| Flexible bionic robotic fish is a typical flexible multi-body system that the dynamic behavior is affected by multi-physical fields caused by factors such as structures,material properties and external environments.The flexible ionic polymer metal composite（IPMC）is representative in the application of soft smart materials with low driving voltage,high energy conversion rate,light weight and simple structure,which is suitable for the tail fin drive of small bionic fish.Since it is difficult to accurately describe its large overall deformation,absolute nodal coordinate formulation（ANCF）has been widely used for the great advantages in describing large deformation and large displacement problems.The feasibility of using ANCF to model IPMC dynamics is explored in this paper.Focus on the caudal fin drive,the small body/caudal fin（BCF）bionic fish is researched in this paper.The tail fin is simplified as two types:an IPMC beam type and an IPMC-rigid beam hybrid type,and the dynamic modeling of the IPMC beam is carried out using ANCF.Based on the Nemat-Nasser model of white box theory,the mechanical-electric coupling relationship of IPMC is studied to establish the simplified fish body model and analysis its different motions.The reduced ANCF beam element is used in dynamic modeling,and an accurate generalized elastic force expression is obtained through considering the influence of deformation curvature.The dynamic equation can accurately describe the large geometric deformation of the flexible beam,and valid the theory by a flexible simple pendulum.In this paper,simulations of an IPMC beam-type and an IPMC-rigid beam hybrid type tail fin which driven by square wave voltage are calculated,and compare the displacement changes of the tail fin tip.The oscillation laws under different amplitudes and frequencies of the driving voltage considering the fluid resistance are analyzed.Results show that,increase the driving voltage amplitude,reduce the voltage frequency and the fluid resistance within a certain range can improve the driving efficiency of IPMC.In addition,by calculating the equivalent coupling piezoelectric coefficient d31,the equivalent piezoelectric bimorph model of the IPMC beam is simulated in the ANSYS software.The linear relationship between the maximum tip displacement and the driving voltage is obtained. |
