5. Concept Layout

The chapter presents the design of the device actuators and sensors in terms of concept developing, dimensioning, testing and prototyping. Inspired by soft robotics concept, the design of actuators is based on the characteristics of dielectric elastomers and their relationship between voltage applied and material elongation. Smart material properties are exploited in the multiple layers actuator proposed, capable of performing both linear elongation and bending, by means of the application of different voltage levels to different layers. Calculations of the torques required by the hand actions and, consequently, the maximum stress are presented. Then, the choice of the material leads to the identification of the correct dimensioning of the system, in terms of voltage to be applied and thick of the actuator layers. In order to control the actuation according to the human will, sensors based on physiological signals are required. EMG and MMG based sensors are chosen, specifying the sensors number and positioning required for an effective human will identification. Pressure sensors, realized with dielectric elastomers, give the feedback of the system. Calculations relating voltage measured and pressure applied on the sensors are presented. Finally, the prototyping and testing phase is described, in which two mockup hands are realized for a proof of concept while EMG and MMG sensors are tested. Experimental setup and qualitative results are extensively described.