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Fig. 7. Fore-aft (blue) and lateral (green) center of mass (COM) wall reaction
forces, COM fore-aft and lateral instantaneous velocity for two steps (one
stride) during climbing for (A) a cockroach, (B) a gecko and (C) the
spring-mass model (template). Cockroaches and geckos show similar COM wall
reaction forces and velocities. This pattern can be represented by the
template described in Fig. 8.
The fore-aft and lateral forces are in-phase and the lateral force is one-half
the oscillation frequency of fore-aft force. The velocities are phase-delayed
from the corresponding forces by approximately
/2. Climbing velocity for
the cockroach is 20 cm s-1, the gecko 49 cm s-1, and the
template 18 cm s-1. Broken lines indicate body weight. The stepping
patterns are shown below for a normalized stride. Black bars represent stance
period and white spaces the swing period.