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A fault adaptive control methodology for mobile robots is presented. The robot is modeled as a continuous system with a supervisory controller. The physical processes of the robot are modeled using bond graphs, and this forms the basis of a combined qualitative reasoning and quantitative model-based estimation scheme for online fault detection and isolation during robot operation. A hierarchical-control accommodation framework is developed for the supervisory controller that determines a suitable control strategy to accommodate the isolated fault. It is shown that for small degradations in actuation effort, a robust controller achieves fault accommodation without significant loss of performance. However, for larger faults, the supervisor needs to switch among several controllers to maintain acceptable performance. The switching stability among a set of trajectory tracking controllers is presented. Simulation results verify the proposed fault adaptive control technique for a mobile robot.
Date of Publication: June 2003