Dielectric elastomer actuators for binary robotics and mechatronics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections."February 2006."Includes bibliographical references (p. 145-153).Future robotics and mechatronics applications will require systems that are simple, robust, lightweight and inexpensive. A suggested solution for future systems is binary actuation. Binary actuation is the mechanical analogy to digital electronics, where actuators "flip" between two discrete states. Systems can be simple since low-level feedback control, sensors, wiring and electronics are virtually eliminated. However, conventional actuators, such as DC motors and gearbox are not appropriate for binary robotics because they are complex, heavy, and expensive. This thesis proposes a new actuation technology for binary robotics and mechatronics based on dielectric elastomer (DE) technology. DE actuators are a novel class of polymer actuators that have shown promising low-cost performance. These actuators were not well understood and, as a result, faced major reliability problems. Fundamental studies conducted in this thesis reveal that reliable, high performance DE actuation based on highly viscoelastic polymers can be obtained at high deformation rates, when used under fast, intermittent motion.(cont.) Also, analytical models revealed that viscoelasticity and current leakage through the film govern performance. These results are verified by an in-depth experimental characterizion of DE actuation. A new DE actuator concept using multi-layered diamond-shaped films is proposed. Essential design tools such as reliability/performance trade-offs maps, scaling laws, and design optimization metrics are proposed. A unit binary module is created by combining DE actuators with bistable structures to provide intermittent motion in applications requiring long-duration stateholding. An application example of binary robots for medical interventions inside Magnetic Resonance Imaging (MRI) systems illustrates the technology's potential.by Jean-Sébastien Plante.Ph.D