Fraunhofer-Institut für Optronik, Systemtechnik und Bildauswertung IOSB

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  • Publication
    Extending Reward-based Hierarchical Task Network Planning to Partially Observable Environments
    ( 2024)
    Mannucci, Tommaso
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    Zimmermann, Robert
    ;
    Frese, Christian
    Rapid, recent developments in robotic applications demand feasible task planning algorithms capable of handling large search spaces. Hierarchical task network (HTN) planning complies with such demand by extending classical planning with task decomposition. Recent advances have extended HTN planners to include the use of reward functions, increasing their flexibility. Nonetheless, such planners assume a fully observable environment, which is often violated in realistic domains. This work contributes to this challenge by presenting POST-HTN, a tree-search based solver which accounts for partial observable environments. A qualitative comparison of POST-HTN with the PC-SHOP HTN solver is given in multiple domains, such as industrial inspection, which is executed on a mobile robot in the real world.
  • Publication
    Cooperative Automated Driving for Bottleneck Scenarios in Mixed Traffic
    ( 2023-06)
    Baumann, M.V.
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    Beyerer, Jürgen
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    Buck, H.S.
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    Deml, Barbara
    ;
    Ehrhardt, Sofie
    ;
    Frese, Christian
    ;
    Kleiser, Dominik
    ;
    Lauer, Martin
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    Roschani, Masoud
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    Ruf, Miriam
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    Stiller, Christoph
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    Vortisch, Peter
    ;
    Ziehn, Jens
    Connected automated vehicles (CAV), which incorporate vehicle-to-vehicle (V2V) communication into their motion planning, are expected to provide a wide range of benefits for individual and overall traffic flow. A frequent constraint or required precondition is that compatible CAVs must already be available in traffic at high penetration rates. Achieving such penetration rates incrementally before providing ample benefits for users presents a chicken-and-egg problem that is common in connected driving development. Based on the example of a cooperative driving function for bottleneck traffic flows (e.g. at a roadblock), we illustrate how such an evolutionary, incremental introduction can be achieved under transparent assumptions and objectives. To this end, we analyze the challenge from the perspectives of automation technology, traffic flow, human factors and market, and present a principle that 1) accounts for individual requirements from each domain; 2) provides benefits for any penetration rate of compatible CAVs between 0 % and 100 % as well as upward-compatibility for expected future developments in traffic; 3) can strictly limit the negative effects of cooperation for any participant and 4) can be implemented with close-to-market technology. We discuss the technical implementation as well as the effect on traffic flow over a wide parameter spectrum for human and technical aspects.
  • Publication
    Workspace monitoring and planning for safe mobile manipulation
    ( 2020)
    Frese, Christian
    ;
    Zube, Angelika
    ;
    Frey, Christian
    In order to enable physical human-robot interaction where humans and (mobile) manipulators share their workspace and work together, robots have to be equipped with important capabilities to guarantee human safety. The robots have to recognize possible collisions with the human co-worker and react anticipatorily by adapting their motion to avert dangerous situations while they are executing their task. Therefore, methods have been developed that allow to monitor the workspace of mobile manipulators using multiple depth sensors to gather information about the robot environment. This encompasses both3D information about obstacles in the close robot surroundings and the prediction of obstacle motions in the entire monitored space. Based on this information, a collision-free robot motion is planned and during the execution the robot continuously reacts to unforeseen dangerous situations by adapting its planned motion, slowing down or stopping. For the demonstration of a manufacturing scenario, the developed methods have been implemented on a prototypical mobile manipulator. The algorithms handle both robot platform and manipulator in a uniform manner so that an overall optimization of the path and of the collision avoidance behavior is possible. By integrating the monitoring, planning, and interaction control components, the task of grasping, placing and delivering objects to humans in a shared workspace is demonstrated.
  • Publication
    A Cooperative HCI Assembly Station with Dynamic Projections
    ( 2020)
    Lengenfelder, Christian
    ;
    Frese, Christian
    ;
    Zube, Angelika
    ;
    Voit, Michael
    ;
    Beyerer, Jürgen
    This paper presents a cooperative human-computer interaction (HCI) assembly station which is assisting a worker during a manual assembly process. The worker's identity, body pose and height is determined to provide individualized assistance like a robot arm which is holding workpieces in a position which is ergonomic for the worker. A second robot arm is equipped with a camera and projector to precisely project information directly on the workpiece. Safe and intuitive human-robot collaboration is achieved by means of workspace monitoring, force detection, compliant control, and hand-guiding. A distinctive feature of this assembly station is that new assembly steps and documentation can be added interactively directly at the workstation during an assembly by interacting with the projected GUI through hand gestures. This paper will detail an assembly station that was developed in a laboratory environment.
  • Publication
    Generic Convoying Functionality for Autonomous Vehicles in Unstructured Outdoor Environments
    ( 2020)
    Albrecht, Alexander
    ;
    Heide, Nina Felicitas
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    Frese, Christian
    ;
    Zube, Angelika
    Autonomously following a leading vehicle is a major step towards fully autonomous vehicles. The contribution of this work consists in the development, implementation, and validation of two following modes: 1) Exact following: accurate compliance with the reference path. 2) Flexible following: tolerate deviation from the reference path in order to avoid obstacles. The proposed method can easily be integrated into existing frameworks for autonomous vehicles. Therefore our approach is flexible enough to be applied to a large variety of different vehicles. To demonstrate the feasibility of our approach an experimental validation is carried out on two autonomous vehicles with major differences in kinematics, weight, and size: A cross-country wheelchair and an off-road truck. Both exact and flexible following have been successfully demonstrated in unstructured outdoor environments.
  • Publication
    Algorithmen-Toolbox für autonome mobile Robotersysteme
    ( 2017)
    Emter, Thomas
    ;
    Frese, Christian
    ;
    Zube, Angelika
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    Petereit, Janko
    Schwere Arbeitsmaschinen werden häufig in Umgebungen eingesetzt, die für den Menschen erhebliche Gesundheitsrisiken bergen. Ziel aktueller Forschungsaktivitäten am Fraunhofer IOSB ist es, Baumaschinen mit Autonomiefähigkeiten auszustatten, sodass diese selbstständig in der Gefahrenzone agieren können. Hierfür wurde eine Algorithmen-Toolbox für autonome Robotersysteme entwickelt, die Komponenten beinhaltet, die sich von der Umgebungswahrnehmung über die Aufgaben- und Bewegungsplanung bis hin zur konkreten Nutzfunktionsdurchführung erstrecken. Um die Forschungsergebnisse evaluieren zu können, wurde ein Technologiedemonstrator aufgebaut, der in der Lage ist, selbstständig kontaminierte Erdschichten abzutragen. ...
  • Publication
    Neue Ansätze zur Kollisions-Vermeidung. Mensch-Roboter-Kooperation
    ( 2016)
    Frese, Christian
    ;
    Martin, Manuel
    ;
    Voit, Michael
    ;
    Zube, Angelika
    Die gemeinsame Nutzung des Arbeitsraums durch Menschen und Roboter ist ein wichtiger Schritt auf dem Weg zur zukünftigen industriellen Produktion. Damit eine effiziente Zusammenarbeit funktioniert, sind intuitive und sichere Interaktions- und Steuerungsmöglichkeiten erforderlich.
  • Publication
    Model predictive contact control for human-robot interaction
    ( 2016)
    Zube, Angelika
    ;
    Hofmann, J.
    ;
    Frese, Christian
    For shared human-robot workspaces and safe physical human-robot interaction, robots have to react adequately to intended and unintended contacts with their environment. In this contribution, a Nonlinear Model Predictive Control approach is presented that allows to move the robot end-effector along Cartesian trajectories while at the same time the robot reacts compliantly to contacts based on the estimated contact force. The impairment of the trajectory following task during contacts is minimized by exploiting the robot redundancy. The controller is based on the kinematic robot model. That means no exact knowledge of the robot dynamics is required and the approach is applicable to both fixed-base and mobile manipulators. In contrast to classical control strategies, joint constraints and self-collisions can be directly considered. In order to reduce the amount of unintended contacts, the control approach can also be combined with a collision avoidance extension. The developed algorithms are validated in experimental results on a KUKA LWR IV.
  • Publication
    Machine vision. Automated visual inspection: Theory, practice and applications
    (Springer, 2016)
    Beyerer, Jürgen
    ;
    Puente Leon, Fernando
    ;
    Frese, Christian
    The book offers a thorough introduction to machine vision. It is organized in two parts. The first part covers the image acquisition, which is the crucial component of most automated visual inspection systems. All important methods are described in great detail and are presented with a reasoned structure.The second part deals with the modeling and processing of image signals and pays particular regard to methods, which are relevant for automated visual inspection.
  • Publication
    Sampling-based path planning to cartesian goal positions for a mobile manipulator exploiting kinematic redundancy
    ( 2016)
    Seyboldt, Ruben
    ;
    Frese, Christian
    ;
    Zube, Angelika
    A robot path planner is presented which integrates both collision-free path planning and finding an inverse kinematics solution in a single search stage. Thereby the degrees of freedom resulting from redundant robot kinematics with regard to goal positions specified in the Cartesian workspace are used to optimize the path length, whereas the usual two-stage approach of decoupled inverse kinematics computation and path planning in the configuration space fails to exploit this potential. In addition to sampling-based exploration of the configuration space, the proposed algorithm uses a computationally efficient gradient descent method for approaching the Cartesian goal pose. Furthermore, the planner is extended by the possibility to respect end-effector path orientation constraints. A detailed evaluation of the planning performance in comparison with a two-stage planner is presented.