Dynamic Modeling of Multi-link Swimming Robot Capable of 3-D Motion

This paper presents a three-dimensional (3-D) dynamic model for free-swimming, flexible multi-link robots using Schiehlen method within the framework of multi-body dynamics. The swimming robots, like robotic fish and robotic dolphin, consist of a sequence of propulsive modules in series, which propels itself via undulatory/oscillatory locomotion and performs up-and-down motion by artificial pectoral fins. Mechanically, this robotic configuration is simply considered as an open, tree-structured multi-body system. The expressions for the hydrodynamic forces and momentums on the moving modules are based on quasi-steady hydrodynamics and oscillatory foil theory, and these are coupled with kinematic and dynamic analyses to derive complete dynamic equations in a form suited for controller design and computer simulation. The matching results between simulation with experimental results on a four-link, multi-mode robotic fish show good agreement, which partially demonstrates the validity of the proposed model and the potential of its use for other flexible links based robots.