2013

@INPROCEEDINGS{nuechter2013e, author = {J. B\k{e}dkowski and K. Majek and A. N{\"u}chter}, title = {{General Purpose Computing on Graphics Processing Units for Robotic Applications}}, journal = {Journal of Software Engineering for Robotics (JOSER)}, year = {2013}, volume = {4}, number = {1}, pages = {23--33} }

This paper deals with research related with the improvements of state of the art algorithms used in robotic applications based on parallel computation. The main goal is to decrease the computational complexity of 3D cloud of points processing in applications as: data filtering, normal vector estimation, data registration, and point feature histogram calculation. The presented results improve the efficiency of existing implementations with minimal lost of accuracy. The main contribution is a regular grid decomposition originally implemented for nearest neighborhood search. This data structure is the basis for all presented methods, it provides an efficient method for decreasing the time of computation. The results are compared with well-known robotic frameworks such as PCL and 3DTK.

@INPROCEEDINGS{busch2013a, Author = {S. Busch and K. Schilling and P. Bangert and F. Reichel}, Booktitle = {19th IFAC Symposium on Automatic Control in Aerospace, W{\"u}rzburg, germany}, Month = {September}, Title = {Robust Satellite Engineering in Educational Cubesat Missions in the Example of the UWE-3 Project}, Year = {2013} }

With the introduction of the cubesat standard hands-on satellite engineering received a significant boost at educational university programs. However, not all missions could demonstrate successful operation in orbit. Besides technical challenges due to the extremely limited mass and volume imposed by the standard, cubesat projects at university level typically inhere challenges due to high student fluctuation together with significant launch delays and limited financial budgets. In order to ensure feasibility and continuity over long time, special care in the engineering process, especially design, production, integration and testing, has to be taken. This contribution gives an overview about tools and procedures developed in the context of the University of Wuerzburgs UWE project, which support robust satellite engineering despite mentioned challenges.

@INPROCEEDINGS{busch2013b, Author = {Busch, Stephan and Schilling, Klaus}, Booktitle = {19th IFAC Symposium on Automatic Control in Aerospace, W{\"u}rzburg, germany}, Month = {September}, Title = {Robust and Efficient OBDH Core Module for the Flexible Picosatellite Bus UWE-3}, Year = {2013} }

Pursuing the ambitious goal to establish formations of cooperating small satellites, the University of Wuerzburg established a road map for technology implementations leading towards the realization of coordinated formations of picosatellites. Within the recent developments of the third generation of UWE satellites, special focus was put on the design of a robust and efficient Onboard Data Handling core module. The core module plays a central role in the design philosophy of the UWE-3 bus as it can be seen as the fundamental core which is the only subsystem continuously operating. It is built around two redundant ultra low power microcontrollers in dynamically decided master-slave configuration. One of the main features of the core module software is its flash protection and recovery, where both microcontrollers mutually protect each other by periodically comparing the content of the flash memories with each other and perform corrections if required. This contribution gives a short overview of the UWE-3 picosatellite bus and elaborates in detail on design and test of the OBDH core module.

@INPROCEEDINGS{busch2013c, Author = {Busch, Stephan and Bangert, Philip and Reichel, Florian and Schilling, Klaus}, Booktitle = {Proceedings of the 64. IAC Congress, Beijing, China}, Number = {IAC-13,B4.6B,3x18186}, Title = {The UWE Satellite Bus, a Modular and Flexible Architecture for Future Picosatellite Formations}, Year = {2013} }

Demonstration of a formation of cooperating distributed picosatellites in orbit is the midterm objective of the UWE program (University Wuerzburg's Experimental satellites). The program was initiated in 2005 with the successful launch of the first German picosatellite UWE-1, which had the main objective to establish a robust communication link to the ground segment. The successor UWE-2 was launched in 2009, aiming to demonstrate the capabilities of picosatellites in the field of attitude determination. Taking forward the research activities centered on the UWE program, the next satellite UWE-3 is scheduled to be launched in late 2013. With UWE-3 for the first time a modular and flexible design of the picosatellite bus was introduced. A standardized mechanical and electrical subsystem interface interconnected by a backplane allows for rapid and compact integration of the entire satellite bus without the need for any wired connections. Thus, the UWE-3 architecture supports easy maintenance, extension and replacement of subsystems in any configuration, even after final integration. The design particularly supports reusability and continuous design advancements of the individual subsystems for future missions UWE-4 to UWE-8. This contribution outlines the UWE program roadmap and elaborates on design and test results of the UWE Satellite Bus implemented with UWE-3.

@INPROCEEDINGS{nuechter2013b, author = {J. Elseberg and D. Borrmann and A. N{\"u}chter.}, title = {A Study of Scan Patterns for Mobile Mapping}, booktitle = {ISPRS Archiv Photogrammetry and Remote Sensing. Proceedings of the ISPRS Conference on Serving Society with Geoinformatics (ISPRS-SSG '13), Spatial Inf. Sci., XL-7/W2}, pages = {75-80}, year = {2013}, address = {Antalya, Turkey}, month = {November} }

Mobile terrestrial scanning systems automate terrestrial laser scanning. Continous scanning mobile terrestrial systems constantly spin the terrestrial laser scanner and thus combine terrestrial scanning with kinematic laser scanning. This paper presents a scan pattern analysis for these systems. We aim at finding the most advantageous combination of terrestrial and kinematic systems. The resulting 3D point cloud depends on the scan pattern and the trajectory and velocity of the mobile system.

@INPROCEEDINGS{nuechter2013c, author = {J. Elseberg and D. Borrmann and A. N{\"u}chter}, title = {{Algorithmic solutions for computing accurate maximum likelihood 3D point clouds from mobile laser scanning platforms}}, journal = {Remote Sensing}, year = {2013}, volume = {5}, number = {11}, pages = {5871--5906}, month = {November} }

Mobile laser scanning puts high requirements on the accuracy of the positioning systems and the calibration of the measurement system. We present a novel algorithmic approach for calibration with the goal of improving the measurement accuracy of mobile laser scanners. We describe a general framework for calibrating mobile sensor platforms that estimates all configuration parameters for any arrangement of positioning sensors, including odometry. In addition, we present a novel semi-rigid Simultaneous Localization and Mapping (SLAM) algorithm that corrects the vehicle position at every point in time along its trajectory, while simultaneously improving the quality and precision of the entire acquired point cloud. Using this algorithm, the temporary failure of accurate external positioning systems or the lack thereof can be compensated for. We demonstrate the capabilities of the two newly proposed algorithms on a wide variety of datasets.

@INPROCEEDINGS{Freimann2013Cubesat2013, author = {A. Freimann and A. Kleinschrodt and M. Schmidt and K. Schilling}, title = {Advanced Autonomy Concept for Low-Cost Ground Stations}, booktitle = {5th European CubeSat Symposium}, year = {3 - 5 June, 2013}, pages = {67}, address = {Brussels}, organization = {Ecole Royale Militaire} }

A CubeSat mission requires an implementation of a satellite ground station in order to control the satellite. Due to the commonly low budgets of CubeSat missions an application of professional and expensive hardware is not feasible. In the scope of the recent success of small satellite missions many low-cost ground stations were established. In this context low-cost means that they are mainly composed of commercial off-the-shelf components. These ground stations are typically used by their associated research institutes for providing access to their small satellites. In the last few years, several projects were initiated to network these stations (e.g. the ESA project GENSO or the Japanese GSN initiative). While these projects try to use standardised software for ground station operation, we developed a concept which has been well adapted for the ground station of the University of Würzburg. A ground station design with highly autonomous functions has been implemented without custom-built hardware. The entire ground station serves as an independent communication node to provide access to the CubeSats of the UWE series. This design allows commanding of multiple satellites from almost every distant computer with internet access. The ground station itself is responsible for establishing and maintaining the communication link. Therefore, the ground station system performs all necessary tasks such as tracking of the antenna, correction of Doppler shift, autonomous reconfiguration, hardware monitoring, weather observation, data handling and autonomous fault correction.

@INPROCEEDINGS{freimannbaykosmTA2013, author = {Andreas Freimann and Mirko Rummelhagen and Florian Reichel and Michael Marszalek and Marco Schmidt and Klaus Schilling}, title = {Analysis Of Wireless Networks for Satellite Swarm Missions}, booktitle = {Proceedings of the 3rd IFAC Symposium on Telematics Applications}, year = {2013} }

Swarm missions are a promising approach for novel space applications, increasing operational robustness and flexibility. The communication within swarms is one main field of research in the project "BayKoSM - Bayerische Kompetenzen fuer Schwarm-Missionen", which will make contributions to different technological areas of swarm missions. Swarms of small satellites in low earth orbits will be used to execute cooperative tasks. Hereby, new challenges to communication networks are arising which require investigation of specific protocols and communication devices. This paper analyses different communication and energy issues for an implementation of a swarm mission in space.

@INPROCEEDINGS{freimannbaykosmSFFMT, author = {Andreas Freimann and Marco Schmidt and Klaus Schilling and Joao Graciano and Gerhard Fellinger and Hakan Kayal and Peter Spies and Henrik Zessin and Patrick Henkel and Florian Reichel and Mirko Rummelhagen and Michael Marszalek and Reinhard Bollert}, title = {The BayKoSM Project: Technologies for Swarm Missions}, booktitle = {Proceedings of the 5th International Conference on Spacecraft Formation Flying Missions and Technologies}, year = {2013} }

The BayKoSM project is a cooperation of several universities and companies in Bavaria, funded by the Bavarian government. The aim of the project is the development of key technologies for swarms of mobile vehicles. These swarms consist of either pico satellites or uninhabited aerial vehicles (UAVs). The paper describes the corresponding technologies and how they are used within the scope of BayKoSM for intelligent swarm behavior.

@inproceedings{Her13, author = {Herrmann, C. and Schilling, K.}, title = {Improving Patient Comfort using Model Predictive Control in Robot-Assisted Radiotherapy}, booktitle = {Proceedings of the 2013 IEEE International Conference on Robotics and Automation (ICRA)}, year = {2013}, pages = {5426--5432}, address = {Karlsruhe, Germany}, month = {May 6-10}, }

Moving tumors, especially in the vicinity of lungs, pose a challenging problem in radiotherapy as healthy tissue should not be irradiated. We developed a system to compensate tumor motion with the robotic treatment couch HexaPOD to improve treatment quality. The HexaPOD, carrying the patient, counteracts the tumor motion so that it is eliminated in the beams-eye-view of the linear accelerator. The focus of this work is on two control methods for the HexaPOD in order to realize reference tracking. The first method is a simple position control scheme to enable reference tracking. It is reformulated as second method to be adopted by a model predictive controller to better account for patient comfort and to maintain tracking accuracy. The performance of both methods is compared in experiments with real hardware using prerecorded patient trajectories and human volunteers whose breathing motion was compensated.

@inproceedings{Hess2013a, Title = {Trajectory Planning for Car-Like Robots Using Rapidly Exploring Random Trees}, Author = {Heß, Robin and Kempf, Florian and Schilling, Klaus}, Booktitle = {Telematic Applications, Volume } # 3 | Part # { 1}, Year = {2013}, Editor = {Lee, Jang-Won}, Number = {1}, Organization = {IFAC}, Pages = {44-49}, Volume = {3}, }

This work presents the RRT-planning algorithm adapted to a mobile car-like robot. Based on an short overview of the RRT-approach, all necessary components, adapted to target vehicle, are shown. A possible state space model, including a valid metric, is presented, as well as a control input selection approach. In order to avoid undesired circular motion, we introduced a circle limitation for the control input selection algorithm. Several simulation results are presented for different environments. We show the limitation and propose a solution implementing this algorithm on real hardware. Finally a conclusion is drawn, summarizing the results and giving an outlook to future work.

@inproceedings{Hess2013, Title = {Remote Biological and Robotic Sensor Networks for Environmental Monitoring}, Author = {Heß, Robin and Kempf, Florian and Tautz, Jürgen and Schilling, Klaus}, Booktitle = {Telematic Applications, Volume } # 3 | Part # { 1}, Year = {2013}, Editor = {Lee, Jang-Won}, Number = {1}, Organization = {IFAC}, Pages = {138-143}, Volume = {3}, }

Environment monitoring of large areas requires for many in-situ pollutant measurements. An efficient approach which integrates biological and robotic systems is presented in this contribution. In this approach bees provide an early detection capacity which is complemented by mobile robots to verify pollution indications by obtaining more detailed in-situ measurements. This contribution reports on the system architecture and the challenging technical components related detecting the sampling location of the bees by observing their dancing behavior, the autonomous transfer of the rovers to these target positions for detailed measurements, the integration of the obtained data from the different sources into an overall characterization of the area?s pollution status and an autonomous flexible alerting system.

@inproceedings{kronhaus2013c, title = {Discharge Characterization of the Coaxial Magnetoisolated Longitudinal Anode Hall Thruster}, journal = {Journal of Propulsion and Power}, doi = {10.2514/1.B34754}, year = {2013}, author = {Kronhaus, I. and Kapulkin, A. and Balabanov, V. and Rubanovich, M. and Guelman, M. and Natan, B.}, }

The coaxial magnetoisolated longitudinal anode concept was introduced to improve efficiency and lifetime of low power Hall thrusters (≤350 W). The coaxial magnetoisolated longitudinal anode represents a significant departure from conventional Hall thrusters and has not been thoroughly studied yet. The high efficiency of the thruster, as validated by measurements, increases the need for a better understanding of the physical processes in this type of thruster. An analysis of the coaxial magnetoisolated longitudinal anode discharge based on experimental measurements was conducted for this aim. The experimental setup includes electrical probes mounted on a fast moving positioner, enabling one to obtain the spatial distribution of plasma parameters inside the thruster channel. The results confirmed the basic assumptions used in the physical model of the coaxial magnetoisolated longitudinal anode concept and revealed new phenomena related to the radial nonuniformity of the discharge. In particular, focusing equipotentials were discovered not only in the anode cavity but also in the dielectric channel, where the area of intense ionization was located. The physical processes contributing to the formation of the focusing equipotentials are discussed.

@inproceedings{kronhaus2013b, author = {Kronhaus, I. and Schilling, K.}, title = {Pico-Satellite Orbit and Attitude Control by Electric Propulsion}, book={In Proceedings of 19th IFAC Symposium on Automatic Control in Aerospace}, month={September}, city={Wuerzburg}, country={Germany}, year={2013} }

Coming Soon

@inproceedings{kronhaus2013A, title={Pico-satellite orbit control by vacuum arc thrusters as enabling technology for formation of small satellites}, author={Kronhaus, I., Pietzka, M., Schilling, K. and Schein, J.}, booktitle={ 5th International Conference on Spacecraft Formation Flying Missions and Technologies}, year={2013} }

Coming Soon

@INPROCEEDINGS{KleinschrodtACA2013, author = {A Kleinschrodt and P. Bangert and M. Schmidt and K. Schilling and E. Boie and M. Haunschild}, title = {Automatic identification and monitoring system for the large-scale railway transportation- GP-AIMS}, journal = {19th IFAC Symposium on Automatic Control in Aerospace}, year = {September 2-6, 2013} }

The globalized economy relies on fast, reliable and cost ecient ways of transporting goods over wide distances. Until the recent past, vessel and air transportation were the preferred choice for long distance transportation. Facing a problematical economic development as well as rising fuel costs, rail road transportation is getting more and more interesting. The GP-AIMS feasibility study investigates ways to achieve a space-based monitoring system for large-scale railway transportation in order to support the railroad sector by optimizing rail-workload and at the same time increasing security. The monitoring of the trains will be achieved by a small satellite system, which forwards sensor information from the train to a distant Mission Control Center. Furthermore, GMES data acquired by the two German Earth observation satellites TerraSAR-X and TanDEM-X deliver information about the current state of the track.

@inproceedings{Kurz2013, Title = {Safe Navigation for autonomous Robot systems – SiNafaR}, Author = {O. Kurz and M. Stahl and D. Aschenbrenner and M. Fritscher and R. Hess and K. Schilling}, Booktitle = {European Navigation Conference ENC 2013}, Year = {2013}, }

Nowadays, due to the constantly increasing prices of raw material, the production and the storage of valuable goods, proper security services are required for companies to protect their inventory. Huge technological and staff budgets are required to apply this course of action for large scale objects and areas. Robotic systems, consisting of multiple heterogeneous assets, raise the possibility to support security service tasks within the explained domain. The object of interest in this scenario is a container terminal where an existing staff of watchmen shall be assisted by a team of \acp{UAV} and \acp{UGV}. From the view of the physical protection experts of Wilkon e.K., the presented scenario displays the following special requirements for a surveillance system: Points of interest, regular patrolling, visual information, interventions and usability. According to these requirements, the proposed applications demand a complex technological system. Legal aspects have to be considered as well as technological challenges. In this context the project SiNafaR (Safe Navigation for autonomous Robot systems) aims for identifying requirements, legal aspects in Germany, and finding technological solutions for heterogeneous multi robotic systems in the civilean sector; especially in the domain of security services covering large areas. A heterogeneous network of UGV and UAV builds the foundation for the work within the SiNafaR project.

@article{Kurz2013a, Title = {Safe Navigation for autonomous Robot systems}, Author = {O. Kurz and M. Stahl and D. Aschenbrenner and M. Fritscher and R. Hess and K. Schilling}, Journal = {Coordinates Magazine}, Year = {2013}, Number = {4}, Volume = {10} }

Nowadays, due to the constantly increasing prices of raw material, the production and the storage of valuable goods, proper security services are required for companies to protect their inventory. Huge technological and staff budgets are required to apply this course of action for large scale objects and areas. Robotic systems, consisting of multiple heterogeneous assets, raise the possibility to support security service tasks within the explained domain. The object of interest in this scenario is a container terminal where an existing staff of watchmen shall be assisted by a team of \acp{UAV} and \acp{UGV}. From the view of the physical protection experts of Wilkon e.K., the presented scenario displays the following special requirements for a surveillance system: Points of interest, regular patrolling, visual information, interventions and usability. According to these requirements, the proposed applications demand a complex technological system. Legal aspects have to be considered as well as technological challenges. In this context the project SiNafaR (Safe Navigation for autonomous Robot systems) aims for identifying requirements, legal aspects in Germany, and finding technological solutions for heterogeneous multi robotic systems in the civilean sector; especially in the domain of security services covering large areas. A heterogeneous network of UGV and UAV builds the foundation for the work within the SiNafaR project.

@INPROCEEDINGS{Leutert2013a, author = {Leutert, F. and Herrmann, C. and Schilling, K.}, title = {A Spatial Augmented Reality system for intuitive display of robotic data}, booktitle = {Human-Robot Interaction (HRI), 2013 8th ACM/IEEE International Conference on}, year = {2013}, pages = {179-180}, isbn = {978-1-4673-3099-2} }

In the emerging field of close human-robot-collaboration the human worker needs to be able to quickly and easily understand data of the robotic system. To achieve this even for untrained personnel, we propose the use of a Spatial Augmented Reality system to project the necessary information directly into the users' workspace. The projection system consists of a fixed as well as a mobile projector mounted directly on the manipulator, allowing for visualizing data anywhere in the surroundings of the robot. By enabling the user to simply see the necessary complex information he can better understand the data and behavior of the robotic assistant and has the opportunity to analyze and potentially optimize the working process. Together with an input device, arbitrary interfaces can be realized with the projection system.

@INPROCEEDINGS{nuechter2013a, author = {A. N{\"u}chter and J. Elseberg and D. Borrmann}, title = {{Irma3D -- An Intelligent Robot for Mapping Applications}}, booktitle = {Proceedings of the 3rd IFAC Symposium on Telematics Applications (TA '13)}, pages = {Coming Soon}, year = {2013}, month = {November} }

Motivated by the increasing need of rapid characterization of environments in 3D, we designed a robot system that automates the work of an operator of terrestrial laser scanners. The built system enables to work without using special targets or markers and thus enables the surveyors to save more than 75\% of the time spent in the field. Another impulse for developing the platform is the demand for a remote multi-sensor inspection tool. The robot is capable of surveying remote sites or danger areas, such as plants, underground mines, tunnels, caves, or channels. The results are precise, multi-modal digital 3D maps. This paper presents the recently developed robot Irma3D, its hardware, the developed interconnected software modules, the associated sensor calibration methods and a few applications.

@INPROCEEDINGS{nuechter2013d, author = {A. N{\"u}chter and J. Elseberg and D. Borrmann}, title = {{Automation in 3D Laser Scanning -- From an Automated Tripod towards Optimal 3D Point Clouds from Mobile Laser Scanning}}, journal = {GIM International}, year = {2013}, volume = {27}, number = {9}, month = {September} }

Coming Soon

@inproceedings{ravandoor_mpi, author = {K. Ravandoor and S. Busch and L. Regoli and K. Schilling}, title = {Evaluation and Performance Optimization of PMD Camera for RvD Application}, booktitle = {19th IFAC Symposium on Automatic Control in Aerospace}, city = {Wuerzburg}, country = {Germany}, year = {2013} }

Over several decades spacecraft that have reached end of life have been adding space debris. There are spacecraft with precious functional payloads on-board but have lost the ability to actively control their attitude and orbit. Proposals have been made to either mitigate them or when possible extend their life by docking them with a service spacecraft. On-orbit servicing involves the challenge of bringing an active satellite in contact with a non-cooperative one. This requires the servicer to make observations of the target to be able to characterize target's motion and to prepare itself for docking or grasping maneuvers. The criticality of proximity operations require high availability of relative navigation information in real-time. This paper focuses on applying Photonic Mixer Device, a Time of Flight based 3D imaging sensor, for relative motion estimation of the target. While much research has been done on evaluation and characterization of PMD and other ToF based cameras, they are mostly restricted to terrestrial applications. The objective of the research activities done here are to understand the dynamics of the sensor and to adapt the camera to optimize its performance for scenarios typically encountered in RvD.

@inproceedings{Regoli2013a, author = {L. Regoli and C. Herrmann and K. Ravandoor and K. Schilling}, title = {New Testing Facility for Proximity Operations in Space}, booktitle = {Proceedings of 19th IFAC Symposium on Automatic Control in Aerospace}, year = {2013}, month = {September 2-6}, pages = {xx--xx}, address = {Würzburg, Germany} }

On-Earth testing of space scenarios is one of the key steps during the development of new technologies, being the reproduction of space-like conditions one of the main challenges. In this paper, a testbed designed and developed for testing of proximity operations scenarios such as rendezvous and docking (RvD) or formation flying is presented. The testbed is based on two industrial manipulators and has been developed and used for the validation of pose estimation algorithms for RvD with non-cooperative targets at the University of Würzburg.

@inproceedings{regoli2013a, author = {Regoli, L., Scharnagl, J., Ravandoor, K., Schilling, K.}, title = {Pose Estimation and Collision Avoidance for Rendezvous and Docking in Space Using Photonic Mixer Devices}, booktitle = {In Proceedings of 64th International Astronautical Congress}, month = {September}, city = {Beijing}, country = {China}, year = {2013} }

A system composed by three main blocks, namely a pose estimation, a collision detection and a collision avoidance is presented. The system has been designed specifically for the scenario of rendezvous and docking in space with non-cooperative targets. With the idea of dealing with objects of partly unknown geometry, the required information for the pose estimation has been kept to a minimum. By working with a 3D visual sensor (PMD camera), the estimated pose is then fed into a collision detection algorithm, capable of predicting any foreseen collision in a sliding time window of up to 10 minutes. Finally, based on that prediction and in the case a collision is foreseen, a collision avoidance algorithm calculates an adequate maneuver designed to avoid the collision and go to a safe point from where to start a new approach maneuver or to abort the mission, according to the desired strategy. The functionality of the whole system is demonstrated with the help of an application example running in a testing environment based on two industrial manipulators, especially adapted for the application in scope.

@INPROCEEDINGS{reichel2013, Author = {Reichel, Florian and Bangert, Philip and Busch, Stephan and Ravandoor, Karthik and Schilling, Klaus}, Booktitle = {19th IFAC Symposium on Automatic Control in Aerospace, W{\"u}rzburg, germany}, Month = {September}, Title = {The Attitude Determination and Control System of the Picosatellite UWE-3}, Year = {2013}} }

The picosatellite UWE-3 is the third generation of CubeSats at the University Würzburg. It is equipped with all necessary satellite systems, among them an advanced attitude determination and control system (ADCS), which will enable the satellite to determine its orientation in space in real-time and, within its actuator capabilities, to control and change this attitude. The hard- and software of the ADCS are described, as well as experiments performed with dedicated test setups, and the obtained results are presented.

@inproceedings{scharnagl2013a, author = {Scharnagl, J., Regoli, L., and Schilling, K.}, title = {On-line Collision Detection in Space Using Photonic Mixer Devices}, booktitle = {In Proceedings of 19th IFAC Symposium on Automatic Control in Aerospace}, month = {September}, city = {Würzburg}, country = {Germany}, year = {2013} }

This paper presents a collision detection system especially designed for Rendezvous and Docking (RvD) maneuvers to passive objects in space. It is based on 3D images provided by a Photonic Mixer Device (PMD) and makes use of the output of a pose estimation algorithm developed particularly for this 3D information. The algorithm on-line predicts the trajectory of the observed object and detects possible collisions along this trajectory. The intersection tests performed for that purpose consist of examining multiple oriented bounding boxes that surround target and observer spacecraft. Different scenarios including approaching, departing, rotating and by-passing were conducted in a laboratory setup with two robot manipulators holding a client mockup model and a PMD camera. By the help of these scenarios the functionality of the developed algorithm in common RvD maneuvers was evaluated and confirmed.

@inproceedings{schilling2013a, author = {K. J. Schilling}, title = {Preparing Technologies for Cooperating Pico-Satellite Networks: The UWE-3 and -4 Misions }, booktitle = {Proceedings IAA International Workshop on Constellations and Formation Flying, Lisbon}, year = {2013}, ID = {IWSCFF-2013-01-06} }

Cooperating distributed pico-satellites raise technology challenges in order to realize a network in orbit composed of satellites, each at only a mass of about 1 kg. This objective is addressed by the UWE-program (University Würzburg’s Experimental satellites), providing a roadmap to pico-satellite formation flying. While UWE-1 (launched 2005) addressed aspects related to internet in space as basis for a distributed communication system, UWE-2 (launched 2009) dealt with attitude determination. This contribution addresses technologies for attitude and orbit control, as implemented at the pico-satellites UWE-3 and -4, to be launched in 2013.

@inproceedings{schilling2013b, author = {K. Schilling}, title = {Technologies to Realize Distributed Networked Pico-Satellite Systems }, booktitle = {Proceedings 9th IAA Symposium on Small Satellites for Earth Observation, Berlin}, year = {2013}, ID = {IAA-B9-0502} }

Coming Soon.

@inproceedings{srini2013a, author = {L. Srinivasan and K. Schilling}, title = {Telerobotics for Education: A Marriage of Pedagogy and Technology Management}, booktitle = {Advances in Control Education, Volume # 10 | Part# 1}, year = {2013}, pages = {198-202}, city = {Sheffield}, DOI = {10.3182/20130828-3-UK-2039.00076} }

Distance learning need not always be benchmarked against classroom learning. Common research patterns suggest a tendency to want to converge remote learning to its traditional counterpart, but an experience of running a tele-education robotics course for over 10 years indicates this is not necessary for effective education. An important reason why tele-laboratories and remote learning courses fail after an initial hype could be a lack of focus on technology management including state of the art from concerned fields including pedagogy and technology, and consider cultural change impacting student models with passing generations of students. This work describes how our tele-laboratory was designed and built, how student numbers started dropping after the first five years and what has been changed in the last three years to attract students. A statistical analysis of student numbers and anonymous feedback is also presented to show how interest has been rekindled and how word-of-mouth publicity has resulted in students from newer institutions across Germany taking up our course. Results from an independent review of the course conducted by the Virtual University of Bavaria, of which our tele education course is a part since 2005, are also presented corroborating other results in this paper.

@inproceedings{srini2013b, author = {L. Srinivasan and K. Schilling}, title = {Augmented Reality Navigation Paradigm for Time Delayed Teleoperation}, booktitle = {Telematic Applications, Volume # 3 | Part# 1}, year = {2013}, pages = {1-6}, city = {Seoul}, month = {November}, DOI = {10.3182/20131111-3-KR-2043.00002} }

What has so far not been published, is the effect of changing the way human teleoperators are allowed to navigate from a time delayed state. This paper describes the implementation and evaluation of a new paradigm for time delayed teleoperation - exocentric navigation and publishes experimental results of this paradigm in comparison with the more commonly used navigation algorithm which will be termed egocentric navigation. A typical example for egocentric navigation is steering of a car, where navigation is a continuous process with orientation and displacement occurring simultaneously. Exocentric navigation approaches the navigation problem as a two step process, orientation followed by displacement. It can be viewed as partial autonomy in navigation, where orientation is autonomously performed by the remote robot without assistance and displacement is determined by the human operator using, in most instances, a joystick that controls both direction and speed. Evaluation of the exocentric paradigm consists of testing it with respect to navigation, perception and manipulation. System performance is measured in terms of navigation times and number of collisions and operator performance is measured using Situational Awareness Global Assessment Technique (SAGAT). The new paradigm is tested on users both with and without prior experience with results aimed at aiding human operator training.

@inproceedings{srini2013c, author = {L. Srinivasan and J. Scharnagl and Z. Xu and N. Faerber and B.D. Kumar and K. Schilling}, title = {Design and Development of a Robot Teleoperation System Using Duplex WebSockets Suitable for Variable Bandwidth Networks}, booktitle = {Telematic Applications, Volume # 3 | Part# 1}, year = {2013}, pages = {57-61}, city = {Seoul}, month = {November}, DOI = {10.3182/20131111-3-KR-2043.00029} }

This paper addresses the development of a new teleoperation framework for remote robotics. The status of existing robotic teleoperation systems is introduced, with emphasis on several technological drawbacks and is followed by a description of the design, development and implementation of a new framework based on bleeding edge technologies in internet protocols and software engineering related to robotics. As a first implementation, an update of an existing tele-robotics laboratory is in progress aiming round-the-clock networked access, suited for even the most demanding online learning platforms. A comparison between the current and previous teleoperation system is also published verifying the implemented framework.

@inproceedings{srini2013d, author = {L. Srinivasan and J. Scharnagl and K. Schilling}, title = {Analysis of WebSockets As the New Age Protocol for Remote Robot Tele-Operation}, booktitle = {Telematic Applications, Volume # 3 | Part# 1}, year = {2013}, pages = {83-88}, city = {Seoul}, month = {November}, DOI = {10.3182/20131111-3-KR-2043.00032} }

This paper addresses the replacement of acknowledgement based protocols for teleoperation. The initial sections compare the currently used protocols like HTTP and TCP to WebSockets and examine the structural difference of using one over the other, for a real-time teleoperation scenario. A detailed analysis of HTTP and WebSockets is performed using live teleoperation by multiple users performing temporally seperated tests under variably delayed network conditions. The existing teleoperation laboratory at the University of Wuerzburg was used as the test bed to compare these protocols and final teleoperation results in terms of bandwidth, frame-rate, navigation efficiency and situational awareness are presented and discussed.

@ARTICLE{Wil13, author = {Wilbert, J. and Baier, K. and Herrmann, C. and Flentje, M. and Guckenberger, M.}, title = {Accuracy of Real-time Couch Tracking During 3-dimensional Conformal Radiation Therapy, Intensity Modulated Radiation Therapy, and Volumetric Modulated Arc Therapy for Prostate Cancer}, journal = {International Journal of Radiation Oncology Biology Physics}, year = {2013}, volume = {85}, pages = {237--242}, number = {1}, month = {January}, doi = {10.1016/j.ijrobp.2012.01.095} }

Purpose: To evaluate the accuracy of real-time couch tracking for prostate cancer. Methods and Materials: Intrafractional motion trajectories of 15 prostate cancer patients were the basis for this phantom study; prostate motion had been monitored with the Calypso System. An industrial robot moved a phantom along these trajectories, motion was detected via an infrared camera system, and the robotic HexaPOD couch was used for real-time counter-steering. Residual phantom motion during real-time tracking was measured with the infrared camera system. Film dosimetry was performed during delivery of 3-dimensional conformal radiation therapy (3D-CRT), step-and-shoot intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT). Results: Motion of the prostate was largest in the anterioreposterior direction, with systematic (S) and random (R) errors of 2.3 mm and 2.9 mm, respectively; the prostate was outside a threshold of 5 mm (3D vector) for 25.0%+/-19.8% of treatment time. Real-time tracking reduced prostate motion to S=0.01 mm and R=0.55 mm in the anterioreposterior direction; the prostate remained within a 1-mm and 5-mm threshold for 93.9%+/-4.6% and 99.7%+/-0.4% of the time, respectively. Without real-time tracking, pass rates based on a g index of 2%/2 mm in film dosimetry ranged between 66% and 72% for 3D-CRT, IMRT, andVMAT, on average. Real-time tracking increased pass rates to minimum 98% on average for 3D-CRT, IMRT, and VMAT. Conclusions: Real-time couch tracking resulted in submillimeter accuracy for prostate cancer, which transferred into high dosimetric accuracy independently of whether 3D-CRT, IMRT, or VMAT was used.

@INPROCEEDINGS{xu2013a, author = {Xu, Z.; Kawashima, H. and Schilling, K.}, title = {Readiness in Formation Control of Multi-Robot System}, booktitle = {American Control Conference (ACC)}, year = {2013}, pages = {3038-3044}, address = {Washington, DC}, month = {Juni 17-19} }

To analyze the performance of the formation system in response to inputs/disturbances from outside of the formation, we propose the notion of readiness, which describes the initial conditions of the formation in terms of a certain set of input space. A higher readiness means better initial conditions of the system with better performance in maintaining or recovering the original formation shape against the exogenous inputs/disturbances. Optimization method based on calculus of variations is used in the analysis for deriving the optimality conditions. Simulations modeled on both unicycle and car-like robots demonstrate the features and the potential applications of the proposed notion.

@INPROCEEDINGS{xu2013b, author = {Xu, Z.; Egerstedt, M.; Droge, G. and Schilling, K.}, title = {Balanced Deployment of Multiple Robots Using a Modified Kuramoto Model}, booktitle = {American Control Conference (ACC)}, year = {2013}, pages = {6153-6159}, address = {Washington, DC}, month = {Juni 17-19}, }

In this paper, we study the problem of making multiple agents spread out equidistantly on a circle. The proposed solution is a new Kuramoto-like model for multi-robot coordination, in which the standard sine-terms have been replaced by cosines. This new interaction model enables the balanced deployment of agents on a circle, while only taking into account the local information of each agent's two neighbors on a cycle graph. This means that individual agents do not need to know the (relative) states of all agents nor how many other agents are indeed present in the network. We illustrate the operation of the proposed protocol in simulation as well as extend it to a nonlinear scenario by optimizing over the coupling weights.