In-space and planetary surface assembly for human exploration is a challenging domain that encompasses various technological thrusts to support human missions. NASA is developing autonomous assembly agents to build structures like habitats and antennae on the Moon. These modular and reconfigurable Assembler robots will provide robotic assembly of structures, even in locations that prohibit constant human oversight and teleoperation.
Assemblers are a team of modular robots that work together to build things. Each Assembler is a stack of one or more Stewart platforms, or hexapods, made up of two plates connected by six linear actuators for movement, enabling a full six-degree-of-freedom pose of the top plate relative to the bottom plate. An end effector on each Assembler enables gripping, lifting, and welding/joining. The Assemblers system architecture features novel control algorithms and software, sensors, and communicator technology that coordinate operations of Assembler teams. The control system includes an important module for task management that estimates how many robots are needed, the optimal number of hexapods in each Assembler, and the estimated voltage needed.
There are also modules for trajectory generation, joint control, sensor fusion, and fault detection. The novel control system directs the Assembler operations for high accuracy and precision, yet there is built-in dynamic resilience to failure. For example, if a single hexapod on an Assembler fails, the system deems it rigid in its last pose and redistributes the work to the other Assemblers. The image shows a storyboard of operations for how Assemblers might build a solar array. NASA has developed a hardware demo with communications between subsystems, backed up by detailed simulations of the kinematics and actuator dynamics.
Compared with existing short-reach/ high-accuracy and long-reach/low accuracy-assembly robots, Assemblers provides both long- and short-reach capability with accuracy and precision. The technology builds upon recent advancements in lightweight materials, state estimation, modern control theory, and machine learning. This system is capable of scheduling, reconfiguring, and executing structural assembly tasks; assessing construction; and correcting errors in assembly as needed.
Estimates indicate the Assemblers can enable 5- to 15-year mission life. Their applications include fabrication of structures on orbit or on the lunar surface including habitats, power trusses, science equipment, telescope supports, refueling stations, aeroshells, antennae, gravity-generator facilities, or solar arrays, as well as advanced industrial manufacturing and assembly.