Modeling of underwater snake robots moving in a vertical plane in 3D

Increasing efficiency by improving the locomotion methods is a key issue for underwater robots. Consequently, an accurate dynamic model is important for both controller design and for the development of efficient locomotion methods. This paper presents a model of the kinematics and dynamics of an underwater snake robot moving in a vertical plane in 3D. The fluid contact forces (hydrodynamic forces) and torques (fluid moments) are modeled using analytical fluid dynamics. Hydrodynamic forces and torques, i.e. linear and nonlinear drag forces, current effects, added mass and fluid torque effects, are considered. In addition, this modeling approach also takes into account the hydrostatic forces (gravitational forces and buoyancy). The model is given in a closed form and is thus in a form that is well-suited for modern model-based control schemes. The proposed model is easily implemented and simulated, regardless of the number of robot links. Simulation results for lateral undulation and eel-like motion with a ten link robotic system are presented.