Alexander Dietrich

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The technological progress in the field of robotics results in more and more complex manipulators. However, having an increasing number of degrees of freedom raises the question of how to use them effectively. In turn, establishing manipulators in human environments, e.g., as service robots, calls for the fulfillment of various constraints and tasks at the(More)
The mobile humanoid Rollin'Justin is a versatile experimental platform for research in manipulation tasks. Previously, different state of the art control methods and first autonomous task execution scenarios have been demonstrated. In this video two new applications with challenging task requirements are presented. One is the catching of one or even two(More)
As a result of intensive research over the last few decades, several robotic systems are approaching a level of maturity that allows robust task execution and safe interaction with humans and the environment. Particularly when considering the aging of the population, service and household robotics is expected to play an important role in future domestic(More)
— A ball catching scenario with the mobile humanoid Rollin' Justin is presented. It can catch up to two simultaneously thrown balls with its hands, reaching a catch rate of over 80%. All DOF (degrees of freedom), i.e., the arms, the torso, and the mobile platform, are used for the reaching motion and the system works completely wirelessly using only onboard(More)
One of the fundamental demands on robotic systems is a safe interaction with their environment. For fulfilling that condition, both collisions with obstacles and the own structure have to be avoided. We address the problem of self-collisions and propose an algorithm for its avoidance which is based on artificial repulsion potential fields and applicable to(More)
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(More)
A feedback control to generate jumping motions for compliantly actuated multilegged robots is proposed. The method allows to specify the direction of the jumping motion. This is achieved by a constraint that defines a one-dimensional submanifold and a bang-bang control which generates a limit cycle on this submanifold. The approach is based on classical(More)
Many houseworks such as cleaning the floor or wiping the windows require to manipulate tools over wide areas. It is necessary to move along a path while manipulating a tool with the whole body and applying exactly the right amount of force to successfully accomplish the task. So mastering such a challenge demands detailed knowledge about the involved(More)
Reactively dealing with self-collisions is an important requirement on multidegree-of-freedom robots in unstructured and dynamic environments. Classical methods to integrate respective algorithms into task hierarchies cause substantial problems: Either these unilateral safety constraints are permanently active, unnecessarily locking DOF for other tasks, or(More)
One characteristic attribute of mobile platforms equipped with a set of independent steering wheels is their omnidirectionality and the ability to realize complex translational and rotational trajectories. An accurate coordination of steering angle and spinning rate of each wheel is necessary for a consistent motion. Since the orientations of the wheels(More)