Control of a fully-actuated airship for satellite emulation

Over the past four years, researchers at McGill University have developed a novel concept for studying dynamics and control of robotic grasping of objects in space. This problem arises in several applications - those currently under investigation include on-orbit servicing of satellites and removal of space debris. The main difficulty in experimental testing of such tasks is how to emulate the gravity-free environment of space here on the ground. A number of experimental facilities have been developed around the world to emulate the gravity-free conditions for space robotics research. For example, one popular approach involves floating the system under investigation - a robotic arm or a mock-up satellite - on air-bearings on a glass- covered or granite table. A few research establishments have invested in neutral buoyancy water tanks for three- dimensional, high-fidelity, albeit very costly, emulation of weightlessness. We have proposed a novel idea which involves using a small helium blimp to emulate a free-floating object. Although not perfect, this concept is simpler, less expensive to implement and is more suitable for 3D emulation of the gravity-free conditions of space. An experimental facility has been developed in the Aerospace Mechatronics Laboratory to implement this concept in an indoor laboratory setting. The main components of our facility are: a six-degree-of-freedom robotic manipulator placed on a 3 m linear track, a spherical helium airship 6 ft in diameter, made neutrally buoyant and balanced, a Vicon six-camera system and associated control hardware and software interfaces. This video submission focuses on the control of the airship for satellite emulation.