Abstract
In the space environment the absence of gravity calls for constant safe attachment of any loose object, but the low-pressure conditions prohibit the use of glue-type adhesives. The attachment system of freely hunting spiders, e.g. Evarcha arcuata, employs van der Waals forces and mechanical interlocking. Furthermore, detachment is achieved passively and requires little force. Hence, the spider serves as a model for a versatile legged robot for space applications, e.g. on the outer surface of a space station. In this paper, we analyse the dry attachment systems ofE. arcuataand geckos as well as the kinematics of freely hunting spiders. We generalise the results of biological studies on spider locomotion and mobility, including the major movement and the position constraints set by the dry adhesion system. From these results, we define a simplified spider model and study the overall kinematics of the legs both in flight and in contact with the surface. The kinematic model, the data on spider gait characteristics and the adhesion constraints are implemented in a kinematic simulator. The simulator results confirm the principal functionality of our concept.
Highlights
The space environment is technically highly challenging and any space-adapted autonomous system has to be conceived carefully (Bellingham and Rajan 2007).Since almost all spacecraft are situated in rather remote locations during duty and cannot be accessed for repair, absolute reliability is mandatory
We generalise the results of biological studies on spider locomotion and mobility, including the major movement and the position constraints set by the dry adhesion system
The present study demonstrates that the same result in control can be achieved in a system with drastically reduced kinematic complexity compared to the animal model
Summary
The space environment is technically highly challenging and any space-adapted autonomous system has to be conceived carefully (Bellingham and Rajan 2007). They exploit an intermolecular attraction – van der Waals forces – without requiring sticky fluids as mediators In consequence, these attachment mechanisms principally qualify for application in non-atmospheric, low-pressure environments. The spider attachment system works – in contrast to the muscularly mediated one of the geckos – completely passively; it is only controlled by the movement of the animal’s leg and control of attachment can be integrated into the leg’s movement control Starting from these basic assumptions, we analysed the spiders’ strategies to attach to smooth surfaces to conceptualise a technical solution principally able to walk freely on the outer surface of a space station.
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