Hydrodynamic Force Estimation for Hexapod Robot Walking in Tidal Current Environment

This paper presents the horizontal drag force with different angle of attack over the robotic body for four degree of freedom hexapod robot model. In order to analyse the main hydrodynamic characteristics several estimations are made on the basis of fundamental hydrodynamic theories and fluid dynamics. The motion of the ocean water at its Ekman layer is described by the Navier-Stokes equation. For the complex body structure of the robot. In this study, through numerical calculation the Reynolds number is measured in order to understand the type of water flow over the structure. The relative velocity vectors, Reynolds number, drag and lift forces for each state of motion is obtained in both static water condition and in ocean current condition. Drag and lift forces are calculated differently for several relative velocities for the same and opposite direction of water flow and robot motion. A hydrodynamic analysis using Computational Fluid Mechanics software packages is conducted in order to verify the estimated parameters and confront the numerical solutions and characterize the hydrodynamic forces. This analysis and results further implemented to modern adaptive drag force model-based controller in horizontal flow disturbance control for underwater hexapod walking robot