Andreas Stemmer

The DLR Lightweight Robot – Design and Control Concepts for Robots in Human Environments

– The paper seeks to present a new generation of torque‐controlled light‐weight robots (LWR) developed at the Institute of Robotics and Mechatronics of the German Aerospace Center., – An integrated mechatronic design approach for LWR is presented. Owing to the partially unknown properties of the environment, robustness of planning and control with respect to environmental variations is crucial. Robustness is achieved in this context through sensor redundancy and passivity‐based control. In the DLR root concept, joint torque sensing plays a central role., – In order to act in unstructured environments and interact with humans, the robots have design features and control/software functionalities which distinguish them from classical robots, such as: load‐to‐weight ratio of 1:1, torque sensing in the joints, active vibration damping, sensitive collision detection, compliant control on joint and Cartesian level., – The DLR robots are excellent research platforms for experimentation of advanced robotics algorithms. Space and medical robotics are further areas for which these robots were designed and hopefully will be applied within the next years. Potential industrial application fields are the fast automatic assembly as well as manufacturing activities done in cooperation with humans (industrial robot assistant). The described functionalities are of course highly relevant also for the potentially huge market of service robotics. The LWR technology was transferred to KUKA Roboter GmbH, which will bring the first arms on the market in the near future., – This paper introduces a new type of LWR with torque sensing in each joint and describes a consistent approach for using these sensors for manipulation in human environments. To the best of ones knowledge, the first systematic experimental evaluation of possible injuries during robot‐human crashes using standardized testing facilities is presented.

An Analytical Method for the Planning of Robust Assembly Tasks of Complex Shaped Planar Parts

The paper addresses the automatic assembly of planar parts with complex geometry. Its main focus is on the automatic generation and parameterization of the assembly sequence, which should provide maximal robustness with respect to positioning errors of the robot and residual position uncertainties of vision based object localization. The assembly utilizes active or passive compliance of the robot in order to align the parts automatically. Success of the automatic alignment, i.e., the convergence of the assembly process can be guaranteed using the means of regions of attraction (ROA). The planning optimizes the assembly trajectories and parameters in such a way that the ROA is maximized for a given part geometry. For the convergence analysis, passivity properties of the robot and the environment are used. The method is validated through extensive experiments and can be successfully applied also for the automated assembly planning with passive compliance devices, as widely used today in industrial automation.

Anthropomorphic Soft Robotics - from Torque Control to Variable Intrinsic Compliance

The paper gives an overview on the developments at the German Aerospace Center DLR towards anthropomorphic robots which not only try to approach the force and velocity performance of humans, but also have similar safety and robustness features based on a compliant behaviour.We achieve this compliance either by joint torque sensing and impedance control, or, in our newest systems, by compliant mechanisms (so called VIA - variable impedance actuators), whose intrinsic compliance can be adjusted by an additional actuator. Both approaches required highly integrated mechatronic design and advanced, nonlinear control and planning strategies, which are presented in this paper.

Robotic assembly of complex planar parts: An experimental evaluation

In this paper we present an experimental evaluation of automatic robotic assembly of complex planar parts. The torque-controlled DLR light-weight robot, equipped with an on-board camera (eye-in-hand configuration), is committed with the task of looking for given parts on a table, picking them, and inserting them inside the corresponding holes on a movable plate. Visual servoing techniques are used for fine positioning over the selected part/hole, while insertion is based on active compliance control of the robot and robust assembly planning in order to align the parts automatically with the hole. Execution of the complete task is validated through extensive experiments, and performance of humans and robot are compared in terms of overall execution time.

Robust Assembly of Complex Shaped Planar Parts Using Vision and Force

The paper addresses the fusion of vision and force-torque information for robotic assembly tasks. The torque-controlled DLR light-weight robot is used, which is specially designed for fast and safe interaction with a changing environment. The image processing is based on standard hardware components and uses color segmentation and affine invariant feature classification. It provides a position estimation within the region of attraction (ROA) of a compliance based assembly strategy. The assembly planning toolbox is based on a theoretical analysis and the maximization of the ROA. This guarantees the local convergence of the assembly process under consideration of the part geometry. The convergence analysis uses the passivity properties of the robot and the environment. The method is validated through extensive experiments

Aus der Forschung zum Industrieprodukt: Die Entwicklung des KUKA Leichtbauroboters

Zusammenfassung Forschungsergebnisse in marktfähige Produkte zu verwandeln erfordert ein beträchtliches Maß an Ausdauer und starkes Unternehmertum. Der KUKA Leichtbauroboter (LBR) ist das jüngste Ergebnis einer langjährigen Forschungs- und Entwicklungskooperation zwischen der KUKA Roboter GmbH in Augsburg und dem Institut für Robotik und Mechatronik des DLR in Oberpfaffenhofen. Dieser Beitrag schildert den Weg der Produktentstehung, den innovativen Charakter des LBR und zeigt erste Anwendungsbeispiele. Abstract Transforming research results into marketable products requires considerable endurance and a strong sense of entrepreneurship. The KUKA lightweight robot (LWR) is the latest outcome of a bilateral research collaboration between KUKA Roboter, Augsburg, and the Institute of Robotics and Mechatronics at the German Aerospace Center (DLR), Oberpfaffenhofen. The stages of product genesis, the most innovative features and first application examples are presented.

Narrow passage sampling in the observation of robotic assembly tasks

The observation of robotic assembly tasks is required as feedback for decisions and adaption of the task execution on the current situation. A sequential Monte Carlo observation algorithm is proposed, which uses a fast and accurate collision detection algorithm as a reference model for the contacts between complex shaped parts. The main contribution of the paper is the extension of the classic random motion model in the propagation step with sampling methods known from the domain of probabilistic roadmap planning in order to increase the sample density in narrow passages of the configuration space. As a result, the observation performance can be improved and a risk of sample impoverishment reduced. Experimental validation is provided for a peg-in-hole task executed by a lightweight-robot arm equipped with joint torque sensors.