[meteorite-list] 'Hedgehog' Robots Hop, Tumble in Microgravity
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 10 Sep 2015 13:14:46 -0700 (PDT)
'Hedgehog' Robots Hop, Tumble in Microgravity
Jet Propulsion Laboratory
September 3, 2015
Hopping, tumbling and flipping over are not typical maneuvers you would
expect from a spacecraft exploring other worlds. Traditional Mars rovers,
for example, roll around on wheels, and they can't operate upside-down.
But on a small body, such as an asteroid or a comet, the low-gravity conditions
and rough surfaces make traditional driving all the more hazardous.
Enter Hedgehog: a new concept for a robot that is specifically designed
to overcome the challenges of traversing small bodies. The project is
being jointly developed by researchers at NASA's Jet Propulsion Laboratory
in Pasadena, California; Stanford University in Stanford, California;
and the Massachusetts Institute of Technology in Cambridge.
"Hedgehog is a different kind of robot that would hop and tumble on the
surface instead of rolling on wheels. It is shaped like a cube and can
operate no matter which side it lands on," said Issa Nesnas, leader of
the JPL team.
The basic concept is a cube with spikes that moves by spinning and braking
internal flywheels. The spikes protect the robot's body from the terrain
and act as feet while hopping and tumbling.
"The spikes could also house instruments such as thermal probes to take
the temperature of the surface as the robot tumbles," Nesnas said.
Two Hedgehog prototypes -- one from Stanford and one from JPL -- were
tested aboard NASA's C-9 aircraft for microgravity research in June 2015.
During 180 parabolas, over the course of four flights, these robots demonstrated
several types of maneuvers that would be useful for getting around on
small bodies with reduced gravity. Researchers tested these maneuvers
on different materials that mimic a wide range of surfaces: sandy, rough
and rocky, slippery and icy, and soft and crumbly.
"We demonstrated for the first time our Hedgehog prototypes performing
controlled hopping and tumbling in comet-like environments," said Robert
Reid, lead engineer on the project at JPL.
Hedgehog's simplest maneuver is a "yaw," or a turn in place. After pointing
itself in the right direction, Hedgehog can either hop long distances
using one or two spikes or tumble short distances by rotating from one
face to another. Hedgehog typically takes large hops toward a target of
interest, followed by smaller tumbles as it gets closer.
During one of the experiments on the parabolic flights, the researchers
confirmed that Hedgehog can also perform a "tornado" maneuver, in which
the robot aggressively spins to launch itself from the surface. This maneuver
could be used to escape from a sandy sinkhole or other situations in which
the robot would otherwise be stuck.
The JPL Hedgehog prototype has eight spikes and three flywheels. It weighs
about 11 pounds (5 kilograms) by itself, but the researchers envision
that it could weigh more than 20 pounds (9 kilograms) with instruments
such as cameras and spectrometers. The Stanford prototype is slightly
smaller and lighter, and it has shorter spikes.
Both prototypes maneuver by spinning and stopping three internal flywheels
using motors and brakes. The braking mechanisms differ between the two
prototypes. JPL's version uses disc brakes, and Stanford's prototype uses
friction belts to stop the flywheels abruptly.
"By controlling how you brake the flywheels, you can adjust Hedgehog's
hopping angle. The idea was to test the two braking systems and understand
their advantages and disadvantages," said Marco Pavone, leader of the
Stanford team, who originally proposed Hedgehog with Nesnas in 2011.
"The geometry of the Hedgehog spikes has a great influence on its hopping
trajectory. We have experimented with several spike configurations and
found that a cube shape provides the best hopping performance. The cube
structure is also easier to manufacture and package within a spacecraft,"
said Benjamin Hockman, lead engineer on the project at Stanford.
The researchers are currently working on Hedgehog's autonomy, trying to
increase how much the robots can do by themselves without instructions
from Earth. Their idea is that an orbiting mothership would relay signals
to and from the robot, similar to how NASA's Mars rovers Curiosity and
Opportunity communicate via satellites orbiting Mars. The mothership would
also help the robots navigate and determine their positions.
The construction of a Hedgehog robot is relatively low-cost compared to
a traditional rover, and several could be packaged together for flight,
the researchers say. The mothership could release many robots at once
or in stages, letting them spread out to make discoveries on a world never
Hedgehog is currently in Phase II development through the NASA Innovative
Advanced Concepts (NIAC) Program, and is led by Pavone. The flight development
and testing were supported by NASA's Center Innovation Fund (CIF) and
NASA's Flight Opportunities Program (FOP), which were led by Nesnas. NIAC,
CIF and FOP are programs in NASA's Space Technology Mission Directorate,
located at the agency's headquarters in Washington. JPL is managed by
the California Institute of Technology for NASA. Stanford University,
MIT and JPL collaborate on the project.
For a complete list of the selected proposals and more information about
For more information about the Space Technology Mission Directorate, visit:
Jet Propulsion Laboratory, Pasadena, Calif.
elizabeth.landau at jpl.nasa.gov
Received on Thu 10 Sep 2015 04:14:46 PM PDT