Dali Sun – Publications
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2011
2010
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Dali Sun, Alexander Kleiner and 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), pp. 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
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Dali Sun, Alexander Kleiner and 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, pp. 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
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Alexander Kleiner, Christian Dornhege and 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), pp. 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.
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Alexander Kleiner and Dali Sun.
Decentralized SLAM for Pedestrians without direct Communication.
In
Proceedings of the IEEE/RSJ International Conference on Intelligent
Robots and Systems (IROS 2007), pp. 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.
