The first construction workers on Mars may not need
hardhats.
NASA researchers have successfully demonstrated the first use
of multiple rovers that work tightly in sync to perform tasks
such as coordinated grasping, lifting and moving of an
extended payload, while navigating through obstacles on
natural terrain.
“The Robotic Work Crew behaves a lot like its human
counterpart might during a home construction project. Consider
the challenge two people face when transporting a long, heavy
board through a busy work site,” said Paul Schenker,
supervisor of the Mechanical and Robotics Technologies Group
and principal investigator for the project at NASA’s Jet
Propulsion Laboratory (JPL) in Pasadena, Calif.
“Each person alone, or in this case each rover, has a variety
of behaviors for how to carry smaller things,” Schenker
explained. “The trick is to combine such individual behaviors
to safely carry and manipulate bigger things. The rovers must
share the workload and thinking, exchange important sensory
cues and quickly comply with each other’s motions.”
During outdoor tests near JPL, in which the deployment of a
solar power station was simulated, two such cooperating rovers
autonomously approached, gripped and carried a 2.5-meter- (8-
foot-) long container over distances of more than 50 meters
(164 feet).
The Robotic Work Crew can traverse uneven, hazardous terrain.
The crew visually detects and tracks its goal, identifies
nearby objects in its path and works collectively to avoid
obstacles. Throughout this process, the robots constantly
update each other about payload forces and motions as felt at
their respective grippers. If the beam is slipping, the rovers
collectively sense the problem and compensate.
New software called Control Architecture for Multi-robot
Planetary Outposts is the shared brain that commands the team
of rovers. “The two robots tightly coordinate their individual
sensory and control behaviors in an uncertain, fast-changing
environment to accomplish a common goal,” said Terry
Huntsberger, project system engineer at JPL, who along with
his colleague Paolo Pirjanian, led the development of the new
control software.
“The robot team robustly fuses this information into a bigger
picture, coming up with a best cooperative control solution,”
Huntsberger continued. “We can easily add new behaviors and
additional robots to the system. New behaviors can be simple,
or more complex, with some behaviors building on top of
numerous others already in place.”
The JPL researchers say the rovers function much like a
construction crew without a foreman. They note that once the
system has been programmed with basic behaviors and
coordination models, it is a truly distributed and autonomous
intelligence across the robot team that gets the job done,
responding to situations of the minute.
“Mars is hundreds of millions of miles from Earth; we can
hardly predict every scenario the rovers may encounter or
foresee every rock and hill,” said Schenker. “But, it is
possible to give two or more rovers a set of instinctively
reactive behaviors, a shared network of sensing and control,
and a democratic decision-making process that enables them to
decide the best action strategies. Call it a case of robots
networking for success,” he said.
Although work on the Robotic Work Crew is in the early stages,
the underlying multi-robot cooperation technologies appear
essential to building outposts for a sustained human and/or
robotic presence on Mars and the creation of large surface-
science networks. The software and technical approach also has
promise for future robotic assembly and maintenance of
spacecraft in orbit, such as the deployment of large optical
structures or power stations, as well as setting up camp on
Mars before humans arrive and supporting their work
thereafter.
NASA’s Cross Enterprise Technology Development Program
provided funding for this work. The California Institute of
Technology in Pasadena manages JPL for NASA. JPL is the lead
U.S. center for robotic exploration of the solar system.
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