On Designing Compliant Actuators Based On Dielectric Elastomers for Robotic Applications 523 On Designing Compliant Actuators Based On Dielectric Elastomers for Robotic Applications

This chapter reports on advances done in the design of compliant, Dielectric Elastomer based Linear Actuators (DELA). Dielectric Elastomers (DE) are incompressible deformable dielectrics which can experience deviatoric (isochoric) finite deformations in response to applied large electric fields while, at the same time, alter the applied electric fields in response to the deformations undergone (Kofod et al., 2003; Pelrine et al., 1998; 2000; Toupin, 1956). Thanks to the strong electromechanical coupling, DE intrinsically offer great potentialities for conceiving novel solid-state mechatronic devices and in particular actuators. These devices can be profitably used for robotic applications (Bar-Cohen, 2004; Biddiss & Chaua, 2008; Kim & Tadokoro, 2007; Plante & Dubowsky, 2008). In fact, concerning conventional actuation technologies (such as electric motors), some basic problems remain unaddressed or, at least, improvable, such as: • The need to increase flexibility and simplify design solutions. For an important number of applications, conventional systems are too heavy, inefficient (in terms of high power consumptions), too expensive and still relatively complex. • The need to design human-friendly machines (Bicchi & Tonietti, 2004). In order to achieve highly precise position control, many industrial mechatronic systems (especially industrial robots) are designed to be very fast and stiff and thus potentially dangerous to humans. A possible way to greatly increase safety, is the design of robotic structures which are less precise but more compliant when compared to the traditional ones. To this respect, it is possible to concentrate the compliance in the actuated joints by using compliant (soft) actuators. • The need for modern robots to interact with unstructured environments and to actively control force and stiffness at the contact interface. A promising approach is to rely on a mechanical system that is inherently compliant and to use active control strategies to vary this compliance (Biagiotti et al., 2004). The main advantages are a lower request both on actuator and controller bandwidth and improved stability (Paul & Shimano, 1976; Williamson, 1993). 28