Experiments in autonomous navigation and control of multi-manipulator, free-flying space robots.

摘要

Although space presents an exciting frontier for science and manufacturing, it has proven to be a costly and dangerous place for humans. It is an ideal environment for sophisticated robots capable of performing tasks that currently require the active participation of astronauts. The Aerospace Robotics Laboratory, working with NASA, has developed an experimental model of a multi-manipulator, free-flying space robot capable of capturing and manipulating free-floating objects without human assistance.;The experimental robot model uses air-cushion technology to simulate, in 2-D, the dragfree, zero-g characteristics of space. Fully self-contained, the vehicle/manipulator system is equipped with gas-jet thrusters, two two-link manipulators, an electrical power system, digital and analog I/O capabilities, high-speed vision, and a multi-processor real-time computer. These subsystems have been carefully integrated in a modular architecture that facilitates maintenance and ease-of-use.;A sophisticated control system was designed and implemented to manage and coordinate the actions of the vehicle/manipulator system. A custom on-board vision system is used for closed-loop endpoint control and object tracking in the robot's local reference frame. A multi-camera off-board vision system provides global positioning information to the robot via a wireless communication link. Successful rendezvous, tracking, and capture of free-flying, spinning objects is facilitated by simultaneously controlling the robot base position and manipulator motions. These actions are coordinated by a sophisticated event-driven finite-state machine.;A graphical user interface enables a remotely situated operator to provide high-level task description commands to the robot, and to monitor the robot's activities while it carries out these assignments. The user interface allows a task to be fully specified before any action takes place, thereby eliminating problems associated with communications delays.;The success of this project was predicated on viewing it first and foremost as a systems engineering problem. A design philosophy that emphasized maintaining a systems perspective while utilizing a modular implementation served to guide virtually every phase of its development. This approach to systems engineering is expounded upon in the early chapters of the thesis and contributes to the general applicability of the concepts and ideas presented in the later ones.