Insect climbing: surface attachment, sloped locomotion and implications for robotics
Final Report Abstract
The project aimed at the examination of insect locomotion on variable slopes and substrates with variable slipperiness. Speckled cockroaches (Nauphoeta cinerea) and American cockroaches (Periplaneta americana) were used for the experiments. After selecting the specimens for good running abilities and willingness spherical Styrofoam markers were applied to the dorsal sides of the specimens in order to facilitate the digitization process. Initial experiments focused on level and vertical locomotion on slippery and non-slippery substrates in N. cinera. Subsequently, similar experiments were carried out with P. americana. In contrast to the experiments with N. cinera in those with P. americana slope angles were changed in steps of 15° from level up to vertical conditions. Upwards and downwards locomotion were tested in both species. The arenas used for the experiments were running tracks of 50 cm length and 3.5 to 4 cm width equipped with floors covered with 30 micron grit sandpaper. The walls of these tracks were 5 cm high and highly slippery to prevent the animals from escaping. The central section of the walkway was made of exchangeable hardboard pieces. The pieces were either covered with non-slippery 30 micron grit aluminium oxide sandpaper or slippery 12 micron grit sandpaper. Walls made of Perspex permitted the acquisition of sagittal plane kinematics in the central region of the running tracks. In order to stimulate the animals for quick escape runs the specimens were spurred by short puffs of air or by touching the feet or cerci with a fine paint brush. Straight and continuous runs were recorded on hard drive. Dynamics and kinematics of level running animals turned out to be unexpectedly complex. Vertical climbing, in contrast, was much simpler than assumed before. Thus, compared to level locomotion N. cinerea used significantly lower running speeds on vertical substrates. Due to the high temporal overlap of the consecutive sets of legs, low speeds led to increased duty factors and increased numbers of legs in contact with the ground. However, on level ground a new gait was found for high running speeds, which was not described before for terrestrial arthropods. Thus, cockroaches but also mites and probably other arthropods change at their highest running speeds from the wellknown alternating leg coordination scheme to metachronal leg coordination. Despite low duty factors, this new gait results in reduced vertical peak forces, low vertical amplitudes of the COM, and an increase in the minimum number of legs on the ground. Metachronal leg coordination at high running speeds is particularly useful in animals with limited capabilities for elastic energy storage within the legs. Animals that use this gait can increase their energy efficiency without the need of elasticity. Moreover, controllability of their movements is increased which might result in a higher dynamic stability. All of these features are highly interesting for fast poly-pedal robotic implementations. Accordingly, I decided to focus on the examination of advantages and disadvantages of the new coordination pattern and associated body dynamics.
Publications
- (2015). Kinematic adjustments for climbing: cockroaches running on vertical and level substrates of different slipperiness. Annual Main Meeting of the Society for Experimental Biology. Prague
Weihmann T., Brun P., Pycroft E. and Federle W.
- (2015). Requirements and limits of anatomy-based predictions of locomotion in terrestrial arthropods with emphasis on arachnids. Journal of Paleontology 89, 980-990
Weihmann T., Goetzke H. H. and Günther M.
(See online at https://doi.org/10.1017/jpa.2016.33) - (2016). Metachronal leg coordination and body dynamics in rapid running cockroaches. Annual Main Meeting of the Society for Experimental Biology, Brighton
Weihmann T. and Federle W.
