Bot Feet Aid Copter
Helicopters are pretty useful
vehicles, but they come with a
range of inherent problems
including low speed, high
complexity, rotor lift
dissymmetry, gearbox and drive
train vibration, and so on.
Because they are essentially
flying weed whackers, you can’t
land one in the woods, and
their skid-based landing gear requires a flat and stable
surface. The latter characteristic puts serious limits on their
use in natural disaster zones, on ships at sea, and in other
places where they might be needed.
However, the folks at the US Defense Advanced
Research Projects Agency (DARPA, www.darpa.mil) have
been working with Georgia Tech ( www.gatech.edu) to
improve their ability to operate from angled, irregular, and
moving surfaces. The result is a
novel robotic landing gear
system that uses four articulated
jointed legs that are equipped
with force-sensitive contact
sensors. In flight, the legs fold
up to the fuselage. When
landing, they extend and —
using the sensors —
automatically determine the
correct angle to keep the vehicle
level and prevent the rotors
from striking the ground.
A test flight demonstrated: (1) a 500 percent reduction
in damage resulting from hard landings; ( 2) stable takeoff
and landing on slopes up to 20° and on irregular terrain;
and ( 3) the ability to land on ships in violent sea conditions
— all without adding much extra weight.
Is there a video, you ask? Well, sure:
DARPA’s unmanned helicopter fitted with
robotic landing gear.
by Jeff and Jenn Eckert
Hedgehogs in Space
Typically, vehicles designed to move around on the moon, Mars, and
other extraterrestrial locations roll around on wheels or tracks. As
demonstrated by NASA’s Spirit rover, this isn’t necessarily the most effective
way to travel in microgravity or over rough surfaces — particularly on
smaller bodies such as comets and asteroids. Taking a completely different
approach is Hedgehog: a prototype being developed along two different
but parallel lines by NASA’s Jet Propulsion Lab ( www.jpl.nasa.gov),
Stanford University ( www.stanford.edu), and MIT ( web.mit.edu).
Specifically designed to hop and tumble on the surface instead of relying
on wheels, the cube-shaped robot’s movement is created by alternately
spinning and braking three internal flywheels, corresponding to X-Y-Z
Cartesian axes. It also incorporates spikes on each corner to protect the
vehicle and act like feet.
Future versions could incorporate various instruments in the spikes such
as probes and sensors. Hedgehog can operate the same no matter which
side it lands on, so tip-overs are not an issue. The standard procedure is to
point itself in the desired direction (yaw), then hop long distances using
one or two spikes, or just tumble short distances by rolling from one face
to another. It can also perform a “tornado” maneuver in which is spins and
launches itself from the surface to, e.g., escape from a sinkhole.
The prototypes weigh about 11 lb ( 5 kg) but could end up twice as
heavy when equipped with cameras and instruments. A significant
advantage is that a Hedgehog robot is relatively cheap by rover standards,
so several could be released by the mothership, letting them spread out to
SERVO 01.2016 7
Hoppy Hedgehog robot surmounts microgravity
and hazardous terrain.