智能装配规划中的拆卸方向计算

提出了基于装配约束的离散化单位球面的拆卸方向计算方法．首先利用离散化的单位球面计算局部拆卸方向集，通过离散点坐标的加权平均求取拆卸方向集的质心；然后通过可拆卸性判断获得可行的全局拆卸方向．应用表明，该方法可有效地降低复杂产品拆卸方向求解的计算复杂度．     

基于几何推理的装配序列自动规划研究

以问题规约的求解策略和分解法规划产生的装配序列,提出与或图表达装配体拆卸序列解空间,通过求解拆卸序列与或图的解空间,得到装配体的拆卸序列;将拆卸序列反向得到装配序列,为降低装配体拓扑联接图的复杂度,以作业组件做出识别,文中提出判断零件可拆卸性的三个条件,使大部分零件无需进行干涉检验,而由逻辑推理即可判断是否满足拆卸条件,避免了多次试凑,有更高求解效率,可更广泛地用于装配序列求解上。     

基于规则和爆炸图的装配序列规划

提出局部爆炸图的概念，运用几何干涉规则生成各直角坐标方向的局部爆炸图；在确立各方向的合并顺序后，用合并规则生成各零件的合并约束前元集；并据此进行局部爆炸图合并求解装配序列，实现了规则推理和几何推理算法的紧密结合，有效地避免了装配序列组合爆炸，降低了装配规划的计算复杂度，保证规划所得装配序列的可行性和实用性．     

基于几何推理的装配序列自动规划研究

文章以问题规约的求解策略,以分解法规划产生的装配序列,提出与或图表达装配体拆卸序列解空间。通过求解拆卸序列与或图的解空间得到装配体的拆卸序列,将拆卸序列反向得到装配序列。为降低装配体拓扑联接图的复杂度,对作业组件做出识别。另外提出了判断零件拆卸性的三个条件,大部分零件无需进行干涉检验,而白逻辑推理即可判断是否满足拆卸条件,避免了多次试凑,具有更高的求解效率,可更广泛地用于装配序列求解。     

基于深度强化学习的双向装配序列规划

为了解决复杂装配模型的序列规划问题,并使算法对任意初始状态具有较高的适应性,本文提出了一种包含正向装配以及逆向拆解的一体化双向装配序列规划方法BASPW–DQN.针对复杂装配模型,首先进行了一体化装配序列规划的问题描述与形式化表示;在此基础上,引入了课程学习及迁移学习方法,对包含前向装配和逆向错误零件拆卸两部分过程的双向装配序列规划方法进行研究.在所搭建的ROS-Gazebo与TensorFlow相结合的仿真平台上进行了验证,测试结果证明此双向网络对于任意初始状态(包括零装配、部分装配、误装配等初始状态)的装配任务均可以在较少步数内完成,验证了所提方法对于解决装配序列规划问题的有效性与适应性.     

基于改进人工萤火虫算法的装配序列规划研究

装配是装备保养维护的重要环节,高效和无损地装配好拆卸维护的零件在战场上尤为重要.为了解决装配序列规划最优解问题,根据装配序列规划的特点,提出了基于人工萤火虫算法的离散SA-GSO算法.首先利用干涉矩阵对装配序列进行了可行性分析,并根据操作实际设定了适应度函数;然后针对人工萤火虫算法存在的易早熟等缺陷,利用模拟退火原理进行优化并对算法进行离散化,以适用于装配序列最优解问题;最后进行了实例验证,实验结果证明了该算法的可行性及有效性.     

基于扩展干涉矩阵和遗传算法的拆卸序列规划

为高效求解非标准正交轴向上的装配体拆卸序列,将常用的基于全局坐标系的干涉矩阵扩展为包含基于装配体坐标系的全局干涉矩阵与基于零件坐标系的本地干涉矩阵干涉信息的扩展干涉矩阵,丰富了拆卸方向表达的多样性,并通过其检验拆卸序列的几何可拆性.在得到可行拆卸序列的基础上建立了目标函数,利用遗传算法对拆卸序列进行优化.通过一个实例验证了该方法在拆卸方向多样化方面的可行性和有效性.     

基于装配约束动态管理的虚拟拆卸

装配约束是虚拟拆卸环境下必须考虑的装配体的重要信息，提出虚拟拆卸过程中装配约束的动态管理机制，并实现了基于装配约束导航的虚拟拆卸。装配约束的动态管理包括虚拟环境下装配约束的获取、表达以及拆卸过程中装配约束的动态维护，即装配约束的动态解除和产生，文中用装配约束图表达零件间的装配约束，提出装配约束的间接解除方法，并实现了基于装配约束推理的零件可拆卸方向的推导。最后，通过一个简单装配体的拆卸实例，对文中方法进行了验证。     

基于成本和并行装配的装配序列有向图求解

针对虚拟装配中装配序列规划问题,引入了有向图来描述装配过程中的零件以及零件间的装配约束关系。结合装配成本、并行装配、装配经验优化了装配关系有向图的拓扑排序算法。提出了将装配方向变化次数作为衡量装配成本的一项重要指标。提出了将单次可装配的零件数量作为装配优先方向的参考依据。文章最后给出了装配序列生成的具体算法。     

用户关注度相关的装配模型动态可视化

为了方便地展示复杂模型各零件之间的三维结构,并清楚地揭示出它们之间的层次装配约束关系,提出一个面向用户交互的装配模型浏览系统.通过构造层次有向拆卸图来保存各零件的拆卸顺序,并采用递归法创建其干涉矩阵和拆卸有向图;装配约束图中的各顶点均用相应零件的图像来表示,以便于用户直观地选择所关注零件.由于采用了focus+context的方式来生成装配约束图,用户所关注零件的局部邻域被自动调整到视图的中心,并且放大显示.另外还提出了一种基于用户关注度的零件颜色自动选取算法,通过鲜明的颜色对比进一步突出用户所关注的装配关系.实验结果证明,该系统有效地提高了用户交互以及装配效率.     

An New Approach to Represent Assembly Sequences

How to identify all feasible assembly sequences and compactly represent them is very important and necessary to computer-aided assembly sequence planning. An approach to get precedence relationships between components directly from assembly modeling is proposed in this paper. A representation method called disassembly sequence graph (DSG) is also presented in this paper. An example has been provided to illustrate the proposed approach.     

Feature-based assembly modeling and sequence generation

A feature-based model is proposed for assembly sequence planning automation. The fundamental assembly modeling strategy for a product is based on the mating features of its components. The objectives of this study are to integrate assembly planning of a product with its CAD model, generate a correct and practical assembly sequence and establish a software system to carry out the planning process. A disassembly approach in assembly planning is used in this study. The degree of freedom information between two mating features is used to characterize their kinematic conditions. Boolean operations of the degrees of freedom on all features of a component provides its local degree of freedom, which is used to set up the functional precedence relation. In some cases, where the functional precedence relation cannot be detected by geometric reasoning, clipping of the known `common sense' relation is applied by a user. A bounding box checking approach is used to ensure no global collision during assembly. Furthermore, a set of criteria based on assembly feasibility, manipulability, assembly direction, cost and stability is used to choose a good assembly sequence.     

设备拆装混合现实系统中的拆装逻辑设计

针对机械部件在拆装过程中存在设备投资大、损耗程度高、危险性大、拆装效率低等问题, 本文采用混合现实技术, 设计出一套虚拟拆装系统. 其中, 拆装逻辑是拆装系统的核心, 拆装系统的通用性取决于拆装逻辑的设计. 为了解决虚拟拆装系统通用性差的问题, 本文通过对常见机械模型的连接方式和装配关系进行分析和总结, 设计出一种基于图遍历算法的数据结构来表达各个模型的逻辑关系, 并针对特种阀门、六关节机械臂等设备的拆装进行实验. 实验结果表明: 该拆装逻辑解决了拆装顺序的可定义和通用性等问题, 能够对模型部件按工艺流程进行虚拟拆解和装配, 最终实现虚拟拆装系统的通用性.     

Selective disassembly for virtual prototyping as applied to de-manufacturing

Selective disassembly involves separating a selected set of components from an assembly. Applications for selective disassembly include de-manufacturing (maintenance and recycling), and assembling. This paper presents a new methodology for performing design for selective disassembly analysis on the CAD model of an assembly. The methodology involves the following three steps: (i) identifying the components to be selectively disassembled for de-manufacturing by a software program or designer, (ii) determining an optimal (e.g. minimal cost) disassembly sequence for the selected components that involves a computationally efficient two-level reduction procedure: (a) the determination of a set of sequences with an objective of minimal component removals via a wave propagation approach that topologically order components in an assembly for selective disassembly, and (b) the evaluation of resulting sequences based on an objective function (e.g. minimal cost) to identify an optimal sequence, and (iii) Performing disassembly design decisions based on the evaluated optimal sequence. Preliminary implementation results of the selective disassembly methodology in sequencing and disassembly cost evaluation, and application of the selective disassembly technique for de-manufacturing assessment are presented.     

Robustness analysis of non-ordinary Petri nets for flexible assembly/disassembly processes based on structural decomposition

Design of robust supervisory controllers for manufacturing systems with unreliable resources has received significant attention recently. Robustness analysis provides an alternative way to analyse a perturbed system to quickly respond to resource failures. Although we have analysed the robustness properties of several subclasses of ordinary Petri nets (PNs), analysis for non-ordinary PNs has not been done. Non-ordinary PNs have weighted arcs and have the advantage to compactly model operations requiring multiple parts or resources. In this article, we consider a class of flexible assembly/disassembly manufacturing systems and propose a non-ordinary flexible assembly/disassembly Petri net (NFADPN) model for this class of systems. As the class of flexible assembly/disassembly manufacturing systems can be regarded as the integration and interactions of a set of assembly/disassembly subprocesses, a bottom-up approach is adopted in this article to construct the NFADPN models. Due to the routing flexibility in NFADPN, there may exist different ways to accomplish the tasks. To characterise different ways to accomplish the tasks, we propose the concept of completely connected subprocesses. As long as there exists a set of completely connected subprocesses for certain type of products, the production of that type of products can still be maintained without requiring the whole NFADPN to be live. To take advantage of the alternative routes without enforcing liveness for the whole system, we generalise the concept of persistent production proposed to NFADPN. We propose a condition for persistent production based on the concept of completely connected subprocesses. We extend robustness analysis to NFADPN by exploiting its structure. We identify several patterns of resource failures and characterise the conditions to maintain operation in the presence of resource failures.     

An Approach to Assembly Sequence Plannning Based on Hierarchical Strategy and Genetic Algorithm

Using group and subassembly cluster methods, the hierarchical structure of a product is ?generated automatically, which largely reduces the complexity of planning. Based on genetic algorithm, the optimal of assembly sequence of each structure level can be obtained by sequence-by-sequence search. As a result, a better assembly sequence of the product can be generated by combining the assembly sequences of all hierarchical structures, which provides more parallelism and flexibility for assembly operations. An industrial example is solved by this new approach.