Impedence Control for Variable Stiffness Mechanisms with Nonlinear Joint Coupling

The current discussion on physical human robot interaction and the related safety aspects, but also the interest of neuro-scientists to validate their hypotheses on human motor skills with bio-mimetic robots, led to a recent revival of tendondriven robots. In this paper, the modeling of tendon-driven elastic systems with nonlinear couplings is recapitulated. A control law is developed that takes the desired joint position and stiffness as input. Therefore, desired motor positions are determined that are commanded to an impedance controller. We give a physical interpretation of the controller. More importantly, a static decoupling of the joint motion and the stiffness variation is given. The combination of active (controller) and passive (mechanical) stiffness is investigated. The controller stiffness is designed according to the desired overall stiffness. A damping design of the impedance controller is included in these considerations. The controller performance is evaluated in simulation

The optimal use of vision as part of the manipulation of micron-sized objects

This project concerns the development and integration of a sub-millimeter objects manipulation setup and will take part in a CTI project named “Manipulating Microscale Objects with Nanoscale Precision”. On the way of manipulating microscale objects, we need to build a first setup adapted for sub-millimeter objects in order to be able to perform experiences and to validate some assumptions and choices. In the Laboratoire de Systèmes Robotiques (LSRO), ultra high precision parallel robots are developed and, in particular, the Delta3 a micromanipulator that presents three degrees of freedom (XYZ) and has a range of 4mm. This robot might be used within this project. The goal of this project is to develop an interface between vision system, robot and user that will allow measuring the position repeatability of different microscale objects during a manipulation task

Leitfaden zum wissenschaftlichen Arbeiten im Fach Kunstgeschichte

Dieser Leitfaden dient als erste Orientierung für die eigenständige Erstellung wissenschaftlicher Vorträge und Erarbeitung wissenschaftlicher Texte. Dabei gibt es verschiedene Möglichkeiten, diesen Leitfaden zu nutzen: Sie können ihn – wie ein Buch – als eine erste Einführung in die wissenschaftliche Auseinandersetzung mit kunsthistorischen Fragen verwenden oder aber anlassbezogen einzelne Kapitel herausgreifen und wiederlesen, etwa immer dann, wenn Sie an der Ausarbeitung eines Referats oder einer schriftlichen Hausarbeit sitzen. Für beide Verwendungsarten ist der Text ausgelegt. Wir hoffen, Ihnen damit einen Kompass für Ihre Erkundungen im Feld der Kunstgeschichte an die Hand geben zu können: Der Wege gibt es viele – nach und nach werden Sie unterschiedliche Herangehensweisen und Themenfelder kennenlernen

Leitfaden zum wissenschaftlichen Arbeiten im Fach Kunstgeschichte

Dieser Leitfaden dient als erste Orientierung für die eigenständige Erstellung wissenschaftlicher Vorträge und Erarbeitung wissenschaftlicher Texte. Dabei gibt es verschiedene Möglichkeiten, diesen Leitfaden zu nutzen: Sie können ihn – wie ein Buch – als eine erste Einführung in die wissenschaftliche Auseinandersetzung mit kunsthistorischen Fragen verwenden oder aber anlassbezogen einzelne Kapitel herausgreifen und wiederlesen, etwa immer dann, wenn Sie an der Ausarbeitung eines Referats oder einer schriftlichen Hausarbeit sitzen. Für beide Verwendungsarten ist der Text ausgelegt. Wir hoffen, Ihnen damit einen Kompass für Ihre Erkundungen im Feld der Kunstgeschichte an die Hand geben zu können: Der Wege gibt es viele – nach und nach werden Sie unterschiedliche Herangehensweisen und Themenfelder kennenlernen

The intelligent design of evolution

Research on humanoid robots for use in servicing tasks, e.g. fetching and delivery, attracts steadily more interest. With Rollin’ Justin a mobile robotic system and research platform is presented that allows the implementation and demonstration of sophisticated control algorithms and dexterous manipulation. Important problems of service robotics such as mobile manipulation and strategies for using the increased workspace and redundancy in manipulation task can be studied in detail. This paper gives an overview of the design considerations for a mobile platform and their realizations to transform the formerly table-mounted humanoid upper body system Justin into Rollin’ Justin, a fully self-sustaining mobile research platform

Experimental Study on Dynamic Reactionless Motions with DLR’s Humanoid Robot Justin

The capabilities of DLR’s multi-DOF humanoid robot Justin are extended with the help of a dynamic torque control component for base reaction minimization. Since the mobile base of the robot comprises springs, reactions induced by arm/torso motions lead to vibrations and deteriorate the performance. The control component is derived from the equation of motion of the robot, represented as an underactuated system, and partitioned into a “driven” subsystem (one of the arms), and a “compensating” subsystem (the other arm, with or w/o torso contribution). The control component is then embedded into the existing sophisticated controller structure of Justin, as a feedforward component, with additional control signals from an augmented PD feedback controller. It was possible to obtain satisfactory performance with a very “soft” compensatory subsystem. The experimental results confirmed the potential of this model-based approach for use in a complex multi-DOF system. As far as we know, this is the first time that a dynamic-coupling compensating controller is applied to a real system of such complexity, utilizing thereby a torque control interface

Kinematically Optimal Catching a Flying Ball with a Hand-Arm-System

A robotic ball-catching system built from a multi- purpose 7-DOF lightweight arm (DLR-LWR-III) and a 12 DOF four-fingered hand (DLR-Hand-II) is presented. Other than in previous work a mechatronically complex dexterous hand is used for grasping the ball and the decision of where, when and how to catch the ball, while obeying joint, speed and work cell limits, is formulated as an unified nonlinear optimization problem with nonlinear constraints. Three different objective functions are implemented, leading to significantly different robot movements. The high computational demands of an online realtime optimization are met by parallel computation on distributed computing resources (a cluster with 32 CPU cores). The system achieves a catch rate of > 80% and is regularly shown as a live demo at our institute

Dynamic Whole-Body Mobile Manipulation with a Torque Controlled Humanoid Robot via Impedance Control Laws

Service robotics is expected to be established in human households and environments within the next decades. Therefore, dexterous and flexible behavior of these systems as well as guaranteeing safe interaction are crucial for that progress. We address these issues in terms of control strategies for the whole body of DLR's humanoid Justin. Via impedance control laws, we enable the robot to realize main tasks compliantly while, at the same time, taking care of aspects like physical limitations and collision avoidance with its own structure and the environment autonomously. The controller provides a natural redundancy resolution between the arms, the torso and the wheeled platform. A low-dimensional task space interface is proposed that can be used by planning tools. Thereby, planning time can be saved significantly. Experimental results on DLR's Justin are presented to validate our approach