Dynamics And Control Of The Smart Maintenance And Inspection Robotic Free-flyer (SMIRFF)

Abstract

The aim of the future space missions would be exploring near earth planets and asteroids. This would mean longer flight durations requiring a space habitat. Longer flight durations would require frequent maintenance and repairs of the space habitat. This would involve the risk of exposing astronauts to the harsh environments while conducting extra-vehicular activities. This risk can be minimised by using a tele-operated free- flying robot. Free- flying robots are a unique class of robots which do not have rigid fixed base and oat in space. A concept of Smart Maintenance Inspection and Robotic Free- flyer (SMIRFF) is presented in this thesis. SMIRFF is a compact free- flyer with two robotic arms. It uses cold-gas thrusters to position and orient itself in space. With an array of on-board sensors, cameras and robotic arms, SMIRFF is capable of performing visual inspection along with minimal maintenance and repair works. SMIRFF weighs roughly around 10 Kg. Since NASA has been exploring the possibilities of using 3-D printing technology, custom made versions of this robot can be additively manufactured for task specific purposes. The aim of the thesis is to derive the kinematics of SMIRFF using modified Denavit-Hartenberg parameters. Using these kinematic relations, the non-linear dynamical model is constructed using an Iterative Newton-Euler method. A simulation showing the effect of simple manipulator arm motion on the base is demonstrated. The next step involves showing usefulness of the simulation environment, SimMechanics (MATLAB/SIMULINK) in simulating such complex multi-body systems. Finally, a quaternion based feedback controller is used to control the attitude of the floating base by counteracting the reaction moments generated due to the motion of the manipulator arms.