Abstract
Conventional rigid actuators, such as DC servo motors, face challenges in utilizing them in artificial muscles and soft robotics. Dielectric elastomer actuators (DEAs) overcome all these limitations, as they exhibit complex and fast motions, quietness, lightness, and softness. Recently, there has been much focus on studies of the DEAs material’s non-linearity, the non-linear electromechanical coupling, and viscoelastic behavior of VHB and silicone-based conical DEAs having compliant electrodes that are based on graphite powder and carbon grease. However, the mitigation of overshoot that arises from fast response conical DEAs made with solid electrodes has not received much research focus. In this paper, we fabricated a conical configuration of multi-walled carbon nanotube/polydimethylsiloxane (MWCNT/PDMS) based DEAs with a rise time of 10 ms, and 50% peak overshoot. We developed a full feedback state-based linear-quadratic regulator (LQR) having Luenberger observer to mitigate the DEAs overshoot in both the voltage ON and OFF instances. The cone DEA’s model was identified and a stable and well-fitting transfer function with a fit of 94% was obtained. Optimal parameters Q = 70,000, R = 0.1, and Q = 7000, R = 0.01 resulted in the DEA response having a rise time value of 20 ms with zero overshoot, in both simulations and experiments. The LQR approach can be useful for the control of fast response DEAs and this would expand the potential use of the DEAs as artificial muscles in soft robotics.
Highlights
The fabrication and control of high-performance dielectric elastomers actuators (DEAs) can improve the state-of-the-art of artificial muscles and soft robotics [1,2]
The linear-quadratic regulator (LQR) approach can be useful for the control of fast response DEAs and this would expand the potential use of the DEAs as artificial muscles in soft robotics
The results show that the output of the DEA had no overshoots during both the voltage ON/OFF instances by optimally tuning the Q and R weight matrices, and a rise time of 20 ms was attained for both the closed-loop simulation and closed-loop experiment
Summary
The fabrication and control of high-performance dielectric elastomers actuators (DEAs) can improve the state-of-the-art of artificial muscles and soft robotics [1,2]. DEAs are essentially two compliant electrodes sandwiching an insulating dielectric elastomer. The electrostatic pressure generated upon the voltage activation of the DEA causes the dielectric membrane to squeeze in the thickness direction and extend in the areal direction [3]. Various materials have been used in the fabrication of DEAs: Acrylic VHB 4910/4905 and silicone sheets have been used to make the insulating dielectric elastomer membranes while the electrodes were made from graphite powder or carbon grease [5]. These electrode materials would shift or enter the dielectric membrane and cause premature failure and inconsistent
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