Measurement of hydrodynamic forces and moment acting on Crabster, CR200 using model tests

Crabster CR200 is a remotely operated vehicle which has six artificial and articulated legs driven by BLDC motors. It is supposed to walk on the sea floor. As a result, the robot has a very complicated appearance and hydrodynamic forces and moment acting on the robot experience a variety of changes according to configurable legs and body postural position. This paper describes the experiments to estimate lift force, drag force and pitching moment acting on CR200 using a 1/4 length ratio scaled model. A 6-axis Force/Torque sensor was adopted and installed in the middle of inner space of the model to measure the forces and moment. The experiments were conducted in a circulating water channel whose width and depth are 3.5m and 3.0m, respectively. To define hydrodynamic characteristics effected by the floor, the authors approached in two ways. The first is that CR200 was assumed to stand on the ground. The other is when the robot is placed in the middle of stream of water flow.