Benchmarking of a Commercially Available Stacked Dielectric Elastomer as an Alternative Actuator for Rehabilitation Robotic Exoskeletons

Abstract

Recent commercial availability of a stacked dielectric elastomer actuator (SDEA) has opened up possibilities of their use as "artificial muscles" for rehabilitation robots and powered exoskeleton devices. Made by CTsystems, this actuator (CT_SDEA) is made from soft materials, and offers a lightweight and acoustically noiseless alternative to DC motor actuators used in conventional rehabilitation robotic systems. The purpose of the present work was to benchmark the electromechanical properties of CT-SDEAs to assess its capabilities and limitations for mechanizing rehabilitation robots. The CT-SDEAs tested in this study showed 21 ms electrometrical delay, and their calculated strain-rate was 660 %/s. They could generate 21.74 N of force and have a 426 W/kg power-to-mass ratio. Their longitudinal strain was measured at 3.3%. Additionally, their steady state current consumption was measured 39 $\mu$ A. CT-SDEAs' fast response, short electromechanical delay and high strain-rate, make them highly suitable for closed-loop control. Additionally, their force generation capability, fast response, high power-to-mass ratio, and low steady state power consumption make them a strong candidates for exoskeleton applications. It's longitudinal strain (3.3%) however, was less than that of skeletal muscle (20%). Depending on the application, their use may require the addition of mechanical linkages, for force to displacement conversion.