Towards a self-deploying and gliding robot

Strategies for hybrid locomotion such as jumping and gliding are used in nature by many different animals for traveling over rough terrain. This combination of locomotion modes also allows small robots to overcome relatively large obstacles at a minimal energetic cost compared to wheeled or flying robots. In this chapter we describe the development of a novel palm sized robot of 10\,g that is able to autonomously deploy itself from ground or walls, open its wings, recover in midair and subsequently perform goal- directed gliding. In particular, we focus on the subsystems that will in the future be integrated such as a 1.5\,g microglider that can perform phototaxis; a 4.5\,g, bat-inspired, wing folding mechanism that can unfold in only 50\,ms; and a locust-inspired, 7\,g robot that can jump more than 27 times its own height. We also review the relevance of jumping and gliding for living and robotic systems and we highlight future directions for the realization of a fully integrated robot

Comparative studies of courtship behaviour in sympatric sibling species of Zaprionus (Diptera - Drosophilidae)

Zaprionus tuberculatus and Z. sepsoides are two sibling species of drosophilid fly which are sympatric throughout tropical Africa. Their sexual behaviour has previously received little study. In this thesis, the courtship behaviours of the two species are described, and the descriptions compared with previously published descriptions by other authors. Three different laboratory-bred strains of Z. sepsoides, and two of Z. tuberculatus, were studied, and their male courtship "songs" (produced by male wing vibration) were compared. The main objects of the project were to study the mechanisms by which members of these two species identify the sex of other individuals (sexual dimorphism being slight); and the isolating mechanisms operating between the two species. Preliminary observations suggested that males could probably identify females by chemosensory cues. However, males would sometimes also court each other. Further experiments on the males' ability to distinguish sex-specific pheromones gave ambiguous results. There were no grounds to suspect that females could distinguish between the sexes by chemosensory means, and further experiments gave no evidence for such an ability. Preliminary observations indicated that that there was an effective pre-mating reproductive barrier between male Z. sepsoides and female Z. tuberculatus, but male Z. tuberculatus were sometimes able to copulate with female Z. sepsoides. These interspecific matings resulted in infertile eggs. Further experiments seemed to confirm that the isolating mechanism between the two species is asymmetric, the onus of species recognition lying largely on Z. sepsoides. Male Z. sepsoides apparently recognise a female's species by chemosensory means, while female Z. sepsoides recognize a male's species by his "Type-2" courtship "song". There was also some evidence that female Z. sepsoides could distinguish between males of the two species by olfactory means. Z. tuberculatus were not shown to be able to distinguish reliably between the two species. The relevance of these findings to current theories about mechanisms of speciation is discussed.</p

Hysteresis of soft joints embedded with fluid-filled microchannels

Many arthropods are known to achieve dynamic stability during rapid locomotion on rough terrains despite the absence of an elaborate nervous system. While muscle viscoelasticity and its inherent friction have been thought to cause this passive absorption of energy, the role of embedded microstructures in muscles and muscle joints has not yet been investigated. Inspired by the soft and flexible hinge joints present in many of these animals, we have carried out displacement-controlled bending of thin elastic slabs embedded with fluid-filled microchannels. During loading, the slab bends uniformly to a critical curvature, beyond which the skin covering the channel buckles with a catastrophic decrease in load. In the reverse cycle, the buckled skin straightens out but at a significantly lower load. In such a loading–unloading cycle, this localized buckling phenomenon results in a dynamic change in the geometry of the joint, which leads to a significant hysteresis in elastic energy. The hysteresis varies nonlinearly with channel diameters and thicknesses of the slab, which is captured by a simple scaling analysis of the phenomenon

Do morphological adaptations for gliding in frogs influence clinging and jumping?

The ability to glide has evolved in multiple taxa and is usually associated with highly specialized morphological adaptations. Traits that evolve for one reason, can, however, influence other traits and abilities. In this study, we examined the influence of adaptations for gliding on the jumping and clinging abilities of frogs by comparing specialized flying frogs (Rhacophorus) and unspecialized non-flying frogs (Polypedates) from the family Rhacophoridae. Flying frogs had more webbing, longer legs, and greater clinging abilities than non-flying frogs. Clinging abilities, jumping distance, and gliding distance all correlated positively with body size for both flying and non-flying frogs. We did not, however, find any significant differences between the two groups in horizontal jumping distance or glide distance from a low starting point of 1.56 m. The morphological adaptations that evolved for gliding have not significantly influenced the flying frogs' short-distance jumping abilities, but may have influenced their clinging abilities. Alternatively, there may have been direct selection for clinging ability because of flying frogs' increased need, compared with other frogs, to land on vertical surfaces without slipping off