Modeling of Planar Hydraulically Amplified Self-Healing Electrostatic Actuators

Abstract

With the advantages of high actuation strain and specific power and ability of self-healing after dielectric breakdown, the planar hydraulically amplified self-healing electrostatic (pHASEL) actuators are promising for extensive emerging applications of soft robots. However, the relationship between the output and the input of actuator should be quantified to provide precise driven behavior data for motion mechanism. Due to the interdependence of output length and force, we mainly investigate the voltage-length-force relationship of the pHASEL actuator in this paper. The output forces include electrostatic force, elastic force, and corrective elastic force, namely hydrostatic force. We deduce the electrostatic force model which is approximated to be an infinite parallel capacitor including three dielectric layers. The elastic force is produced by the main elastomer covered by electrode and the marginal elastomer, and they are predicted by Neo-Hookean model under biaxial condition. Since the aggregation of dielectric liquid used in pHASEL causes significant error in the electrostatic force prediction, we suggest calibrating the volume to reduce the error by nearly 50%. The influence by cambered shape elastomer is also deduced. To validate the proposed model, the output forces and the applied voltage under different sizes of pHASEL actuators are measured under different stretching lengths. The results demonstrate that the model can well describe the voltage-length-force relationship.