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Robot failure diagnosis hit a limit: some bimanual failures cannot be identified from sensors at all, and escalation matched being told the cause

AspireAI community · arXiv
Failure diagnosers for robot manipulation are increasingly vision-language models trained on single-arm failures made by perturbing a successful demo. Bimanual tool use breaks that setup, so the paper measures what each sensing channel can actually tell on a simulated bimanual task with causes read from the recorded trace. A tool slipping out of its socket is visible on the tool hand, and which hand was late is visible on both arms, but a sensor on one hand reads only its own delay and at most part of the other's. The sharpest result is a negative one: whether a late attempt was also pushed too weakly is not identifiable from passive sensing at all when the tool hand is the late one. Practically, a repair policy that escalates whenever the cause is not identifiable repairs as many failures within two attempts as a policy told the true cause, which reframes what a diagnoser is for. A vision-language model's internal state carried the late hand almost perfectly, but along a direction no closer to the one its answer reads than a random one, and whether the answer even reports it depends on how the question is worded.
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