Behavior based water depth estimation for diver type small humanoid robot

For the purpose of extending application area of a humanoid robot, we study recognition method for motion change under water and guess the depth from the surface of water. A property of an action under water is different from the one performed on land because of the influence of resistance inertia force by water wave. Therefore, it is more difficult to control actions under water. We use a small humanoid robot ldquoRobovie-Mrdquo and put a diving suit on it. When the robot stands up under water, its motion of standing up has to be adjusted. The robot falls down and floats up onto the surface of water it is gets up with the same motion at a different depth. The stand up motion should differ depending on its depth from the surface of water. We propose a method of estimating the robot´s depth under water by measuring the motion of standing up and inclination angle of the upper body.