Towards an Autonomous Walking Robot for Planetary Surfaces

In this paper, recent progress in the development of the DLR Crawler - a six-legged, actively compliant walking robot prototype - is presented. The robot implements a walking layer with a simple tripod and a more complex biologically inspired gait. Using a variety of proprioceptive sensors, different reflexes for reactively crossing obstacles within the walking height are realised. On top of the walking layer, a navigation layer provides the ability to autonomously navigate to a predefined goal point in unknown rough terrain using a stereo camera. A model of the environment is created, the terrain traversability is estimated and an optimal path is planned. The difficulty of the path can be influenced by behavioral parameters. Motion commands are sent to the walking layer and the gait pattern is switched according to the estimated terrain difficulty. The interaction between walking layer and navigation layer was tested in different experimental setups

Multisensor Data Fusion for Robust Pose Estimation of a Six-Legged Walking Robot

For autonomous navigation tasks it is important that the robot always has a good estimate of its current pose with respect to its starting position and - in terms of orientation - with respect to the gravity vector. For this, the robot should make use of all available information and be robust against the failure of single sensors. In this paper a multisensor data fusion algorithm for the six-legged walking robot DLR Crawler is presented. The algorithm is based on an indirect feedback information filter that fuses measurements from an inertial measurement unit (IMU) with relative 3D leg odometry measurements and relative 3D visual odometry measurements from a stereo camera. Errors of the visual odometry are computed and considered in the filtering process in order to achieve accurate pose estimates which are robust against visual odometry failure. The algorithm was successfully tested and results are presented

Stereokamerabasierte Navigation eines Krabbelroboters auf unebenem Gelände

Im Rahmen dieser Diplomarbeit wird ein Algorithmus zur Navigation eines mobilen Roboters in unbekanntem unebenem Gelände entwickelt, der allein auf den Bildern einer Stereokamera basiert und der daher auch für Laufroboter geeignet ist. Der Navigationsalgorithmus soll den Roboter auf einem möglichst kurzen und sicheren Weg zu einem Zielpunkt führen, dessen Koordinaten relativ zum Startpunkt des Roboters vom Benutzer vorgegeben werden. Es werden die Ergebnisse einer Literaturrecherche zu vorhandenen Navigationsansätzen für planetare Rover vorgestellt. Basierend auf diesen Erkenntnissen wird ein Navigationsalgorithmus für unebenes Gelände entworfen, welcher die Lösung der Teilaufgaben Lokalisation, Kartenerstellung, Geländebewertung, Pfadplanung und Bewegungssteuerung beinhaltet. Der Algorithmus wird implementiert und auf einem radgetriebenen Roboter sowie auf einem sechsbeinigen Laufroboter in verschiedenen ebenen und unebenen Umgebungen getestet. Die Ergebnisse der Tests werden dargestellt und Möglichkeiten zur Erweiterung des Navigationsalgorithmus werden genannt

A Comparison of Johansen and Phillips-Hansen Cointegration Tests of forward market efficiency - Baillie and Bollerslev revisited

A navigation algorithm for mobile robots in unknown rough terrain has been developed. The algorithm is solely based on stereo images and suitable for wheeled and legged robots. The navigation system is able to guide the robot along a short and safe path to a goal specified by the operator and given in coordinates relative to the starting point of the robot. The algorithm uses visual odometry for localization. The terrain is modeled from stereo images and its traversability is estimated. A D* Lite planner is used for efficiently planning a short and safe path by incorporating terrain traversability in the planning process. The robot actively explores its environment as it follows the path to the goal. The algorithm has been tested on a wheel driven mobile robot and on a six-legged walking robot on rough terrain