Electrostatic layer jamming variable stiffness based on AC waveform regulation

Abstract As a method to achieve variable stiffness of soft robots, electrostatic layer jamming (ELJ) has the disadvantages of low breakdown strength and a single stiffness control method. In this paper, we propose to replace the air of the traditional ELJ device with giant electrorheological fluid (GERF) and introduce the method of adjusting the stiffness by AC waveform to solve these problems. We perform friction experiments on ELJ devices (ELJ-GERF, ELJ-Air, ELJ-Oil) under three different dielectrics of GERF, air, and silicone oil. The results show that the breakdown probability of ELJ-Air increased significantly when the applied voltage is greater than 3000 V, while ELJ-GERF and ELJ-Oil can withstand voltage exceeding 5000 V. ELJ-GERF has higher breakdown strength than ELJ-Air. At the same time, the AC waveform can regulate the stiffness of the three devices. By applying voltages with three different AC waveforms (sine wave, square wave, and triangle wave), all three devices exhibit different stiffness properties. The stiffness of ELJ-GERF is increased by 2.6 times, 4.5 times, and 2.7 times under the sine wave, square wave, and triangular wave respectively compared with DC voltage. The other two devices also have a certain increase in stiffness.