Inflatable soft robots powered by dielectric elastomer actuators show promise for extra-terrestrial applications. These must be stowed in a deflated configuration for launch, necessitating a method for inflation. Traditional methods, such as stored compressed gas, introduce unwanted mass, volume, and rigidity.
Gas Forming Reactions offer an alternative mechanism. Isolating citric acid in a silicone membrane creates a soft balloon which can be safely placed inside a soft structure and surrounded by bicarbonate. By adding an electrical connection inside and a soft electrode to the exterior we can electronically rupture the balloon to release the acid and trigger inflation.
Silicone is used in the space industry for protecting underlying materials from atomic oxygen. This oxygen reacts with the silicone to form silicon dioxide, which is highly resistant to further attack. Our work is focussed on exploring the use of dielectric elastomer transducers (DETs) in the space sector. These devices often use silicone as their key elastomeric component, if a DET becomes oxidised its motion is at least severely impaired if not completely halted. We have developed a solution to this problem in the form of a protective coating. We present here results of ground-based testing testing of the coating.
Soft robots with many degrees of freedom, modelled after snakes or tentacles, can locomote through a combination of controlled friction and phased multi-segment deformation. Using different periodic motions (gaits) snakes (and snake-like robots) are able to cross open space, climb narrow passages, side-wind across granular substrates, and more. Unlike their biological counterparts, snake-like robots should be able to adapt easily to space flight by utilising controllable friction elements in the form of electro-adhesive pads to selectively attach to and detach from surfaces and objects. They could operate on the interior and exterior of satellites to perform maintenance and repair, or even explore the surfaces of small astronomical bodies which do not produce enough gravity to allow for traditional wheeled rovers.
Dielectric elastomer actuators (DEAs) are an ideal candidate for the driving system of such a robot, and have already demonstrated the ability to form multi-degree of freedom actuators of varying design. They are lightweight, use minimal current to maintain a given position, have high energy density, and are capable of self-sensing their strain, reducing the need for external monitoring. We present here the design and analysis of a lightweight DEA snake-like robot incorporating electro-adhesive elements for operating in zero-gravity environments, including different gait waveforms for enhanced performance and finite element analysis for design optimisation. We conclude with discussion of future improvements, such as the incorporation of dielectric elastomer switches for greater autonomy.
Dielectric Elastomer Transducers (DETs) integrated into inflatable structures can form the basis for soft, low mass robots. Such robots will have very high packaging efficiency and be simple to deploy. These attributes, combined with the high power density of DETs make them ideal for space robots. In this paper we present a study of different motions achieved from the actuation of three distinct simple experimental designs. Firstly, the dome actuator constructed from a sheet of silicone rubber with segmented electrodes. Secondly, an elongation of the former, capable of producing locomotory motion from phased actuation of segments. Finally, a rolled cylindrical design varying the seam geometry, and electrode position and composition to produce different resonant and non-resonant motion. This study is comprised of experimental results, and finite element modelling of each design using commercially available FEM software. The different structures are simulated undergoing inflation and actuation, and the results compared to experimental data. Modal analyses of the inflated cylindrical structures are also compared with the frequency responses of the experimental models. Extrapolation of these basic units to more complex structures, designed to complement or replace existing space equipment, is presented for discussion alongside the remaining challenges.
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