Dynamic Modeling of Flexible Bio-mimetic Robotic Fish Driven by MFC Based on the Absolute Nodal Coordinate Formulation

With the development of bionic fish research, the bionic fish design driven by intelligent materials has gradually emerged. When used as an actuator, piezoelectric fiber composite material, macro-fiber composite (MFC) has excellent flexibility and piezoelectric actuation characteristics. Therefore, using MFC as the actuating device of bionic robotic fish has a good application prospect. With this comes two unsolved problems: the rigid-flexible-fluid coupling problem caused by the flexible caudal tail in the process of swimming in a large swing and the electromechanical coupling problem of MFC material. This paper takes the Body and Caudal Fin (BCF) propulsion flexible bionic fish actuated by MFC as the object of study. The main driving caudal fin was simplified into a basal plate with MFC patches bonded on both sides, and its dynamics modeling was derived by the absolute nodal coordinate formulation (ANCF). In this paper, the MFC constitutive model and Lighthill’s slender body theory considering electromechanical coupling effect are introduced to calculate the influence of electricity and fluid on the fishtail model. The deformation coordination condition is used to realize the deformation coupling problem between plate elements. Finally, a rigid-flexible coupled dynamic model is established to solve the large swinging swimming problem of robotic fish tail fin in absolute coordinate system, and the generalized time-delay method is used to solve the dynamic equation of the system. The numerical simulation of the dynamic response of the caudal fin model under multiple physical fields is realized. The work in this paper has certain theoretical value and application value for the design of the driving part of the bionic robotic fish using MFC.