Development of a large space robot: A multi-segment approach

Abstract

A multi-segment robot is developed as a concept for use in space based construction operations. The multi-segment robot is envisioned as a member of a class of large space robots, or space cranes, used in the assembly of advanced spacecraft. The problems that arise when the requisite robot size becomes large are explored. The unique capabilities of the multi-segment robot are discussed. The multi-segment robot involves a collection of common bodies, or segments, that are pinned together to form a snake-like, or train, configuration. A degree of freedom representing rotation is retained at each pinned connection. Reaction flywheels are suspended within each segment and provide the control necessary to position each body segment. Algorithms are developed to position this serpentine robot to a prescribed location and orientation. The first algorithm is used to compute a general shape, based on a constrained polynomial function, that locates the robot tip at the proper position. Next, an algorithm is developed that is used to position the discrete bodies along the shape function and determines their relative positions. This information is used as the target values in a control system that uses the reaction flywheels to position each body into the desired relative position. An n-body simulation program is developed based on Newton-Euler equations of motion for the robot. The simulation is used to develop the robot control strategy, to verify its performance, and to size prototype hardware. Two cases are analyzed to investigate the dexterity of the proposed configuration. Robot design issues are explored as they relate to the multi-segment robot. A prototype system is designed, fabricated, and tested. Motion tests are included that compare experimental results with pertinent analytical predictions. Collectively, the present study demonstrates the viability of the proposed concept for addressing the unique problems associated with large robotic operations in space.