Abstract: Modeling a dielectric electroactive polymer (EAP) actuator is crucial for the design and optimization of actuators. By combining the large deformation elastic theory of membranes and Maxwell stress, this paper builds a model that describes the electromechanical coupling of dielectric EAP materials. A negative stiffness preload mechanism is analyzed which can significantly improve the actuation characteristics of an EAP actuator, and a model of a conically-shaped dielectric EAP actuator with negative stiffness preload mechanism is founded. By computing the nonlinear ordinary differential algebraic equations, the main factors that contribute to the performance of the conically-shaped dielectric EAP actuator are analyzed. The voltage-displacement curves and principal stretch ratio and the distribution of principal stress in the membrane under different voltages are obtained. At the same time, the force-displacement curve of the EAP actuator with voltage on or off is also derived. Finally, factors contributing to the deviation between theoretical analysis and experimental results are listed. The results show that the proposed model can guide the design and application of conically-shaped dielectric EAP actuators.

Key words: negative stiffness, dielectric EAP, preload mechnism, actuator, electromechanical coupling