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Journal of Robotics
Volume 2012 (2012), Article ID 694673, 15 pages
http://dx.doi.org/10.1155/2012/694673
Research Article

Fault-Tolerant Control Strategy for Steering Failures in Wheeled Planetary Rovers

1Institute of System Dynamics and Control, German Aerospace Center (DLR), 82205 Weßling, Germany
2Institute of Robotics and Mecatronics, German Aerospace Center (DLR), 82205 Weßling, Germany
3Space Mechanics and Control Division, National Institute for Space Research (INPE), 12227-010 São José dos Campos, SP, Brazil

Received 1 June 2012; Accepted 27 November 2012

Academic Editor: Kazuya Yoshida

Copyright © 2012 Alexandre Carvalho Leite et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Fault-tolerant control design of wheeled planetary rovers is described. This paper covers all steps of the design process, from modeling/simulation to experimentation. A simplified contact model is used with a multibody simulation model and tuned to fit the experimental data. The nominal mode controller is designed to be stable and has its parameters optimized to improve tracking performance and cope with physical boundaries and actuator saturations. This controller was implemented in the real rover and validated experimentally. An impact analysis defines the repertory of faults to be handled. Failures in steering joints are chosen as fault modes; they combined six fault modes and a total of 63 possible configurations of these faults. The fault-tolerant controller is designed as a two-step procedure to provide alternative steering and reuse the nominal controller in a way that resembles a crab-like driving mode. Three fault modes are injected (one, two, and three failed steering joints) in the real rover to evaluate the response of the nonreconfigured and reconfigured control systems in face of these faults. The experimental results justify our proposed fault-tolerant controller very satisfactorily. Additional concluding comments and an outlook summarize the lessons learned during the whole design process and foresee the next steps of the research.