Development of a situation awareness measure to evaluate advanced alarm systems in nuclear power plant control rooms

The process controller is required to remain updated regarding developments in the dynamically changing process state, this being referred to as the maintenance of situation awareness. Alarm systems play an important role within this task, and therefore a measure of how effective the system is for enhancing the operator's situation awareness is desirable. One proposed measure is the Situation Awareness Control Room Inventory (SACRI). The methods and results of four simulator studies undertaken to develop and evaluate SACRI are outlined in this paper. It is concluded that SACRI is of use alongside measures such as detection time and diagnostic accuracy in simulator-based evaluations of alarm system design.     

Implementation of supervisory control using extended finite-state machines

This article aims at bridging the gap between traditional designs to discrete-event control problems and supervisory control theory of Ramadge and Wonham. We propose to implement supervisory control by extending the plant's finite state machine with Boolean variables, guard formulas and updating functions. Boolean variables are used to encode the supervisor's states, event observation is captured by a set of Boolean functions that update the value of variables, and control is introduced by guarding events with Boolean formulas. The framework developed in this work is fundamental in our ongoing research on communication between supervisors in a distributed discrete-event system.     

The impact of computer-based procedures on team performance,communication, and situation awareness

In nuclear power plants, operating procedures are adopted to aid the operators in performing their tasks. With the evolution of computer hardware and software, the analog human-machine systems of the main control room in the nuclear power plant have been replaced with digital systems. Moreover, automated operations now outnumber manual operations. The purpose of this study was to evaluate the impact of computer-based procedures on the team performance, communication, and situation awareness of operators in the main control room. To achieve the purpose, a within-subjects experiment was designed and then a survey was conducted. The results showed that the teams had better objective performance and higher situation awareness when using computer-based procedures. In addition, the teams also had lower human error and lower communication rates when using computer-based procedures. This study proposes that computer-based procedures are advantageous to the operation of the systems of the main control rooms in nuclear power plants.Relevance to industryComputerized procedures system is one of the specific features for advanced nuclear power plant. This study explores and analyzes the team performance, communication, and situation awareness difference between paper-based, electronic, and computer-based procedures in detail. It may provide practical information for how to apply computer-based procedures to perform the tasks in the main control room of the advanced nuclear power plant.     

Comparative study of three training methods for enhancing process control performance: Emphasis shift training,situation awareness training,and drill and practice

Three training methods to improve attention management skills in process control were compared. Forty students from technical disciplines participated in a five-hour module of emphasis shift training (EST), EST combined with situation awareness training (EST/SA), and drill and practice (D&P) on a simulated process control task. Participants were then tested three times for 45 min each (immediately after training, two weeks after training, and six weeks after training) for system control performance and diagnostic performance on familiar and nonfamiliar fault states. D&P led to superior diagnostic performance on familiar system faults. EST/SA training supported the diagnosis of novel system faults. EST was less effective than expected for system control performance. Implications for training design in process control are discussed.     

Simulation-based evaluation of an in-vehicle smart situation awareness enhancement system

Situation awareness (SA) constitutes a critical factor in road safety, strongly related to accidents. This paper describes the evaluation of a proposed SA enhancement system (SAES) that exploits augmented reality through a head-up display (HUD). Two SAES designs were evaluation (information rich vs. minimal information) using a custom-made simulator and the Situation Awareness Global Assessment Technique with performance and EEG measures. The paper describes the process of assessing the SA of drivers using the SAES, through a series of experiments with participants in a Cave Automatic Virtual Environment. The effectiveness of the SAES was tested in a within-group research design. The results showed that the information rich (radar-style display) was superior to the minimal (arrow hazard indicator) design and that both SAES improved drivers’ SA and performance compared to the control (no HUD) design.

Practitioner Summary: Even though driver situation awareness is considered as one of the leading causes of road accidents, little has been done to enhance it. The current study demonstrates the positive effect of a proposed situation awareness enhancement system on driver situation awareness, through an experiment using virtual prototyping in a simulator.     

Who benefits from simulator training: Personality and heart rate variability in relation to situation awareness during navigation training

Objective

This study tested the relationship between individual differences and Situation Awareness (SA) during training in a navigation simulator.

Background

Simulators have become an important tool in the training and education of maritime personnel with a view to improving decisions and performance. There are a few, inconclusive empirical studies that have focused on mapping personality characteristics and their link to the ability to generate and maintain SA during simulator training.

Method

Thirty-six first-year students from the Royal Norwegian Navy Officer Candidate School participated in the study. SA was measured using both subjective and observer ratings.

Results

The results indicated that low scores on Neuroticism and high scores on Extraversion and Conscientiousness (resilient personality type) predicted both subjective and observer-rated SA. Furthermore, participants with high SA were able to modulate their Heart Rate Variability (HRV), with suppression of HRV during navigation training as well showing recovery of HRV.

Application

The potential applications of this research include the assessment of personality differences as a tool in selecting navigators, and the use of HRV as an objective index of adaptability to environmental demands.     

Mechanisms for maintaining situation awareness in the micro-neurosurgical operating room

Interactions in micro-neurosurgical operating rooms form a complex orchestration of labor and information flows. In the center, there is the focus on patient safety and outcome quality in shortest possible time, while a neurosurgeon is fully focused on the task using a surgical microscope. To guarantee a successful outcome, maintaining a high level of situation awareness (SA) is essential. Suspension of action due to instrument exchange, interaction with a device, or communication affects information flows and collaboration. Situation awareness underlies these interactions. To further understand the mechanisms of SA, we used observations and interviews to gain insight into interactions in micro-neurosurgical theaters. We describe behaviors and strategies exhibited to maintain the interaction flow, in particular, between the scrub nurse and the surgeon. Results show how interactions based on action prediction and active observation within the well-organized environment are influenced, both positively and negatively, by the reliance of the work on the microscope. From this understanding, we discuss the opportunities in future technologies and interfaces for supporting situation awareness maintenance in operating rooms.     

离散事件系统的混合分散监控

研究了混合信息下的分散监控综合问题.首先提出δ-可观察(hδ-可观察)可控闭语言是(状态部分可观察下)状态反馈综合解存在的充要条件,并由此得到n-联合可观察、可控闭的系统约束是保证混合分散监控器存在的充要条件,进而得到纯分散监控器(控制器)存在的充要条件为n-可观察(n-hδ-可观察)可控闭语言被满足.最后,又通过研究系统约束与混合约束的关系,提出混合分散监控器存在的充分条件是可观察、可控闭语言与可观察可控谓词被满足.     

工控网络安全态势感知算法实现

为了探知工控系统的网络安全态势,准确判断系统运行状况,提出了安全态势感知方法.针对已有的完整性攻击研究,建立基于拜占庭将军问题的工控网络安全态势感知模型以及相应的安全态势感知算法.本文提出的算法主要通过三个部分实现:首先对控制回路内的各节点信息进行采集与处理,得到系统中各节点状态;然后,利用所得节点状态,执行算法流程,确定系统内存在的恶意节点;最终获取准确的工控网络安全态势.实验结果表明:该态势感知模型与算法能准确提炼系统中的恶意节点并判断当前系统安全态势.     

Improving situation awareness in crisis response teams: An experimental analysis of enriched information and centralized coordination

In responding to an emergency, the actions of emergency response teams critically depend upon the situation awareness the team members have acquired. Situation awareness, and the design of systems to support it, has been a focus in recent emergency management research. In this paper, we introduce two interventions to the core processes of information processing and information sharing in emergency response teams to analyze their effect on the teams’ situation awareness: (1) we enrich raw incoming information by adding a summary of the information received, and (2) we channel all incoming information to a central coordinator who then decides upon further distribution within the team. The effect of both interventions is investigated through a controlled experiment with experienced professional responders. Our results show distinctly different effects for information enrichment and centralization, both for the teams and for the coordinators within the team. While the interaction effects of both conditions cannot be discerned, it is apparent that processing non-enriched information and non-centralized information sharing leads to a worse overall team situation awareness. Our work suggests several implications for the design of emergency response management information systems.     

Alarm-initiated activities: an analysis of alarm handlingby operators using text-based alarm systems in supervisory control systems

Alarms constitute a significant aspect of the operator-system interface in human supervisory control tasks: they have the potential to display information that is of critical importance to overall system safety and integrity. This paper considers the trend toward the use of visual display terminals for the presentation of alarms, specifically in the use of scrolling text displays. It is suggested that this form of information display may not best serve all aspects of alarm handling. To illustrate why this is so, an analysis of human alarm handling activities is presented. The focus on text-based displays and annunciators allows the authors to concentrate on a number of problems associated with the alarm design using a specific medium. From this discussion, the alarm initiated activities model is developed. By considering the activities that people engage in when dealing with alarms, an insight is offered into the information requirements that can be used to inform the design of alarm systems.     

Analysis of information exchange activities to actualize and validate situation awareness during shift changeovers in nuclear power plants

Shift work situations occur in almost all safety‐critical organizations, and the investigations of some catastrophes like Chernobyl, Exxon Valdez, and the Gol/Legacy mid‐air collision indicated that shift work information exchange played an important role during the evolution of the situation before the accidents. Inadequate communications during shift changeovers challenged operators' work in the moments that preceded these accidents, because they got inadequate information about the current situation. Our research focuses on the information exchange activities (verbal, written, and nonverbal) of nuclear power plant control operators during shift changeovers. Our aim is to investigate how verbal exchanges and other representations enable operator crews to share information regarding the events that occurred in the previous shift to achieve adequate situation awareness. Our findings indicated the importance and richness of the information exchange during the shift changeover process to update and validate individual and collective situation awareness, showing that information adequately shared enables the ad hoc configurations of regulation loops and a safer use of simplified strategies that can be understood and be validated by other operators, reducing the occurrence of cognitive overloads and contributing to the construction of a common cognitive ground that enhances system resilience. © 2010 Wiley Periodicals, Inc.     

离散事件系统的混合可靠分散监控

在研究基于混合信息的分散监控时,由于部分监控器与部分控制器发生失败,故提出了一种新型的混合可靠分散监控问题.通过修改局部可控事件集与不可控事件集,提出新的可控语言与可靠联合可观察语言定义,进而得到混合可靠分散监控器存在的充分必要条件就是整体约束语言是可靠联合可观察,可控闭的.之后,又通过研究整体约束与混合子约束之间的关系,给出了判别混合可靠分散监控器存在的一个充分条件,即混合子约束分别满足基于谓词的可观察,可控性与基于语言的联合可观察,可控封闭性.     

Ocular measures of redundancy gain during visual search of colour symbolic displays

Sixteen observers participated in a visual search experiment in which colour coding, search type, and the amount of pre-search information available to the observers were varied. Observers searched simulated symbolic tactical displays to find the number of target symbols (i.e. exhaustive search) or the quadrant of the display in which a single target symbol was located (i.e. self-terminating search). Displays varied in the way in which the symbology was colour coded: colour was either relevant (i.e. redundant with symbol shape) or irrelevant (orthogonal to symbol shape), or the display was monochrome. Half of the observers were cued with regard to the coding scheme prior to display onset, while the other observers were not. There was no overall difference in search time or accuracy, number of eye fixations, or pupillary response between cued and non-cued observers, but only because cued and non-cued observers used the coding schemes differently. Redundancy gain was only evident for cued observers, who searched colour relevant displays faster and with fewer fixations than colour irrelevant or monochrome displays. Non-cued observers' search pattern did not differ across colour coding schemes, but they searched colour irrelevant and monochrome displays faster than the cued observers. Differences between cued and non-cued observers' search strategy are discussed with regard to their implications for design and evaluation of colour multipurpose displays.     

Predictive models of human supervisory control behavioral patterns using hidden semi-Markov models

Behavioral models of human operators engaged in complex, time-critical high-risk domains, such as those typical in Human Supervisory Control (HSC) settings, are of great value because of the high cost of operator failure. We propose that Hidden Semi-Markov Models (HSMMs) can be employed to model behaviors of operators in HSC settings where there is some intermittent human interaction with a system via a set of external controls. While regular Hidden Markov Models (HMMs) can be used to model operator behavior, HSMMs are particularly suited to time-critical supervisory control domains due to their explicit representation of state duration. Using HSMMs, we demonstrate in an unmanned vehicle supervisory control environment that such models can accurately predict future operator behavior both in terms of states and durations.     

Fault management in process control: eye movements and action

Operators controlled a simulated thermal hydraulic system based on Crossman's waterbath task. They were required to keep the system at set points for temperature, level and flow rates. The system was subjected to disturbances and to failures, which the operators were required to manage. Behavioural data were collected in the form of keystroke commands, and in addition eye movements were measured. Evidence for ‘cognitive lockup’ and for a preference for serial fault management were found. Fixation durations do not change, but faulty subsystems are examined more frequently. During lockup other subsystems may be examined but action on them is delayed. Eye movements give considerable additional insight into the nature of process control information processing compared with traditional measures of operator performance.     

Relative coobservability for decentralised supervisory control of discrete-event systems

In this paper, we study the concept of relative coobservability in decentralised supervisory control of discrete-event systems under partial observation. This extends our previous work on relative observability from a centralised setup to a decentralised one. A fundamental concept in decentralised supervisory control is coobservability (and its several variations); this property is not, however, closed under set union, and hence there generally does not exist the supremal element. Our proposed relative coobservability, although stronger than coobservability, is algebraically well behaved, and the supremal relatively coobservable sublanguage of a given language exists. We present a language-based algorithm to compute this supremal sublanguage; the algorithm allows straightforward implementation using off-the-shelf algorithms. Moreover, relative coobservability is weaker than conormality, which is also closed under set union; unlike conormality, relative coobservability imposes no constraint on disabling unobservable controllable events.     

A path analysis model of individual variables predicting safety behavior and human error: The mediating effect of situation awareness

Situation awareness is often argued to be an indicator of safety performance. Several factors may influence situation awareness that need to be identified and analyzed. This study investigated the influence of some variables on safety performance and examined the mediating effect of situation awareness. This study was conducted on 601 workers of different industries in Iran. All variables were measured via a multi-sectional questionnaire in a self-report manner. Path analysis modeling was used for data analysis. To measure the validity of the model, the RMSEA, CFI, and R² coefficients were employed. The results revealed that safety knowledge and sleepiness had significant direct and indirect effects on safety behavior and human error. Fatigue had only a mediating effect on safety behavior and error via situation awareness. Safety locus of control had only a mediating effect on human error through situation awareness. Whereas better safety knowledge and an internal safety locus of control could boost siaituation awareness, daily sleepiness and fatigue had significant, detrimental effects on situation awareness. These variables explained 38% of the variations in situation awareness. A proportion of the effect of personal variables on safety behavior and human error was mediated by situation awareness; thus, situation awareness is the direct cause of some safe behaviors and human errors.     

事件反馈与状态反馈的混合模监控

在监控理论中 ,处理状态膨胀的标准方法之一是基于语言或谓词的模监控 .但文献中没有涉及同时基于语言与谓词的混合模监控 .本文研究混合模监控综合及其性质 .通过提出状态反馈与某一事件反馈的等价关系 ,给出了两者相连接的定义 ,进而得到了混合模监控器等价于子监控器与子控制器的连接 .并讨论了混合模监控器具有非阻塞性与无死锁性所满足的条件 ,即基于语言的闭环系统行为的封闭性与谓词的Σu-不变性 ,而其是无死锁的充要条件是子监控器与子控制器必须均是无死锁的并满足d-不变关系