Design and Experimental Evaluation of a Hybrid Wheeled-Leg Exploration Rover in the Context of Multi-Robot Systems
Bremen, Germany, 2018. University of Bremen.
This cumulative dissertation deals with the electromechanical design, electromechanical implementation, locomotion control, and experimental evaluation of a novel type of hybrid wheeled-leg exploration rover. The actively articulated suspension system of the rover is the basis for advanced locomotive capabilities of a mobile exploration robot. The developed locomotion control system abstracts the complex kinematics of the suspension system and provides platform control inputs usable by autonomous behaviors or human remote control. Design and control of the suspension system as well as experimentation with the resulting rover are in the focus of this thesis. The rover is part of a heterogeneous modular multi-robot exploration system with an aspired sample return mission to the lunar south pole or currently hard-to-access regions on Mars. The multi-robot system pursues a modular and reconfigurable design methodology. It combines heterogeneous robots with different locomotion capabilities for enhanced overall performance. Consequently, the design of themulti-robot system is presented as the frame of the rover developments. The requirements for the rover design originating from the deployment in a modular multi-robot system are accentuated and summarized in this thesis. With the active suspension rover on the one hand and a heterogeneous multi-robot system on the other hand, a combination of different locomotion modes is pursued in both, individual (sub-)systems and heterogeneous multi-robot systems. The two main topics of this thesis are: (1) Electromechanical system design, motion control design and experimental evaluation of an active suspension system. The developed rover suspension takes inspiration from wheeled and legged locomotion. Two versions of an active suspension consecutively building on each other are implemented within this thesis. (2) Design of heterogeneous modular multi-robot systems for planetary exploration missions. Different combinations of heterogeneous robots with driving, walking and climbing capabilities are instantiated. Three different multi-robot systems, subsequently building on each other, are developed in the scope of this thesis. With this thesis it is shown that the combination of different locomotion modes results in improved capabilities for negotiating challenging terrain. In case ofmulti-robot systems this is for example related to soil sampling within permanently shaded crater regions at the lunar south pole. In the context of the hybrid rover system an increased adaptability to natural terrain is shown. Experiments in laboratory indoor tests as well as an extended four week field trial are conducted and evaluated in this thesis. Special attention is given to the energy consumption of the suspension system, the quality of ground adaption, and the ability of slope climbing in different configurations of the suspension system.
PhD, Multi-Robot System, Rover, Active Suspension System