No abstract

Future space exploration will likely include teams of autonomous robots that can perform various tasks in order to minimize human risk and maximize mission efficiency. One particular task may include the autonomous construction of a lunar or Martian habitat to prepare for long-duration human habitation on an extraterrestrial surface. This paper describes the development of an autonomous team of two robots that cooperatively transports a long construction object. Three major aspects of the project are discussed: the measurement of robot states, the design of cooperative control laws that govern the motion of the two-robot team, and the design of the central-PC infrastructure.

The attitude dynamics of a spacecraft with an attached robot arm is a subtle problem in dynamics and control. In this work, we discuss a robotic testbed designed to engage students in addressing this example of a complex class of rigid body dynamics. A planar, multi-degree-of-freedom robotic arm is designed and constructed with sensors and wireless communication to measure and record power usage and maneuver kinematics. Each arm segment is actuated by either direct-drive motors or a scissored pair of control-moment gyroscopes (CMGs) in order to allow the power requirements and capabilities of each design in a planar system to be compared. A scissored pair of CMGs is more like a joint motor than a single CMG because the output torque is aligned with the joint axis. The simplified dynamics of a scissored pair are also more easily understood at an undergraduate level. The testbed uses an air bearing system on a sheet of glass to support the arm segments, significantly reducing the effects of gravity and friction. Prior student groups have built and flown CMGactuated robots on the NASA microgravity research aircraft. However, one flight per year provides little opportunity for feedback and design improvement. With an in-house test setup, students can design a series of experiments and verify their work throughout the year. This testbed will provide students with a research tool for exploring the differences between CMG and direct drive actuators.