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Meeting Abstract

16 A-6   11:15 - 11:30  Robophysical modeling of the coordination between body undulation and leg movement in centipedes Wang, T*; Chong, B; He, J; Diaz, K; Erickson, E; Goldman, DI; Georgia Institute of Technology; Georgia Institute of Technology; Georgia Institute of Technology; Georgia Institute of Technology; Georgia Institute of Technology; Georgia Institute of Technology tianyuwang@gatech.edu

Centipedes that locomote using retrograde (head-to-tail) waves of limb stepping can display body undulations at high speed [Manton, Zool. J. Linn. Soc., 1952] but little is known how these animals coordinate body undulation with stepping patterns to generate effective motion. Positing that locomotion on flat frictional terrain in centipedes is dominated by dissipative forces, to capture body/limb stepping interaction effects in this regime, we developed a reduced-dimension servo-motor driven robophysical model (L = 70 cm, 8 leg pairs) which we programmed to generate two waves: one of stepping and the other of body bending, both propagating from head to tail. We expected that the model would achieve effective performance when body and limb waves possessed the same spatial wavenumber (i.e., n_{leg}=n_{body}). In fact, when n_{leg}=n_{body}=1, effective forward motion (27.5±0.3 cm/cycle) occurred only at a particular coordination (a body-limb wave phase lag = 1.5?); deviations from this phasing resulted in lower performance, including backward motion (e.g., -17.2±0.2 cm/cycle when body-limb phase lag = 0.5?). Increasing the spatial wavenumber in limb waves (n_{leg}=1.6), allowed robust locomotion with speeds of 15.4±7.0 cm/cycle over body-leg phase lags ranging from 0 to 2?, compared to speeds of 8.6±17.1 cm/cycle when n_{leg}=1.0. To test if mismatched body-limb wavenumbers occur in centipedes, we studied the body-leg coordination in Scolopendra polymorpha (N=3, L =7.7±1.5 cm, 19 joints and leg pairs) running on a treadmill using a high-speed camera and markerless tracking tools [Mathis et al, Nat. Neurosci., 2018]. We observed that the spatial frequencies in body waves (n_{body}=1.6±0.2) and limb waves (n_{leg}=2.2±0.2) differed, and hypothesize that when running at high speed, centipedes use different number of waves on their legs and body to avoid having to maintain a precise body-limb wave phasing, thereby ensuring robust locomotor performance.