

介绍了表面贴装胶粘剂的涂覆工艺,对工艺方法选择、胶粘剂性能及选择,工艺设计等作了详细的分析比较,提出了工艺优化所需的相应的对策。     

Monopulse Cassegrain antenna design using evolutionary algorithms

Using evolutionary programming (EP), monopulse Cassegrain antennas with four feeds can be designed for the desired sum gain, side lobe level and minimum possible antenna size. A method is proposed to achieve the optimum monopulse difference pattern. cos^q(θ) type feeds are considered as the feed system and the final designs have been checked using real feeds. Proper cost functions are proposed to achieve the desired gain, side lobe level and optimum slope in the difference pattern, taking into account the feasibility of the feed system. The effects of the parameters involved in the optimization are investigated.     

Optimization of high-speed metal-semiconductor-metal photodetectors

Circular-aperture Metal-Semiconductor-Metal (MSM) photodetectors have been fabricated in order to decrease the device capacitance. The frequency-response of the MSM photodetectors has been calculated using a first-order approximation. The design of the circular-aperture detectors and conventional square-aperture detectors has been optimized using this approximation. The largest 3 dB bandwidths are obtained with 33 fingers for the circular detectors and 29 for the square detectors. These numbers do not change regardless of the size of the MSM photodetectors     

Images encryption by the use of evolutionary algorithms

Increasing information transmission in public networks raises a significant number of questions. For example, the security, the confidentiality, the integrity and the authenticity of the data during its transmission are very problematical. So, encryption of the transmitted data is one of the most promising solutions. In our work, we focus on the security of image data, which are considered as specific data because of their big size and their information which are of two-dimensional nature and also redundant. These data characteristics make the developed algorithms in the literature unavailable in their classical forms, because of the speed and the possible risk of information loss. In this paper, we develop an original “images encryption” algorithm based on evolutionary algorithms. The appropriateness of the proposed scheme is demonstrated by the sensitivity to images, the key and the resistibility to various advanced attacks.     

SMT生产线中贴片机平衡优化方法研究

贴片机是SMT生产线中的核心设备,其生产效率的高低直接决定着整条生产线的产出,因此提高其生产效率具有十分重要的意义。根据SMT生产模式以及生产线优化对象的不同,分别从单机优化、线体平衡、归组优化和生产计划优化四个方面进行阐述,着重探讨了SMT生产线中贴片机平衡优化的思想、方法以及经验,并结合具体的案例进行分析。     

Fast optimal video placement algorithms for hierarchicalvideo-on-demand systems

The multilevel hierarchical network architecture has been shown to be a scalable and cost efficient solution for large video-on-demand (VOD) systems. The predominant operation cost of a hierarchical VOD system consists of network transmission cost and video storage cost. How to minimize the operation cost under several operating constraints is an important issue. Many operating constraints, such as the storage capacity limitation at each level of servers, have made the problem intractable. We proposed several efficient heuristic video placement algorithms that can achieve near optimal operating cost. We have also proposed a time-variant arrival traffic model with arrival rate matching the statistics gathered from commercial systems     

Optimization of image coding algorithms and architectures usinggenetic algorithms

This paper addresses the application of genetic algorithm (GA)-based optimization techniques to problems in image and video coding, demonstrating the success of GAs when used to solve real design problems with both performance and implementation constraints. Issues considered include problem representation, problem complexity, and fitness evaluation methods. For offline problems, such as the design of two-dimensional filters and filter banks, GAs are shown to be capable of producing results superior to conventional approaches. In the case of problems with real-time constraints, such as motion estimation, fractal search and vector quantization codebook design, GAs can provide solutions superior to those reported using conventional techniques with comparable implementation complexity. The use of GAs to jointly optimize algorithm performance in the context of a selected implementation strategy is emphasized throughout and several design examples are included     

Commissioning of a state-controlled high-powered electrical driveusing evolutionary algorithms

The subject of this research is the automated startup procedure of a PI state-controlled rolling-mill motor by using evolutionary algorithms. Compared to the conventional PI speed control, applying the method of deliberate pole placement to the state controller design succeeds in improving the transient response of setpoint and disturbance changes. To put the PI state-controlled drive with observer into operation to obtain a controller with a high robustness and dynamics, the precise knowledge of this physical parameter is necessary. An evolution-based system is used to solve the estimation problem. A high degree of reliability respecting multimodal characteristics and robustness against random noise is expected from the identification method. Evolutionary algorithms fulfill this requirement. With genetic operators like mutation, crossover, and selection, evolutionary algorithms mimic the principles of organic evolution in order to solve the optimization problem     

SMT辅助材料优化选型工艺试验研究

选取了三类耗材选型方案来进行工艺试验研究,主要包括焊膏、清洗剂、助焊剂．并且依托于典型的印制板以及元器件来完成试验件。基于方案中的耗材基础性能测试、印制板组件试验件焊点机械强度测试以及焊点微组织结构分析来完善耗材选型,优化匹配性设计,确定最终耗材型号,进一步提高焊点质量和可靠性。