Antagonistic dielectric elastomer actuator for biologically-inspired robotics

Abstract

For optimal performance, actuators designed for biologically-inspired robotics applications need to be capable of mimicking the key characteristics of natural musculoskeletal systems. These characteristics include a large output stroke, high energy density, antagonistic operation and passive compliance. The actuation properties of dielectric elastomer actuators (DEAs) make them viable for use as an artificial muscle technology. However, much like the musculoskeletal system, rigid structures are needed to couple the compliant DEA layers to a load. In this paper, a cone DEA design is developed as an antagonistic, multi-DOF actuator, viable for a variety for biologically-inspired robotics applications. The design has the advantage of maintaining pre-strain through a support structure without substantially lowering the overall mass-specific power density. Prototype cone DEAs have been fabricated with VHB 4910 acrylic elastomer and have characteristic dimensions of 49mm (strut length) and 60mm (DEA diameter). Multi-DOF kinematical outputs of the cone DEAs were measured using a custom 3D motion tracking system. Experimental tests of the prototypes demonstrate antagonistic linear (±10mm), rotational (±25°) and combined multi-DOF strokes. Overall, antagonistic cone DEAs are shown to produce a complex multi-DOF output from a mass-efficient support structure and thus are well suited for being exploited in biologically-inspired robotics.

A Reconfigurable Crawling Robot Driven by Electroactive Artificial Muscle

“…All experiments were controlled by MATLAB (MathWorks) and all data was collected by a DAQ device (National Instruments, BNC-2111) at a sampling frequency of 20,000 Hz. It can be seen that the force-stroke relationships for all four samples are approximately linear, which agrees with a previous double cone DEA study [15]. As h increases, the maximum blocking force that can be exerted by the DEA increases at the same nominal electric field, while the maximum stroke reduces.…”

Dielectric Elastomer Actuator for Soft Robotics Applications and Challenges

“…The strut double-cone actuator is capable of vertical strokes as well as rotation and lateral strokes. Using a strut double-cone actuator made of VHB 4910, a maximum of 49.5 • rotational stroke, 8.1 mm lateral stroke, and 11.3 mm vertical stroke were produced at 3 kV [74,75]. Using this approach, up to six degrees of freedom can be achieved by patterning the electrodes [76] and eyeball movement devices were made by applying this advantage [77].…”

“…Its output can be amplified further by using them in bundles [44]. In addition, by adopting a biased spring [44,[71][72][73][74][75][76][77][78] or a bi-stable structure [73] that can store elastic energy, larger stress can be output.…”

Contactless coupling of dielectric elastomer membranes with magnetic repulsion

“…Out-of-plane biasing can also be achieved using an antagonistic DEA configuration, as demonstrated by Artificial Muscle Incorporated's Universal Muscle Actuator [10], which connected two offset membranes via a co-axial central disk to form a recessed conical shape. Coupling DEA membranes in an antagonistic configuration draws clear parallels to the skeletal muscle architectures in nature and similarly generates benefits such as maximizing stroke and offering dual capabilities for either bi-directional push/pull actuation (when each membrane is driven out-of-phase) or increased holding force (when the membranes are activated in-phase and in tension against each other) [11]. DEAs with antagonistically-coupled membranes have been exploited for numerous applications including bistable structures [12] and bio-inspired robotics such as manipulators [13] and walking [14], crawling [15] and flapping wing [16] robots.…”

“…DEAs with antagonistically-coupled out-of-plane membranes have typically relied on either a rigid [2,3,11] or hydrostatic [17] coupling between each membrane. Rigid coupling using a rod [2,3] or disk [11] creates a double cone configuration while hydrostatic coupling utilizes fluid pressure from an internally sealed volume to deform each DEA membrane into a hemispherical diaphragm [17]. If an incompressible fluid is used in the hydrostatically-coupled configuration, then each DEA diaphragm is, in effect, also rigidly coupled.…”