Towards holonomic electro-elastomer actuators with six degrees of freedom

Abstract

Functionally efficient six degree of freedom (DOF) actuators have not yet been developed in a scale-invariant and inherently compliant unified form. This has primarily been due to the use of conventional serial or parallel kinematical configurations and electromagnetic motors, pneumatics and hydraulics. Contrary to traditional technologies, utilizing electro-active elastomers enables multi-DOF actuation and holonomic operation with minimal structural complexity. Conical dielectric elastomer actuators (DEAs) are compact multi-DOF actuator–sensors that are scalable and can be entirely polymeric, making them suitable for a variety of applications including minimally invasive medical devices. In this paper, cone DEAs are developed towards integrated 6-DOF actuation with muscle-like performance from a single structure. This is achieved by demonstrating the feasibility of holonomic 6-DOF actuation and through experimental characterization of a 5-DOF prototype. The 5-DOF prototype (50 mm length, 60 mm diameter) produced rotational actuation outputs of ±21.7° and ±9.42 mN m and linear actuation outputs of ±4.45 mm (±9.1%) and ±0.55 N. Finally, combined multi-DOF actuation is demonstrated as part of development towards scalable holonomic electro-active elastomer actuators.

Multi-functional dielectric elastomer artificial muscles for soft and smart machines

“…The kinematics of the convex conical 5 degree of freedom actuator has recently been studied by Conn and Rossiter 49,50 (Fig. 9), an actuator that can be manufactured using print technology.…”

“…They have shown how this rotation can be achieved on a planar actuator using a non-uniform curved electrode patterning. 50 DE artificial muscles provide an attractive mechanism for multi-freedom devices that are fully soft and flexible with no rigid framework. Potz et al 43 demonstrated a soft rolling robot consisting of an inflated elastomer cylinder with an electro-active skin in four segments.…”

Elastic actuation for legged locomotion

“…This double cone DEA design, as applied by [5] and [6], consists of two single DE membranes stretched over a rigid rod in the center which maintains the tension. The two single conical DEA membranes can be actuated separately to produce bidirectional actuation.…”

“…In nature, groups of muscles are typically configured to work antagonistically to perform multi-DOF movements. Taking inspiration from this, many multi-DOF DEAs have been developed: [4] produced a spring roll design with two DOF and a 5 DOF cone DEA is proposed by [5] and [6], which can be extended this into a 6 DOF elastic cube actuator [7].…”

Modeling a soft robotic mechanism articulated with dielectric elastomer actuators

“…This mechanism can generate a mono- directional or bidirectional movement. As an extension of this linear actuator a six degree of freedom conical DEAs is established to produce rotational actuation outputs which can be exploited in minimally invasive medical devices [12]. Those proposed mechanisms, which are flexible and have a high energy density, show promising properties in various applications.…”