Characterization and modeling of viscoelastic hysteresis in a dielectric elastomer actuator

This paper presents characterization and modeling for viscoelastic hysteresis exhibited by dielectric elastomer actuator (DEAs). Firstly, output-input characteristics in terms of hysteresis, asymmetry and output nonlinearity are quantitatively described by proposed indicators. Their variations with the excitation frequency are investigated, revealing significant asymmetric property and strong frequency-dependence. Next, the Hammerstein model with a cascaded structure is proposed for viscoelastic hysteresis description. A modified Prandtl-Ishlinskii model, representing the static nonlinear element, is employed to characterize the asymmetric property of static hysteresis, while a finite-impulse-response based adaptive filter as the linear part captures the dynamic effect. The hysteresis loops of DEAs under the input voltages with different frequencies, waveforms and amplitudes are experimentally measured and compared with those predicted results. The relative error in terms of root-mean-square value ranges from 1.92% to a maximum of 5.53% over a wide frequency range of 0.1-10 Hz, demonstrating the effectiveness of the proposed model of rate-dependent hysteresis in DEAs. This work can be useful to promote the applications of DEAs to soft robotics and haptics.