Project CTU0208813 supported
by the Grant Agency of CTU, Prague, CR
Inicialization research project. A supervisory power
plant operator model explores the physiological principles of influences of
emotions and workload to cognition. Also user specific profile is considered
with the aim of improvement real-time prediction of power plant operator
behavior.The objectives of this project were the following: 1) to evaluate and
validate quantitatively the safety assessment of power plant control under the
safety critical conditions through simulation, 2) to monitor and predict human
power plant operator behaviour under the normal and safety critical
circumstances. Two basic simulation system architectures correspond to these
two problems. Each problem leads to particular tasks, which can be analysed and
studied through the simulation: analysis of personality type and user specific
approaches to reasoning and task analysis, identifying of safety critical
situations, which cannot be solved in a optimal way because of the limitation
human operator’s resources; analysis of the human operator errors; studies of
bi-directional interactions among human operator’s cognitive and emotional
states on the one hand and the workload on the other hand.
One of the main goals of inicialization projects
supported by the Grant Agency of CTU is the continuation of the inicialised
research under supporting by other projects. This research continuus under the
project financied from the Phare funds. See [MUSIP].
Project Staff:
Ing. Ladislava Janku*
Ing. Milan Šorf, Ph.D.
Ing. Marcela Fejtova
Ing. Martin Salac
Ing. Ladislava Dobias
Ing. Jan Macek
*Project manager
Project
Overview:
The exponential expansion and the tremendous growth of applying computational intelligence techniques in industrial simulations are apparent. Investigations on the simulation of cognition and man-machine interactions have recently received remarkable attention particularly for the following four application areas: design, safety assessment, training, and accident analysis.
Applications of models of cognitive behaviour in the area of design enable in essential to compare and evaluate the effectiveness of the different man-machine interfaces, evaluate their strengths and weaknesses. Cognitive approaches to the safety assessment require models of human machine interaction, simulation of human cognitive processes, simulation of plant and control systems and appropriate data and parameters reflecting the real world situation as well as possible. Applications of the cognitive models in training reflect the necessity to explore precious, structured human behaviour representations. Accident analysis is oriented to the identification of the causes of accident. There are two basic groups of accident causes - system failures and human operator errors. The analysis of the accidents caused by the human factor requires a special framework [1].
During the recent years, a wide spectrum of simulations of human behaviour and cognition, covering the whole area from artificial intelligence and fuzzy logic to control theoretic techniques, appeared on the scene [2]. However, there is still great deal the can be done in the area of a real-time monitoring of a human operator’s psychical stress and/or fatigue levels and integration of such estimators in simulation systems. This technique appears as a suitable approach promising control process fault minimization through the elimination of faults caused by the human factor. An experimental Yoshikawa and Takahashi’s study [3, 4] focused on a research in the line of human’s cognitive features, appears as a fundamental work in this field. A concept of the two-way adaptive human machine interface was presented. Basic concept was later integrated in Mutual Adaptive Interface [5, 6, 7].
In 1991, the model CAMEO (Cognitive and Action Modelling of Erring Operator, [8]) was presented which has been developed with the aim of simulating behaviour of a human operator in pretty complex working environments, such as nuclear power plants. This human operator behaviour model consisted of three sequentially connected modules - Perception and Recognition, Decision Making and Action modules, long term and short term memories and Attention Resource Controller, and was inspired by the human cognitive mechanism of the information processing and retrieval. It was implemented in G2 language [9].
Another working model was AIDE, which has been developed with the aim of simulating behaviour of military pilots [10]. It consisted of two basic elements: the model of competence and the model of performance. It has been developed using AI formalism.
The model CES (Cognitive Environmental Simulation, [11]) was focused on modelling cognitive behaviour of the nuclear power plant human operators under the emergency circumstances. This model is based on assumption that the people have limited resources, particularly when they are under the psychical stress. Not all the available knowledge can be utilised in an optimal way. The model CES consisted of the knowledge base representing all knowledge of the supervisory human operator and the basic processing mechanism, which is based on the use of analysts, which are AI operators equivalent to agents, already utilised by AIDE [12]. Three basic cognitive functions are simulated: monitoring the plant behaviour and its analysis (Behaviour Analysts), building explanation for unexpected conditions (Situation Analysts) and managing the response (Response Plan Analysts).
The system MIDAS (Man Machine Interaction Design and Analysis System, [13]) explores all the strengths of modular architectures. The basic structure of this system contains the model of the controlled process and the model of human operator. These two models interact with each other dynamically. This architecture enables to simulate failures of the system under the control through the probabilistic modules.
Papenhuijzen [14, 15] presented the model of the navigator embedded in a generic architecture that discriminates between two major operator functions: between the function of the supervisor and the function of the actuator. Papenhuijzen’s model differentiated among three cognitive activities - state estimation, track planning and track following - represented by the specific sub-models. A link to control theory techniques can be observed in this approach.
This section refers to the process of designing a simulation system. We considered the simulation system development as a recursive process expanded into iterative loops.
The objectives of this study are the following:
1) to evaluate and validate quantitatively the safety assessment of power plant
control under the safety critical conditions through simulation, 2) to monitor
and predict human power plant operator behaviour under the normal and safety
critical circumstances. Two basic simulation system architectures correspond to
these two problems. Both are discussed in the section 3.5.
Each problem leads to particular tasks, which
can be analysed and studied through the simulation: analysis of personality
type and user specific approaches to reasoning and task analysis, identifying
of safety critical situations, which cannot be solved in a optimal way because
of the limitation human operator’s resources; analysis of the human operator errors; studies
of bi-directional interactions among human operator’s cognitive and emotional
states on the one hand and the workload on the other hand.
As we said,
there ate two main objectives of the simulation. The simulation system
architecture shown on Fig. 1a reflects several aspects of the human machine
interaction and can be utilised for the precious explorations of problems
arising under the safety critical condition. On contrary, the second simulation
architecture takes in account also the real-time monitoring of the power plant
operator behaviour and a system ability to estimate current cognitive state of
the operator (stress & fatigue levels).

Fig. 1a: A human behaviour simulation system architecture – human machine interaction simulation.

Fig. 1b: A human behaviour simulation system architecture – real-time monitoring and prediction of the human power plant operator behaviour.
This section
describes the components of the simulation system in detail. Both the component characteristics and the
simulated interactions and dependencies are explored.
There are two important reasons for which the user profile technique should be utilised. The first one is implied by the appearance of the different personality types in the population of power plant operators. The second one reflects user specific approaches to problem solving, user specific preferences etc. Most models described in section 2 have been developed on assumption, that the differences between human operators, influencing the processes of cognition, are inconsiderable. Such systems consider unique human operator models and cannot be used in tasks focused on a real-time prediction of behaviour of the particular human operator. We consider the ability of models to account specific aspects of behaviour, given by the particular personality types. From this point of view, each personality type is characterised by its own model of cognition.

Fig. 2: A structure of the Intelligent User Profile
The way in which the intelligent user profile influences the simulation process depends on the following interactions - the interaction among the intelligent user profile and cognitive processes or functions, the influence of the intelligent user profile to the emotion dynamics and the other interactions between the user profile and emotions, the influence of the environmental aspects to the weights of particular user profile items.
The presented simulation architecture takes in account estimated stress and/or fatigue levels of real power plant human operators. A vast amount of physiological data collected during the simulated experiments gives a satisfactory baseline for estimation procedures. Intelligent techniques have been applied to perform collected data analysis. All these techniques contain knowledge on relationships among physiological parameters (heart frequency, respiratory frequency, skin galvanic reaction, systolic and diastolic blood pressures, muscular tonus, etc.) and levels of stress or fatigue.
Because of impossibility to connect all the measurement equipment to one computer or to synchronise collected data sample per sample, a semi-distributed system for the data collection, based on the client-server paradigm, has been developed. Basic system structure is shown on Fig. 3.

Fig. 3: Semi-distributed architecture for data collection and analysis
The clients - data collection modules, collect data obtained from different measurement equipment. After the signal segmentation and time-stamps assignment to these segments, the simple or more sophisticated real-time pre-processing techniques are applied. Characteristic features are computed for each segment and, accompanied by the appropriate time-stamp, are sent to server. Simultaneously, the collected signal segments with time stamps are stored in the local databases. The way in which the data are processed at the level of clients - data collection modules - depends at any given time on the operations supported by the procedures implemented in these modules; they can be renovated in a very simple way. This semi-distributed approach to data collection and processing enables to make the best account of computational resources; it also reduces an amount of data transferred to the server. Server is also responsible for starting and stopping clients at any time and for the client synchronization. In section 5, the system implementation has been described in more detail.
From the theoretical viewpoint, the techniques of real time estimation of the stress and fatigue levels can be considered as pattern classification methods. As we have already mentioned, all these techniques contain knowledge on relationships among physiological parameters and levels of stress or fatigue. Our previous research in essence involved application on artificial intelligence methods – fuzzy rule system, feed-forward neural net, expert system [16]. We also verified the methodology of human operator’s psychical stress estimation based on measurement of physiological parameters and their processing through the application of computational intelligence approaches [17].
The basic
constituents, which need to be included in each model of cognition, are
cognitive functions and cognitive processes [2]. Cognitive functions are
Perception, Interpretation, Planning and Execution. Cognitive processes are
Memory/Knowledge Base and Allocation of Resources. Also the connections between
cognitive functions and cognitive processes are considered.
The short-term
memory is modelled through the set of variables, which can be divided in
several subsets: a subset cognitive representations of plant simulation user
interface elements, a subset of cognitive representations of simulated
environmental conditions and events, a subset of goals, a subset of performed
actions, a subset of tasks to be solved, a
Examples: a variable reflecting the current state of the user interface element
of the armature No. 002 of the primary cooling circuit; a current state of some
user interface.
Long-term
memory is modelled as a structure of organised knowledge. It specifies safety
critical situation, standardised procedures, etc.
The mechanism
of perception has been simulated through the cyclic scanning both of the
variables of the user interface and of the variables of the simulated
environmental conditions, elements and events. Contents of these variables are
copied to the corresponding cognitive representation variables. The model of attention has driven variable
selection and timing of the scanning procedures.
We consider a
full ability of simulation to explain the perceived situation both in case of
expected or unexpected findings. This cognitive function of interpretation has
been simulated through the application of the diagnostic expert system.
A process of
plan generation can leads to the identification of standardised procedures or,
when these procedures are not available, to the complex planning process, in
which the plan of actions, which have to be performed, is generated. Each plan is generated with the respect to
the identified state of a power plant simulation; a current plan, and the step
of a current plan execution. These steps of execution take in account such
situations in which the executed plan cannot be interrupted or modified.
This section
deals with the basic principles of the simulation of influences of emotions
and/or user specific characteristics to cognition. There are three ways in which the cognition can be influenced by
the user specific characteristic and emotions: knowledge management and
activation, attention focusing, and limited resources.
This part of simulation has been inspired by the psychological principle that the human power plant operators have limited resources. They are not able to fully utilise all their knowledge in high workload or safety critical situations.
The influences of emotions of a real power plant operator to his/her cognitive processes and behaviour are not inconsiderable. The basic psychological principle is that the emotions can influence a quality of some cognitive functions and processes, e.g. a level of concentration, change the boundaries of the limited resources and influence the processes of knowledge management, e.g. some associations are reinforced, another are reduced. The seven essential emotions have been simulated.
An integration of emotions into the power plant operator model sets several new requirements to the whole simulation process. The way in which the emotions are activated depends on the following interactions - the interaction among emotions and cognitive processes or functions, the emotion dynamics, the interactions between user profile and emotions, and the interaction between emotions and environmental aspects, including simulated examples of power plant behaviour. Notice, that most of interactions are bi-directional.
The emotion dynamics simulation reflects essential biological neuro-hormonal interactions. The basic reference model structure was inspired through the discovered characteristics and functions of hypothalamus. This model is under the development.
Observable power plant behaviour affects human operator cognitive activities. Essential power plant simulator architecture is shown on Fig. 4. Complexity and flexibility of the power plant simulation have been balanced to the complexity and flexibility of the human operator cognitive model. In comparison to real power plant and control systems, the model embodies some substantial and significant simplifications.

Fig. 4: Simulator Architecture
This constituent of whole simulation system covers both the normal and safety critical examples. It consisted of a model of physical behaviour of the most important state variables and parameters, and of an interface supporting human machine interaction. Both plant and control process simulations are able to simulate dynamical behaviour of the real plant-control process system.
User interface is oriented to establish real connection with a real human operator or with the cognitive model of his or her. It provides information both through the graphical and command constituents.
Except the
human-machine interface discussed in the previous chapter, the simulation
system embodies its own interface, which has been developed with the aim of the
numerical and/or graphical presentation of the collected physiological data and
the model of cognition behaviour. Though this interface forms an independent
unit, it is not fully separated from the simulation process. However, it
enables to interfere to the simulation process through the special commands.
Whole interface is made up of the following constituents: collected data
monitoring unit, collected data displaying unit, model of cognition monitoring
unit, displaying of the selected characteristic of the model of cognition unit,
displaying of the user profile parameters unit.
This section
describes several selected parts of the presented ongoing project, which have
been already successfully implemented and tested.
Goal: Human operator personality type classification.
Implementation: In contrast to the standard personality type classification process involving psychological investigation, presented approach is based on the human operator’s physiological parameters measurement (pulse frequency, systolic and diastolic blood pressures, skin resistance, muscular tonus). Personality type classification consists in neuroticism and tendency to risk behaviour classification. Five approaches have been applied and compared one to one – expert system (ES), machine learning (ML), combination of expert system and machine learning, fuzzy clustering, and fuzzy preference expert systems (PES) complemented by an aggregation mechanism [18, 19].
Results: Results acquired by individual methods do not differ very significantly. Table 1 gives an overview of the success rates of the applied AI methods.
Table 1: The success rate of the different classification approaches
|
|
Neuroticism |
TRB |
Neuroticism and
TRB |
|
Expert System |
70% |
68% |
60% |
|
Machine Learning |
72% |
72% |
72% |
|
Combination of ES and ML |
94.9% |
83% |
81.4% |
|
Fuzzy Clustering |
60% |
58% |
55% |
|
Fuzzy PES & aggregation |
93% |
90% |
90% |
These results are discussed in [18] in more detail.
Goal: Computational
representation of user specific knowledge.
Implementation: This research activity is
deeply involved with the psychology of cognition, particularly with the task
analysis and solving problem areas. Simulation consisted of three essential
components: modelling user specific task analysis procedures and approaches to
problem solving, modelling user specific experience, and modelling additional
static user specific knowledge. Notice, that this list is not exhaustive by any
means. From the computational reasons, we reduce the count of the components
forming user specific knowledge. All experiments assume simple examples of
critical safety situation, which require exploring of power plant operator
knowledge in an optimal way and a plan of actions generation. Modelling user
specific task analysis procedures reflects the differences in cognition. Tested
users have been demanded to solve selected examples of critical safety
situations and to describe the cognitive process of a problem analysis and a
plan of specific actions generation. User specific experience has been
represented through the list of critical safety situations, applied successful
and unsuccessful plans, and a counts and dates of the appearances of these
situations. Last two items enable to simulate experience forgetting. Additional user specific knowledge
represents static knowledge, which is not covered in two previous knowledge
simulation constituents, and which is not shared with the other power plant
operators.
Results: Made experiments have acknowledged an
assumption of the improvement of a success rate and performance of the plan
generation algorithms, when the user specific experience has been added to the
simulation. The observed improvement was about 25% (average value) in
performance measured in time needed for the plan generation. An influence of
user specific cognitive approaches and processes can make the whole generation
of the plan of actions best or worse. It’s apparent, that this technique
enables make more precious prediction on of power plant supervisory operator
behaviour. The obtained results have seemed as work of promise; but it has been
already obvious, that the development of a methodology of the result evaluation
is needed.
Goal: Implementation
of the data collecting system.
Implementation: The data collection system
exploring the server-client architecture has been implemented in MATLAB. The
basic server functionality covers starting and stopping the clients, their
synchronization and storing collected data in a database. The basic client
functionality includes physiological signal segmentation, assignment of the
time-stamps to theses segments, computing features and characteristics from the
measured data and sending these features to the server. The measured signal is also stored locally –
each client is able to store the time-stamped signal segments in a local
database. Following modules are included: ECG Module, EOG Module, Skin Galvanic
Response Module, Systolic Blood Pressure Module, Diastolic Blood Pressure
Module, Muscular Tonus Module, Respiratory Frequency Module.
Results: This architecture enables to make the best of the parallel processing of the measured signals. Numerical aspects of this implementation, the module structures, communication design, etc. are discussed in [20] in detail.
Goal: Automatic human operator’s stress level estimation based on the real-time analysis of the collected physiological data.
Implementation: Two computational intelligence approaches were applied to estimate the psychical stress level – fuzzy rule system & feed-forward neural net. Both classification approaches performed classification to the categories described by the same three-value scale – low psychical stress, medium psychical stress, high psychical stress. Fuzzy rule system consisted of 27 fuzzy rules defined for 3 inputs & 3 outputs (classification to 3 classes). Applied neural net classifier consisted in 3-layer feed forward neural net (3 neurons in input layer, 7 neurons in hidden layer & 3 neurons in output layer). Well-known back-propagation algorithm was used for this neural net learning. Two types of neuron output functions were used – linear & sigmoid functions [19]. A set of simple functions describing the relations among the psychical stress levels and simulated physiological parameters were created. These functions were derived from the real physiological data histories. Training data was generated using these functions, and it consisted of a matrix of 27 input vectors (blood pressures, heart rate, respiratory rate).
Goal: A
simulation of influences of stress level and workload to cognitive processes
Implementation: Influences of workload and
stress level have been simulated through the exploration of the following
principles: resource limitation, knowledge activation, level of attention
setting. While most human machine interaction systems assume unlimited and
boundless capabilities of knowledge activation and a cognitive task performing,
psychological studies advert to the fact that humans cannot explore or their
resources and knowledge in an optimal way. This psychological principle is
simulated through the limited resources. Only a specified amount of knowledge
can be active at any given time. Only a specified amount of actions can be
performed at any given time. The influence of attention has been simulated
through the parallelism in thinking and through the association of such
knowledge, which is not related to any solved problem.
Results: Made experiments are focused to the discovering of critical safety situations, which cannot be successfully solved by the power plant operators.
From the viewpoint of safety assessment in the area of supervision of large technological processes, the human-machine systems performing real-time power plant operator’s psychical state analysis and his/her future behaviour prediction as suitable systems for the safety risks minimization.
The objectives of this ongoing project have covered the evaluation of the safety assessment of power plant control under the safety critical conditions through simulation, and real-time monitoring and prediction of human power plant operator behaviour. The simulation system architectures have been presented and discussed in detail. The presented simulation system consisted of the following constituents: a simulation of plant and control processes, user interface model, a power plant operator model, a physiological data collection and evaluation system, a system performing estimation of the psychical and fatigue levels, prediction of power plant operator behaviour, and simulation system interface.
We described a supervisory power plant operator model, which explores the physiological principles of influences of personality types, emotions and workload to cognition. A concept of intelligent user profile has been presented. This concept has been implied by the appearance of the different personality types in the population and reflects also user specific characteristics, user specific approaches to problem solving, preferences etc. The theoretical foundations of model allow the formulation of rules describing interactions among emotions, user specific characteristics, workload, psychical stress and fatigue levels and cognition.
Because of this paper deals with the ongoing project, only particular experiments and results have been described in detail: computational personality classification techniques, modelling user specific knowledge, a system performing a real-time physiological data collection and processing, psychical stress level estimation techniques, modelling interactions among a workload, an estimated stress level and cognition. Made experiments seem to be very promising.
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Publications:
-
Janků, L. - Lhotská, L - Eck, V. -
Matoušek, K. Some Aspects of the
Simulation of Cognitive Behaviour of a Supervisory Human Operator in Complex
Working Environment, inTrappl (ed.): Cybernetics and
Systems, Austrian Society for Cybernetics Studies, Vienna, 2002, ISBN
3-85206-160-1
-
L. Janků
- V. Eck, L - Lhotská - V. Křemen - J. Macek - L.
Dobiáš - J. Dostál, P. Stejskal (EDOST s.r.o.): Analýza nehod a stanovení spolehlivosti řízení průmyslových
systémů: aplikace simulací kognitivních procesů řídicího
operátora; in Štěpánková, O. - Lhotská, L. - Krautwurmová,
H. (editors): Intelligent Methods for Quality Improvement in Industrial
Practice. Prague : CTU FEE, Department of Cybernetics, The Gerstner Laboratory,
2002. 143 p. ISSN 1213-3000.
This
research was performed in co-operation with Dr. Ing. Lenka Lhotska and Dr. Ing.
Vladimir Eck. The work of them was funded by the Ministry of Education
of Czech Republic under the research program ‘Transdisciplinary Biomedical
Engineering Research’, No. MSM
210000012.