Workers’ rest allowance and smoothing of the workload in assembly lines

Ergonomic aspects have a crucial role in manual assembly systems. They impact on the workers’ health, final product quality and productivity. For these reasons, there is the necessity to integrate them into the assembly line balancing phase as, whereas, only time and cost variables are considered. In this study, human energy expenditures are considered as ergonomic aspects and we integrate them, for the first time, into the assembly line balancing problem type 2 through the rest allowance evaluation. We consider as an objective function the minimization of the smoothness index. Firstly, a new optimal method based on mixed integer linear programming and a new linearization methodology are proposed. Then, a heuristic approach is introduced. To complete the study, a computational experimentation is presented to validate the mathematical model and to compare the methodologies proposed in terms of computational time, complexity and solution. Additionally, we provide a detailed analysis of the impact that rest allowance evaluation can have on productivity comparing the results obtained, taking into account the rest allowance integration before, during and after the assembly balancing process.     

结构振动试验转接器的设计及安装问题

一些产品及其相关部件在作振动试验时，由于产品的外形或特殊要求不能直接安装在振动台面上，需要通过特别设计的转接器（夹具）来进行连接，这种夹具实际上是一种附加结构，它作为台面与试件之间的中介，如设置不当将影响振动试验结果的可靠性。本文通过对某事例的分析与研究，从试验频带、允许误差、跟随条件以及安装共振频率等方面阐明与讨论了相关夹具的特性、设计原则与安装等问题。     

采用离散元法分析路面结构的疲劳特征

为了在考虑疲劳损伤和恢复性能的基础上,获取路面结构在重复荷载作用下的疲劳特征,采用离散元方法建立了路面结构模型,并分析了在正弦重复荷载作用下路面结构沥青层底部的受力特性.由于路面荷载的随机性,分别以荷载大小、荷载间歇时间、荷载作用次序为考察对象,分析其对路面结构沥青层底受力特征的影响.研究结果表明:随着周期荷载作用次数的增大,沥青层底部拉应力快速增大至某一基础值,并在此基础值附近呈周期性波动,拉应变则在以一定幅值波动的同时,呈现整体水平先急剧增大后缓慢增大的规律;延长荷载作用的间歇时间,虽然一定程度上增大了拉应力和拉应变的波动幅值,但却显著降低了沥青层底拉应力和拉应变的整体水平;不同的荷载作用次序在沥青层底引起的应力应变状态不同,从小至大序列的荷载对沥青层造成的损伤明显小于从大至小序列的荷载.     

支持向量机多分类问题研究

支持向量机是典型的两类分类方法,如何将其推广到多分类问题是学者们正在研究的一个热点。对比分析几种常用的多类方法的优缺点,利用标准数据集对多类支持向量机的速度和精度两方面进行试验分析。研究表明,对于大规模的多类分类问题,有向无环图简单易行,具有理想的训练速度与精度,具有一定的参考价值。     

开卷机剩余长度计算与自动减速原理

在唐钢彩涂入口段,为了保证生产的连续性,当开卷机带钢即将没有的时候,需要自动减速停车,使带尾停在合适的位置,以方便接下来的操作。为达到自动减速,必须准确计算出开卷机的剩余长度,从而准确地确定自动减速时机。因此,介绍了开卷机剩余长度计算与自动减速原理。开卷机的剩余长度计算方法的应用很广,此计算方法也可应用与出口卷曲机的长度计算和其他相关的生产线中的长度计算,对保证生产的连续及操作的简化都起着重要的作用。     

共振仪共振相位差测量系统设计

针对波尔共振仪的共振相位差测量,提出了同步跟随相位测量方法.设计了一套跟随振动系统摆盘的受控刻度盘系统,刻度盘以振动系统的摆盘的最大转速为转动速度,刻度盘上的任意一点在水平方向的投影与振动系统摆盘的摆动为等效的振动.完整的同步跟随相位测量系统由振动系统摆盘测量系统、受控刻度盘系统和驱动同轴盘测量系统组成.同步跟随刻度盘根据振动系统摆盘测量系统所采集的数据取代摆盘,并与驱动同轴盘同轴,当同步跟随的刻度盘与振动系统摆盘达到同步时,在共振发生时同步跟随的刻度盘和驱动同轴盘也几乎同步转动,所以驱动同轴盘零指针总指向同步跟随的刻度盘一个相位值,驱动同轴盘与刻度盘之间给出相位差.同步跟随相位测量方法将不受环境因素影响,便于在不同照明条件下布置多台实验仪器.     

JF132型克劳斯惯性台架式摩擦材料试验机电-液伺服系统设计

介绍了ＪＦ１３２型克劳斯试验机电－液伺服系统的组成、特点及工作原理，建立了系统的动态方程及结构方框图；分析了系统动态响应频率和阻尼比，提出了系统的校正方法，并探讨了应用电－液比例阀的可能性；通过对稳态误差的分析，指出制动器安装的正确与否将直接影响系统的测试精度。     

浅析转动小刀架车削圆锥零件的技巧

转动小刀架车削圆锥零件是普通车床加工圆锥体最常见的方法。为了提高普通车床采用转动小刀架车削圆锥零件的加工质量和效率,本文从几个方面浅谈一下转动小刀架车削圆锥零件的技巧。     

Reliability of different thresholds for defining muscular rest of the trapezius muscles in computer office workers

This study aimed at documenting the reliability of different thresholds used for defining the muscular rest of the trapezius muscles of 27 computer office workers, using surface electromyography (EMG) signals collected in the field. Measurement strategies for increasing the reliability of the results were also explored. Ten different thresholds to define muscular rest were compared: 1) five normalised (individualised) thresholds; 2) three absolute thresholds (in μV); 3) two absolute but individualised thresholds. The reliability was assessed using both a 15-min standardised computer task and 45 min of regular computer work. The main findings were: 1) overall, in a repeated measures study design, muscular rest variables were more reliable with the use of absolute thresholds when compared to normalised and individualised thresholds; 2) excellent reliability (index of dependability >0.75) can be reached when averaging the scores over 2 days; 3) using a standardised task instead of regular work does not necessarily lead to more reliable results.     

Additional effort estimation due to ergonomic conditions in order picking systems

Within a warehouse, the picking activity often relies on human operators. Therefore, when designing and evaluating a manual picking system, it is important to consider that, besides the high flexibility the pickers are able to warrant, they inevitably require an additional effort due to their ergonomic working conditions. In this paper, the authors propose a new model to consider such additional effort, starting from the concepts of human availability and rest allowance. The new method allows the evaluation of the current configuration of a certain warehouse, considering two different operative situations (directly employed operators and indirectly employed ones). Moreover, it makes it possible to estimate and to understand the benefits that can be achieved by introducing some ergonomic improvements. The proposed procedure has also been applied to a real industrial case study.