| 21. |
- Junges, Robert, 1982-
(författare)
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A Learning-driven Approach for Behavior Modeling in Agent-based Simulation
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Agent-based simulation is a prominent application of the agent-based system metaphor. One of the main characteristics of this simulation paradigm is the generative nature of the outcome: the macro-level system behavior is generated from the micro-level agent behavior. Designing this agent behavior becomes challenging, as it is not clear how much each individual agent will contribute to the macro-level phenomenon in the simulation.Agent learning has proven to be successful for behavior configuration and calibration in many domains. It can also be used to mitigate the design challenge here. Agents learn their behaviors, adapted towards their micro and some macro level goals in the simulation. However, machine learning techniques that in principle could be used in this context usually constitute black-boxes, to which the modeler has no access to understand what was learned.This thesis proposes an engineering method for developing agent behavior using agent learning. The focus of learning hereby is not on improving performance, but in supporting a modeling endeavor: the results must be readable and explainable to and by the modeler. Instead of pre-equipping the agents with a behavior program, a model of the behavior is learned from scratch within a given environmental model.The following are the contributions of the research conducted: a) a study of the general applicability of machine learning as means to support agent behavior modeling: different techniques for learning and abstracting the behavior learned were reviewed; b) the formulation of a novel engineering method encapsulating the general approach for learning behavior models: MABLe (Modeling Agent Behavior by Learning); c) the construction of a general framework for applying the devised method inside an easy-accessible agent-based simulation tool; d) evaluating the proposed method and framework.This thesis contributes to advancing the state-of-the-art in agent-based simulation engineering: the individual agent behavior design is supported by a novel engineering method, which may be more adapted to the general way modelers proceed than others inspired by software engineering.
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| 22. |
- Karlsson, Lars, et al.
(författare)
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To secure an anchor : a recovery planning approach to ambiguity in perceptual anchoring
- 2008
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Ingår i: AI Communications. - Amsterdam : IOS Press. - 0921-7126 .- 1875-8452. ; 21:1, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- An autonomous robot using symbolic reasoning, sensing and acting in a real environment needs the ability to create and maintain the connection between symbols representing objects in the world and the corresponding perceptual representations given by its sensors. This connection has been named perceptual anchoring. In complex environments, anchoring is not always easy to establish: the situation may often be ambiguous as to which percept actually corresponds to a given symbol. In this paper, we extend perceptual anchoring to deal robustly with ambiguous situations by providing general methods for detecting them and recovering from them. We consider different kinds of ambiguous situations. We also present methods to recover from these situations based onautomatically formulating them as conditional planning problems that then are solved by a planner. We illustrate our approach by showing experiments involving a mobile robot equipped with a color camera and an electronic nose.
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| 23. |
- Larsson, Johan, et al.
(författare)
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A navigation system for automated loaders in underground mines
- 2006
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Ingår i: Field and Service Robotics. - Berlin : Springer Berlin/Heidelberg. - 9783540334538 ; , s. 129-140
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Konferensbidrag (refereegranskat)abstract
- For underground mining operations human operated LHD vehicles are typically used for transporting ore. Because of security issues and of the cost of human operators, alternative solutions such as tele-operated vehicles are often in use. Tele-operation, however, leads to reduced efficiency, and it is not an ideal solution. Full automation of the LHD vehicles is a challenging task, which is expected to result in increased operational efficiency, cost efficiency, and safety. In this paper, we present our approach to a fully automated solution currently under development. We use a fuzzy behavior-based approach for navigation, and develop a cheap and robust localization technique based on the deployment of inexpensive passive radio frequency identification (RFID) tags at key points in the mine.
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| 24. |
- Larsson, Johan, et al.
(författare)
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An evaluation of local autonomy applied to teleoperated vehicles in underground mines
- 2010
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Ingår i: 2010 IEEE International Conference on Robotics and Automation (ICRA). - : IEEE conference proceedings. - 9781424450381 ; , s. 1745-1752
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Autonomous vehicles are being increasingly introduced in the mining industry. While these may offer high safety and high productivity, fully autonomous solutions are not always applicable or economically viable. Teleoperation is an attractive option, since it increases safety and comfort of the drivers. Unfortunately, the difficulty to operate the vehicle remotely often results in reduced productivity. In this paper, we show that techniques from the field of mobile robotics can be used to mitigate this problem. We extend a commercial teleoperation system for use in underground mines with a local autonomy functionality, with the main purpose to evaluate if the achieved productivity improvement motivates development of general algorithms and a fully commercial implementation. We then describe a user study performed in an underground mine with a 38 tonne articulated wheel loader, which proves that local autonomy gives a significant improvement in productivity of the teleoperation system, while retaining or even reducing the maintenance costs.
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| 25. |
- Larsson, Johan, et al.
(författare)
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Fast laser-based feature recognition
- 2005
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Konferensbidrag (refereegranskat)abstract
- This paper we present our methods for feature recognition used for high speed reactive navigation based on a topological map, with none or sparse metric information. Our methods for corridor and intersection detection yields execution times of only a fraction of what we have found previously described in the relevant literature, and have proven robust and reliable in experiments performed both in office environment and in our test mine [Larsson et al., 2005]. A. Related Work Our Corridor
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| 26. |
- Larsson, Johan, et al.
(författare)
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Flexible infrastructure free navigation for vehicles in underground mines
- 2008
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Ingår i: 4th international IEEE conference intelligent systems, IS '08. - New York : IEEE. - 9781424417391 ; , s. 2-45-2-50
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Konferensbidrag (refereegranskat)abstract
- During the last decade, mining companies and mobile equipment manufacturers have pursued improved efficiency, productivity, and safety in underground mining operations by automating some of the functions of underground vehicles. The work presented in this paper is the result of an effort to develop new flexible infrastructureless guidance system for autonomous tramming of center-articulated underground mining vehicles.
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| 27. |
- Larsson, Johan, et al.
(författare)
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Laser-based corridor detection for reactive navigation
- 2008
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Ingår i: Industrial robot. - : Emerald. - 0143-991X .- 1758-5791. ; 35:1, s. 69-79
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Tidskriftsartikel (refereegranskat)abstract
- For mobile robots operating in real-world environments, reactive navigation is a useful complement (or even replacement) to pure plan-based metric navigation. Reactive navigation is performed with respect to local perceived features, rather than a global metric reference frame, and can provide reduced installation costs, increased flexibility, and robustness to changes in the environment. To be effective, however, reactive navigation requires fast and reliable perception of the relevant features in the environment. Corridor-like structures are one of the most common features that are used for this purpose. In this paper, we propose a new method for corridor detection from laser data, based on the Hough transform, which is fast, reliable, and noise tolerant. We describe the algorithm, report an extensive experimental evaluation of its performance, and motivate the research with a real application involving the autonomous operation of a loader vehicle in an underground mine.
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| 28. |
- Larsson, Johan, et al.
(författare)
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Laser based intersection detection for reactive navigation in an underground mine
- 2008
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Ingår i: IEEE/RSJ international conference on intelligent robots and systems, 2008, IROS 2008. - 9781424420575 ; , s. 2222-2227
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Konferensbidrag (refereegranskat)abstract
- In this paper we propose a new feature detection algorithm to enable junction recognition intended for high speed reactive navigation in tunnel like environments. We also present an extensive experimental evaluation of the algorithm based on data recorded in a real mine. The algorithm is faster and has less environmental constraints than similar algorithms that can be found in the litterature.
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| 29. |
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| 30. |
- Lidén, Mats, 1976-, et al.
(författare)
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Two- and three-dimensional CT measurements of urinary calculi length and width : a comparative study
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The standard imaging procedure for a patient presenting with renal colic is unenhanced CT. The CT measured size has a close correlation to the estimated prognosis for spontaneous passage of a ureteral calculus. Size estimations of urinary calculi in CT images are still based on 2d-reformats. In the present study we developed and validated a calculus oriented 3dmethod for measurements of length and width of urinary calculi and compared those with corresponding 2d measurements in axial and coronal reformats.Methods: Fifty unenhanced CT examinations demonstrating urinary calculi were included. A 3d-symmetric segmentation algorithm was validated against reader size estimations. The calculus-oriented size from the segmentation was then compared to the size in axial and coronal reformats.Results: The validation showed 0.1±0.7 mm agreement against reference measure. There was a 0.4 mm median bias for 3d-estimated calculus length compared to 2d (p<0.001), but no significant bias for 3d-width compared to 2d.Conclusion: The size of the urinary calculus becomes underestimated if its orientation is not aligned to the axial or coronal image plane. Future studies aiming to correlate calculus size with patient outcome should use a calculus oriented size estimation.
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