Scaled tremor suppression with folded dielectric elastomer stack actuators

Abstract

Pathological tremor produces undesired movements that decrease quality of life. Typical treatments such as medications and surgery have varying efficacy, risks, and side effects. Mechanical tremor suppression offers a potential alternative to these treatments: mechanical tremor suppression applies torques about joints to oppose the tremor-producing muscular torque and reduce tremor motion. Typical actuators create bulky exoskeletons that are not suitable for clinical implementations. However, dielectric elastomers enable soft, low-profile actuation that improves the potential for clinical implementation of mechanical tremor suppression. Recent research performs theoretical evaluation of dielectric elastomer-based tremor suppression, demonstrating the ability of dielectric elastomer stack actuators (DESAs) to produce very effective and robust tremor suppression via tremor-active control. A tremor-active approach only actuates to reduce tremor while the human motor system compensates for DESA passive dynamics. This approach leverages the low mechanical impedance of dielectric elastomers to compensate for their low actuation levels. This paper performs benchtop experimental testing of scaled tremor-active suppression using folded DESAs to validate previous theoretical studies. Since DESA manufacturing by folding can only achieve relatively thick layers, the DESAs do not possess the necessary actuation levels to suppress typical tremor amplitudes. Therefore, this paper evaluates a scaled system using a piezoelectric bimorph cantilever beam to represent human motion. Experiments demonstrate the effectiveness of a tremor-active impedance controller for DESA-based tremor suppression. Scaling up to DESAs with higher actuation levels will enable suppression of typical hand tremors.