SPHERES Reconfigurable Framework and Control System Design for Autonomous Assembly

Abstract

Abstract:Reconfigurable control system design is a key component for enabling autonomous on-orbit assembly. Current research on reconfigurable control systems focuses on adapting to failures. However, for assembly scenarios, the reconfiguration is necessitated by changing mass and stiffness properties. This paper provides a brief description of existing reconfigurable control system technology and develops a framework to incorporate reconfiguration into an existing baseline system to account for mass property variations. The reconfigurable control system framework has been developed and implemented using the SPHERES (Synchronized Position Hold Engage Reorient Experimental Satellites) testbed as the baseline system. The framework highlights the elements that need to be updated, introduces a variable p that captures the configuration, and details the updates necessary in the key algorithms to calculate the model online using p. Results are presented from the implementation on the SPHERES, focusing on the reconfigurable estimator. Plans are presented for an integrated assembly test that demonstrates the maintenance of stability, fuel efficiency, and accuracy throughout configuration changes that occur during assembly. Introduction:Reconfigurable control systems are used in a variety of applications, such as docking, servicing, high efficiency flight, and assembly. Autonomous assembly is a critical technology for future missions such as large space telescopes, on-orbit space stations, and a lunar base. One particular scenario for autonomous on-orbit assembly is to use an assembler tug to maneuver the different payload items. In this scenario, the dynamics of the assembler tug will vary greatly at each docking and undocking maneuver, based on the properties of the payload, such as mass and inertia. Depending on the relative sizes of the tug to the payload, this could be a very significant change. In order to maintain adequate control performance, it is important to account for the property changes. The implementation of a reconfigurable control system would be able to account for the frequent mass property changes, while also introducing adaptability into the system design. The sequence of assembly would not need to be pre-determined, nor would all configurations have to be pre-computed.

Design and Operational Elements of the Robotic Subsystem for the e.deorbit Debris Removal Mission

“…There are four major groups of robotic applications in space that can be defined. Using the Shuttle and Space Station Robotic Manipulator System (SRMS, SSRMS), respectively, the International Space Station (ISS) was assembled out of several modules by applying the principle of in-space robotic assembly (ISRA) (Mohan and Miller, 2009 ). Small robotic satellites are planned to serve for inspection purposes (Stoll et al, 2012 ) and NASA's Robonaut (Diftler et al, 2012 ) or comparable systems such as DLR's humanoid robot Justin (Zacharias et al, 2010 ) are candidates for future extra-vehicular activity (EVA) support operations.…”

Utilizing Artificial Intelligence to achieve a robust architecture for future robotic spacecraft

“…Using the Shuttle and Space Station Robotic Manipulator System (SRMS, SSRMS), respectively, the International Space Station (ISS) was assembled from several modules using in-space robotic assembly (ISRA) [1]. Small robotic satellites are planned to serve for inspection purposes [2] and NASA's Robonaut [3] or comparable systems such as DLR's humanoid robot Justin [4] are candidates for future EVA support operations.…”