Closed loop control of force operation in a novel self-sensing dielectric elastomer actuator

Closed loop feedback is essential in achieving the precise control of dielectric elastomer actuators (DEAs) due to their inherent nonlinear viscoelasticity. A novel self-sensing mechanism that uses capacitive sensing to detect the actuation of force in a dielectric elastomer sensing actuator (DESA) is proposed in this paper. In contrast to a conventional self-sensing DEA, it consists of an electro-active region (AR) for the actuation together with an independent electro-sensing region (SR). By doing so, the self-sensing mechanism does not exhibit long-term drift in the correlation between the structural deformation and the capacitive change, which is commonly found in conventional self-sensing DEAs. The results show that the proportional-integral (PI) controlled DESA performs effectively under uniaxial actuation. The DESA can suppress the relaxation of the viscoelastic DE and thus enable a constant force output. It also shows that the sensing capacity of the DESA can be enhanced further with appropriate electrode arrangement and motion-constraining. Furthermore, the results show that the DESA senses the off-plane expansion distinctly compared with the in-plane deformation, which helps to detect any wrinkling of the structure.