复杂产品开发项目系统化管理方法

为了克服传统的产品工程设计过程与项目开发过程相分割对产品项目开发整体绩效的不良影响,本文提出了一种复杂产品开发项目系统化管理方法。首先,产品工程设计过程用设计结构矩阵来描述并从改善信息流的角度对设计结构矩阵予以优化从而识别出具有迭代关系的活动。具有迭代关系的活动或通过解开迭代关系而变为串行或并行的活动或通过强化其迭代关系而组合成一个单一的活动。基于设计结构矩阵的优化结果是一组数量不多的设计结构矩阵。针对每一个设计结构矩阵构造相应的CPM网络图并计算相应的关键路径以及识别关键活动。然后,通过传统的“赶工计算”或增加关键路径上串行活动的并行度来识别可行的优化项目实施方案。最后,案例分析证明了该方法的可行性和有效性。     

Performance evaluation of tandem and conventional AGV systems using generalized stochastic Petri nets

This paper investigates the different policies and concepts followed in the traffic management of automated guided vehicle (AGV) systems, and develops the controls for automatically eliminating potential vehicle conflicts in an AGV system. The planning of the AGV system is performed in such a way that there are no conflicts or deadlocks for the vehicles using stochastic Petri nets (SPNs). The major effort is devoted to determining the benefits of the tandem AGV control in comparison with the conventional AGV control method. SPNs have been used to model the different designs of flexible manufacturing systems (FMSs) and with different policies for the movement of material, vehicle path control, inventory planning and tool control. The SPN model is solved and the performance of the system can be evaluated. In this study, the effort is directed to model an FMS with two different types of AGV traffic management methods, namely the conventional and tandem AGV control. A SPN program is used which takes the FMS Petri net model as the input and evaluates the different properties of the Petri net. Finally the performance measures are obtained, which helps in evaluating and comparing the two different AGV traffic management methods.     

A Novel Improved Bat Algorithm in UAV Path Planning

Path planning algorithm is the key point to UAV path planning scenario. Many traditional path planning methods still suffer from low convergence rate and insufficient robustness. In this paper, three main methods are contributed to solving these problems. First, the improved artificial potential field (APF) method is adopted to accelerate the convergence process of the bat’s position update. Second, the optimal success rate strategy is proposed to improve the adaptive inertia weight of bat algorithm. Third chaos strategy is proposed to avoid falling into a local optimum. Compared with standard APF and chaos strategy in UAV path planning scenarios, the improved algorithm CPFIBA (The improved artificial potential field method combined with chaotic bat algorithm, CPFIBA) significantly increases the success rate of finding suitable planning path and decrease the convergence time. Simulation results show that the proposed algorithm also has great robustness for processing with path planning problems. Meanwhile, it overcomes the shortcomings of the traditional meta-heuristic algorithms, as their convergence process is the potential to fall into a local optimum. From the simulation, we can see also obverse that the proposed CPFIBA provides better performance than BA and DEBA in problems of UAV path planning.     

Optimal inventory costs in a complementary flexible manufacturing system

Flexible manufacturing systems (FMS) have provided job shop-type operations a variety of solutions to their widely documented inefficiencies. FMS come with a wide spectrum of capabilities and are used in a wide variety of manufacturing environments. The present study proposes there are situations where inventory control issues need to be considered during the FMS set-up planning. It has developed a non-linear mathematical programming model, which also has binary variables, to optimize inventory costs during the set-up planning for a sample FMS installation. The solution to the mathematical model is non-trivial. It shows that using this model in conjunction with analytical methods such as constraint propagation and generate-and-test, and sigmoid function approximations, facilitates robust solutions to some of the subproblems of the FMS set-up problem. The study also provides an exchange curve based framework for analysing the implications of inventory policy variables on decisions made at the FMS set-up stage.     

Path planning of functionally graded material objects for layered manufacturing

Path planning is a fundamental process-planning task in layered manufacturing. However, currently, most researches focus on path planning of homogeneous objects and few approaches for path planning of functionally graded material objects have been reported in the literature. Unlike homogeneous objects, functionally graded materials objects contain continuously varying material information as well as geometry information, which makes their path planning more complex and difficult than those of homogeneous objects. This paper presents an approach for path planning of functionally graded material objects. First, the continuous material distribution in each layer is changed into discrete step-wise gradings by subdividing the functionally graded materials slice into multimaterial subregions, which can be regarded as homogeneous material regions so that the functionally graded material layer can be built by mixing materials into desired volume ratio. Then the tool paths and process parameters for each multimaterial subregion in the slice are generated separately. An algorithm that summarized the procedure is described and an example is also presented.     

Sequential quadratic programming-based fast path planning algorithm subject to no-fly zone constraints

Path planning plays an important role in aircraft guided systems. Multiple no-fly zones in the flight area make path planning a constrained nonlinear optimization problem. It is necessary to obtain a feasible optimal solution in real time. In this article, the flight path is specified to be composed of alternate line segments and circular arcs, in order to reformulate the problem into a static optimization one in terms of the waypoints. For the commonly used circular and polygonal no-fly zones, geometric conditions are established to determine whether or not the path intersects with them, and these can be readily programmed. Then, the original problem is transformed into a form that can be solved by the sequential quadratic programming method. The solution can be obtained quickly using the Sparse Nonlinear OPTimizer (SNOPT) package. Mathematical simulations are used to verify the effectiveness and rapidity of the proposed algorithm.     

A Hybrid Path Planning Method Based on Articulated Vehicle Model

Due to the unique steering mechanism and driving characteristics of the articulated vehicle, a hybrid path planning method based on the articulated vehicle model is proposed to meet the demand of obstacle avoidance and searching the path back and forth of the articulated vehicle. First, Support Vector Machine (SVM) theory is used to obtain the two-dimensional optimal zero potential curve and the maximum margin, and then, several key points are selected from the optimal zero potential curves by using Longest Accessible Path (LAP) method. Next, the Cubic Bezier (CB) curve is adopted to connect the curve that satisfies the curvature constraint of the articulated vehicle between every two key points. Finally, Back and Forth Rapidly-exploring Random Tree with Course Correction (BFRRT-CC) is designed to connect paths that do not meet articulated vehicle curvature requirements. Simulation results show that the proposed hybrid path planning method can search a feasible path with a 90-degree turn, which meets the demand for obstacle avoidance and articulated vehicle back-and-forth movement.     

An heuristic for configuring a mixed uni/bidirectional flow path for an AGV system

An heuristic methodology has been developed in the present work for configuring a mixed (hybrid) uni/bidirectional flow path for an AGV material handling system. The given unidirectional flow path layout, material flow intensities and vehicle travelling time matrix among various processing centres are taken as input information to this technique. A multiplicative function of material flow intensities between any two centres is used as a criterion for selectively configuring a path as a bidirectional one. The highest such product indicates that the shorter path between that pair of centres is a strong candidate for being configured as bidirectional. The heuristic has been applied to an illustrative FMS and various alternate flow path designs have been obtained. Simulation is then performed with the aim of comparing the productive potentials of the facility when it is operated on either unidirectional, or mixed uni/bidirectional, or allbidirectional flow path design alternatives. The benefits of bidirectional flows over unidirectional counterpart are significant in terms of system throughput rates and optimal AGV fleet sizes. However, traffic control becomes an important issue as vehicle interference and blocking increases with increase in bidirectionality in the network. The decision related to location and capacity planning of vehicle buffering zones is also addressed.     

Control policy simulation based on machine age in a failure prone one-machine,one-product manufacturing system

This paper deals with the production planning problem of a flexible manufacturing system (FMS). This problem is within the class of problems which are usually faced during the life cycle of FMS. There are basically two approaches used to solve this problem: analytical and simulation. The objective of this paper is to develop a methodology for determine the control policy for a given FMS by using the combination of both analytical and simulation approaches. The production rate control of a one-machine one-product system is presented to illustrate our approach. The contribution of the analytical part of the proposed model consists of generating a near-optimal controller based on the concept of an age-dependent hedging point policy. This sub-optimal policy is used as input of the simulation part and the improvement of operating conditions (control policies) achieved with a constant demand rate. The proposed model includes also a stochastic demand and lot sizes in production which consists of similar products batches with bulk arrivals. The robustness of the controller against both demand rates and production types has been validated.     

Toward Knowledge-Based Control Of Flexible Manufacturing Systems

This paper examines the use of artificial intelligence (AI) concepts to augment/enhance flexible manufacturing system (FMS) control systems by providing flexibility in decision-making to manage and control the system. Such a system would use a “knowledge-based” approach to system control. The paper first defines the problems and issues in FMS planning and control and then examines the AI technology that can be used to solve them. The paper shows that the FMS control structure is conceptually similar to an Al-based opportunistic hierarchical planning architecture. The paper concludes by discussing the prospects for knowledge-based control of FMSs in view of current technology.     

基于线性时序逻辑的移动端快递派送路径规划

研究了快递派送的路径规划。针对目前快递派送任务点较多,快递员不熟悉派送区域的问题,提出了一种基于线性时序逻辑(LTL)的移动端多点快递派送路径规划方法。该方法利用移动端的百度地图应用包实现快递员的定位与导航任务,提出两层(顶层、底层)规划策略。顶层规划避开百度地图实际道路环境繁琐又庞大的建模,将快递派送问题转化为旅行推销员问题(TSP),仅将快递员派送任务地点建模为一个有限状态的加权切换系统,状态之间的切换权重基于百度地图的自驾导航距离,而非简单的直线距离,以达到底层规划结果符合实际环境,确保最后搜索的路径最优性,同时利用线性时序逻辑语言描述多点快递派送任务,从而将切换系统信息与派送任务信息相融合,构建一个任务可行网络拓扑,并在该网络拓扑上基于Dijkstra算法搜索出快递员离散的最优路径。底层规划完成离散路径的连续化,离散路径的任意相邻任务点间的路径规划基于百度地图实现,从而实现顶层规划的离散路径连续化,获得快递员可派单的实际派送路线。实验结果表明该方法能够解决多点派送任务与派送区域受约束的问题,并保证快递员派单路径的最优性。     

基于变间距螺旋线的计算机控制抛光轨迹规划

目的 改善抛光轨迹以获得更好的加工精度。方法 分析计算机控制抛光中常使用的阿基米德螺旋线轨迹,发现使用该方法加工回转曲面时,由于投影行距变化,导致轨迹间去除区域的接触情况变化较大,将影响抛光后的表面质量。为此引入面积重叠率这一概念,以量化分析去除区域的接触面积变化情况,同时提出一种变间距的螺旋线轨迹规划方法,该方法可确保加工轨迹产生的去除区域均匀一致。结果 分别采用2种螺旋线轨迹规划方法对同一初始表面（面形误差为峰谷值Epv=9.04 µm,均方根值Erms=0.6228 µm）进行仿真加工,采用变间距螺旋线所得抛光后面形误差为Epv=2.15 µm,Erms=0.018 µm,而采用阿基米德螺旋线所得抛光后面形误差为Epv=3.47 µm,Erms=0.036 µm。结论 仿真结果表明,采用变间距螺旋线轨迹抛光后的表面质量相比阿基米德螺旋线轨迹有较大的提高。     

投影变换矩阵式及变换矩阵

根据几何原理构造了投影体系矩阵(PSM),利用向量几何的形式,建立投影(包括平行投影和中心投影)变换矩阵式。得出投影体系矩阵的逆阵就是投影变换矩阵(PTM)的结论。这种构造变换矩阵的方法与实际投影(观察)过程相同。通过应用程序设计说明它简明、直观且几何意义明确,并且在中心投影(透视投影)中不会产生变形。文中还讨论了投影坐标变换和投影深度坐标等问题。     

Production planning for flexible flow systems with limited machine flexibility

A flexible manufacturing system (FMS) is highly capital-intensive and FMS users are concerned with achieving high system utilization. The production planning function for setting up an FMS prior to production should be developed in order to make the most of the potential benefits of FMSs. We consider two production planning problems of grouping and loading a flexible flow system, which is an important subset of FMSs where the routing of parts is unidirectional. We show that considering this routing restriction as well as limited machine flexibility strongly affects both the solution techniques and the quality of the solutions. Because of the complexity of the problem, we present a heuristic approach that decomposes the original problem into three interrelated subproblems. We show that the proposed approach usually finds a near-optimum solution and is superior to an approach that exists in the literature of FMS production planning. We also introduce effective heuristic methods for two new subproblems that arise because of the unidirectional flow precedence and flexibility constraints. Computational results are reported and future research issues are discussed.     

Computer-based FMS facilities design tool

FMS layout design is a complex process, involving a large number of alternatives, which contributes generously to the usual two-year FMS planning lead time. The need for a comprehensive, yet easy-to-use methodology or tool which can reduce this large number of alternatives to a more reasonable figure has motivated this research. A survey of existing FMSs was undertaken with the intention of identifying some of the more common (dominant) types of layouts, and to develop, if possible, a methodology for the selection of such layouts. However, almost every FMS was found to have a unique layout. For a given FMS under consideration, the capabilities with respect to the parts which can be manufactured is essentially given. The determining features of the resultant design of the FMS, therefore, are primarily based upon the design of the material handling system which integrates the FMS. However, as the number of machines in a FMS increase, the number of part sequences and alternate configurations increase at a dramatic rate. To assist in the preliminary design process, an interactive computer-based program has been developed to aid the search for non-inferior layouts to suit the exact part sequence needs of each FMS. Six criteria-three related to the distances parts travel during manufacturing and three related to the capital costs of the FMS-are provided to assist the user in selecting an appropriate arrangement. The program is described and its use is demonstrated in developing improved arrangements over an example FMS which was published in the literature. Although the reader is cautioned that the results were developed using only static measures, the results do indicate that significantly improved designs are possible using the proposed methodology     

A multi-objective production planning model in a flexible manufacturing environment

Production planning for flexible manufacturing systems (FMS) has been studied using different methods, including simulation; queueing networks; and several single-objective mathematical programming techniques. The decision making process for production planning in FMS usually involves multiple conflicting objectives. Thus, goal programming (GP) can be effectively applied to this decision problem. This study discusses the superior aspects of the GP model over other models, when solving the production planning problem for FMS. A GP model is presented and the implementation results of an illustrative problem are analysed.     

基于多体系统传递矩阵法和遗传算法的一种物理参数识别方法

将多体系统传递矩阵法与遗传优化算法相结合,形成了一种新的基于多体系统传递矩阵法和遗传算法的物理参数识别方法(MS-TMM&GA).应用多体系统传递矩阵法进行动力学建模以及固有振动特性分析.将参数识别问题转化为优化问题,结合遗传算法,对由系统固有频率和增广特征矢量构造的目标函数全局最小值优化求解.给出了通过系统模态参数识别物理参数的计算步骤以及流程图.通过两个数值算例,表明了该方法的可行性及有效性.该方法对多体系统传递矩阵法和遗传算法进行了结合与拓展,无需建立复杂多体系统的总体动力学方程,涉及矩阵阶次低,即可快速获得高精度的优化计算结果.     

基于动态运动基元的移动机器人路径规划

针对二维环境下移动机器人路径规划问题,提出一种基于动态运动基元(DMPs)的路径规划方法。该方法首先用手柄来控制机器人,记录机器人的运动轨迹,然后将记录的轨迹作为DMPs算法的学习样本,利用轨迹样本进行训练获得DMPs算法的模型参!,从而实现机器人的路径规划。当运动环境中有障碍物时,在已有学习基础上通过设计耦合因子规划出避障路径,在此基础上,改变机器人运动的目标位置,可以完成对新目标的泛化推广。仿真和实验结果表明,DMPs算法在移动机器人路径规划上具有可行性。     

A generic Petri net model for flexible manufacturing systems and its use for FMS control software testing

Developing a flexible manufacturing system (FMS) controller is a complicated task both in the hardware development and software development. To test the control software prior to putting it into use is crucial for the development of a FMS controller. An intelligent testing environment for FMS controllers is under development, the aim of which is to reduce manual work in the testing. To reach this objective the automatic building of a behavioural model of the FMS is demanded. This paper proposes a generic Petri net (GPN) model and approach for the development of control software for FMSs. The principle of this approach is based on checking the control parts of FMSs with the help of temporal relationships between physical operations, and the specification of the FMS controller with GPN. The strategy of GPN modelling is then incorporated with more general problem solving strategies in artificial intelligence. A template is first defined for a GPN model, and then the model for FMS individuals is established in the form of instances of the template. The transitions of the GPN are represented with the proposed general expressions with two syntaxes, 'verb+ noun' and 'verb+ noun+ where', from which the GPN can be formulated. GPN makes it simple to express FMS controls, and procedural language can also be used for information processing. A case study for the testing of FMS controller software is provided to show effectiveness and cost saving over development with conventional methods in which only ordinary Petri net and procedural language are used.     

Fibromyalgia syndrome in Turkish hemodialysis patients

The aim of our study was to evaluate the frequency of fibromyalgia syndrome (FMS) in hemodialysis (HD) patients and to assess whether this syndrome is associated with gender, age, duration of HD, or various laboratory parameters. This study was composed of 221 chronic HD patients (99 females and 122 males), and we recorded each participant's age, gender, causes of kidney failure, HD duration, education level, and symptoms related to FMS, which was diagnosed according to the 2010 American College of Rheumatology criteria. We documented the laboratory parameters for all patients. In addition, patients with FMS filled out the Fibromyalgia Impact Questionnaire. Twenty‐two patients met the diagnostic criteria for FMS (9%), and there were no statistically significant differences related to age, gender, or HD duration between FMS and non‐FMS groups (P > 0.05). In addition, the education levels were lower in patients diagnosed with FMS (P < 0.05), and there were statistically significant differences related to sleep disturbance, fatigue, and cognitive symptoms between the two groups (P < 0.05) as well. However, their laboratory parameters were similar (P > 0.05). There was a higher prevalence of FMS in HD patients than in the general population. Sleep disturbances, fatigue, education level, and cognitive symptoms were associated with FMS, but there was no correlation between the laboratory parameters and this condition.