Design Principles for Using Dielectric Elastomer Transducers Applied to Powered Prosthetics and Orthotics

The advancement of powered prostheses and orthoses is restricted by the shortcomings of available actuator technologies such as electric motors, hydraulics, and pneumatics. Dielectric elastomer transducers (DETs) are a kind of artificial muscle that promises to overcome the shortcomings of the actuators commonly used in powered prostheses and orthoses. However, while much research has investigated how to design DETs themselves for optimal performance, little guidance is available for designing the devices that use DETs in their actuation systems. This work addresses this lack of guidance by reexamining the fundamental principles of DET operation, and then explains four design principles based on those fundamentals. The usefulness of these principles is demonstrated in two example designs that are proofs-of-concept for solutions to actuation challenges. The first design is a variable-stiffness actuator that uses dielectric elastomers to create variable stiffness without the mechanical complexity that plagues state-of-the-art variable stiffness actuator designs. The second design is an ankle-foot orthosis that uses a dielectric elastomer transducer to provide toe li assistance for foot drop patients without the drawbacks of current foot drop solutions.