Mitigating the Coupled Effects of Rate-Dependent Viscoelasticity and Mechanical Resonance in Dielectric Elastomer Actuators via Modified Repetitive Control

This study introduces a modified repetitive control (MRC) scheme aimed at achieving high-precision tracking control for dielectric elastomer actuators (DEAs) by eliminating the intertwined effects of rate-dependent viscoelasticity and mechanical resonance. The research begins by systematically characterizing the nonlinear dynamic responses of a DEA, encompassing elements such as nonlinear electromechanical effect, viscoelasticity, and mechanical resonance (with natural frequencies at 3.5 and 7.0 Hz), along with their interdependencies. In order to simplify the DEA model, the rate-dependent viscoelasticity is treated as a bounded periodical disturbance, allowing the system to be reduced to a cascading structure comprising a nonlinear electromechanical module and an identified linear model. The MRC scheme is then developed through the following two key steps: establishment of a stable approximate inverse model utilizing the zero-phase-error-tracking approach; and design of a spectrum-selection filter to prevent the amplification of nonharmonic components. The effectiveness of the proposed scheme is subsequently validated in the periodic tracking experiments. Experimental results underscore the capability of the MRC scheme to effectively eliminate rate-dependent viscoelasticity, mechanical vibration, and their coupling across a broad frequency spectrum (0.1–10.0 Hz). Further tracking experiments validate its effectiveness for various references and robustness. This article accomplishes high-precision tracking control over a wide frequency range without necessitating a complex modeling process, thereby facilitating broader applications of DEAs.