Poka: a necro-robot beetle with a measured payload ratio of 6847 %

ABSTRACT This paper is concerned with the design, manufacture and validation of ‘Poka’, a novel millimetre-scale necro-robot aimed at bridging the performance gap between miniature robots and insects. To create Poka, we use the exoskeleton of a deceased five-horned rhinoceros beetle ( Eupatorus gracilicornis ) as a mechanical chassis, which is mechatronically functionalised to enable ambulation. When comparing the payload ratio, PR , of Poka against reported values of the rhinoceros beetle Xyloryctes thestalus , we find that Poka’s PR is more than 2-fold higher, reaching a measured maximum of 6847% (i.e. 68.47 times its own body weight). The specific power at maximum payload, P s,t , is nevertheless of the same order of magnitude in both Xyloryctes thestalus (0.21 W/kg) and Poka (0.28 W/kg). Poka’s highest average speed, is achieved at a PR = 2739%, after which it progressively decreases with increasing payload ratio, reaching its minimum at maximum payload ratio. When comparing Poka’s maximum measured PR of 6847% against those of sixteen other ambulating robots, we find that Poka’s PR far exceeds that of any other robot to date, the highest being otherwise from SuperBot who has a PR = 530%. Poka’s payload ratio is therefore the highest robot payload ratio recorded to date and we attribute this to (a) the use of the beetle body as a natural composite chassis with high specific properties, and (b) the additive manufacture of bionic beetle parts using low density but stiff polylactic acid, designed with structurally stable geometries.