Figure 1.

(A) The utilized hexapod walking robot in Bull Rock cave. The unstructured environment causes motion disturbances, which result in sensory event mistiming. The sensory phase ϕ^x measurement is compared to its estimation ${\widehat{\varphi }}^x$, where their difference is the phase error e. We distinguish two types of phase error: event absence, ${\varphi }^x>{\widehat{\varphi }}^x$, and disruption, ${\varphi }^x<{\widehat{\varphi }}^x$. An example of event absence is illustrated in (B), where at the beginning of the stance phase, the front leg finds itself in a depression (orange dot) and thus detects the ground contact later than expected (blue dot). In the disruption example (C), at the end of the swing phase, the front leg hits elevated terrain (orange dot) and thus detects the ground contact sooner than expected (blue dot).