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• Albert-Ludwigs-Universität Freiburg
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Dali Sun – Publikationen

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2016

• Dali Sun, Florian Geißer und Bernhard Nebel.
  Towards Effective Localization in Dynamic Environments.
  In Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2016). 2016.
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  Localization in dynamic environments is still a challenging problem in robotics – especially if rapid and large changes occur irregularly. Inspired by SLAM algorithms, our Bayesian approach to this so-called dynamic localization problem divides it into a localization problem and a mapping problem, respectively. To tackle the localization problem we use a particle filter, coupled with a distance filter and a scan matching method, which achieves a more robust localization against dynamic obstacles. For the mapping problem we use an extended sensor model which results in an effective and precise map update effect. We compare our approach against other localization methods and evaluate the impact the map update effect has on the localization in dynamic environments.

2014

• Dali Sun, Alexander Kleiner und Bernhard Nebel.
  Behavior-based Multi-Robot Collision Avoidance.
  In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA-14), S. 1668-1673. 2014.
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  Autonomous robot teams that simultaneously disatch transportation tasks are playing a more and more important role in the industry. In this paper we consider the multi-robot motion planning problem in large robot teams and present a decoupled approach by combining decentralized path planning methods and swarm technologies. Instead of a central coordination, a proper behavior which is directly selected according to the context is used by the robot to keep cooperating with others and to resolve path collisions. We show experimentally that the quality of solutions and the scalability of our method are significantly better than those of conventional decoupled path planning methods. Furthermore, compared to conventional swarm approaches, our method can be widely applied in large-scale environments.

2013

• Christian Becker-Asano, Dali Sun, Corinna N. Scheel, Brunna Tuschen-Caffier und Bernhard Nebel.
  Analyzing for emotional arousal in HMD-based head movements during a virtual emergency.
  In Intl. Workshop on Emotion and Computing in conj. with KI2013. 2013.
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  This paper reports on results of a statistical analysis of human players' head-movements. Forty-one participants were asked to cope with an unexpected emergency in a virtual parking lot. Before the virtual reality exposure began, half of the participants watched an emotion-inducing movie clip and the other half an emotionally neutral one. The analysis of the acquired questionnaire data reveals, however, that this emotion induction method seems to have been rather ineffective. Thus, it is not surprising that only very weak between group effects are found when analyzing for differences in head movements around the emergency event. In general, horizontal head movement speed is found to be on average significantly faster during the first fifteen seconds directly after the emergency event as compared to just before and another fifteen seconds later. These findings are in line with previous results of an analysis of the acquired physiological data, further substantiating the conclusions drawn.

2012

• Corinna N. Scheel, Birgit Kleim, Julian Schmitz, Christian Becker-Asano, Dali Sun, Bernhard Nebel und Brunna Tuschen-Caffier.
  Psychophysiologische Belastungsreaktivität nach einem simulierten Feuer in einer Parkgarage.
  Zeitschrift für Klinische Psychologie und Psychotherapie 41 (3), S. 180-189. 2012.
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  Theoretischer Hindergrund: Bewältigungsverhalten in Notfallsituationen wird meistens retrospektiv erfasst oder ist aufgrund der Verschiedenheit der Notfallsituationen schlecht vergleichbar. Methoden der Virtuellen Realität (VR) ermöglichen die Erfassung von Verhaltensparametern und psychophysiologischen Belastungsreaktionen während eines belastenden Ereignisses und erlauben zudem das standardisierte Wiederholen für mehrere Personen. Fragestellung: Ziel unserer Studie war es, ein neues Notfallszenario (Feuer in einer Parkgarage) in VR zu entwickeln und zu testen, ob sich anhand dessen substanzielle psychische und physiologische Belastungsreaktionen induzieren lassen. Methode: Mehrfach im Untersuchungsablauf wurden das emotionale Erleben und physiologische Parameter erhoben. Ergebnisse: Das VR Szenario führte bei den teilnehmenden Probanden sowohl zu subjektiven als auch zu physiologischen Veränderungen im Sinne einer Stressinduktion. Das von uns entwickelte Szenario erscheint daher brauchbar, Verhaltensstrategien und Bewältigungsverhalten in Notfallsituationen zu simulieren. Schlussfolgerungen: Möglichkeiten und Grenzen der VR-Methode mit Blick auf klinisch-psychologische Implikationen werden diskutiert.

2011

• Alexander Kleiner, Dali Sun und D. Meyer-Delius.
  ARMO: Adaptive Road Map Optimization for Large Robot Teams.
  In Proc. of the IEEE/RSJ Int. Conf. on Intelligent Robots and Systems (IROS). 2011.
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  Autonomous robot teams that simultaneously dispatch transportation tasks are playing more and more an important role in present logistic centers and manufacturing plants. In this paper we consider the problem of robot motion planning for large robot teams in the industrial domain. We present adaptive road map optimization (ARMO) that is capable of adapting the road map in real time whenever the environment has changed. Based on linear programming, ARMO computes an optimal road map according to current environmental constraints (including human whereabouts) and the current demand for transportation tasks from loading stations in the plant. For detecting dynamic changes, the environment is describe by a grid map augmented with a hidden Markov model (HMM). We show experimentally that ARMO outperforms decoupled planning in terms of computation time and time needed for task completion.

• Christian Becker-Asano, Dali Sun, Birgit Kleim, Corinna Scheel, Brunna Tuschen-Caffier und Bernhard Nebel.
  Outline of an Empirical Study on the Effects of Emotions on Strategic Behavior in Virtual Emergencies.
  In Affective Computing and Intelligent Interaction, S. 508-517. 2011.
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  The applicability of appropriate coping strategies is important in emergencies or traumatic experiences such as car accidents or human violence. In this context, emotion regulation and decision making are relevant. However, research on human reactions to traumatic experiences is very challenging and most existing research uses retrospective assessments of these variables of interest. Thus, we are currently developing and evaluating novel methods to investigate human behavior in cases of emergency. Virtual reality scenarios of emergencies are employed to enable an immersive interactive engagement (e.g., dealing with fire inside a building) based on the modification of Valve’s popular Source 2007 game engine. This paper presents our ongoing research project, which aims at the empirical investigation of human strategic behavior under the influence of emotions while having to cope with virtual emergencies.

• Brunna Tuschen-Caffier, Birgit Kleim, Christian Becker-Asano, Dali Sun, Bernhard Nebel und Corinna Scheel.
  Bewältigungsverhalten in virtuellen Notfallsituationen.
  In 7. Workshop Kongress für Psychologie und Psychotherapie. 2011.
  (BIB)
  

• Christian Becker-Asano, Dali Sun, Birgit Kleim, Corinna N. Scheel, Brunna Tuschen-Caffier und Bernhard Nebel.
  CoVE: Coping in Virtual Emergencies.
  In Workshop on Emotion and Computing - Current Research and Future Impact, S. 1. 2011.
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  The applicability of appropriate coping strategies is important in emergencies or traumatic experiences such as car accidents or human violence. However, research on human reactions to traumatic experiences is very challenging and most existing research uses retrospective assessments of these variables of interest. Thus, we are currently developing and evaluating novel methods to investigate human behavior in cases of emergency. Virtual Reality (VR) scenarios of emergencies are employed to enable an immersive interactive engagement (e.g., dealing with fire inside a building) based on the modification of Valve’s popular Source 2007 game engine. Preliminary results of a first empirical study (cp. Figure 1) suggest that our VR scenario has a similar fear-inducing effect as a short movie clip (Becker- Asano, Sun, Kleim, Scheel, Tuschen-Caffier, and Nebel, 2011), which previously has been evaluated to induce fear. In addition, the neutral VR experiences during the training sessions did never elicit fear in our participants, letting us conclude that the interactively presented emergency itself was indeed the fear eliciting factor in the experimental sessions. In the long run, we aim at a more detailed analysis that includes the personality questionnaire and physiological data, which will be analyzed in correlation with the trajectories of the participants in the VR emergency.

2010

• Dali Sun, Alexander Kleiner und and C. Schindelhauer.
  Decentralized Hash Tables For Mobile Robot Teams Solving Intra-Logistics Tasks.
  In Proceedings of the 9th Int. Joint Conf. on Autonomous Agents and Multiagent Systems (AAMAS 2010), S. 923-930. 2010.
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  Although a remarkably high degree of automation has been reached in production and intra-logistics nowadays, human labor is still used for transportation using handcarts and forklifts. High labor cost and risk of injury are the undesirable consequences. Alternative approaches in automated warehouses are fixed installed conveyors installed either overhead or floor-based. The drawback of such solutions is the lack of flexibility, which is necessary when the production lines of the company change. Then, such an installation has to be re-built. In this paper, we propose a novel approach of decentralized teams of autonomous robots performing intra-logistics tasks using distributed algorithms. Centralized solutions suffer from limited scalability and have a single point of failure. The task is to transport material between stations keeping the communication network structure intact and most importantly, to facilitate a fair distribution of robots among loading stations. Our approach is motivated by strategies from peer-to-peer-networks and mobile ad-hoc networks. In particular we use an adapted version of distributed heterogeneous hash tables (DHHT) for distributing the tasks and localized communication. Experimental results presented in this paper show that our method reaches a fair distribution of robots over loading stations.

2009

• Dali Sun, Alexander Kleiner und T. M. Wendt.
  Multi-Robot Range-Only SLAM by Active Sensor Nodes for Urban Search and Rescue.
  In Robocup 2008: Robot Soccer World Cup XII, S. 318-330. Springer 2009.
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  To jointly map an unknown environment with a team of autonomous robots is a challenging problem, particularly in large environments, as for example the devastated area after a disaster. Under such conditions standard methods for Simultaneous Localization And Mapping (SLAM) are difficult to apply due to possible misinterpretations of sensor data, leading to erroneous data association for loop closure. We consider the problem of multi-robot range-only SLAM for robot teams by solving the data association problem with wireless sensor nodes that we designed for this purpose. The memory of these nodes is utilized for the exchange of map data between multiple robots, facilitating loop-closures on jointly generated maps. We introduce RSLAM, which is a variant of FastSlam, extended for range-only measurements and the multi-robot case. Maps are generated from robot odometry and range estimates, which are computed from the RSSI (Received Signal Strength Indication). The proposed method has been extensively tested in USARSim, which serves as basis for the Virtual Robots competition at RoboCup, and by real-world experiments with a team of mobile robots. The presented results indicates that the approach is capable of building consistent maps in presence of real sensor noise, as well as to improve mapping results of multiple robots by data sharing.

2007

• Alexander Kleiner, Christian Dornhege und Dali Sun.
  Mapping disaster areas jointly: RFID -Coordinated SLAM by Humans and Robots.
  In Proceedings of the IEEE International Workshop on Safety, Security and Rescue Robotics (SSRR 2007), S. 1-6. 2007.
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  We consider the problem of jointly performing SLAM by humans and robots in Urban Search And Rescue (USAR) scenarios. In this context, SLAM is a challenging task. First, places are hardly re-observable by vision techniques since visibility might be affected by smoke and fire. Second, loop-closure is cumbersome due to the fact that firemen will intentionally try to avoid performing loops when facing the reality of emergency response, e.g.USAR, while they are searching for victims. Furthermore, there might be places that are only accessible to robots, making it necessary to integrate humans and robots into one team for mapping the area after a disaster. In this paper, we introduce a method for jointly correcting individual trajectories of humans and robots by utilizing RFID technology for data association. Hereby the poses of humans and robots are tracked by a PDR (Pedestrian Dead Reckoning), and slippage sensitive odometry, respectively. We conducted extensive experiments with a team of humans, and a human-robot team within a semi-outdoor environment. Results from these experiments show that the introduced method allows to improve single trajectories based on the joint graph, even if they do not contain any loop.

• Alexander Kleiner und Dali Sun.
  Decentralized SLAM for Pedestrians without direct Communication.
  In Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2007), S. 1461-1466. 2007.
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  We consider the problem of Decentralized Simultaneous Localization And Mapping (DSLAM) for pedestrians in the context of Urban Search And Rescue (USAR). In this context, DSLAM is a challenging task. First, data exchange fails due to cut off communication links. Second, loop-closure is cumbersome due to the fact that fireman will intentionally try to avoid performing loops, when facing the reality of emergency response, e.g. while they are searching for victims. In this paper, we introduce a solution to this problem based on the non-selfish sharing of information between pedestrians for loop-closure. We introduce a novel DSLAM method which is based on data exchange and association via RFID technology, not requiring any radio communication. The approach has been evaluated within both outdoor and semi-indoor environments. The presented results show that sharing information between single pedestrians allows to optimize globally their individual paths, even if they are not able to communicate directly.

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