单输入多输出耦合设计任务二阶段迭代模型研究

产品开发过程中单输入多输出耦合设计任务间存在复杂的信息依赖关系。采用单阶段方法的任务执行方式时,因所执行的任务数量多并且需传递的信息量大,致使任务间存在的复杂信息关系难以被理清,从而导致任务执行过程中的方案分配不够合理,任务间的迭代返工次数过多,产品开发周期过长。针对这些问题,在深入分析单输入多输出耦合设计任务单阶段迭代模型的基础上,提出了一种任务迭代过程中的信息处理策略,并构建了一种单输入多输出耦合设计任务的二阶段迭代模型及其求解执行时间的数学模型。应用该数学模型,可以计算得到最佳二阶段设计任务分配方案。以某发动机开发项目为例,进行了该方法的应用分析。研究表明,采取二阶段迭代模型,任务迭代执行时间比单阶段短,并且通过合理分配在1,2两个阶段执行的任务,能够获得最短的二阶段任务迭代执行时间。该方法根据任务间不同的信息关系选择合适的任务迭代模型,能够有效缩短产品开发周期,可为产品设计人员在产品开发过程中选择合理的任务执行方式提供一定的理论参考。     

Research on a two-stage iterative model of coupling design task with single input and multiple output北大核心CSCD

In the process of product development, there is a complex information-dependent relation between coupling design tasks with single input and multiple output. Because of the large amount of executed tasks and transmitted information, the complicated relationship between these tasks is hard to be sorted out by using the single-stage task execution method, which may lead to problems such as the unreasonable allocation of tasks in the process of task execution, excessive iteration rework times between tasks and too long product development cycle. To solve these problems, an information processing strategy for the task iteration was put forward, and a two-stage iteration model and the mathematical model of calculating task execution time were built based on the deep analysis of a single-stage iteration model for the coupling design task with single input and multiple output. The best two-stage task allocation scheme was obtained by working out this mathematical model. The effectiveness of this method was proved through the example of an engine development project. The results showed that the iterative execution time of tasks was shorter than single-stage by using the two-stage iteration model and the shortest iterative execution time of the two-stage iteration model could be obtained by reasonably assigning tasks into two phases. The method selects the appropriate task iterative model according to the different information relations between tasks, which can effectively shorten the product development cycle and provide some theoretical reference for product designers to choose reasonable task execution way in the process of product development.     

An ant colony optimisation algorithm for balancing two-sided U-type assembly lines with sequence-dependent set-up times

Some practical arrangements in assembly lines necessitate set-up times between consecutive tasks. To create more realistic models of operations, set-up times must be considered. In this study, a sequence-dependent set-up times approach for two-sided u-type assembly line (TUAL) structures is proposed for the first time. Previous studies on TUAL have not included set-up times in their analyses. Furthermore, an algorithm based on the Ant Colony Optimization (ACO) algorithm, which is using a heuristic priority rule based procedure has been proposed in order to solve this new approach. In this paper, we look at the sequence-dependent set-up times between consecutive tasks and consecutive cycles, called the “forward set-up time” and the “backward set-up time”, respectively. Additionally, we examine the “crossover set-up time”, which arises from a new sequence of tasks in a crossover station. In order to model more realistic assembly line configurations, it is necessary to include sequence-dependent set-up times when computing all of the operational times such as task starting times and finishing times as well as the total workstation time. In this study, the proposed approach aims to minimize the number of mated-stations as the primary objective and to minimize the number of total workstations as a secondary objective. In order to evaluate the efficiency of the proposed algorithm, a computational study is performed. As can be seen from the experimental results the proposed approach finds promising results for all literature-test problems.     

Increasing production rate in U-type assembly lines with sequence-dependent set-up times

U-shaped assembly lines are commonly used in just-in-time production systems as they have some advantages over straight lines. Although maximizing production rates on these lines by assigning tasks to stations is common practice in industrial environments, studies on the stated assembly line balancing problem are limited. This article deals with maximizing the production rate on U-shaped assembly lines under sequence-dependent set-up times. Sequence-dependent set-up times mean that after a task is performed, a set-up time, the duration of which depends on adjacent tasks, is required to start the next task operation. These set-ups are considered by dividing them into two groups, named forward and backward set-ups, to make the problem more practical. Two heuristics based on simulated annealing and genetic algorithms are improved beside the mathematical model. Experimental results show that solving the stated problem using the mathematical model is nearly impossible, while heuristics may obtain solutions that have acceptable deviations from the lower bounds.     

Introducing new parts into existing cellular manufacturing systems based on a novel similarity coefficient

Over the last three decades, designing cellular manufacturing systems (CMS) still centres on assigning machines to machine cells and parts to part families. This task ends after assigning these part families to the appropriate machine cells. In the past, testing CMS was evaluated according to the efficiency of clustering, but actual testing of CMS after installation is still unexplored. Introducing one or more new parts (products) into CMS without any changes in the installation of the cells during processing of the current parts is a new concept to be considered and evaluated. Transferring these systems from traditional ideologues to advanced ideologues (agile systems) is highly desired. This concept can be considered as part (product) flexibility in CMS. To address this concept, a new similarity coefficient between the new part and the existing manufacturing cell will be created. New productivity and flexibility measurements in CMS will also be suggested. A new strategy for accepting a new part into CMS will be proposed based on machine utilization and flexibility in the cells, cell utilization and flexibility in the system, product flexibility (system flexibility), and similarity of this part with existing manufacturing cells. A complete analytical example will be presented.     

A heuristic model for dynamic flexible job shop scheduling problem considering variable processing times

In real scheduling problems, unexpected changes may occur frequently such as changes in task features. These changes cause deviation from primary scheduling. In this article, a heuristic model, inspired from Artificial Bee Colony algorithm, is proposed for a dynamic flexible job-shop scheduling (DFJSP) problem. This problem consists of n jobs that should be processed by m machines and the processing time of jobs deviates from estimated times. The objective is near-optimal scheduling after any change in tasks in order to minimise the maximal completion time (Makespan). In the proposed model, first, scheduling is done according to the estimated processing times and then re-scheduling is performed after determining the exact ones considering machine set-up. In order to evaluate the performance of the proposed model, some numerical experiments are designed in small, medium and large sizes in different levels of changes in processing times and statistical results illustrate the efficiency of the proposed algorithm.     

基于支持向量机的产品感性意象值预测方法

为设计出符合消费者感性需求的产品,提出基于支持向量机的产品感性意象值预测方法。先确定产品的感性意象、造型设计要素以及感性评价矩阵。在此基础上,以造型设计要素为自变量,以感性意象评价值为因变量,利用LIBSVM软件,通过对惩罚函数、不敏感损失函数以及核函数等相关参数的分析设置,建立产品感性意象值的预测模型。结合办公座椅进行研究,结果表明支持向量机具有较高的预测精度,所提出的方法是正确可行的。     

A case for information theory-based modelling of human multitasking performance

Technological advances have led to increased prevalence of human multitasking. Traditionally, multitasking performance is measured for each individual task, utilising multiple performance metrics. Recently, the human operator informatic model (HOIM) has been developed as a quantitative model of human–machine interaction capable of measuring multitasking performance with a single metric. In this study, we investigated the performance effects of both a different number of tasks and five different task combinations while maintaining a constant level of overall difficulty. Results indicate that, at a constant difficulty level, neither number of tasks nor task combination significantly affects multitasking performance, indicating the reliability of input baud rate as a measure of system complexity. No task interaction effects were found among the different tasks. This study demonstrates the application of information theory for modelling of human multitasking performance and makes a case for the use of the HOIM in future studies of human information processing.     

An exact solution approach for disassembly line balancing problem under uncertainty of the task processing times

The purpose of this work is to efficiently design disassembly lines taking into account the uncertainty of task processing times. The main contribution of the paper is the development of a decision tool that allows decision-makers to choose the best disassembly alternative (process), for an End of Life product (EOL), and assign the corresponding disassembly tasks to the workstations of the line under precedence and cycle time constraints. Task times are assumed to be random variables with known normal probability distributions. The case of presence of hazardous parts is studied and cycle time constraints are to be jointly satisfied with at least a certain probability level, or service level, fixed by the decision-maker. An AND/OR graph is used to model the precedence relationships among tasks. The objective is to minimise the line cost composed of the workstation operation costs and additional costs of workstations handling hazardous parts of the EOL product. To deal with task time uncertainties, lower and upper-bounding schemes using second-order cone programming and approximations with convex piecewise linear functions are developed. The applicability of the proposed solution approach is shown by solving to optimality a set of disassembly problem instances (EOL industrial products) from the literature.     

Machine cell formation for production management in cellular manufacturing systems

The formation of machine-part families is an important task in the design of cellular manufacturing systems. Manufacturing cell grouping has the effect of reducing material handing cost and work in process. Among the many methods utilized in machine cells formation, the similarity coefficient method is most widely used. Production sequence and product volumes, if incorporated properly in determining the machine cells, can enhance the quality of solutions and reduce the number of intercellular movements. Measures for cell formation based on operations sequence utilizing ordinal production data are few and have many limitations, such as counting the number of the trips for each individual part instead of counting the weights of the batches. A new ordinal production data similarity coefficient based on the sequence of operations and the batch size of the parts is introduced. Furthermore, a new clustering algorithm for machine cell formation is proposed. The new similarity measure showed more sensitivity to the intercellular movements and the clustering algorithm showed better machine grouping.     

Sequence dependent set-up times and job sequencing

On many machine tools the set-up times are sequence dependent; that is, the time to set-up for the new part is dependent upon the part for -which the machine is currently set-up. In scheduling lots on the machine, the set-up time is often a significant component of the total time required to complete each lot. Set-up times are frequently not available to the production scheduler, and when they are, they frequently are only averages which conceal the sequence dependency of the set-up times. In this paper, we first develop a procedure that classifies set-up operations and predicts the set-up times and we then develop a method for sequencing the jobs so as to minimize the total set-up time. An example using real world data is used to illustrate these procedures     

Research on rush order insertion rescheduling problem under hybrid flow shop based on NSGA-III

Rush order insertion is widespread in the enterprises that apply make-to-order production mode which affects the stability of production system. This article studies rush order insertion rescheduling problem (ROIRP) under hybrid flow shop (HFS) with multiple stages and multiple machines. A mathematical model simultaneously considering constraints such as lots, sequence-dependent set-up times and transportation times with objectives to minimise makespan, total transportation time and total machine deviation between the initial scheduling plan and the event-driven rescheduling plan is developed and NSGA-III is applied to solve the problem. Three groups of experiments are carried out which verify the suitability of NSGA-III for HFS scheduling problem with multi-objective and multi-constraint, the effectiveness of NSGA-III for the proposed ROIRP and the feasibility and effectiveness of the proposed model and algorithm in solving the ROIRP of a realistic ship pipe parts manufacturing enterprise.     

Multiperiod production planning carrying over set-up time

Set-ups eat production capacity time and continue troubling production planning, especially on bottlenecks. The shortening of production planning periods to days, shifts or even less has increased the relative length of set-up times against the periods. Yet, many production planning models either ignore set-up times or, paradoxically, split longer multiperiod batches by adding set-ups at breaks between planning periods. The MILP-based capacitated lot-sizing models that include set-up carry-overs, i.e. allow a carry-over of a set-up of a product to the next period in case a product can be produced in subsequent periods, have incorporated fixed set-up fees without consideration of capacity consumed by set-up time. Inspired by production planning in process industries where set-up times still remain substantial, we incorporated set-up time with associated cost in two modifications of carry-over models. Comparison with an earlier benchmark model without set-up carry-over shows that substantial savings can be derived from the fundamentally different production plans enforced by carry-overs. Moreover, we show that heuristic inclusion of carry-overs by removal of set-ups from non-carry-over solutions is inefficient.     

A mathematical programming model for reconfiguration of flexible manufacturing cells

In flexible manufacturing cells, changes in demand size, product mix, part variety, existing routings and set-up/operation times may require reconfiguration of the cells. In this study, an approach is developed to decide when and how such a reconfiguration should be carried out for existing cells. This study considers reconfiguration in terms of changing part routings, adding a new machine type in a cell, duplicating an existing machine type, removing an existing machine from a cell and transferring a machine to another cell. The study also shows the total number of tools of each type on each machine located in each cell after reconfiguration. To make the optimal reconfiguration decisions, a mathematical programming model to minimize the total reconfiguration cost is developed. The developed model considers the lower and upper bounds on machine utilizations and the time limits on machine cycle times to decide when to reconfigure the system.     

Effective two-phase p-median approach for the balanced cell formation in the design of cellular manufacturing system

In this paper, we present an effective two-phase p-median approach for the balanced cell formation (CF) in the design of cellular manufacturing system. In phase 1, the p-median mathematical model of machine CF, which adopts a linear integer programming formulation, is developed. Our formulation uses a new similarity coefficient based on the generalised nonbinary part-machine incidence matrix (PMIM) which incorporates realistic manufacturing aspects such as setup time, processing time, operation sequences and lot size of parts and duplicate machine types. In phase 2, a systematic part assignment procedure based on the new classification scheme of part types is established in pursuit of balancing the workload among machine cells. New efficiency measures for evaluating the quality of the binary and nonbinary PMIM-based block diagonal solutions are proposed to judge the degree of cell load imbalance. Computational experiments with moderately intermediate-sized data-sets selected from the literature show effectiveness of our two-phase p-median approach for the balanced CF.     

认知老化视角下健康管理终端的多层次任务交互设计研究

目的 为提升老年群体居家场景下的慢病健康管理体验,聚焦认知老化现象,提升不同操作任务与认知需求的适配度,优化家庭健康管理终端产品交互设计。方法 通过文献查阅归纳老年人在认知活动中感知觉、智力、情感等相关特征要素,完成认知老化特征向设计指标映射;与此同时,引入SRK认知理论及其决策图,对设计载体完成关键任务分层;进一步将上述设计指标与任务层级作为模型变量,通过问卷数据分析,构建结构方程模型并获取分析结果,明确不同任务层级下的设计指标权重。结论 以家庭健康管理产品交互设计为例,通过结构方程模型分析,发现感官性体验对完成技能型任务具有显著正向影响、感官性体验和可用性体验对完成规则型任务具有显著正向影响、感官性体验和可用性体验及情感性体验均对知识型任务有显著正向影响,并获取每个体验维度中应重点关注的评价指标。实现从不同任务类型的角度分层次优化交互体验,为居家场景下的医疗健康管理产品适老化交互设计提供理论参考。     

Dynamic allocation of communicating tasks in computational grids

This paper studies task allocation in computational grids operating in a dynamic and uncertain environment. Computational grids consist of loosely coupled heterogeneous resources or agents with finite buffer capacities. These grids are primarily used to process large-scale applications consisting of several interdependent tasks. The task allocation problem is modeled as an infinite horizon Markov decision process, with the resource service times and the task arrivals following general probability distributions. We explicitly consider the communication cost between agents incurred in coordinating the execution of interdependent tasks. We show that a stationary optimal policy exists for this task allocation problem. Furthermore, we develop an action elimination procedure for reducing the complexity of computational methods in finding the optimal policy. We also present a real-time heuristic policy based on certain structural properties of the problem. Finally, computational results are presented that compare the performance of the heuristic policy with respect to other approaches for allocating tasks in the grid. Results from this paper are also applicable to the task allocation problem in manufacturing and service areas such as distributed design, project management and supplier coalitions.     

Assembly sequence planning for processes with heterogeneous reliabilities

Stochasticity in assembly processes is often associated with the processing time and availability of machinery, tools and manpower, however in this paper it is determined by probability of an assembly task successful completion which here is referred to as task reliability. We present a mathematical model for optimising the expected assembly cost, and consider two scenarios: the first a situation where a failure of one assembly task requires rework of that task alone; second a situation in which a failure in the midst of the process requires resumption of previously completed tasks. In the worst case scenario the assembly process must restart from the beginning. We show that the first scenario is insensitive to sequencing unless there are set-up costs. In the second scenario the process is sensitive to tasks’ sequence. We present a heuristic that argues for accomplishing more uncertain tasks (with less reliability) earlier in the process to decrease the expected cost of assembly, and show that in a mutually dependent assembly process, when tasks’ reliabilities are similar, the cheaper tasks should be executed earlier in the process.     

基于实时装配状态感知和直观性交互的虚拟现实辅助维修训练

为了提高虚拟维修训练时零件的定位精度,丰富人机交互功能,反映贴近实际的操作过程,提高操作者的训练质量,基于虚拟现实辅助技术,研究了装配约束感知与建立算法,可实现根据当前的装配状态实时建立正确的装配约束.基于直观性交互建立了"导师&助教"多模式指导方法.在Unity3D环境中开发了虚拟手、虚拟工具的无标记交互操作方式,并...     

基于边向量斜率比较的简单多边形顶点凸凹性快速判别算法

对于给定的平面简单多边形顶点序列,判别多边形方向和顶点凸凹性的传统方法为:先计算多边形相邻边向量的叉积或相邻3个顶点所确定三角形的有向面积,再由叉积或有向面积的符号来确定顶点的凸凹性,使得处理一个顶点需要2次以上的乘法运算。笔者通过边向量斜率的计算和比较,将多边形顶点的凸凹性与边向量的斜率联系起来,并采用“假设-检验”方法,提出了一种快速判别简单多边形方向与顶点凸凹性的新算法,其时间复杂度为)(nO,判别多边形任一顶点凸凹性所需的乘法运算平均不超过1次。该算法原理直观简单,实现容易。实际运行结果表明,该算法速度快捷、运行稳定。