Condition Assessment of Dielectric Liquid Actuator Based on High Voltage Dielectric Spectrum

In actuators driving based on Maxwell stress, high voltage is necessary to obtain the expected contraction because it is proportional to the voltage square. Therefore, the dielectric material constituting the actuators should have a high dielectric breakdown voltage. Moreover, considering the operation condition of the actuators, the material should exhibit a low dielectric loss. We prepared a HASEL (Hydraulically Amplified Self-healing Electrostatic Actuator) actuator using silicone or vegetable oil and observed its contraction under a square waveform voltage. At that time, the current responses during polarization and depolarization were acquired. In this paper, we proposed a method that can evaluate the change in the dielectric spectrum, such as impedance trajectory and Maxwell stress, with the contraction of the actuator from the current responses. When the HASEL actuator using silicone oil droved continuously, the contractions saturated after moving a few times because silicone oil has better insulation performance than vegetable oil and is easy to electrify. This tendency can be read from the changes in impedance trajectory and Maxwell stress. From the above, the proposed method enabled condition assessment under high voltage based on the dielectric spectrum.