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3D Kinematic Modeling and Evaluation of Rough-Terrain Locomotion Modes for an ExoMars-like Mobility Subsystem

Wiese, Tim (2017) 3D Kinematic Modeling and Evaluation of Rough-Terrain Locomotion Modes for an ExoMars-like Mobility Subsystem. DLR-Interner Bericht. DLR-IB-RM-OP-2017-201. Master's. Technische Universität München. 118 S.

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One of the main challenges of planetary rover missions is the traversability of rough terrain areas, steep slopes and very soft soil fields. In the past, rovers repeatedly struggled while driving especially in these soft soils, with the Spirit rover even having to be abandoned. With ESA's upcoming ExoMars mission, a rover with an articulated suspension will land on Mars in 2021 that offers additional degrees of freedom through its actuated deployment joints. A full-body kinematic model allows to take full advantage of such a locomotion system. In this thesis, such a model was derived for EXM-BB2, a mobility subsystem prototype for the ExoMars rover. The model allows to specify desired body velocities and additional constraints on joint rates to achieve desired motions and includes a slip formulation on wheel level. Additionally, kinematic redundancies can be exploited by the introduction of secondary sub-tasks through null-space projection. Based on this model, two locomotion modes were implemented for increased traversability performance in rough terrain: Balancing, a mode for body pose adjustment that allows to increase the rover's tip-over stability and decrease its body tilt, and Wheel Walking, a mode for increasing gradeability on slopes and traction in soft soils. The effectiveness of the kinematic model and the locomotion modes were shown in a series of tests in the Planetary Exploration Laboratory at DLR. Balancing was able to reduce the rover body pitch and yaw angle by 5 degrees in uneven terrain and decrease side-slip while driving sideways along a slope by more than 50 percent. Wheel Walking managed to outperform Normal Driving (which only actuates the rover wheels) significantly in terms of traction on a slope. Using Wheel Walking, the rover managed to traverse a 30 degree slope with 70 percent of slip while Normal Driving failed at 21 degrees. Additionally, using Wheel Walking, energy consumption for slope traversal could be reduced by 50 percent.

Item URL in elib:https://elib.dlr.de/114850/
Document Type:Monograph (DLR-Interner Bericht, Master's)
Title:3D Kinematic Modeling and Evaluation of Rough-Terrain Locomotion Modes for an ExoMars-like Mobility Subsystem
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Date:October 2017
Refereed publication:No
Open Access:Yes
Number of Pages:118
Keywords:Kinematic modeling, ExoMars, balancing, wheel walking, mars rover, mars exploration, space robotics
Institution:Technische Universität München
Department:Fakultät für Informatik
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space System Technology
DLR - Research area:Raumfahrt
DLR - Program:R SY - Space System Technology
DLR - Research theme (Project):R - Project MOREX [SY]
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Robotics and Mechatronics (since 2013)
Deposited By: Wiese, Tim
Deposited On:17 Nov 2017 15:26
Last Modified:31 Jul 2019 20:12

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