Development of the functional unit of a completely soft octopus-like robotic arm

In the presented paper the realization of an artificial functional unit of muscular hydrostat inspired by the octopus is shown. The octopus has been chosen because it shows high manipulation capabilities and dexterity without a skeletal support, thus it is a good example of Embodied Intelligence. Inspiration from Nature concerns the features that are interesting from a robotic point of view for the development of an artificial muscular hydrostat: in particular actuators arrangement and their antagonistic mechanism. The main focus was on the two key elements of the unit: soft actuators and support structure. Shape memory alloys (SMA) has been chosen for actuation technology, whereas the support structure is a braided sleeve, that provides spatial continuity to the action of the actuators. Two contiguous units have been built and tested in water. Capabilities of shortening, elongation and bending have been observed and their performances evaluated. A maximum elongation of 43% has been recorded from shortened to elongated condition, with a diameter variation of 25%, finding a good match with the expected results from the support structure models. Relative angle between extremities has been measured during bending in two conditions and their efficiency has been compared.