Year: 2021
Type: conference-paper
Abstract: View Video Presentation: https://doi.org/10.2514/6.2021-2018.vid Manipulator-equipped microgravity robots (free-flyers) have been proposed for on-orbit activities including assisting astronauts with daily tasks and serving as mobile workers in microgravity assembly scenarios. An emerging class of free-flyer, assistive free-flyers (AFFs), will engage in complex manipulation scenarios such as grasping and moving new objects. This introduces a notable source of uncertainty in the form of inertial parametric uncertainty stemming from grappling unknown or poorly-characterized objects. This paper explicitly demonstrates the value---and perhaps even necessity---of control that can account for parametric uncertainty in these AFF manipulation scenarios, which involve more agile motion and larger end effector mass fractions than more traditional on-orbit free-flyer control situations. In this case study, a six degree of freedom base AFF with a two-link manipulator grapples an unknown point mass. The free-flying manipulator dynamics are detailed and a complex feasible reference trajectory, representative of those potentially seen by future AFFs, is provided. Two non-adaptive controllers, proportional-derivative (PD) and feedback linearization, are compared with sliding mode adaptive control for varying grappled mass fraction. A Lyapunov-based convergence analysis of the adaptive controller is also explicitly provided. Drawing from the prior free-flying literature, the value of parameter-aware control design for emerging AFF control scenarios is demonstrated.
Source: AIAA SciTech Forum
DOI: 10.2514/6.2021-2018
Institution: Massachusetts Institute of Technology
Language: English
Subfield: Aerospace Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
Awards: THE RISKS AND CHALLENGES OF THE SPACE ENVIRONMENT HAVE LOGICALLY LED TO PROPOSALS TO USE ROBOTS TO PERFORM TASKS FOR EFFICIENCY AND SAFETY REASONS. ROBOTIC FREE FLYERS (AUTONOMOUS OR CONTROLLABLE ROBOTS THAT OPERATE IN MICROGRAVITY LOCAL TO A HOST) HAVE MULTIPLE ONGOING RESEARCH AREAS INCLUDING AUTONOMOUS DOCKING SYSTEMS VISUAL SIMULTANEOUS LOCALIZATION AND MAPPING (SLAM) OF SPACE ENVIRONMENTS CHARACTERIZING CONTROL METHODS FOR DOCKED/CONNECTED BODIES AND THE APPLICATION OF THESE AREAS TO VARIOUS PRACTICAL SITUATIONS. THE ONGOING DEVELOPMENT NEEDED TO INCREASE THE TECHNOLOGY READINESS LEVEL (TRL) OF ROBOTIC FREE FLYERS PROMISES TO ALLOW FOR THE PERFORMANCE OF TASKS PREVIOUSLY DELEGATED TO SCARCE ASTRONAUT ON-ORBIT TIME INCREASE MISSION SAFETY AND EVEN LAY THE GROUNDWORK FOR ON-ORBIT ASSEMBLY AND SERVICING TECHNIQUES. FREE FLYER RESEARCH IS LARGELY CONSTRAINED BY THE TESTBEDS AVAILABLE. THE SIGNIFICANCE OF RECENT UPGRADES TO THE MIT SPHERES SATELLITES ONBOARD THE ISS IS NOT OVERSTATED IN NOTING THAT THEY PROVIDE THE WORLD S FIRST RECONFIGURABLE ON-ORBIT TESTBED OF MULTI-SATELLITE DOCKING. RELATEDLY RESEARCH INTO FREE FLYING SPACE ROBOTIC MANIPULATORS COULD WELL BE APPLIED TO THE SPHERES TESTBED. APPLICATIONS OF MANIPULATORS TO FREE FLYERS INCLUDE THE ABILITY TO PERCH TO PREVENT FREE FLOATING. THE NASA TECHNOLOGY ROADMAPS POINT TO THE DEVELOPMENT OF ROBOTIC MOBILITY AND MANIPULATION SYSTEMS (TABS 4.2 AND 4.3). RECOGNIZING THE VALUE OF THE CURRENT CONFIGURATION OF THE HALO-ENABLED SPHERES TESTBED AND INTEREST IN SATELLITE/FREE FLYER MANIPULATION ACTIVITIES MY PROPOSED RESEARCH AIMS TO INVESTIGATE AREAS OF IMPROVEMENT IN FREE FLYER MANIPULATION CAPABILITY AND ITS APPLICATION IN ENHANCING BOTH IVA AND EVA MOBILITY. SPECIFICALLY THIS RESEARCH CAN BE BROKEN DOWN INTO THE FOLLOWING 3 OBJECTIVES: 1. DRIVE DEVELOPMENT OF THE MIT ARM OR SIMILAR FREE FLYER MANIPULATORS 2. DESIGN ALGORITHMS FOR USEFUL IVA/EVA APPLICATIONS OF FREE FLYER MANIPULATORS WITH AN EMPHASIS ON PERCHED ACTIVITY 3. VALIDATE FREE FLYER MANIPULATOR SYSTEMS THROUGH GROUND AND ON-ORBIT TEST SCENARIOS THE GOAL OF THIS STUDY IS TO INVESTIGATE MANIPULATOR DESIGNS FOR BOTH PERCHING AND GRAPPLING MANIPULATORS CREATING THE CONTROL ALGORITHMS NECESSARY FOR THEIR USE IN DOCKING AND OBJECT MANIPULATION AND TESTING THEIR SUCCESS IN GROUND ANALOGUES AND ON-ORBIT. SUITABLE ROBOTIC MANIPULATORS WILL BE DEVELOPED TO FULFILL BOTH THE PERCHING AND GRAPPLING ROLES FOLLOWED BY GROUND TESTS VERIFYING A SET OF CONTROL LAWS FOR MANEUVERS THAT HAVE APPLICABILITY IN FREE FLYER MOBILITY AND EVA/IVA MANIPULATION TASKS. ADDRESSING NASA TECHNOLOGY NEEDS THIS INVESTIGATION FURTHER OFFERS THE OPPORTUNITY TO EXPAND ON-ORBIT CONSTRUCTION CAPABILITY ASSIST WITH ASTRONAUT EVA/IVA ACTIVITIES AND INCREASE THE OVERALL EFFICIENCY AND SAFETY OF SPACEFLIGHT OPERATIONS., G5688757940, Graduate Research Fellowship Program (GRFP)
OpenAlex ID: W3118835410