Continuum analysis of a soft bending actuator dynamics

Abstract

Soft fiber-reinforced bending actuators are extensively used in different applications such as gripping mechanisms and rehabilitation robots. Modeling their dynamics is challenging due to their inherent nonlinearity that rises from both their material behavior and their geometrical features. This paper presents a continuum nonlinear model of the dynamic response of this actuator to inflation. The model is developed by considering the deformation to be hyperelastic and taking Rayleigh’s dissipative function into account. The deflection functions are obtained by solving the resulting differential equations using semi-inverse techniques. After fabricating a prototype and verifying the model experimentally in both time and frequency domains, it is further studied using bifurcation analysis concerning changes in the actuator’s geometrical parameters. Moreover, by analyzing the model in the frequency domain, a hardening behavior is observed in the system’s frequency response. In addition, the system’s response amplitude is inspected to decrease dramatically in higher frequencies, meaning that the actuator does not go back to its reference state owing to high actuation speed.