Model-Based Approach to Rover Health Assessment - Mars Yard Discoveries

This paper presents the modeling process and test results of the MONSID fault diagnosis system as applied to the mobility subsystem of JPL's Athena development rover. Athena's mobility system includes independent steering and driving motors for six wheels as well as wheel position sensors. The rover mobility system proved particularly challenging to model due to limited visibility into lower level wheel assembly hardware, a high degree of terrain interaction, and incomplete understanding of Athena behavior. However, even with simplified models, MONSID proved able to detect 16 distinct anomaly types during functional tests and simulated science activities carried out in JPL's Mars Yard. These faults included simulated and actual motor faults as well as instances of stalls due to terrain. Additionally, several detected faults were discovered during MONSID testing that were not anticipated. System characterization during the modeling process revealed several hardware and operational problems, leading to updates in Athena's control firmware and sensor processing software.