Mathias Brandstötter

YuMi, Come and Play with Me! A Collaborative Robot for Piecing Together a Tangram Puzzle

Human-robot collaboration is a novel hot topic in robotics research opening a broad range of new opportunities. However, the number of sensible and efficient use cases having been presented and analysed in literature is still very limited. In this technical article, we present and evaluate a collaborative use case for a gaming application in which a two-arm robot has to piece a Tangram puzzle together with a human partner. Algorithms and methods employed for this purpose are presented, performance rates are given for different setups, and remaining problems and future developments are outlined.

Safety & Security – Erfolgsfaktoren von sensitiven Robotertechnologien

ZusammenfassungRoboter unterscheiden sich von klassischen Maschinen, indem sie vielfältig und an ihre Aufgabenstellung anpassbar mit der Umwelt interagieren können. Sie bilden daher jene Interaktionsmechanismen, durch welche informationstechnische Systeme aktiv und direkt auf die reale Welt Einfluss nehmen. Jegliche potentielle Gefahr für Mensch und Umwelt wurde durch Abgrenzung der Roboter von ihrer Umwelt sichergestellt. Eben diese Verbannung hinter physische Barrieren und die Implementierung als Insellösung ohne direkte Verbindung mit der informationstechnischen Außenwelt wird durch neue sensitive Robotertechnologien zur Mensch-Roboter-Kollaboration und den Forderungen von Industrie 4.0 nach vollständiger Vernetzung der Systeme aufgebrochen. Robotersicherheit gewinnt hierdurch einen besonderen Stellenwert als wesentliche Systemeigenschaft dieser modernen Robotertechnologie. Hierbei umfasst der deutsche Begriff Sicherheit die – im Englischen einerseits durch Safety umrissene physische Sicherheit – sowie andererseits die durch Security definierte informationstechnische Cyber-Sicherheit. Der Umstand, dass die flexible Funktionalität eines Roboters im überwiegenden Maße durch Software eingeprägt wird, begründet die enge Interaktion von Safety und Security und erfordert daher eine gesamtheitliche Betrachtung dieses Themenkomplexes.Im Rahmen dieses Beitrags wird daher auf die wesentlichen Aspekte von Safety und Security in der Robotik eingegangen. Hierbei betrachten die Autoren einerseits die sicherheitsrelevanten Aspekte für den Systementwurf und der Sicherheitsverifizierung. Andererseits schlagen sie zur Verifikation der Cyber-Sicherheit entsprechende Software-Entwurfsprinzipien und zu deren Verifikation die Anwendung von auf die Robotik zugeschnittener Software-Penetration-Tools vor. Dabei beschränken sich die Autoren aber nicht nur auf die Darstellung beider Themenbereiche an sich, sondern skizzieren auch die wesentlichen Wechselwirkungen von Safety und Security bzw. deren gesamtheitliche Sicherstellung in modernen Robotersystemen.AbstractRobots differ from classic machines such that they can interact with the environment in a variety of ways according to a given task. They therefore form interaction mechanisms by which information technology systems actively and directly influence the real world. Any potential danger to humans and the environment has been prevented by isolating the robots from their environment. It is precisely the separation of the robots behind physical barriers and stand-alone systems without direct connection with the information technology outside, which is now broken by new sensitive robot technologies for human robot collaboration and the requirements of industry 4.0 for complete networking of the systems. Robot safety and security, thus, gains particular importance as the essential system property of this modern robot technology. The fact that the flexible functionality of a robot is predominantly imprinted by software justifies the close interaction between safety and security and therefore requires a holistic view of these issues.

Virtual Compliance Control of a Kinematically Redundant Serial Manipulator with 9 DoF

Kinematically redundant serial manipulators are currently used in industry either to avoid singular configurations or to increase dexterity. However, the surplus degrees of freedom of such mechanisms can also be used to ensure, or at least increase safety in a human-robot collaborative scenario. In this work the behaviour of a serial manipulator with nine rotary joints is described where one joint module is equipped with a capacitive proximity sensor exemplarily. The compliance of the robot arm is realized by an impedance controller to achieve dynamic behaviour, which simulates a spring-mass-damper system at one point of the kinematics chain. Usually, this enables the robot-arm to avoid, or at least reduce contact with an approaching human body and to continue its primary task simultaneously.

Implementation of a Capacitive Proximity Sensor System for a Fully Maneuverable Modular Mobile Robot to Evade Humans

This paper describes an advanced approach for a dynamic collision prevention system for robots dedicated to collaborative applications in a shared human robot work environment. We developed a firmware that incorporates proximity sensor information along with a kinematic algorithm to achieve sensitive robotics for a modular mobile robot platform. The utilized sensor technology is based on capacitive sensing, capable to reliably detect humans in the vicinity of the robot platform. The kinematic algorithm is flexible in its design as it is scalable to an unlimited number of wheels and takes into account different geometric architectures such as standard and omni-directional wheels. The dynamic collision avoidance of approaching humans has been successfully demonstrated in a variety of experimental test scenarios demonstrating the capabilities of a sensitive mobile robot.

Analysis of Kinematic Singularities for a Serial Redundant Manipulator with 7 DOF

In this work, the kinematic singularities of serial manipulators with 7 rotational joints are analyzed and their effects on the possible end effector movement are studied. We obtain the numerical kinematic singularities through algebraic varieties and demonstrate this on the kinematically redundant serial manipulator KUKA LBR iiwa. The algebraic equations for determining the variety are derived by taking the determinant of the 6-by-6 submatrix of the Jacobian matrix of the forward kinematics. By using the primary decomposition, the singularities can be decomposed and classified. Further analysis of the kinematic singularities including the inverse kinematics of the redundant manipulator provide us valuable insights. Firstly, there are kinematic singularities where the inverse kinematics has no effect on the self-motion and cannot be used to avoid obstacles. Secondly, there are kinematic singularities, which lead to a single closed-loop connection with the serial redundant manipulator, so that a kinematotropic mechanism is achieved.

Intuitive Hand Guidance of a Force-Controlled Sensitive Mobile Manipulator

The demand for a highly flexible and adaptable industrial infrastructure has gained importance due to increasing product variability, small batch sizes and the need for cost-effective production. Moving from fixed production lines towards mobile manipulation with the possibility for fast and easy reprogramming could provide a solution for these challenges. The ambitious goal of completely programming robot systems without a single line of code is being addressed in this work. More specifically, we present an efficient and natural approach for programming sensitive mobile manipulators through hand guidance using a force torque-sensor that is mounted close to the end effector. The proposed control strategy is explained in detail and results of conducted laboratory tests are presented.

Kinematic Analysis for a Planar Redundant Serial Manipulator

A planar serial manipulator with three rotational joints (planar 3R) can be seen to be a kinematically redundant system if only the position of the end-effector is taken into account. Configuration sets of serial manipulators of planar 3R will be considered in this work in detail. The configuration set is the solution set of all rotational joint angles (actually, we use the tangent of the half-angle) fulfilling the kinematic mapping. Then the configuration set will be an algebraic set if we fix the end-effector or the end-effector follows algebraic motions (for instance, algebraic curves in the special Euclidean group). We show the characteristic of configuration curves among the workspace in terms of the number of real connected components. The configuration curve has either one connected component or two connected components. Furthermore, we also studied the torque variation among the real connected components of the configuration set.

Validation of Relevant Parameters of Sensitive Manipulators for Human-Robot Collaboration

The development of sensitive manipulators has decisively enlarged the range of robot applications in recent years. This robot class enables direct interaction between humans and robots, even in an industrial environment. High demands from the industry are placed on robot systems in general, such as robustness, precision, high and constant speed, etc., of which collaborative robots are not excepted. In this paper important parameters of sensitive robots are listed and well-known systems from different manufacturers are compared by extensive measurements. Peculiarities are identified, analysed, and presented and valuable suggestions for programmers and applicators are derived.