Control-moment gyroscopes (CMGs) have been used for attitude control on spacecraft that require large torques. We propose them for use in multibody robotic systems where high agility (or dexterity) and low power are important design goals. Although many CMG arrangements are possible, our baseline concept includes a scissored pair of CMGs for each rotational joint. A scissored pair is an array of two single-gimbal CMGs with parallel gimbal axes and opposite angular velocities. The scissored-pair arrangement ensures that the sum of the CMGs' angular momentum aligns with a single axis, like that of a reaction wheel, which drastically simplifies the control algorithms. This architecture offers singularity-free, reactionless slewing of a multi-joint robotic arm. We describe the implementation of this concept as a manipulator arm on a free-flying MaintenanceBot. When a joint is actuated, the torque comes not from a direct-drive motor that interacts with its neighboring body, but from manipulating the distribution of momentum among the CMGs and the body to which they are mounted. Perhaps the most important impact of reactionless CMG-based control is that it requires only 1%-10% the electrical power for a comparable RWA-based or joint-driven robotic system. This entirely new approach to actuating kinematic chains in orbit holds promise for highly effective in-situ construction and repair of satellites. The CMG-based MaintenanceBot architecture can radically outperform other systems in power for high-agility maneuvers. Furthermore, this architecture opens up a large trade space for power vs. agility, allowing highly effective MaintenanceBots to be incorporated for relatively low power-specific mass. Or, for a given mass, the MaintenanceBot can withstand more demanding operations for longer than competing architectures. A prior paper presented a preliminary design for the CMG-actuated MaintenanceBot. In this paper, we present new results from the incorporation of robot arm dynamics into the simulation and the development of algorithms (i.e. inverse kinematics) to position the arm.
Architecture for low-power, high-agility multibody control
2005
15 Seiten, 13 Quellen
Aufsatz (Konferenz)
Englisch
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