Armilleye: flexible platform for underwater stereo vision

The paper describes ArmillEye, a 3-degree of freedom (DOF) flexible hybrid platform designed for agile underwater stereoptic vision. Effective telecontrol systems of remote operated vehicles require active and dexterous camera support in order to allow the operator to easily and promptly change the point of view, also improving the virtual reconstruction of the environment in difficult operative conditions (dirtiness, turbulence, and partial occlusion). The same concepts hold for visual servoing of autonomous underwater vehicles. ArmillEye was designed for this specific application; it is based on the concept of using a parallel-hybrid mechanism architecture that, in principle, allows us to minimize the ad hoc waterproof boxes (generally only for cameras) while the actuators, fixed to the base of the mechanism, can be placed into the main body of the underwater vehicle. This concept was revealed effective and was previously proposed for underwater arms. The synthesis of ArmillEye followed the specific aims of visual telecontrol and servoing, specifying vision workspace, dexterity, and dynamics parameters. Two versions of ArmillEye are proposed: the first one with two cameras to obtain a steroptic vision by using two viewpoints (two rotational freedoms with a fixed tilt or pan axis and vergence); the second one with one camera operated to obtain a stereoptic vision by using one viewpoint (two rotational freedoms with a fixed tilt or pan axis and extrusion).