Decision Analysis of Air Traffic Controller In Order to propose Decision Support Systems

Transcription

1 Decision Analysis of Air Traffic Controller In Order to propose Decision Support Systems David Annebicque, Igor Crévits, Thierry Poulain, Serge Debernard, Patrick Millot LAMIH, University of Valenciennes, Le Mont Houy, CEDEX 9, France (david.annebicque, igor.crevits, thierry.poulain, serge.debernard, ABSTRACT The Air Traffic Controller must take important decisions in each moment. They manipulate a lot of data and parameters. With the increase of traffic it is more difficult to take decision rapidly and safely. In this paper we try to provide some tools able to help the Controller in their work. To do that it is necessary to access to their decision-making process. We propose an approach. This approach is composed of a multiple criteria methodology, and interviews to obtain data. We present next an analysis of these interviews. This analysis show what we can extract from this technique: criteria, preferences for the multiple criteria methodology, and how we use it for propose some tools. The following step will be to integrate the results of these analyses to our system. Keywords: Decision-Making Process, Multiple Criteria Methodology, Decision Aid tools, Interviews Analysis, Air Traffic Control INTRODUCTION 2. AIR TRAFFIC CONTROL Take decisions is an elementary task for the Human. Every day, every hour, Human takes decisions of various kinds. Each decision is taken by evaluating some criteria, with some preferences for each criterion. The decision-maker tries to find a compromise between all these criteria, preferences, and many others parameters. There are domains where take decisions can have catastrophic or beneficial consequences; compromise the integrity of a society or person These decisions are more difficult in function of the context, the workload, the temporal pressure It can be thus interesting to help the decision-makers, help them in the evaluation of the criteria, establish the preferences and find a compromise It is in this domain, and more particularly in decisions in Air Traffic Control (ATC), that our team of the LAMIH lab works. We work on projects in ATC since 20 years. These projects are realized in partnership with DGAC and Air Traffic Controller (ATCo). Taken decision is relatively easy to a Human, but really more difficult for a system. It is thus necessary to well understand how a decision-maker takes decisions, the criteria which are manipulate, the preferences for each criterion We propose in this paper an approach in order to identify the decision making process of a decision maker (here an ATCo), identify the criteria and the preferences depending of some situation, and develop a system able to propose solution, compromise to the controller, in order for example to increase the air traffic, to increase the safety, to reduce delays 2.1. Organization The ATC is organized in 3 layers: Airport control, Approach and terminal control and en-route control. We work at the en-route level. The objective of en-route ATC is to guarantee the safety of aircraft and their passengers. To do this the controllers must take care that aircraft remain separate by a minimum separation distance (5NM in horizontal plan, and 1000 feet in vertical level), while ensuring that they also respect the economic constraints of time and fuel consumption. To simplify the management and the supervision of traffic, airspace is divided in geographical sector and in level of 1000 feet. Two controllers permanently supervise a sector: a Planning Controller (PC) and an Executive Controller (EC). The PC coordinates the movement of aircraft between his sector and the adjacent sectors. This coordination consists in a negotiation of entrance and exit levels. The PC takes care too, to regulate the workload of EC. The EC is in charge of sector supervision, namely to supervise that the aircraft respect the flight plans, and to maintain the safety distances. If the EC detects a possibility of crossing under this safety distance, he/she must do all is possible to restore the separation distances and avoid the conflict. Generally it is necessary to reroute one of the aircraft, and then to take back this aircraft in its original trajectory when the separation is guarantee. This action is called conflict resolution /09/$ IEEE

2 2.2. Motivation of the study Some statistics can quickly demonstrate the problem of ATC. In 25 years ( ) the traffic transiting in the French airspace has increased of 250% [1]. The Air traffic is today higher than aircraft per year. That gives on average aircraft per day. In a sector like Bordeaux for instance, controllers must manage 20 to 25 aircraft per hour. It is the reasonable limit of workload for the controllers. The DGAC foresees that in 10 or 20 years these statistics go double. The controllers risk thus to have some difficulty to manage this increase with actual tools (radar view, strip, telephone ). They risk to be overloaded to certain moment of the day, and this to the detriment of the security. Reduce sectors is impossible, because the conflicts resolutions need a minimal geographical area. A total automation of the ATC is impossible too, outside psychological consequence that this would induce to the passengers, the techniques to realise this automation imply an entirely instrumentation of aircraft, that is not economically conceivable. Currently to avoid this overload of controllers, who could not maintain an optimal security level, different solutions are adopted. For example, the planning of flights and the regulation of the departure of airports, or the coordination between sectors. These solutions allow reducing the complexity of air conflict even to avoid that these conflicts had really happened. 3. PROJECT AMANDA It is in this perspective that the project AMANDA [2, 3], as well as other projects developed in the laboratory [4], take their place. These projects have always the same philosophy, which is to keep Human, operator, in the control loop. These projects do not research to fully automate the management of ATC, which would result in loss of competences for the operators, as well as a loss of situation awareness (SA) [5, 6] AMANDA V2 AMANDA V2 assists controllers (PC and EC) of one sector, in giving some tools which are able to allow a delegation of task [3] but also some tools which allow to share rapidly a same representation of airspace, and conflicts, and thus to maintain a common SA. STAR AMANDA integrates a tool of trajectory calculation and of assistance to the resolution of air conflict, called STAR (French acronym for Tactical help system of Resolution). STAR works in cooperation with the controller. The controller detects a conflict (STAR does not perform the task of conflict detection); he/she has the possibility to use STAR to help his/her to resolve the conflict. To do this the controller indicates the strategy (called directive) that he/she desires apply to resolve the conflict. A directive or strategy is like, for example, AFR1542 PASS_BEHIND KLM1080. STAR takes into account this directive in order to propose a solution. To do this STAR calculates the whole of trajectories which response to the directive, without, of course, creating new conflict. STAR proposes then ONE trajectory to the controller (after a choice in function of some criteria like number of deviation ). The controller can examine the solution proposed by STAR. If the solution is satisfactory, the controller can delegate the effectuation that means the sending of instructions to aircraft. In this case, STAR has in charge to communicate instructions (change of heading, FL ) directly to the aircraft. The controller is thus discharged of the effectuation and communication with pilots. Common Work Space The Common Work Space (CWS) [7, 8] is an essential notion introduced with AMANDA. This space allows a sharing of information between all agents (human, like controllers and artificial like STAR). Each agent can introduce new information in this CWS according to its competencies (know-how), and in accordance to its role (authority) in the process. All the agents can consider this information in order to carry out their tasks, or to control and check those of the other agents. CWS allows mainly maintaining a common situation awareness between the controllers, to share their representation of problems (here in sense of air conflict or loss of separation) to supervise and/or to resolve. The controllers have the responsibility to maintain up to date this space, in order to, on the one hand to preserve a coherent picture of the situation and airspace, and on the other hand to inform the platform, and mainly STAR, with the conflicts that they detect. This version of the platform AMANDA was tested with professional controllers. For details about the results you can read for example [9, 10] AMANDA V3 The objectives of this new study are [11]: the integration of adjacent sectors and improvement of trajectory calculation, STAR. The integration of adjacent sectors consists of an extension of CWS principles to the cooperation between PC of adjacent sectors. This new CWS will: Facilitate the negotiations between sectors; by allowing quickly visualizing the flight concerned by negotiations. This way, the workload, the time necessary, and the risk of ambiguity are reduced. Allow sharing between sectors: changes in the trajectory of aircraft, this should help to reduce uncertainty about the positions and conditions of entry for flights in a sector. Concerning the module of calculation STAR, it is too much "efficacious" compared to the methods and habits

3 of controllers. Indeed, the calculation methods use mathematical methods to provide the new trajectory answering to the directive, and allowing resolving the conflict. That gives thus "perfect" trajectories. This tool does not include additional factors introduced by controllers such as a safety margin above the minimal separation distance (15NM), a deviation rate (heading) comfortable (<30 ), an anticipation of unstable aircraft. 4. MODEL OF THE DECISION-MAKING PROCESS 4.1. Approach The study is divided into three phases [12, 13]. The first phase focuses on the analysis and the structuring of the decision-making process. First, an analysis of the decisions of PC in phases of coordination with the adjacent sectors is required. This phase will conduct in a description of a coherent decision-making process. This point is developed in details in section 4.2. The second phase is methodological. It aims to structure each decision of decision-making process. A general methodological framework must be researched to promote the coherence of each decision considering their links with the decision-making process. Several participants contribute to the decision; each one according to his/her own value system. The methodological framework must also allow structuring the exchanges between the different participants in the decision. It should also help to identify, to represent and to manipulate the different value systems of the participants. This phase is described in section 4.3. The third phase is classic in the field of decision-support. This phase aims to identify and to structure the elements allowing designing some tools to aid the decision makers. It is therefore necessary to collect the decisions elements handled by the controllers Decision-Making Process The decisions of control are in line with a continuum. At the most complete level, they consist of to change the trajectory of the aircraft by applying adjustments to flights parameters of aircraft in order to resolve, operationally, a conflicting situation. The EC has in charge this operational level, and he/she can cooperate with STAR (axis 3 on the figure 1). Previously, these operational decisions have been prepared by the PC who has information before EC. The PC may already identify a conflict situation and inform the EC at the good time. This latter will integrate this new situation in the management of his/her traffic. He/she will specify the preparation, and the pre detection of PC to be able to operationalize later. The EC occupies a central position in the tactical level (figure 1, axis 2) in collaboration with the PC. The CWS constitutes a cooperation help between the two controllers. Finally, at the sector level (figure 1, axis 1), the PC is the first to have available information about flights which preparing to pass in the sector. The PC has a strategic vision of potential conflicting situations. The CWS enables him/her to explain this vision and to share it in order to the EC exploit these information to manage the sector. In the context of this strategic management, PC may contact adjacent sectors in order to, for example, change flights levels of entry of aircraft to avoid a conflict in his/her sector and thus reduce preventively the workload of EC. The CWS is therefore quite naturally an area of strategic management between PC, coherent with the tactical management by the synthetic vision which it presents. Axis 1: Strategic Clusters / Conflicts Coordinations Axis 2: Tactical Choice of directives Axis 3: Operationnal Choice of Trajectory Figure 1 Synthesis diagram of three axes of the study, and the links between them. These three axes are studied as independently as possible with the aim of obtain refined and focused results on a specific problem, and therefore provide the opportunity to go into details each level. But the axes are interconnected; indeed choice a trajectory without having problems is somewhat surprising. It is thus quite logically, that appeared influence between axis 1 and 2 and between axis 2 and 3. The existence of operational decisions quickly appears plausible in the current state of our thinking. These quickly decisions correspond on direct link between the axis 1 and the axis Multiple criteria methodology The job of an ATCo is characterized by the research for a compromise between different systems of value. This is typically the concept of managing flows aircraft. Thereby, the controllers act on the traffic by ensuring optimal security, while trying to reduce delays and the consumption of fuel. ATC is by nature multiple criteria. It is quite unrealistic to summarize the actions taken by the controllers in a single goal, which would be safety, the cost or time. In addition, the actions of the controllers constitute the terminal part of the management of control situations. They are therefore the result of decisions taken previously by controllers. Consequently, it seems appropriate to address the design of aid with the point of view of the methodology of Multiple Criteria Decision Making (MCDM). The MCDM methodology [14] replaces the concept of decision as resulting from a wider concept of the decision-making process wherein several participants

4 can play a role in their own interests. For that reason, the study of decision-making problem is itself accentuated. The MCDM suggests 4 problematics: Choice (one element between all), sorting (with no order), ranking (each element has a precise order), and description (of one element). The MCDM methodology proceeds in four levels (figure 2). The first level is to clearly define the potential actions. The potential actions are all possibilities (real or fictitious) on the basis of which the decision is made. The criteria (level 2) are the factors (witness of the decision) which characterize the potential actions for decide. Preferences (level 3) are a set of rules by which the potential actions are put in relation across criteria. Finally, the level 4 is the establishment of a recommendation; it is the operational level of the methodology, the implementation. Problematic Potential actions Consequences Family of criteria Direction of study Preferences Agglomeration Possible review Recommendation Validation Figure 2. Synthesis diagram of the Multiple criteria Decision Making methodology (MCDM). The study of three axes independently will therefore lead to conduct three MCDM, and to define three problematic; obtain three families of criteria But the recommendations (level 4) will be most certainly more general. For example during cooperation between PC, strategic level, the PC can be lead to justify his/her requests, operational level. In any case, it will result of these three studies only one cooperative system, a single platform. This platform will be composed of different decisions, different tools responding and corresponding to each of the recommendations, but they will be grouped within a single environment, CWS. Human-Machine Cooperation aspect is the unifying thread of this study. This aspect takes place essentially in the level 4, the recommendation. The main objective is to understand the steps and the use that the controllers do of adjacent sectors, their manner of cooperate Human-Machine Cooperation aspect can thus be considered as a synthesis of MCDM Protocol of interviews In order to realize the models and to suggest some decision support tools, it is necessary to understand how the agents (ATCos) work and the data that they manipulate. A protocol constituted of interviews and a review process, is proposed to the professional ATCo. Three interviews are planned, and each during 2 hours. The interviews are based on a real situation presented to the controller. This situation is, in fact, extracted from the previous experiment on AMANDA V2. The interest of use this type of situation is double. Firstly it is some results and data, choices and decisions, made by controllers during these experiments. Secondly, propose a situation on another sector, should be allow obtaining, from the controller, responses more precise, and more detailed, less reflex that it is in their habitual sector of work. Each interview has a defined objective: 1 st interview: to discover the situation, comment and analyse it. 2 nd interview: comeback on the analysis of the situation, questions more precise in function of the previous interview. Explanation of technical words, to avoid all ambiguities. 3 rd interview: discussion about the coordination problematic, possible scenarios, way of doing, data exchange For each interview, a review process is provided, which transcribe all the discussion, sorting, according 6 axes. Axis 1: Conflict detection, choice of aircraft to taken into account in the cluster. Axis 2: Choice of the directive, strategy of resolution Axis 3: Choice of the trajectory to apply Axis 4: Others observations, given by the controllers, but not regarding one of the previous axes. Axis 5: Coordination Axis 6: First idea about the new platform AMANDA v3 Only the results obtain in the two first interviews are analyzed in the following part. 5. FIRST RESUSLTS AND DISCUSSION 5.1. Analysis principles The interviews allow confronting the experimental results of AMANDA V2 to the professional practice of ATCo. Two types of results are available. The content analysis of the interviews provides a first result about the basis of the ATCo profession, useful for the conception of decision support tools. The form taken by the interviews, particularly the situation explained by controllers, allow to identify the nature of the decisions, operate by controllers Results for Axis 1: conflict detection The situation submitted to the judgment of controllers, presents 3 different clusters of aircraft, corresponding to a conflict which is added for each, a restrictive aircraft, regarding to the resolution. A state of the entire situation is also available in the strips and the radar view.

5 All the controllers provided an analysis identical to the objectives of the situation. This result ensures a representativeness of the situation in relation to the practice of the controllers, reinforcing the validity of the results. However, any cluster was retained by the controllers. A different cluster is suggested. The only pertinent cluster, for all the controllers, contains only the aircraft in conflict. In addition, they express a recommendation for an increased surveillance of a third aircraft. For this situation, data are available on the strips to attest of its reality. This first result shows that the controllers use exclusively the data available to regroup the aircraft. The usual notion of conflict and surveillance are sufficient to structure their decisions. A support could be supplied by a confirmation of their judgment. This result shows, in addition, that in any moment of the conflict detection phase, the controllers manipulate, simultaneously, several different clusters. They think only on one possibility, representing the most simply the situation, in the same way that it is presented on the strips. Effectively, no comparison of several possibilities is realized. The decision, operated here, is about the problem description. This result, relative to the practice of controllers, is opposed to the experimental result of AMANDA V2. However, the experimental conditions presented some differences in comparison to the reality. A part of the control task was not simulated and the work environment had no strip (only electronic strip, and no permanent display). The validity of the experimental results is not in reconsideration. The interviews results show the necessity to adapt the results of AMANDA V2 in order to transpose then in real situation Results for Axis 2: conflict resolution In addition to the representation of the situation by the strip, and the radar view, six types of resolution strategy (called directives) are submitted to analyse by the controllers. Three directives proceed to a resolution inside the conflict, that s mean by an action on one of the two conflicting aircraft. One directive implies an outside aircraft of the conflict. A directive presents, voluntarily, a hazardous configuration. The last directive is about a kind of resolution, efficient, but marginal regarding the actual practices. The results show that the controllers strive to accentuate the natural tendency of implicated aircraft in the conflict in order to resolve it. This conducts to increase the distance between aircraft on the conflict point by a deviation of the second aircraft toward the first. The deviation necessary to produce the sufficient distance in order to resolve the conflict is thus reduced. To select the deviated flight, the times of passage on the beacons are available on the strips. This kind of resolution is described by elegant by the controllers. But the global situation can lead to make unsuitable this natural solution. It remains be possible to resolve inside the conflict by acting on the first aircraft, on the conflict point, although the deviation will be most important. If necessary, secondary actions, on restricting aircraft, in order to protect the resolution space, can be carry out. An elegant solution has also a low cost in resources for the controller. The controllers qualify this cost by the word energy. But when an elegant solution can not be carrying out, it is the energy which guides their choices. The less costly action has the preference. At the resolution level, the controllers envisage thus several possibilities, which are compared. Although comparable, these possibilities are not ordered, because they present different characteristics, and only the energy is not sufficient to decide, or to order these possibilities. There is two kind of decision here. At the most global level, a choice decides between the natural resolution and the non-natural resolution. The decision is here about a choice between two categories. In a second time, the variants of the natural resolution are considered. The decisions consist to sort the possibilities between two categories, one of resolution, the other of protection Results for Axis 3: The deviation A trajectory represents the future route of the aircraft, resulting of the deviation, and the put back on the original route. Only one trajectory is submitted to the evaluations of the controllers; with the goal to obtain a critic, as well as alternatives propositions. Any controllers propose neither a critic of the trajectory, nor others possibilities. In addition, the controllers don t mention really the put back on the original route of the deviated aircraft. This part of the deviation is not considered in the management of the conflict, but resulting of the surveillance. However, the controllers talk about the operational point of view of the resolution, by indicating the motivations prevailing over the deviation order. They indicate that the goal is to deviate weakly (5 to 10 ) and as soon as possible the aircraft, specifying, thus, the notion of elegant resolution. They precise too, some rules linking the value of the heading and the distance before the conflict point. The order results, then, of these rules, and not of an explicit research of the god/best value insuring the aircraft separation. These rules are thus associated to objectives data available on the strips. The value of the applicable deviation will result of the time available to resolve the conflict and the controller workload. The controllers don t proceed to an explicit comparison. The rules provide a set of possibilities, ordered, according to the decreasing distance before the conflict point. The decision result thus of this ranking which

6 allow to apply the order the earliest Orientation of the helps At the conflict detection level, the descriptive nature of decisions leads to envisage the help like an automatic detection of conflict. By introducing a redundancy with the ATCo role, help allows to controllers to make a critical about their own decisions; decisions obtained with the classical method of detection. At the conflict resolution level, help is in a first time, a construction of resolution orders; apply to each aircraft in conflict. A resolution order is composed of one deviation angle apply to one aircraft at one instant. Angles considered are: 5, 10, 15, 20, 25 et 30 and the instant have a pitch of 1 minute from the decision instant to a projection in 10 minutes. In a second time, help consist in choose order allowing to resolve. These possible solutions are sorted, specifying their characteristic in: natural solution, solution inside of the conflict, introducing a third aircraft. Note that if the first category does not contain solutions, the controller can foresee the resolution of the conflict by another method, or foresee some complementary actions. At the deviation level, help will consist to propose only one solution, when the deviated aircraft is chosen. The proposition uses the order of solutions given by the most important distance from the conflict point, by increase angle. If the time to apply this solution is passed, the proposition is invalid, and the next is proposed to the controller. 6. Conclusions This paper presents an approach to access to the decision-making process of operators. We, after the use of interviews, obtain much information. From these information, it is possible to establish a list of criteria and preferences for the MCDM. It is also possible to propose a model for the decision-making process. These analysis and results will allow to model and propose news tools for the air traffic controllers. These tools will include the way of doing of the controllers; they will be integrated in their work, and with the actual tools available. This will have to effect to increase the tools acceptation by the users, to avoid the decisional conflict, and to better answer to their needs, in supplying solutions very close to their way of doing. In this project we finish the analysis of the interviews, and we define the first specifications for the new tools. The next step will be to present these specifications to the controllers before to introduce the specifications in our platform AMANDA. REFERENCES [1] DGAC, Direction générale de l aviation civile, contrôle des routes du ciel. tciel.htm. [2] Debernard S., Cathelain S., Crévits I., Poulain P, AMANDA Project: Delegation of tasks in the air-traffic control domain, Cooperative Systems design, IOS PRESS, pp , January, [3] Guiost B., Debernard S., Poulain T., Millot P., Supporting Air-Traffic Controllers By Delegating Tasks, In IEEE-SMC 2004, The Hague, The Netherlands, pp , September, [4] Crévits I., Debernard S., Vanderhaegen F., Millot P., Multi level cooperation in air traffic control, in 4 th International Conference on Human-Machine Interaction and Artificial Intelligence in Aerospace, Toulouse, France, September, [5] Endsley M.R., Automation and situation awareness, Automation and human performance: Theory and applications, Mahwah, NJ: Lawrence Erlbaum Associates, pp , [6] Endsley M.R., Kaber D.B., Level of automation, effects on performance, situation awareness and workload in a dynamic control task. Ergonomics, 42(3), pp , [7] Bentley R., Rodden T., Sawyer P., Sommerville I., An architecture for tailoring cooperative multi-user displays, in Conference proceedings of 4 th Computer supported cooperative work, Toronto, Canada, pp , [8] Pacaux-Lemoine M.-P., Debernard S., A common work space to support the Air Traffic Control, Control Engineering Practice, A journal of IFAC, 10, pp , [9] Guiost B., Debernard S., Common Work Space or How to Support Cooperative Activities Between Human Operators and Machine: Application to Air Traffic Control, 12th International Conference on Human-Computer Interaction, 13, Springer, Beijing, P.R. China, July, [10] Debernard S., Guiost B., Poulain T., Crévits I., Annebicque D., Millot P. Integrating Human Factors in the Design of Intelligent Systems: an example in Air Traffic Control. International Journal of Intelligent Systems Technologies and Applications [11] Annebicque D., Debernard S., Poulain T., Crévits I., AMANDA V3: Toward a Common Work Space between air Traffic Controllers, in ACHI 08, Sainte Luce, Martinique, February, 2008a. [12] Annebicque D., Crévits I., Poulain T., Debernard S., Analysis of Air Traffic Controllers Decisions, in HCP 08, Delft, The Netherlands, June, 2008b. [13] Annebicque D., Crévits I., Poulain T., Debernard S., Knowledge acquisition for the creation of assistance tools to the air traffic control, in Collaborative Decision Making: Perspective and Challenges, IOS Press, CDM'2008, Toulouse, France, July, 2008c. [14] Roy B., Multicriteria Methodology for Decision Aiding, Kluwer. London, 1996.