TRESTLE: Autonomous Assembly by Teams of Coordinated Robots


 

Autonomous assembly of large structures will require teams of robots.  Much like any human work crew, heterogeneous capabilities will also be necessary. The TRESTLE project is developing the architectural framework necessary to coordinate robots performing complex assembly projects. In specific, the project seeks to develop architectural tools used to coordinate actions performed by multiple robots. These tools form the core of an executive layer that orchestrates and monitors tasks across robots to perform assembly tasks. Since the number of possible failure modes over many robots working on long sequences of actions is high, TRESTLE incorporates the ability of humans to cooperatively manage tasks. By employing Sliding Autonomy, we allow the operator to manage the assembly in three different ways. First, a portion of the system's tasks can be predefined to be under operator control.   Second, the operator can intervene and manually switch the system to operator control. Third, the system can automatically shift to operator control after a failure.

TRESTLE will examine tasks such as:

  • Truss Assembly: Truss assembly includes retrieving materials from stockpiles, moving materials to the worksite, coordinating assembly with other agents, and mating compliant structures without causing collisions between agents and the infrastructure.
  • Bracing: Cable bracing under tension can often add strength and rigidity to truss structures.  Bracing along the diagonals of a cube, for example, can greatly increase its strength with minimal increase in weight.
  • Wiring: Many structures need to be wired after assembly.  Though wiring need not be tensioned, as in the case of bracing, but may have complex connectors or irregular waypoints.

Applications

Space Solar Power: Space Solar Power will exploit the radiant energy of the Sun with an orbiting solar array.  Collection of solar energy will be enhanced by site-location above the Earth’s atmosphere, eliminating losses due to weather and the earth's atmosphere. These kilometer scaled facilities positioned high above the earth will require automated construction because their size precludes direct launch or orbital assembly by astronauts. It is anticipated that such facilities will have tens of thousands of parts that must be assembled in microgravity. Maintenance of these facilities will also require automation because temperatures near surface elements will exceed acceptable bounds for humans. It is envisioned that teams of robots will construct these facilities.

TRESTLE is funded by a NSF/NASA/EPRI program that supports research in Space Solar Power.

Surface Based Assembly: As NASA sends rovers to distant planets, it will become important to leverage the robot population by coordinating teams of robots. Rather than sending new robots with all the capabilities required for a single mission, robots will work with their predecessors to perform tasks that no single robot can perform. These robots will be heterogeneous to accomplish a wide variety of tasks and the tasks themselves will be schedule dynamically. While the scheduling of robot teams is being addressed by projects such as FIRE, TRESTLE provides the execution and monitoring support for multiple robots performing coordinated actions.