Matthias Hellerer

The DLR Robot Motion Simulator Part I: Design and setup

In recent years a new generation of motion simulators, based on serial kinematics industrial robots, emerged as alternative to the currently prevalent Steward-platforms. This paper presents the newest addition to this: The DLR Robot Motion Simulator.

The LRU Rover for Autonomous Planetary Exploration and Its Success in the SpaceBotCamp Challenge

The task of planetary exploration poses many challenges for a robot system, from weight and size constraints to sensors and actuators suitable for extraterrestrial environment conditions. In this work, we present the Light Weight Rover Unit (LRU), a small and agile rover prototype that we designed for the challenges of planetary exploration. Its locomotion system with individually steered wheels allows for high maneuverability in rough terrain and the application of stereo cameras as its main sensor ensures the applicability to space missions. We implemented software components for self-localization in GPS-denied environments, environment mapping, object search and localization and for the autonomous pickup and assembly of objects with its arm. Additional high-level mission control components facilitate both autonomous behavior and remote monitoring of the system state over a delayed communication link. We successfully demonstrated the autonomous capabilities of our LRU at the SpaceBotCamp challenge, a national robotics contest with focus on autonomous planetary exploration. A robot had to autonomously explore a moon-like rough-terrain environment, locate and collect two objects and assemble them after transport to a third object - which the LRU did on its first try, in half of the time and fully autonomous.

Compile-time dynamic and recursive data structures in Modelica

The current Modelica Standard (v3.3) does not support dynamic or recursive data structures. For many applications this constitutes a serious restriction rendering certain implementations either impossible or requires elaborate and unelegant constructs. In this paper we will show that support for dynamic and recursive data structures can be implemented in the Modelica IDE Dymola using a variety of advanced constructs. This proves the principle viability of the then proposed inclusion of those data structures in the Modelica Standard.

Wheel-Ground Modeling in Planetary Exploration: From Unified Simulation Frameworks Towards Heterogeneous, Multi-tier Wheel Ground Contact Simulation

Today’s growing scientific interest in extraterrestrial bodies increases the necessity of extended mobility on these objects. Thus, planetary exploration systems are facing new challenges in terms of mission planning as well as obstacle and soil traversability. In order to fit the tight schedules of space missions and to cover a large variety of environmental conditions, experimental test setups are complemented by numerical simulation models used as virtual prototypes. In this context we present an integrated simulation environment which allows for using different available contact models, ranging from simple but real-time capable approximations based on rigid-body modeling techniques up to very accurate solutions based on Discrete Element Method (DEM). The models are explained and classified for their applications. For this work, a one-point Bekker based approach (BCM) and the so-called Soil Contact Model (SCM), which is a multi-point extension of the Bekker–Wong method taking soil deformation into account, are used for further analysis. These two contact models are applied for homogeneous simulations with only one type of contact model for all wheels as well as for a heterogeneous multi-tiered simulation with different contact models for the wheels. It will be shown that the multi-tiered approach enhances the simulation result accuracy compared to the results of a homogeneous model with a low level of detail while speeding up the simulation in comparison to a homogeneous higher-tier model.