4. The Soft Robotics Approach

Starting from the user’s requirements previously defined, a new soft robotics approach was chosen and developed in order to overcome the criticalities arisen in the analysis of the state of the art. One of the key points of soft robotics is biomimicry: in place of heavy, rigid and noisy motors, artificial muscles are in charge of the movement of the soft structure, allowing a number of degrees of freedom unthinkable with traditional mechanics. The shift from hard to soft robotics brings the focus on materials: actuating and sensing devices are embedded in the material itself, which turns out to be smart. In particular, the attention was focused on Electroactive Polymers (EAPs): these polymeric materials work as transducers, converting electrical inputs into mechanical outputs, and vice versa. After an extensive material selection procedure among all the EAPs solutions currently available, Dielectric Elastomers (DEs) emerged as the most suitable materials for the intended application and a mathematical model of their electro-mechanical behavior is presented. The control of the hand exoskeleton is addressed in this section. Its objective is to help the astronaut accomplish the tasks he has to perform. The entire control system is composed of four phases: the recognition of the astronaut’s will (detect and distinguish the different movements), the control strategy, the enhancement of these movements and the measure of the actual position and force. The final measure system was implemented focusing on redundancy, safety control and to assure minimum performances also in off-nominal conditions.