349 research outputs found
Stiffness tailoring of conically-shaped dielectric elastomer linear actuators: design methodology and experimental validation
No full textA design methodology is presented, which makes it possible to optimize conically-shaped dielectric-elastomer (DE) linear actuators for known active material and required stiffness to an external load. The actuators are obtained by coupling DE films with compliant mechanisms that suitably modify the force generated by the elastomer films. The electromechanical properties of the DE films are determined through finite element analysis. The sizing of the compliant mechanisms is obtained through pseudo-rigid-body models and subsequently verified through finite element analysis. Experimental validation show that the designed actuators work as desired
Metodologia per la sintesi progettuale di attuatori ad elastomeri dielettrici.
No full textDielectric Elastomer based linear actuators are usually composed of one or more elastomer films and a flexible supporting frame. This paper 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 Dielectric Elastomer electromechanical parameters 2) design of the flexible frame. The supporting frame is conceived as a compliant mechanism 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 goodness of the proposed method
Optimal design of lozenge-shaped dielectric elastomer linear actuators: Mathematical procedure and experimental validation
No full textA novel mathematical procedure is presented, which makes it possible to optimize lozenge-shaped dielectric-elastomer-based linear actuators for known materials and desired force/stroke requirements. Simulation and experimental results are provided which both demonstrate the efficacy of the proposed optimization procedure with respect to traditional design approaches and show that simpler, cheaper, lighter, and better-behaved lozenge-shaped actuators can be conceived, which do not require any integration of compliant frame elements
Sviluppo concettuale di un dispositivo innovativo per attuatori ad elastomeri dielettrici
No full textGrazie al peso ridotto, all’elevata densità di potenza ed ai costi contenuti, gli attuatori ad elastomeri dielettrici (ED) stanno generando grande interesse in ambito meccatronico ancorché tale tecnologia non abbia tuttora raggiunto la piena maturità. In questo articolo si esaminano le proprietà elettromeccaniche di film di ED sagomati a forma di rombi piani ed accoppiati ad un dispositivo di supporto formato da due meccanismi cedevoli connessi in parallelo. Il primo meccanismo (detto diamante) ha i membri direttamente accoppiati al perimetro dell’ED. Il secondo meccanismo (detto delta) è progettato in modo da modificare la caratteristica di rigidezza dell’insieme diamante-ED, al fine di ottenere un attuatore a forza quasi-costante all’interno di una determinata corsa utile. Il dimensionamento dei meccanismi cedevoli è affrontato attraverso modelli pseudo-rigidi e verificato mediante analisi agli elementi finiti. Vengono infine mostrati i primi prototipi del dispositivo
Design of a single-acting constant-force actuator based on dielectric elastomers
No full textThe interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performancesare influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator, which is capable of supplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator
Positioning technology for stepwise underground robots
No full textPipeline robots, borehole robots or exploring robots that work in underground environments can be classified as underground robots. When an underground robot takes a task, tracing and mapping the track of the robot is very important. This project addresses the development of a positioning technique for stepwise underground robots, which have been developed in Durham University. This research is expected to provide a general benefit to stepwise robotic positioning systems rather than a particular robotic or other situation. The initial period of this project was the most difficult. After a few months of literature searching, no suitable positioning technique had been found. Existing techniques are suitable for surface robots, undersea robots or airborne robots but are far away from the application requirements for underground robots. Positioning technology depends on sensor techniques and measurement technologies. The underground environment restricts the use of absolute measurement technologies. Consequently, underground robotic positioning systems heavily rely on relative measurements, which can cause unbounded accumulation of the positioning errors. Moreover, underground environments restrict the use of many high precision sensors because of restricted space and other factors. Hence, the feasibility of developing high, long-term, accuracy underground robotic positioning systems was problematic. Since it was found that there was a lack of research on underground robotic positioning, fundamental investigation became necessary. The fundamentals include the dominant error and the characters of the accumulation of positioning errors. After the investigation of the fundamentals the difficulty and feasibility of developing a high long-term accuracy positioning system was understood more clearly and the key factors to improve the accuracy of a positioning system were known. Based on these, a novel parallel linkage mechanism based approach was proposed. This approach has flexibility in terms of geometrical structure and provides the possibility to improve long-term accuracy of a positioning system. Although parallel linkage mechanisms have drawn a great deal of attention from researchers in passed years, this is the first time a parallel linkage mechanism has been applied to a robotic positioning system. Consequently, new problems were generated by this application of parallel linkage mechanisms. In this project, a Principal Component Analysis (PCA) method is applied to solve the positioning problems and a particular case has been used to show how to solve these problems. Through this case, the advantages of this approach and the feasibility to improve the positioning accuracy is presented. The methodology that can be used to solve the problems for different particular cases can also be used to carry out study for general situations, which have also been illustrated. Many problems still need to be solved. At the end of this thesis, some further problems are discussed. The author of this thesis believes that the proposed approach can be applied to industrial projects in the near future
Experimental evaluation of optimal conically-shaped dielectric elastomer linear actuators
No full textA conically shaped Dielectric Elastomer (DE) linear actuator is presented which is obtained by coupling a DE film with a compliant mechanism. The compliant mechanism is designed, by means of a pseudo-rigid-body model, to suitably modify the force generated by the elastomer film. The resulting actuator provides a nearly constant force along the entire actuator stroke when the DE film is activated and returns to an initial rest position when the DE film is deactivated. Experimental activity fully validates the proposed concept. Possible applications of this kind of actuator are Braille cells, light weight robots and haptic devices
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