How UGVs physically fail in the field

This paper presents a detailed look at how unmanned ground vehicles (UGVs) fail in the field using information from 10 studies and 15 different models, in Urban Search and Rescue or military field applications. One explores failures encountered in a limited amount of time in a real crisis (World Trade Center rescue response). Another covers regular use of 13 robots over two years. The remaining eight studies are field tests of robots performed by the Test and Evaluation Coordination Office at Fort Leonard Wood. A novel taxonomy of UGV failures is presented which categorizes failures based on the cause (physical or human), its impact, and its repairability. Important statistics are derived and illustrative examples of physical failures are examined using this taxonomy. Reliability in field environments is low, between 6 and 20 hours mean time between failures. For example, during the PANTHER study (F. Cook, 1997) 35 failures occurred in 32 days. The primary cause varies: one study showed 50% of failures caused by effectors; another study showed 54% of failures occurred in the control system. Common causes are: unstable control systems, platforms designed for a narrow range of conditions, limited wireless communication range, and insufficient bandwidth for video-based feedback.