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The base of the design and construction of an adaptive light-weight climbing robot is an understanding of the adaptive nature of small mammals’ motion on sloped supports. In the present study, the locomotor generalist Rattus norvegicus (the rat) served as the main biological paragon. Experiments were performed under X-ray high-speed videography with synchronized substrate reaction force (SRF) measurements, to allow calculation of inverse dynamics. Statistical analyses were performed to examine the effects of different substrate orientations on the kinematic variables. We obtained SRFs, torque and power patterns in the extremities and trunk of rats moving on simulated arboreal substrates at different substrate orientations (0°, 30°, 60°). During locomotion on horizontal substrates, rats prefer symmetrical gaits and switch to synchronous gaits at 60° inclination. Surprisingly, horizontal locomotion and locomotion on moderately inclined substrates (30°) differ only in the power invested in locomotion. Our results suggest that the trunk seems to play a more important role during locomotion at steeper inclines where rats switch to the more quasi-static in-phase gait. We conclude that this may be an indication of a change from a grounded to a climbing gait. Via bionic transfer we derived main basic principles, which we applied to the design of the robot Rat-Nic.
Biologically inspired robots, biomechanics, inverse dynamics, rat locomotion
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