Tech Briefs Magazine - August 2023 - MD-26

A Gripper That Grasps by Reflex
Rather than start from scratch after a failed attempt, the pick-and-place robot adapts in the moment
to get a better hold.
Massachusetts Institute of Technology, Cambridge, MA
W
hen manipulating an arcade claw, a
player can plan all she wants. But
once she presses the joystick button, it's a
game of wait-and-see. If the claw misses
its target, she'll have to start from scratch
for another chance at a prize. The slow
and deliberate approach of the arcade
claw is similar to state-of-the-art pick-andplace
robots, which use high-level planners
to process visual images and plan
out a series of moves to grab for an object.
If a gripper misses its mark, it's back to
the starting point, where the controller
must map out a new plan.
Looking to give robots a more nimble,
human-like touch, MIT engineers have
now developed a gripper that grasps by
reflex. Rather than start from scratch after
a failed attempt, the team's robot adapts in
the moment to reflexively roll, palm, or
pinch an object to get a better hold. It's
able to carry out these " last centimeter "
adjustments (a riff on the " last mile " delivery
problem) without engaging a higher-level
planner, much like how a person
might fumble in the dark for a bedside
glass without much conscious thought.
The new design is the first to incorporate
reflexes into a robotic planning architecture.
For now, the system is a proof of
concept and provides a general organizational
structure for embedding reflexes
into a robotic system. Going forward, the
researchers plan to program more complex
reflexes to enable nimble, adaptable
machines that can work with and among
humans in ever-changing settings.
" In environments where people live and
work, there's always going to be uncertainty, "
said Andrew SaLoutos, a graduate
student in MIT's Department of
Mechanical Engineering. " Someone could
put something new on a desk or move
something in the break room or add an
extra dish to the sink. We're hoping a
robot with reflexes could adapt and work
with this kind of uncertainty. "
Many modern robotic grippers are designed
for relatively slow and precise tasks,
such as repetitively fitting together the
same parts on a factory assembly line.
These systems depend on visual data from
onboard cameras; processing that data
limits a robot's reaction time, particularly if
it needs to recover from a failed grasp.
" There's no way to short-circuit out and
say, oh shoot, I have to do something now
and react quickly, " SaLoutos said. " Their
only recourse is just to start again. And that
takes a lot of time computationally. "
In their new work, Kim's team built a
more reflexive and reactive platform, using
fast, responsive actuators that they originally
developed for the group's mini cheetah
- a nimble, four-legged robot designed
to run, leap, and quickly adapt its
gait to various types of terrain.
The team's design includes a high-speed
arm and two lightweight, multijointed fingers.
In addition to a camera mounted to
the base of the arm, the team incorporated
custom high-bandwidth sensors at the fingertips
that instantly record the force and
location of any contact as well as the proximity
of the finger to surrounding objects
more than 200 times per second.
The researchers designed the robotic
system such that a high-level planner
initially processes visual data of a scene,
marking an object's current
location
where the gripper should pick the object
up, and the location where the
robot should place it down. Then, the
planner sets a path for the arm to reach
out and grasp the object. At this point,
the reflexive controller takes over.
If the gripper fails to grab hold of the
object, rather than back out and start
again as most grippers do, the team
wrote an algorithm that instructs the
robot to quickly act out any of three
grasp maneuvers, which they call " reflexes, "
in response to real-time measurements
at the fingertips. The three
reflexes kick in within the last centimeter
of the robot approaching an object
and enable the fingers to grab, pinch, or
drag an object until it has a better hold.
They programmed the reflexes to be
carried out without having to involve the
high-level planner. Instead, the reflexes
are organized at a lower decision-making
level, so that they can respond as if by instinct,
rather than having to carefully evaluate
the situation to plan an optimal fix.
Now, the engineers are working to include
more complex reflexes and grasp
maneuvers in the system, with a view toward
building a general pick-and-place
robot capable of adapting to cluttered and
constantly changing spaces.
For more information, contact Abby
MIT researchers (from left): Elijah Stanger-Jones, Hongmin Kim, and Andrew SaLoutos have designed a robot
gripper that incorporates reflexes to quickly grasp and sort everyday objects. (Image: Jodi Hilton)
26
Abazorius at abbya@mit.edu; 617-2532709.
Motion
Design, August 2023

Tech Briefs Magazine - August 2023

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