Nonlinear dynamical systems for theory and research in ergonomics

Abstract

Nonlinear dynamical systems (NDS) theory offers new constructs, methods and explanations for phenomena that have in turn produced new paradigms of thinking within several disciplines of the behavioural sciences. This article explores the recent developments of NDS as a paradigm in ergonomics. The exposition includes its basic axioms, the primary constructs from elementary dynamics and so-called complexity theory, an overview of its methods, and growing areas of application within ergonomics. The applications considered here include: psychophysics, iconic displays, control theory, cognitive workload and fatigue, occupational accidents, resilience of systems, team coordination and synchronisation in systems. Although these applications make use of different subsets of NDS constructs, several of them share the general principles of the complex adaptive system.

Practitioner Summary: Nonlinear dynamical systems theory reframes problems in ergonomics that involve complex systems as they change over time. The leading applications to date include psychophysics, control theory, cognitive workload and fatigue, biomechanics, occupational accidents, resilience of systems, team coordination and synchronisation of system components.     

A shuffled frog-leaping algorithm for flexible job shop scheduling with the consideration of energy consumption

Flexible job shop scheduling problem (FJSP) has been extensively investigated and objectives are often related to time. Energy-related objective should be considered fully in FJSP with the advent of green manufacturing. In this study, FJSP with the minimisation of workload balance and total energy consumption is considered and the conflicting between two objectives is analysed. A shuffled frog-leaping algorithm (SFLA) is proposed based on a three-string coding approach. Population and a non-dominated set are used to construct memeplexes according to tournament selection and the search process of each memeplex is done on its non-dominated member. Extensive experiments are conducted to test the search performance of SFLA and computational results show the conflicting between two objectives of FJSP and the promising advantages of SFLA on the considered FJSP.     

Handling the complexities of real-life job shops when implementing workload control: a decision framework and case study

The workload control literature highlights the importance of balancing the shop floor workload, but also acknowledges that this can conflict with processing the most urgent orders – hence, there is a trade-off. In practice, shops contain many complexities, e.g. simultaneous batching and sequence-dependent set-up times that may conflict with processing the most urgent orders and require other solutions than workload balancing to avoid capacity losses. This adds to the trade-off dilemma, which traditionally only considers timing and balancing. This paper develops a framework that determines whether to address a complexity through order release or dispatching. It comprises two dimensions: (i) the typical position of a complexity in the routing of an order and (ii) the criticality of the complexity. A case study is presented, which demonstrates the framework’s utility and illustrates the development of specific solutions designed to handle the complexities. Most complexities present in the case require handling at the order release stage. The challenges of handling multiple complexities at this decision level are evaluated. Finally, the implications for managers and future research are outlined.     

基于随机模型预测控制的数据中心微电网能量优化调度研究

针对数据中心负荷的随机性和可再生能源出力的不确定性,为保证数据中心在实际运行中的稳定性和经济性,提出了一种基于随机模型预测控制的数据中心微电网能量优化调度方法。引入场景分析法描述不确定因素,以数据中心运行成本最低为目标建立优化模型,通过模型预测控制的滚动优化和反馈校正,协调系统内各设备的出力情况,减小数据中心的运行成本,并降低不确定因素对其运行产生的不良影响。以某个典型数据中心微电网系统为例进行仿真分析,仿真结果验证了所提方法的有效性。     

The relationship between physical workload and quality within line-based assembly

Reducing costs and improvement of product quality are considered important to ensure productivity within a company. Quality deviations during production processes and ergonomics have previously shown to be associated. This study explored the relationship between physical workload and real (found during production processes) and potential (need of extra time and assistance to complete tasks) quality deviations in a line-based assembly plant. The physical workload on and the work rotation between 52 workstations were assessed. As the outcome, real and potential quality deviations were studied during 10 weeks. Results show that workstations with higher physical workload had significantly more real deviations compared to lower workload stations. Static work posture had significantly more potential deviations. Rotation between high and low workload was related to fewer quality deviations compared to rotation between only high workload stations. In conclusion, physical ergonomics seems to be related to real and potential quality deviation within line-based assembly.

Practitioner Summary: To ensure good productivity in manufacturing industries, it is important to reduce costs and improve product quality. This study shows that high physical workload is associated with quality deviations and need of extra time and assistance to complete tasks within line-based assembly, which can be financially expensive for a company.     

数据中心电费最小化的负载调度策略

为了降低电费成本,一些数据中心使用绿色能源供电。然而,负载的波动性和电价的时间差异性给数据中心电费成本带来了挑战。针对上述问题,提出一种低成本的负载调度算法,使得数据中心电费最小化。首先,建立电力耗费模型;然后,将电费最小化问题形式化为一个多目标约束的优化问题;最后,求解该优化问题得到相应的负载调度策略。实验结果表明:该算法可以在保证负载性能的前提下,有效降低数据中心的电费成本。     

A defeasible reasoning framework for human mental workload representation and assessment

Human mental workload (MWL) has gained importance in the last few decades as an important design concept. It is a multifaceted complex construct mainly applied in cognitive sciences and has been defined in many different ways. Although measuring MWL has potential advantages in interaction and interface design, its formalisation as an operational and computational construct has not sufficiently been addressed. This research contributes to the body of knowledge by providing an extensible framework built upon defeasible reasoning, and implemented with argumentation theory (AT), in which MWL can be better defined, measured, analysed, explained and applied in different human–computer interactive contexts. User studies have demonstrated how a particular instance of this framework outperformed state-of-the-art subjective MWL assessment techniques in terms of sensitivity, diagnosticity and validity. This in turn encourages further application of defeasible AT for enhancing the representation of MWL and improving the quality of its assessment.     

以瓶颈为中心多层次负荷集成的订单交货期预测方法

针对MTO(make-to-order)生产环境下的订单交货期预测问题,提出了一种集成订单接收、订单投放与车间调度等多层次负荷,以瓶颈为中心的订单交货期预测(bottleneck driven due-date forecasting, BDDF)方法。该方法先根据订单是否通过瓶颈,分类估计“鼓链”与“非鼓链”订单在不同层次的负荷,同时利用Little’s法则估计各个层次的通过时间,求和得到订单的交货期。运用FlexSim建模仿真比较了BDDF方法与两种经典交货期预测方法在不同订单池排序规则、车间调度规则以及保护产能水平组合下的系统绩效。结果表明,BDDF方法在拖期率、平均拖期以及延期标准差指标上均优于两种经典方法。同时,订单池排序规则、调度规则以及保护产能水平都会影响BDDF方法的系统绩效,需要根据实际情况选择合适的参数,以更好地控制订单交货期,避免订单延期。     

成像侦察任务流重构与调峰方法研究

针对成像侦查任务流非均匀并发、任务峰值过高与卫星资源能力有限的情况,研究成像侦察任务流重构与调峰方法,并平滑任务流曲线,为任务规划提供更合理的任务资源映射集。考虑成像侦察任务和任务流的特点,提出成像侦察任务时间区间需求度和资源负载的计算方法,设计成像侦察任务流重构的规则与算法,成像侦察任务流调峰的规则与算法。通过仿真实例验证任务流重构与调峰规则算法的有效性。     

不同天气状况下驾驶员驾驶工作负荷分析

为有效提高驾驶员在不良天气条件下的运行安全,针对晴天、中雨、中雨+雾(能见度100 m)和中雨+雾(能见度50 m)4种不同驾驶条件,利用心率变异性(HRV)指标,对驾驶员驾驶工作负荷特性进行研究.通过随机抽取3名驾驶员,在室内进行对于高速公路不同天气场景的仿真实验,对获得的数据进行统计分析发现,驾驶员在不同天气条件下驾驶工作负荷是有差异的,驾驶工作负荷随天气条件的恶劣程度增加,驾驶环境的能见度对驾驶员驾驶工作负荷影响最大.