Dynamic response characterization of soft fluidic actuators via dielectric elastomer sensors

Fluidic Elastomer Actuators (FEAs) consist of mechanical system capable of undergoing large deformations by means of controlled pneumatic or hydraulic driving force and whose application is becoming widespread across robotics, biomedical devices and even construction engineering. Owing to the large extent of deformation which these systems can undergo, undertaking the simultaneous characterization of their actuation and dynamic response is extremely daunting because it requires dedicated sensing technology with the capability to withstand extensive strains and high sampling frequency. However, suitable sensors for state estimation of soft fluidic actuators is necessary in order to monitor their structural health as well as perform accurate closed-loop feedback control. To this end, in this study we present a Dielectric Elastomer Sensor (DES) that captures the vibration response of a stereotypical soft fluidic system with a free curved surface subject to substantial deformation under the effect of pneumatic actuation. The DES consists of polydimethylsiloxane (PDMS), which was prepared with its elastomer base and curing agent mixed in three different ratios, and carbon nanotubes as the electrode material. The DES manifests linear response to vibration amplitude of the actuated body during vibrational test over measurable frequency up to 100 Hz. The static deformation and vibration amplitude were measured as changes in capacitance across the DES showing that hysteresis during static deformation and cyclic testing is negligible. The sensitivity of the DES while sensing both the static deformation and vibration amplitude of the FEA increased as the static pressure decreased, which followed an exponential function. These results highlight how DES may constitute a valuable sensing device for capturing fast dynamic response of highly deformable devices or structure, pointing at the chance to adopt them in soft robotics control and structural monitoring.