Bracing, Anchoring
Since RoboSimian is still in its early
design phases, its creators have not fully
exercised every capability the robot has,
such as passively stable stances,
multipoint anchored connections, and
bracing itself during forceful
manipulation operations.
"The idea of the multipoint anchor
connections is that in 3D, we can apply
the end-effectors such as in a ladder
climbing scenario," Kennedy
commented. In this scenario,
RoboSimian's hands and feet can grab
the ladder rungs at at least three points
with three end-effectors at any one
time and maintain stability.
Further, if the ladder tips over and
is suddenly like a set of monkey bars,
the robot would be insensitive to the
fact that the ladder is at another angle.
"It would simply go into a sort of
monkey/sloth mode," said Kennedy. If
the robot should try to open a door that is stuck shut, it
could use one lower limb to brace itself while using two
upper limbs to open the door if necessary.
Heading Agnostic Perception
RoboSimian is enabled with heading agnostic
perception, which enables the robot to change direction
without first reorienting itself. "By design, because each
limb is the same and has multiple cameras, there is nothing
different in terms of functionality based on heading,"
explained Kennedy.
There really is no front or back to the robot, so it does
not have to move in a certain direction based on what it is
or is not facing at the moment it changes direction. This
enables the robot to change direction in fewer steps and
movements. "The fewer the steps, the less the risk," smiled
Kennedy.
The robot's axisymmetric distribution of the limb
workspace and visual perception enable the robot with this
heading agnostic perception. Because the four limbs are
basically on a square with sufficient cameras all around to
fill in each hemisphere of visible space with stereo data
(two camera eyes in each case like a human being, but with
more sets of them), and because the cameras build a 3D
model of the world around the robot in every direction, any
set of cameras can point to the direction the robot wants
to take next. "That's why the robot doesn't have to reorient
itself first before moving in a new direction," Kennedy
commented.
The Surrogate
While RoboSimian is great at generalized tasks, it is
slow in benign movement tasks such as just walking across
a long stretch of terrain. So, comes the Surrogate version of
RoboSimian. "We gave it wheel accessories so it can roll.
Wheels make sense for certain operational conditions,"
explained Kennedy.
While there are lots of tracked vehicles with robotic
arms, Surrogate uses what was one of RoboSimian's arms
as its spine. "The seven jointed spine allows us to position
the Surrogate's upper body in any place or orientation in
reach of the spine," said Kennedy. There are two more
limbs on top of that spine that are not as generalized as
the ones on RoboSimian. "They are more like arms and are
more robust on the Surrogate," commented Kennedy.
The Surrogate also has a head and neck with two
cameras on the head, which operators can point at
whatever they are trying to work with. "It is more straight
forward as a bi-manual robot with two limbs like a human
being would use," concluded Kennedy. SV
SERVO 05.2015 13
Early RoboSimian videos: www-robotics.jpl.nasa.gov/roboticVideos/vid1016-152-video.mp4
www-robotics.jpl.nasa.gov/roboticVideos/vid1016-154-video.mp4
RoboSimian competes.