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 (Toupin, 1956; Pelrine et al., 1998; 2000; Kofod et al., 2003). Thanks to the strong electro-mechanical 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; Kim & Tadokoro, 2007; Plante & Dubowsky, 2008; Biddiss & Chaua, 2008). In fact, conventional actuation technologies (such as electric motors) leave some basic problems 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 unsafe. A possible way to greatly increase safety, is the design of robotic structures which are less precise but more compliant when compared to traditional technologies. 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 less demand both on actuator and controller bandwidth and improved stability (Williamson, 1993; Paul & Shimano, 1976). -The need to develop alternative actuators to overcome design limitations which are imposed in few but very important specific applications. For instance, electromagnetic actuators cannot be used in the presence of the high magnetic fields generated by Magnetic Resonance Imaging (MRI) devices. Nevertheless, the possibility to accomplish manipulation tasks within an MRI environment would highly improve the diagnostic capabilities of this technology (Koseki et al., 2007). Thanks to their intrinsic 1) compliance, 2) lightness, 3) pliability and 4) low cost, actuators based on DE can be an explorable solution when trying to assess or improve the aforementioned issues. DELA are usually composed of one or more DE shaped as a thin membrane (film) and a flexible supporting frame. This chapter proposes a methodology that allows to modify the available thrust as a function of the actuator’s length at will of the designer and, in particular, to obtain constant force actuators. The design procedure is divided in two steps: 1) optimization of the DE electromechanical parameters 2) design of the flexible frame. The supporting frame is conceived as a compliant mechanism (Howell, 2001) and makes use of the stiffness characteristics of slider-crank mechanisms with elastic revolute pairs to be coupled (in symmetric or axis-symmetric configurations) with films of different geometries. Three actuator concepts are proposed which highlight the efficacy of the proposed method i.e. Rectangular DELA (1(a), 1(d)), Diamond DELA (1(b), 1(e)) and Conical DELA (1(c), 1(f)).

On Designing Compliant Actuators Based on Dielectric Elastomers for Robotic Applications / G. Berselli; R. Vertechy; G. Vassura; V. Parenti Castelli. - STAMPA. - 0:(2010), pp. 523-550. [10.5772/9311]

On Designing Compliant Actuators Based on Dielectric Elastomers for Robotic Applications

BERSELLI, GIOVANNI;VERTECHY, ROCCO;VASSURA, GABRIELE;PARENTI CASTELLI, VINCENZO
2010

Abstract

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 (Toupin, 1956; Pelrine et al., 1998; 2000; Kofod et al., 2003). Thanks to the strong electro-mechanical 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; Kim & Tadokoro, 2007; Plante & Dubowsky, 2008; Biddiss & Chaua, 2008). In fact, conventional actuation technologies (such as electric motors) leave some basic problems 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 unsafe. A possible way to greatly increase safety, is the design of robotic structures which are less precise but more compliant when compared to traditional technologies. 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 less demand both on actuator and controller bandwidth and improved stability (Williamson, 1993; Paul & Shimano, 1976). -The need to develop alternative actuators to overcome design limitations which are imposed in few but very important specific applications. For instance, electromagnetic actuators cannot be used in the presence of the high magnetic fields generated by Magnetic Resonance Imaging (MRI) devices. Nevertheless, the possibility to accomplish manipulation tasks within an MRI environment would highly improve the diagnostic capabilities of this technology (Koseki et al., 2007). Thanks to their intrinsic 1) compliance, 2) lightness, 3) pliability and 4) low cost, actuators based on DE can be an explorable solution when trying to assess or improve the aforementioned issues. DELA are usually composed of one or more DE shaped as a thin membrane (film) and a flexible supporting frame. This chapter proposes a methodology that allows to modify the available thrust as a function of the actuator’s length at will of the designer and, in particular, to obtain constant force actuators. The design procedure is divided in two steps: 1) optimization of the DE electromechanical parameters 2) design of the flexible frame. The supporting frame is conceived as a compliant mechanism (Howell, 2001) and makes use of the stiffness characteristics of slider-crank mechanisms with elastic revolute pairs to be coupled (in symmetric or axis-symmetric configurations) with films of different geometries. Three actuator concepts are proposed which highlight the efficacy of the proposed method i.e. Rectangular DELA (1(a), 1(d)), Diamond DELA (1(b), 1(e)) and Conical DELA (1(c), 1(f)).
2010
Advances in Robot Manipulators
523
550
On Designing Compliant Actuators Based on Dielectric Elastomers for Robotic Applications / G. Berselli; R. Vertechy; G. Vassura; V. Parenti Castelli. - STAMPA. - 0:(2010), pp. 523-550. [10.5772/9311]
G. Berselli; R. Vertechy; G. Vassura; V. Parenti Castelli
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/76453
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